4.1. The installation of pipelines should be carried out by specialized installation organizations, while the installation technology should ensure high operational reliability of the pipelines.
4.2. Parts, pipeline elements (expansion joints, mud collectors, insulated pipes, as well as pipeline assemblies and other products) must be manufactured centrally (at the factory, workshops, workshops) in accordance with standards, specifications and design documentation.
4.3. The laying of pipelines in a trench, canal or on overground structures should be carried out according to the technology provided for by the project of work and excluding the occurrence of residual deformations in the pipelines, violation of the integrity of the anti-corrosion coating and thermal insulation by using appropriate mounting devices, the correct placement of simultaneously operating lifting machines and mechanisms.
The design of fastening the mounting devices to the pipes must ensure the safety of the coating and insulation of the pipelines.
4.4. Laying of pipelines within the panel support must be carried out using pipes of the maximum delivery length. In this case, the oval transverse seams of pipelines should, as a rule, be located symmetrically relative to the shield support.
4.5. Pipes with a diameter over 100 mm with a longitudinal or spiral seam should be laid with an offset of these seams by at least 100 mm. When laying pipes with a diameter of less than 100 mm, the displacement of the seams must be at least three times the pipe wall thickness.
Longitudinal seams must be within the upper half of the pipe circumference to be laid.
It is allowed to weld steeply curved and stamped pipe bends to each other without a straight section.
Welding of branch pipes and elbows into welded joints and bent elements is not allowed.
4.6. When installing pipelines, movable supports and hangers should be displaced relative to the design position by the distance indicated in the working drawings, in the direction opposite to the movement of the pipeline in working condition.
In the absence of data in the working drawings, the movable supports and hangers of horizontal pipelines must be displaced taking into account the correction for the outside air temperature during installation by the following values:
sliding supports and elements for attaching hangers to the pipe - by half of the thermal extension of the pipeline at the attachment point;
rollers of roller bearings - by a quarter of the thermal elongation.
4.7. When installing pipelines, spring hangers must be tightened in accordance with the working drawings.
During hydraulic tests of steam pipelines with a diameter of 400 mm and more, an unloading device should be installed in spring hangers.
4.8. The pipeline fittings must be installed in a closed state. Flanged and welded connections of valves should be made without pipe interference.
The deviation from the perpendicularity of the plane of the flange welded to the pipe in relation to the pipe axis should not exceed 1% of the outer diameter of the flange, but not more than 2 mm at the top of the flange.
4.9. Bellows (wavy) and stuffing box expansion joints should be assembled assembled.
In the case of underground laying of heating networks, the installation of expansion joints in the design position is allowed only after preliminary tests of pipelines for strength and tightness, backfilling of channelless pipelines, channels, chambers and shield supports.
4.10. Axial bellows and stuffing box expansion joints should be installed on pipelines without breaking the axes of the expansion joints and the axes of the pipelines.
The permissible deviations from the design position of the connecting pipes of the expansion joints during their installation and welding should be no more than those specified in technical conditions for the manufacture and supply of expansion joints.
4.11. When installing bellows expansion joints, their twisting relative to the longitudinal axis and sagging due to their own weight and the weight of adjacent pipelines are not allowed. Slinging of expansion joints should be done only by the branch pipes.
4.12. The installation length of bellows and stuffing box expansion joints should be taken according to the working drawings, taking into account the correction for the outside air temperature during installation.
The expansion joints should be stretched to the installation length using the devices provided for by the expansion joint design or by tensioning mounting devices.
4.13. Stretching of the U-shaped expansion joint should be performed after completion of the pipeline installation, quality control of welded joints (except for the closing joints used for tension) and fastening the structures of fixed supports.
The expansion joint must be stretched by the amount indicated in the working drawings, taking into account the correction for the outside air temperature when welding the closing joints.
The expansion joint must be stretched simultaneously from both sides at the joints located at a distance of at least 20 and not more than 40 diameters of the pipeline from the axis of symmetry of the compensator, using clamping devices, unless other requirements are justified by the project.
On the section of the pipeline between the joints used to stretch the expansion joint, no preliminary displacement of the supports and hangers should be made in comparison with the project (working draft).
4.14. Immediately before assembling and welding pipes, it is necessary to visually inspect each section for the absence of foreign objects and debris in the pipeline.
4.15. Deviation of the slope of the pipelines from the design is allowed by a value of ± 0.0005. In this case, the actual slope must be at least the minimum permissible according to SNiP II-G.10-73 * (II-36-73 *).
The movable supports of pipelines must adjoin the supporting surfaces of structures without a gap or skew.
4.16. While doing installation works the following types of hidden works are subject to acceptance with drawing up inspection certificates in the form given in SNiP 3.01.01-85: surface preparation of pipes and welded joints for anti-corrosion coating; anti-corrosion coating of pipes and welded joints.
On stretching expansion joints, an act should be drawn up in the form given in the mandatory Appendix 1.
4.17. Protection of heating networks from electrochemical corrosion must be performed in accordance with the Instruction for the protection of heating networks against electrochemical corrosion, approved by the USSR Ministry of Energy and the RSFSR Ministry of Housing and Communal Services and agreed with the USSR State Construction Committee.
Before installing the expansion joints in the design position, it is necessary to inspect them by external inspection. As a rule, before the final connection to the pipeline, all expansion joints must be pre-stretched or compressed by the amount specified in the project, and installed on the pipelines together with a spacer (or compression) device, which is removed only after the final fastening of the pipelines to fixed supports. The amount of prestretching of the expansion joint is indicated in the drawings.
Stretching is used for "hot" lines of the pipeline, and compression - for "cold". The stretching or squeezing operation is called pipe cold stress and is performed in order to reduce the stress in the metal due to thermal elongation of the pipeline.
An act is drawn up on the expansion of expansion joints, regardless of the method of its implementation, in which the construction lengths of the expansion joints are indicated before and after the expansion.
U-shaped compassors, as a rule, are installed in a horizontal position and only as an exception vertically or obliquely. When installing such expansion joints vertically or obliquely, at the lower points on both sides of the expansion joints, it is necessary to place drainage nipples for condensate drainage, and in the upper part - air vents.
To provide normal work The U-shaped expansion joint is installed on at least three movable supports (Fig. 5). Two supports are placed on straight sections of the pipeline connected to the compensator (while the edge of the support must be at least 500 mm from the welded joint), the third support is placed under the back of the compensator, usually on a special column.
For preliminary stretching of the U-shaped compensator, a screw device is used, consisting of two clamps, between which a screw and a spacer with a tension nut are installed.
Before stretching, measure the length of the compensator in a free state, and then, by rotating the nut, dilute it to the required amount. The spacer is installed parallel to the back of the compensator. The joint at which the expansion joint will be stretched is indicated in the project. If there is no indication, then in order to avoid skewing, the joint cannot be used for stretching. Directly adjacent to the expansion joint. For this purpose, you need to leave a gap in the adjacent joint.
When lifting, the expansion joints must be gripped at three points and never by the spacer. Only after tacking the joints and sealing the compensator is disconnected from the lifting equipment. It is also necessary to check the reliability of the installation of the spacer.
U-shaped expansion joints are installed in the design position using one or two cranes.
With a group arrangement of U-shaped expansion joints of parallel pipelines (one inside the other) and in some other cases, the preliminary stretching of the expansion joints is replaced by the tension of the pipeline in a cold state. In this case, when installing the expansion joints, the pipeline is assembled in the usual way, but in one of the joints (welded or flanged), a gap is left equal to the specified value of the expansion joint expansion.
Before stretching, make sure that all welded joints in this section of the pipeline are welded, the fixed supports are finally fixed.
When installing expansion joints without preliminary stretching, for the convenience of installing the pipeline into the joint intended for stretching, insert a branch pipe with a length equal to the size of the stretching, and grab it with electric welding to both edges of the pipeline. Sometimes, annular beads are fused at the ends of the pipes to be joined and temporary clamps are installed from the corners (Fig. 6). Elongated tie rods are passed through the holes in them and, tightening the nuts, a temporary spacer insert ring installed between the ends of the joint is clamped. After welding the joint, the clamps are removed.
The flange joint, left for stretching, is temporarily (without permanent gaskets) pulled together with elongated studs, installing them through one and leaving holes for permanent bolts. The diameter and number of cold tensioning studs are specified in the project.
After installing the expansion joints in the design position, welding all joints (except one) and securing the pipeline on all fixed supports on both sides of the expansion joint, remove the temporary spacer ring and tighten the joint for welding by tightening the nuts on the elongated studs. In case of flange connection, the gasket provided by the project is installed before the final tightening. After tightening the flange connection with permanent bolts, the elongated studs are removed, and permanent bolts or studs are installed in their place.
When installing lens expansion joints, it is necessary to ensure that the drain plugs (if any) are in the lower position, and the expansion joint guide cup is welded in in the direction of product movement.
Lens expansion joints are recommended to be installed on pipes, assemblies or blocks before lifting to the design position. The assembled unit or block with lens compensators must be protected from deformation and damage during transportation, lifting and installation. For this, additional stiffness is used on the expansion joints. After installing the nodes on the supports and fastening, the temporary stiffnesses are removed.
When installing vertical sections of pipelines, it is necessary to take measures to exclude the possibility of compression and defomation of expansion joints under the influence of the gravity of the pipelines. For this, in parallel to the expansion joints on the pipelines, three brackets are welded, which are cut off at the end of the installation of the pipeline.
Lens expansion joints are stretched by half of their compensating capacity.
The lens expansion joint is stretched during installation after its welding or final connection on the flanges with the pipeline, as well as after installing all the supports and suspensions of the pipelines and fixing the pipelines in fixed supports.
In this case, the expansion joint is stretched by tightening the assembly joint closest to the expansion joint, in which a corresponding additional gap is specially left.
The compression of the expansion joint is carried out after the final connection with the pipeline, but before being fixed on fixed supports. To compress or stretch the lens expansion joint, a device is used that consists of two clamping clamps fixed to the pipeline on both sides of the expansion joint, and elongated clamping rods with nuts.
When installing several lens expansion joints on the pipeline, the project must provide fixed supports behind each expansion joint in order to exclude the possibility of deflection of the pipeline, which is in a compressed state, and to ensure a more uniform deformation of all expansion joints installed on the pipeline, since the actual stiffness of all expansion joints can be unequal.
For corrugated expansion joints, check before installation headroom; using spacers and pins, set the gap corresponding to the preliminary stretching.
Axial expansion joints are mounted in this sequence. First, they are welded at one end to the pipeline. Between the second end and the pipe to be welded, check the gap equal to the pre-stretching value, stretch the expansion joint using the nuts with studs on it, weld the second end of the expansion joint to the pipeline, and then remove the studs and nuts.
When installing hinged or universal expansion joints, they are welded to the pipeline with both ends in accordance with the installation diagram, without removing the bolts holding the hinge cheeks and protecting the expansion joint from bending.
During installation, stuffing box expansion joints must be installed strictly in line with the pipeline, without distortions in order to avoid jamming of moving parts and damage to the expansion joint packing. Guiding devices of pipelines at the points of connection to stuffing box expansion joints must tightly compress the pipes with rollers fitted to them and center the pipe in horizontal and vertical surfaces, without creating large longitudinal frictional forces.
Gland expansion joints are not stretched after installation, since when the expansion joint is welded to the pipeline, it is moved apart by the amount specified in the project and determined by the distance between the risks applied to its body and the glass. In this case, a gap must be left between the thrust rings on the branch pipe and in the compensator housing in case the temperature drops in comparison with the air temperature at the time of installation. The minimum clearance value for a pipeline section length of 100mm should be 30mm at an outside air temperature at the time of installation below -5 ° C, from -5 ° C to +20 ° C - 50mm, above +20 ° C - 60mm. During installation, it is necessary to ensure that in the event of a breakdown of the fixed supports, the moving part of the pipe does not break out of the compensator body. In most cases, for this, a rim is welded onto the sliding part of the pipe so that it does not interfere with the operation of the compensator.
Compensating devices in heating networks they are used to eliminate (or significantly reduce) the forces arising from thermal elongation of pipes. As a result, pipe wall stresses and forces on equipment and support structures are reduced.
The elongation of pipes as a result of thermal expansion of the metal is determined by the formula
where a- coefficient of linear expansion, 1 / ° С; l- pipe length, m; t - working temperature walls, 0 C; t m - installation temperature, 0 C.
To compensate for the elongation of pipes, special devices are used - compensators, and also use the flexibility of pipes at turns of the route of heating networks (natural compensation).
According to the principle of operation, expansion joints are divided into axial and radial. Axial expansion joints are installed on straight sections heat conductors, since they are designed to compensate for forces arising only as a result of axial elongations. Radial expansion joints are installed on heating systems of any configuration, since they compensate for both axial and radial forces. Natural compensation does not require the installation of special devices, so it must be used first.
In heating networks, axial expansion joints of two types are used: stuffing box and lens ones. In stuffing box expansion joints (Fig. 29.3), the temperature deformations of the pipes lead to the movement of the nozzle 1 inside the body 5, between which the stuffing box packing is placed for sealing 3. The packing is clamped between the thrust ring 4 and the packing follower 2 using bolts 6.
Figure 19.3 Expansion joints
a - one-sided; b - double-sided: 1 - glass, 2 - gland follower, 3 - stuffing box,
4 - thrust ring, 5 - body, 6 - tightening bolts
As a gland packing, an asbestos printed cord or heat-resistant rubber is used. In the process of work, the packing wears out and loses its elasticity, therefore, its periodic tightening (clamping) and replacement are required. For the possibility of carrying out these repairs, stuffing box expansion joints are placed in chambers.
The expansion joints are connected to the pipelines by welding. During installation, it is necessary to leave a gap between the flange of the bowl and the thrust ring of the body, which excludes the possibility of tensile forces in the pipelines in the event of a temperature drop below the installation temperature, and also carefully align the center line to avoid distortions and jamming of the bowl in the body.
Stuffing box expansion joints are made single-sided and double-sided (see Fig. 19.3, a and b). Bilateral ones are usually used to reduce the number of chambers, since a fixed support is installed in the middle of them, separating the pipe sections, the extensions of which are compensated by each side of the compensator.
The main advantages of stuffing box expansion joints are small dimensions (compactness) and low hydraulic resistance, as a result of which they are widely used in heating networks, especially when laying underground. In this case, they are installed at d y = 100 mm or more, with above-ground laying - at d y = 300 mm or more.
In lens compensators (Fig. 19.4), when the temperature lengthens of the pipes, compression of special elastic lenses (waves) occurs. This ensures complete tightness in the system and does not require maintenance of the expansion joints.
Lenses are made of sheet steel or stamped half-lenses with a wall thickness of 2.5 to 4 mm gas welding... To reduce the hydraulic resistance inside the compensator along the waves is inserted smooth pipe(shirt).
Lens expansion joints have a relatively small compensating capacity and a large axial reaction. In this regard, to compensate for temperature deformations of pipelines of heating networks, a large number of waves are installed or their preliminary stretching is performed. They are usually used up to pressures of about 0.5 MPa, since at high pressures, swelling of waves is possible, and an increase in the rigidity of waves by increasing the thickness of the walls leads to a decrease in their compensating ability and an increase in axial reaction.
Ryas. 19.4. Lens three-wave compensator
Natural compensation thermal deformations occur as a result of bending of pipelines. Bent sections (bends) increase the flexibility of the pipeline and increase its compensating capacity.
With natural compensation at the turns of the route, the temperature deformations of the pipelines lead to transverse displacements of the sections (Fig. 19.5). The amount of displacement depends on the location of the fixed supports: the longer the length of the section, the greater its elongation. This requires an increase in the width of the channels and complicates the operation of movable supports, as well as makes it impossible to use modern channelless laying on the turns of the track. The maximum bending stresses arise at the fixed support of the short section, since it is displaced by a large amount.
Rice. 19.5 Scheme of operation of the L-shaped section of the heat pipe
a- with the same length of the shoulders; b- with different shoulder lengths
TO radial expansion joints used in heating networks include flexible and wavy hinge type. In flexible expansion joints, temperature deformations of pipelines are eliminated by bending and twisting specially bent or welded sections of pipes of various configurations: U- and S-shaped, lyre-shaped, omega-shaped, etc. ,a). Their compensating ability is determined by the sum of deformations along the axis of each of the pipeline sections ∆ l= ∆l/2+∆l/ 2. In this case, the maximum bending stresses arise in the segment farthest from the pipeline axis - the back of the compensator. The latter, bending, is shifted by an amount y, by which it is necessary to increase the dimensions of the compensatory niche.
Rice. 19.6 Scheme of operation of the U-shaped compensator
a- without preliminary stretching; b- with preliminary stretching
To increase the compensating ability of the compensator or reduce the amount of displacement, it is installed with a preliminary (mounting) stretch (Fig.19.6, b). In this case, the back of the compensator is curved inward when inoperative and experiences bending stresses. When the pipes are lengthened, the compensator first comes to an unstressed state, and then the back is bent outward and bending stresses of the opposite sign appear in it. If the maximum permissible stresses are reached in the extreme positions, that is, during preliminary stretching and in working condition, then the compensating capacity of the compensator is doubled in comparison with the compensator without preliminary stretching. In the case of compensation for the same temperature deformations in the compensator with preliminary stretching, the backrest will not shift outward and, therefore, the dimensions of the compensatory niche will decrease. The operation of flexible expansion joints of other configurations is approximately the same.
Pendants
Pipeline suspensions (Figure 19.7) are performed using rods 3, directly connected to pipes 4 (fig.19.7, a) or with a traverse 7 , to which on clamps 6 the pipe is suspended (fig.19.7, b), as well as through spring blocks 8 (fig.19.7, v). Swivel joints 2 ensure the movement of pipelines. The guide cups 9 of the spring blocks, welded to the support plates 10, make it possible to exclude the lateral deflection of the springs. Suspension tension is provided with nuts.
Rice. 19.7 Suspensions:
a- traction; b- clamp; v- spring; 1 - support beam; 2, 5 - hinges; 3 - thrust;
4 - pipe; 6 - clamp; 7 - traverse; 8 - spring suspension; 9 - glasses; 10 - plates
3.4 Methods of insulation of heating networks.
Mastic isolation
Mastic insulation is used only when repairing heating networks, laid either in rooms or in passageways.
Mastic insulation is applied in layers of 10-15 mm on the hot pipeline as the previous layers dry. Mastic insulation cannot be done using industrial methods. Therefore, the specified insulating structure is not applicable for new pipelines.
For mastic insulation, sovelite, asbestos and vulcanite are used. The thickness of the thermal insulation layer is determined on the basis of technical and economic calculations or in accordance with applicable standards.
The temperature on the surface of the insulating structure of pipelines in passageways and chambers should not exceed 60 ° C.
The durability of the heat-insulating structure depends on the mode of operation of the heat pipes.
Block isolation
Prefabricated block insulation from preformed products (bricks, blocks, peat slabs, etc.) is arranged on hot and cold surfaces. Products with bandaging of seams in rows are laid on a mastic grease made of asbesurite, the coefficient of thermal conductivity of which is close to the coefficient of the insulation itself; the grease has minimal shrinkage and good mechanical strength. Peat products (peat plates) and corks are laid on bitumen or iditol glue.
Heat-insulating products are fixed to flat and curved surfaces with steel pins welded in advance in a checkerboard pattern with an interval of 250 mm. If the installation of studs is not possible, the products are fixed as mastic insulation. On vertical surfaces with a height of more than 4 m, unloading support belts made of strip steel are installed.
In the process of installation, the products are adjusted to each other, the holes for the studs are marked and drilled. The elements to be mounted are secured with pins or wire twists.
With multilayer insulation, each subsequent layer is laid after leveling and fixing the previous one with overlapping longitudinal and transverse seams. The last layer, fixed with a frame or metal mesh, is leveled with mastic under the rail and then plaster is applied with a thickness of 10 mm. Pasting and painting are performed after the plaster has completely dried.
The advantages of prefabricated block insulation are industrial, standard and prefabricated, high mechanical strength, the possibility of facing hot and cold surfaces. Disadvantages - multi-seam and complexity of installation.
Backfill insulation
On horizontal and vertical surfaces building structures use backfill thermal insulation.
When installing thermal insulation on horizontal surfaces (roofless roofs, ceilings above the basement), expanded clay or perlite serves as the insulating material.
On vertical surfaces, backfill insulation is made of glass or mineral wool, diatomaceous crumbs, perlite sand, etc. For this, a parallel insulated surface is fenced with bricks, blocks or nets, and insulating material is poured (or stuffed) into the resulting space. With a mesh fencing, the mesh is attached to pre-installed staggered pins with a height corresponding to the specified insulation thickness (with an allowance of 30 ... 35 mm). A metal wicker mesh with a cell of 15x15 mm is pulled over them. Bulk material is poured into the resulting space layer by layer from bottom to top with light ramming.
After the end of the backfill, the entire surface of the mesh is covered with a protective layer of plaster.
Backfill insulation is quite effective and easy to use. However, it is not resistant to vibration and has low mechanical strength.
Cast insulation
As insulating material mainly used foam concrete, which is prepared by mixing cement mortar with foam in a special mixer. Thermal insulation layer laid by two methods: the usual methods of concreting the space between the formwork and the insulated surface or gunning.
In the first method the formwork is set parallel to the vertical insulated surface. In the resulting space, the heat-insulating composition is laid in rows, leveling with a wooden trowel. The laid layer is moistened and covered with mats or mats to ensure normal conditions for foam concrete hardening.
Shotcrete method Cast insulation is applied over mesh reinforcement made of 3-5 mm wire with cells of 100-100 mm. The applied sprayed layer adheres tightly to the insulated surface, does not have cracks, cavities or other defects. Shotcrete is carried out at a temperature not lower than 10 ° C.
Cast thermal insulation is characterized by simplicity of the device, solidity, high mechanical strength. The disadvantages of cast insulation are the long duration of the device and the impossibility of performing work at low temperatures.
Installation of heating networks, which should be carried out by the flow method, includes earthwork, assembly and welding, stone, concrete, reinforced concrete, insulation, pressure testing, carpentry and other works.
With a properly organized in-line construction method, work is performed in a specific technological sequence. The flow is organized in such a way as to most economically dispose of forces and resources, to perform a large amount of work in a short time, with low costs and with high quality construction.
Heating networks in cities and other settlements are laid in specially designated for construction engineering structures lanes parallel to the red lines of streets, roads and driveways outside the carriageway and a strip of green spaces. If justified, it is possible to lay networks under the roadway and sidewalks.
For heating networks, underground laying is mainly provided, less often - aboveground(on the territory of enterprises, outside the city, with a high level of groundwater, in permafrost regions and in other cases when underground laying is impossible or impractical).
When laying underground, pipelines of heating networks (heat pipelines) are laid in channels - special building structures that enclose the pipelines, or without channels. Channels can be passable and non-passable. Depending on the adopted design of underground laying (in non-through or through channels, collectors), it is allowed to lay heating networks together with others. engineering networks(water supply, communication cables, power cables, pressure sewerage).
With an overhead (open) laying, heat pipes are laid on brackets along the walls of buildings, on concrete, reinforced concrete and metal supports. When heat pipelines pass through railways and water hazards use bridge structures. Heat pipelines laid under the bed of a river or canal, along the slopes and the bottom of a ravine, are bent in accordance with the terrain. Such structures are called siphons. When laid under the river bed, heat pipes are enclosed in steel pipes (cases). The pipes are held against floating by weights. In this way, other types of underground networks are also built (water supply, gas pipeline and sewerage) when they cross rivers, ravines and other similar obstacles.
Assembly steel pipes large diameters into links using a pipe-laying crane... Before the start of pipe assembly work, pipes are brought into the links and laid out along a pre-marked axis; clean pipe ends from dirt and straighten deformed edges.
Steel pipes are assembled into links in the following sequence: the beds are laid and verified, the pipes are laid on the beds with the help of a pipe-laying crane; clean and prepare the pipe edges for welding; center the joints with a centralizer, supporting the pipes with a pipe-laying crane while tacking the joint with electric welding; weld pipe joints by turning the pipe link; remove the beds and place the assembled link on the inventory pads.
Laying and aligning the beds... The pipelayers, pulling a tape measure along the axis of the link layout, mark the places for laying the beds on it. Then the beds are brought and laid out according to the markings, while the middle of the bed should coincide with the axis of the layout. Four metal pins are hammered at the ends of the extreme legs and twine is pulled between the extreme legs at the level of the top of the legs. Focusing on this level, intermediate beds are installed, cutting off or knocking the soil under them with shovels.
Laying pipes on a bed... Having marked the middle of the pipe with a tape measure, the pipe-laying crane is installed so that its boom is above the center of gravity of the pipe. The pipe is slinged, and the crane operator lifts it by 20-30 cm. After making sure that the slinging is reliable and correct, the crane operator will raise the pipe to a height of 1 m and, at the command of the pipelayer, lay the pipe on the bed. Pipelayers stand at both ends of the pipe to keep it from turning.
Cleaning and preparation of pipe edges for welding... When loading, transporting or unloading, pipe ends may become elliptical, dents, etc. If necessary, the pipe ends should be straightened. The curvatures of the ends are straightened using screw jacks or manually by blows with a sledgehammer with preheating of the pipe at the straightening point.
In the event that the deformed ends cannot be straightened, they are cut off by gas cutting, followed by cleaning the edges.
Using chisels and hammers, pipelayers remove dirt and ice from pipe edges. Electric grinders, files, reversible angled pneumatic brushes clean the edges to a metallic sheen for a length of at least 10 mm from the outside and from the inside.
Joint centering and pipe support during joint tacking... The operator places the pipe-laying crane opposite the middle of the pipe and lowers the sling-towel. The pipelayer raises the pipe and gives the command to lift it by 0.5 m and move it to the docking point. After moving the pipe, the workers lay it on the beds, visually center the joint, straighten and fix the pipe on the beds with wooden stakes. Then a centralizer is installed on the joint and the joint is fixed by turning the handle.
The electric welder, having checked the size of the gap between the ends of the pipes to be joined along the entire circumference with a universal template and making sure that the size of the gap is correct, grabs the joint by welding.
If, when checking with a template, the size of the gap between the ends of the pipes does not meet the standard requirements, the pipelayers loosen the centralizer, the crane operator changes the size of the gap by moving the boom, while the pipelayers help him with crowbars. After obtaining the required clearance, the position of the pipe is finally fixed with wooden wedges, the centralizer lever is tightened to failure and then the joint is tacked by welding. After tacking the joint, the pipelayers remove the centralizer.
Rotating a link when welding pipes... After applying a seam to a quarter of the pipe's circumference, on each side of the pipe, the pipelayers turn the link, securing it with wooden wedges on the beds at the joint.
Installation and welding of movable supports... The movable supports take the load from the weight of the heat conductor, in addition, they provide the movement of the pipeline in the axial direction, which occurs due to a change in its length with a change in temperature. Factory-made movable supports are sliding, skid, roller, suspended. Of the listed structures of movable supports, the most widely used sliding bearings.
Sliding legs can be low or high, normal length and short... The type of support is selected depending on the thickness of the thermal insulation and the distance between the supports. Low (pads) and high supports protect pipes from abrasion when moving heat pipes. In addition, high supports protect the thermal insulation from contact with the duct base.
Sliding supports are installed on supporting stones with some displacement towards the fixed support. At start-up hot water the pipeline will heat up and lengthen somewhat; the sliding support welded to the pipeline will move towards the compensator and take the working position on the support stone. If the sliding support is installed on the support stone without mounting offset, it can come off the support stone during the operation of the heat pipe. The sliding support moves along a metal lining, concreted into the support stone and protruding above its upper plane.
The distance between the sliding supports depends on the distance between the support stones, which in turn is taken depending on the nominal pipe bore.
In places of welded joints, sliding supports are not allowed to be welded. The support must be welded without lateral displacement in relation to the vertical axis of the pipeline.
Having marked out the places of installation of the supports on the pipes, they are adjusted in place, grabbed and welded... Sliding supports are welded before pressure testing of the pipeline, since it is not allowed to carry out welding work on a pipeline that has passed a hydraulic or pneumatic test for density and strength.
Installation of stuffing box expansion joints... Gland expansion joints perceive axial temperature deformations of heating network pipelines and thereby protect the pipeline and fittings from destructive stresses.
Stuffing box expansion joints are made one-sided and two-sided... The compensating capacity of a double-sided expansion joint is twice that of a single-sided expansion joint.
The compensator is connected to the main pipeline for welding.
The compensator is installed in the extended position for the full stroke length, which depends on the compensating capacity, with a gap between the thrust ring of the body and the retaining ring on the bowl. The gap compensates for the change in the length of the pipeline with a decrease in the temperature of the pipes after the installation of the expansion joint (due to a decrease in the outdoor temperature).
When installing the expansion joint, stuffing gland seals (gland) should be carefully packed, since replacing the packing during operation leads to the shutdown of the heating networks. The joints of the stuffing box rings must be offset from one another, the joints of the stuffing box expansion joints must be even, and the craters must be welded.
Installing flanges... Pipeline fittings and line equipment are connected to the pipeline by welding or on flanges tightened with bolts, studs and nuts. At a nominal internal pressure in the pipeline up to 40 kgf / cm2 (4 MPa), bolts are used, at 40 kgf / cm2 and more, studs. The tightness of the flange joint depends on the accuracy of the surface treatment of the flanges, the quality of the bolts and the uniformity of their tightening. Flanges must be parallel to one another.
Flanges are welded perpendicular to the axes of the nozzles... The misalignment should not exceed 1 mm per 100 mm of the outer diameter of the flange (but not more than 3 mm). After fitting the flanges, two or three bolts are installed in place to align the gasket, then the remaining bolts are mounted, nuts are screwed on them and the flange connection is tightened. To avoid distortion, the nuts are tightened gradually in a crosswise order.
The diameter of the bolts must match the diameter of the holes of the flanges to be connected.... The bolt heads are positioned on one side of the joint. Flanged bolts may protrude above the nut by at least three threads and no more than half the bolt diameter. It is necessary that the inner diameter of the gasket matches inner diameter pipes with a tolerance of 3 mm, and its outer diameter should be not less than the diameter of the connecting protrusion and not more than the diameter of the circle tangent to the bolts.
To secure the gasket more tightly, sometimes a protrusion is made on one of the connected flanges, and a depression on the other. The protrusion fits into the recess, and thus the gasket is securely attached between the flanges. For the same purpose, concentrically located recesses - risks are applied to the mirror of the flanges.
When installing pipeline fittings valves, for example, do not over-tighten the flanges with bolts, as the density and strength of the flange connection is reduced.
Stretching U-shaped expansion joints... To increase the compensating capacity, the U-shaped expansion joints are stretched. The amount of stretch indicated in the project should be equal to half the elongation of the compensated section. The compensator is stretched only after fixed supports are installed on both sides of it; thus, when the expansion joint is stretched, the pipeline remains stationary in the places where it is welded to the supports. Only one joint remains unwelded - at the point where the expansion joint is stretched.
The compensator is stretched using corner ties, jacks, hoists, etc.... At an equal distance around the circumference of the pipe of the U-shaped expansion joint, four plates are welded, as well as four plates, to the previously laid pipe. The distance between the plates should not exceed the length of the tie bolts. Tie bolts are inserted into the hole of the plates and, screwing the nuts, stretch the compensator, bringing the edges of the pipes closer to the gap required for welding. The joints are seized by electric welding, the plates are cut with a gas cutter and the joint is welded.
Installation of heating network nodes... The pipelayer removes rust and dirt from the ends of pipes and pipes with a steel brush or file. Then, using a crane, the unit is fed into the heating network chamber, where it is installed in the design position. After that, the edges are adjusted and trimmed and the joints are centered with an external centralizer. The joints are welded, the centralizer is transferred to the next work.
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SNiP 3.05.03-85
________________
Registered by Rosstandart as SP 74.13330.2011. -
Database manufacturer's note.
BUILDING REGULATIONS
HEATING NETWORK
Date of introduction 1986-07-01
DEVELOPED by the Institute Orgenergostroy of the USSR Ministry of Energy (L. Ya. Mukomel - head of the topic; candidate of technical sciences S. S. Yakobson).
INTRODUCED by the USSR Ministry of Energy.
PREPARED FOR APPROVAL by the Glavtekhnormirovanie Gosstroy of the USSR (N. A. Shishov).
APPROVED BY THE RESOLUTION State Committee USSR for construction of October 31, 1985 N 178.
With the entry into force of SNiP 3.05.03-85 "Heating networks" SNiP III-30-74 "Water supply, sewerage and heat supply. External networks and structures" is no longer valid.
AGREED with Gosgortekhnadzor of the USSR April 15, 1985
These rules apply to the construction of new, expansion and reconstruction of existing heating networks,
transporting hot water with temperature t | 200 degrees C and pressure | 2.5 MPa (25 kgf / sq. Cm) |
from a heat source to heat consumers (buildings, structures).
1. GENERAL PROVISIONS
1. GENERAL PROVISIONS
1.1. When building new, expanding and reconstructing existing heating networks, in addition to the requirements of working drawings, work production projects (PPR) and these rules, the requirements of SNiP 3.01.01-85, SNiP 3.01.03-84, SNiP III-4-80 and standards should also be observed ...
1.2. Work on the manufacture and installation of pipelines, which are subject to the requirements of the Rules for the construction and safe operation of steam and hot water pipelines of the USSR Gosgortechnadzor (hereinafter referred to as the USSR Gosgortechnadzor Rules), must be carried out in accordance with the specified Rules and the requirements of these rules and regulations.
1.3. Completed construction heating network should be taken into operation in accordance with the requirements of SNiP III-3-81.
2. EARTH WORKS
2.1. Excavation and foundation works must be performed in accordance with the requirements of SNiP III-8-76, SNiP 3.02.01-83, SN 536-81 and this section.
2.2. The smallest width of the bottom of the trench for channelless pipe laying should be equal to the distance between the outer side faces of the insulation of the outer pipelines of heating networks (associated drainage) with the addition of a nominal diameter on each side for pipelines
the width of the pits in the trench for welding and insulation of pipe joints during channelless laying of pipelines should be taken equal to the distance between the outer side edges of the insulation of the extreme pipelines with the addition of 0.6 m on each side, the length of the pits - 1.0 m and the depth from the lower edge of the pipeline insulation - 0.7 m, unless other requirements are justified by the working drawings.
2.3. The smallest width of the trench bottom for duct laying of heating networks should be equal to the width of the duct, taking into account the formwork (on monolithic areas), waterproofing, associated drainage and drainage devices, trench attachment structures with the addition of 0.2 m. In this case, the trench width must be at least 1.0 m.
If it is necessary for people to work between the outer edges of the canal structure and the walls or slopes of the trench, the width between the outer edges of the canal structure and the clear walls or slopes of the trench must be at least: 0.70 m - for trenches with vertical walls and 0.30 m - for trenches with slopes.
2.4. Backfilling of trenches for channelless and canal laying of pipelines should be performed after preliminary tests of pipelines for strength and tightness, complete performance of insulation and construction and installation works.
Backfilling must be performed in the specified technological sequence:
lining of the sinuses between the ductless pipelines and the base;
simultaneous uniform filling of the sinuses between the walls of the trench and pipelines during channelless laying, as well as between the walls of the trench and channel, chambers during channel laying to a height of at least 0.20 m above pipelines, channels, chambers;
backfilling of the trench up to the design marks.
Backfilling of trenches (pits), to which additional external loads are not transferred (except for the own weight of the soil), as well as trenches (pits) at intersections with existing underground utilities, streets, roads, driveways, squares and other structures settlements and industrial sites should be carried out in accordance with the requirements of SNiP III-8-76.
2.5. After switching off the devices for temporary dewatering, canals and chambers must be visually inspected for the absence of groundwater in them.
3. STRUCTURES AND INSTALLATION OF BUILDING STRUCTURES
3.1. The performance of work on the construction and installation of building structures should be carried out in accordance with the requirements of this section and the requirements:
SNiP III-15-76 - during the construction of monolithic concrete and reinforced concrete structures foundations, supports for pipelines, chambers and other structures, as well as when monolithing joints;
SNiP III-16-80 - when assembling prefabricated concrete and reinforced concrete structures;
SNiP III-18-75 - during installation metal structures supports, spans for pipelines and other structures;
SNiP III-20-74 - for waterproofing channels (chambers) and other building structures (structures);
SNiP III-23-76 - when protecting building structures from corrosion.
3.2. The outer surfaces of the elements of channels and chambers supplied to the route must be covered with a coating or glued waterproofing in accordance with the working drawings.
The installation of the elements of the channels (chambers) in the design position should be carried out in a technological sequence coordinated with the project for the installation and preliminary testing of pipelines for strength and tightness.
Support cushions for sliding supports of pipelines should be installed at the distances provided for in SNiP II-G. 10-73 * (II-36-73 *).
3.3. Monolithic fixed shield supports must be performed after the installation of pipelines in the section of the shield support.
3.4. At the points of entry of channelless pipelines into channels, chambers and buildings (structures), the cases of bushing glands must be put on the pipes during their installation.
At the inlets of underground pipelines into buildings, devices must be made (in accordance with the working drawings) to prevent the penetration of gas into buildings.
3.5. Before installing the upper trays (slabs), the channels must be cleared of soil, debris and snow.
3.6. The deviation of the slopes of the bottom of the heating network channel and drainage pipelines from the design is allowed by +/- 0.0005, while the actual slope must be at least the minimum permissible according to SNiP II-G.10-73 * (II-36-73 *).
The deviation of the installation parameters of other building structures from the design ones must comply with the requirements of SNiP III-15-76, SNiP III-16-80 and SNiP III-18-75.
3.7. The project for the organization of construction and the project for the production of work should provide for the advanced construction of drainage pumping and water discharge devices in accordance with the working drawings.
3.8. Drainage pipes must be inspected and cleaned of soil and debris prior to trenching.
3.9. Layer-by-layer filtering sprinkling of drainage pipelines (except for pipe filters) with gravel and sand must be performed using inventory separating forms.
3.10. The straightness of the sections of drainage pipelines between adjacent wells should be checked by inspection "to the light" using a mirror before and after backfilling the trench. The circumference of the pipe reflected in the mirror must have the correct shape. The permissible horizontal deviation from the circle should be no more than 0.25 of the pipe diameter, but no more than 50 mm in each direction.
Deviation from correct shape vertical circles are not allowed.
4. INSTALLATION OF PIPELINES
4.1. The installation of pipelines should be carried out by specialized installation organizations, while the installation technology should ensure high operational reliability of the pipelines.
4.2. Parts, pipeline elements (expansion joints, mud collectors, insulated pipes, as well as pipeline assemblies and other products) must be manufactured centrally (at the factory, workshops, workshops) in accordance with standards, specifications and design documentation.
4.3. Laying of pipelines in a trench, canal or on overground structures should be carried out according to the technology provided for by the project of work and excluding the occurrence of residual deformations in the pipelines, violation of the integrity of the anti-corrosion coating and thermal insulation by using appropriate mounting devices, the correct placement of simultaneously operating lifting machines and mechanisms.
The design of fastening the mounting devices to the pipes must ensure the safety of the coating and insulation of the pipelines.
4.4. Laying of pipelines within the panel support must be carried out using pipes of the maximum delivery length. In this case, the welded transverse seams of pipelines should, as a rule, be located symmetrically relative to the shield support.
4.5. Pipes with a diameter over 100 mm with a longitudinal or spiral seam should be laid with an offset of these seams by at least 100 mm. When laying pipes with a diameter of less than 100 mm, the displacement of the seams must be at least three times the pipe wall thickness.
Longitudinal seams must be within the upper half of the pipe circumference to be laid.
It is allowed to weld steeply curved and stamped pipe bends to each other without a straight section.
Welding of branch pipes and elbows into welded joints and bent elements is not allowed.
4.6. When installing pipelines, movable supports and hangers should be displaced relative to the design position by the distance indicated in the working drawings, in the direction opposite to the movement of the pipeline in working condition.
In the absence of data in the working drawings, the movable supports and hangers of horizontal pipelines must be displaced taking into account the correction for the outside air temperature during installation by the following values:
sliding supports and elements for attaching hangers to the pipe - by half of the thermal extension of the pipeline at the attachment point;
rollers of roller bearings - by a quarter of the thermal elongation.
4.7. When installing pipelines, spring hangers must be tightened in accordance with the working drawings.
During hydraulic tests of steam pipelines with a diameter of 400 mm and more, an unloading device should be installed in spring hangers.
4.8. The pipeline fittings must be installed in a closed state. Flanged and welded connections of valves should be made without pipe interference.
The deviation from the perpendicularity of the plane of the flange welded to the pipe in relation to the pipe axis should not exceed 1% of the outer diameter of the flange, but not more than 2 mm at the top of the flange.
4.9. Bellows (wavy) and stuffing box expansion joints should be assembled assembled.
In the case of underground laying of heating networks, the installation of expansion joints in the design position is allowed only after preliminary tests of pipelines for strength and tightness, backfilling of channelless pipelines, channels, chambers and shield supports.
4.10. Axial bellows and stuffing box expansion joints should be installed on pipelines without breaking the axes of the expansion joints and the axes of the pipelines.
The permissible deviations from the design position of the connecting pipes of the expansion joints during their installation and welding should be no more than those specified in the technical conditions for the manufacture and supply of expansion joints.
4.11. When installing bellows expansion joints, their twisting relative to the longitudinal axis and sagging due to their own weight and the weight of adjacent pipelines are not allowed. Slinging of expansion joints should be done only by the branch pipes.
4.12. The installation length of bellows and stuffing box expansion joints should be taken according to the working drawings, taking into account the correction for the outside air temperature during installation.
The expansion joints should be stretched to the installation length using the devices provided for by the expansion joint design or by tensioning mounting devices.
4.13. The stretching of the U-shaped expansion joint should be performed after the completion of the pipeline installation, quality control of the welded joints (except for the closing joints used for tension) and fastening the structures of fixed supports.
The expansion joint must be stretched by the amount indicated in the working drawings, taking into account the correction for the outside air temperature when welding the closing joints.
The expansion joint must be stretched simultaneously from both sides at the joints located at a distance of at least 20 and not more than 40 diameters of the pipeline from the axis of symmetry of the compensator, using clamping devices, unless other requirements are justified by the project.
On the section of the pipeline between the joints used to stretch the expansion joint, no preliminary displacement of the supports and hangers should be made in comparison with the project (working draft).
4.14. Immediately before assembling and welding pipes, it is necessary to visually inspect each section for the absence of foreign objects and debris in the pipeline.
4.15. Deviation of the pipeline slope from the design is allowed by +/- 0.0005. In this case, the actual slope must be at least the minimum permissible according to SNiP II-G.10-73 * (II-36-73 *).
The movable supports of pipelines must adjoin the supporting surfaces of structures without a gap or skew.
4.16. When performing installation work, the following types of hidden work are subject to acceptance with drawing up certificates of inspection in the form given in SNiP 3.01.01-85: preparation of the surface of pipes and welded joints for anti-corrosion coating; anti-corrosion coating of pipes and welded joints.
On stretching expansion joints, an act should be drawn up in the form given in the mandatory Appendix 1.
4.17. Protection of heating networks from electrochemical corrosion must be performed in accordance with the Instruction for the protection of heating networks against electrochemical corrosion, approved by the USSR Ministry of Energy and the RSFSR Ministry of Housing and Communal Services and agreed with the USSR State Construction Committee.
5. ASSEMBLY, WELDING AND QUALITY CONTROL OF WELDED CONNECTIONS
5.1. Welders are allowed to tack and weld pipelines if they have documents for the right to perform welding in accordance with the Rules for the certification of welders approved by the USSR Gosgortekhnadzor.
5.2. Before being admitted to work on welding pipe joints, the welder must weld a tolerance joint in production conditions in the following cases:
with a break in work for more than 6 months;
when welding pipelines with a change in the steel group, welding consumables, technology or welding equipment.
On pipes with a diameter of 529 mm and more, it is allowed to weld half of the perimeter of the tolerance joint; at the same time, if the tolerance joint is vertical non-rotating, the overhead and vertical sections of the seam must be welded.
The tolerance joint must be of the same type with the production joint (the definition of the same type of joint is given in the Rules for the certification of welders of the USSR Gosgortekhnadzor).
The tolerance joint is subjected to those types of control that are subjected to production welded joints in accordance with the requirements of this section.
Manufacturing jobs
5.3. The welder is obliged to knock out or weld the stamp at a distance of 30-50 mm from the joint on the side accessible for inspection.
5.4. Before assembly and welding, it is necessary to remove the end caps, strip the edges and adjacent inner and outer surfaces of pipes to a clean metal to a width of at least 10 mm.
5.5. Welding methods, as well as types, structural elements and dimensions of welded joints of steel pipelines must comply with GOST 16037-80.
5.6. The joints of pipelines with a diameter of 920 mm and more, welded without a remaining backing ring, must be made with a weld root of the seam inside the pipe. When welding inside the pipeline, the responsible performer must be issued a work permit for the production of work of increased danger. The procedure for issuing and the form of the work permit must comply with the requirements of SNiP III-4-80.
5.7. When assembling and welding pipe joints without a backing ring, the offset of the edges inside the pipe should not exceed:
for pipelines subject to the requirements of the USSR Gosgortekhnadzor Rules - in accordance with these requirements;
for other pipelines - 20% of the pipe wall thickness, but not more than 3 mm.
In the joints of pipes assembled and welded on the remaining backing ring, the gap between the ring and the inner surface of the pipe should not exceed 1 mm.
5.8. Assembly of pipe joints for welding should be carried out using mounting alignment devices.
Editing of smooth dents at the ends of pipes for pipelines, which are not subject to the requirements of the USSR Gosgortekhnadzor Rules, is allowed if their depth does not exceed 3.5% of the pipe diameter. Pipe sections with deeper dents or tears should be cut out. The ends of pipes with nicks or scuffed chamfers with a depth of 5 to 10 mm should be cut or corrected by hardfacing.
5.9. When assembling a joint using tacks, their number should be for pipes with a diameter of up to 100 mm - 1 - 2, with a diameter over 100 to 426 mm - 3 - 4. For pipes with a diameter over 426 mm, tacks should be placed every 300-400 mm around the circumference.
The potholders should be evenly spaced around the perimeter of the joint. The length of one tack for pipes with a diameter up to 100 mm - 10 - 20 mm, with a diameter over 100 to 426 mm - 20 - 40, with a diameter over 426 mm - 30 - 40 mm. The height of the tack should be with a wall thickness S up to 10 mm - (0.6 - 0.7) S, but not less than 3 mm, with a larger wall thickness - 5 - 8 mm.
The electrodes or welding wire used for tacking must be of the same grade as for welding the main seam.
5.10. Welding of pipelines that are not subject to the requirements of the USSR Gosgortekhnadzor Rules may be performed without heating the welded joints:
at an outside air temperature of up to minus 20 degrees C - when using carbon steel pipes with a carbon content of not more than 0.24% (regardless of the pipe wall thickness), as well as low-alloy steel pipes with a wall thickness of not more than 10 mm;
at an outside air temperature of up to minus 10 degrees C - when using pipes made of carbon steel with a carbon content of more than 0.24%, as well as pipes made of low-alloy steel with a wall thickness of over 10 mm.
At a lower outside air temperature, welding should be carried out in special cabins, in which the air temperature in the area of the welded joints should be maintained not lower than that indicated.
It is allowed to carry out welding work in the open air when heating the welded ends of pipes at a length of at least 200 mm from the joint to a temperature of at least 200 degrees C. After the end of welding, a gradual decrease in the temperature of the joint and the adjacent pipe zone must be ensured by covering them with asbestos cloth or using another method.
Welding (at negative temperatures) of pipelines, which are subject to the requirements of the USSR Gosgortekhnadzor Rules, must be carried out in compliance with the requirements of these Rules.
In case of rain, wind and snow, welding can only be carried out if the welder and the welding site are protected.
5.11. Welding of galvanized pipes should be carried out in accordance with SNiP 3.05.01-85.
5.12. Before welding pipelines, each batch of welding consumables (electrodes, welding wire, fluxes, shielding gases) and pipes must be subjected to an incoming inspection:
for the presence of a certificate with verification of the completeness of the data contained in it and their compliance with the requirements of state standards or technical specifications;
for the presence on each box or other packaging of the appropriate label or tag with verification of the data on it;
for damage (deterioration) of the packaging or the materials themselves. If damage is found, the question of the possibility of using these welding consumables must be resolved by the organization performing the welding;
on the technological properties of electrodes in accordance with GOST 9466-75 or departmental regulatory documents approved in accordance with SNiP 1.01.02-83.
5.13. When applying the main seam, it is necessary to completely overlap and digest the tacks.
Quality control
5.14. Quality control of welding works and welded joints of pipelines should be carried out by:
checking the serviceability of welding equipment and measuring instruments, the quality of the materials used;
operational control during assembly and welding of pipelines;
external examination of welded joints and measurements of the dimensions of the seams;
checking the continuity of joints non-destructive methods control - radiographic (X-ray or gamma rays) or ultrasonic flaw detection in accordance with the requirements of the USSR Gosgortekhnadzor Rules, GOST 7512-82, GOST 14782-76 and other standards approved in the prescribed manner. For pipelines that are not subject to the USSR Gosgortekhnadzor Rules, it is allowed to use magnetographic control instead of radiographic or ultrasonic testing;
mechanical tests and metallographic studies of control welded joints of pipelines, which are subject to the requirements of the USSR Gosgortekhnadzor Rules, in accordance with these Rules;
tests for strength and tightness.
5.15. During operational control of the quality of welded joints of steel pipelines, it is necessary to check the compliance with the standards of structural elements and dimensions of welded joints (blunting and cleaning of edges, the size of the gaps between the edges, the width and reinforcement of the weld), as well as the technology and mode of welding, the quality of welding materials, tacks and welded seam.
5.16. All welded joints are subject to visual inspection and measurement.
Pipeline joints welded without a backing ring with a root weld are subjected to external inspection and measurement of the seam dimensions outside and inside the pipe, in other cases - only outside. Before inspection, the welded seam and adjacent pipe surfaces must be cleaned of slag, splashes of molten metal, scale and other contaminants to a width of at least 20 mm (on both sides of the seam).
The results of external examination and measurement of the dimensions of welded joints are considered satisfactory if:
there are no cracks of any size and direction in the seam and the adjacent area, as well as undercuts, sagging, burn-throughs, unfinished craters and fistulas;
the size and number of volumetric inclusions and sinks between the rolls do not exceed the values given in table. 1;
the dimensions of lack of penetration, concavity and excess of penetration at the root of the seam of butt joints made without a remaining backing ring (if it is possible to inspect the joint from the inside of the pipe) do not exceed the values given in table. 2.
Joints that do not meet the listed requirements are subject to correction or removal.
Table 1
Maximum allowable | Maximum |
|
Volumetric inclusion of a rounded or elongated shape with a nominal wall thickness of pipes to be welded in butt joints or a smaller seam leg in fillet joints, mm: | ||
St. 5.0 to 7.5 | ||
Sinking (deepening) between the rollers and the scaly structure of the seam surface at the nominal wall thickness of the pipes being welded in butt joints or with a smaller seam leg in fillet joints, mm: | ||
Not limited |
||
table 2
Pipelines, | Maximum permissible height (depth),% of the nominal wall thickness | Maximum permissible total length along the perimeter of the joint |
|
Spread | Concavity and lack of penetration at the root of the seam | 10, but not more than 2 mm 20, but not more than 2 mm | 20% of the perimeter |
Do not apply | Concavity, excess penetration and lack of penetration at the root of the seam | 1/3 |
5.17. Welded joints are checked for continuity by non-destructive testing methods:
pipelines subject to the requirements of the USSR Gosgortekhnadzor Rules, with an outer diameter of up to 465 mm - in the volume provided for by these Rules, with a diameter of over 465 to 900 mm in a volume of at least 10% (but not less than four joints), a diameter of over 900 mm - in the volume not less than 15% (but not less than four joints) of the total number of similar joints made by each welder;
pipelines that are not subject to the requirements of the USSR Gosgortekhnadzor Rules, with an outer diameter of up to 465 mm in a volume of at least 3% (but not less than two joints), with a diameter of over 465 mm - in a volume of 6% (but not less than three joints) of the total number of joints of the same type performed by each welder; in the case of checking the continuity of welded joints using magnetographic testing, 10% of the total number of joints subjected to testing should be checked, in addition, by the radiographic method.
5.18. Non-destructive testing methods should be used to expose 100% of welded joints of pipelines of heating networks laid in non-passable channels under the carriageway, in cases, tunnels or technical corridors together with others. engineering communications, as well as at intersections:
railways and tramways - at a distance of at least 4 m, electrified railways - at least 11 m from the axis of the extreme track;
railways of the general network - at a distance of at least 3 m from the nearest construction of the roadbed;
highways - at a distance of at least 2 m from the edge of the carriageway, the fortified shoulder strip or the foot of the embankment;
subway - at a distance of at least 8 m from structures;
power, control and communication cables - at a distance of at least 2 m;
gas pipelines - at a distance of at least 4 m;
main gas pipelines and oil pipelines - at a distance of at least 9 m;
buildings and structures - at a distance of at least 5 m from walls and foundations.
5.19. Weld seams should be rejected if cracks, incomplete craters, burn-throughs, fistulas, as well as lack of penetration in the root of the seam made on the backing ring are found during non-destructive testing.
5.20. When checking the welded seams of pipelines by the radiographic method, which are subject to the requirements of the USSR Gosgortekhnadzor Rules, pores and inclusions, the sizes of which do not exceed the values indicated in table, are considered permissible defects. 3.
Table 3
Nominal | Ultimately permissible sizes pores and inclusions, mm | The total pore length and |
|||||
individual | clusters | inclusions |
|||||
width (diameter) | width (diameter) | width (diameter) | for any 100 mm of a seam, mm |
||||
St. 2.0 to 3.0 | |||||||
The height (depth) of lack of penetration, concavity and excess of penetration at the root of a joint made by one-sided welding without a backing ring should not exceed the values indicated in table. 2.
According to the results of ultrasonic testing, permissible defects of welded joints are considered to be defects, measured characteristics, the number of which does not exceed those indicated in table. 4.
Table 4
Nominal wall thickness | Artificial size | Allowable conditional | The number of defects for any 100 mm of the seam |
|
pipes, mm | corner reflector ("notches"), | length of a single defect, mm | large and small in total | large |
4.0 to 8.0 | ||||
St. 8.0 "14.5 | ||||
Notes: 1. A defect is considered to be large if its nominal length exceeds 5.0 mm with a wall thickness of up to 5.5 mm and 10 mm with a wall thickness of over 5.5 mm. If the conditional length of the defect does not exceed the indicated values, it is considered small. |
||||
5.21. For pipelines that are not subject to the requirements of the USSR Gosgortekhnadzor Rules, pores and inclusions, the sizes of which do not exceed the maximum permissible size according to GOST 23055-78 for welded joints of the 7th class, as well as lack of penetration, concavity and excess of penetration are considered permissible defects in the radiographic method of control at the root of a seam made by one-sided electric arc welding without a backing ring, the height (depth) of which should not exceed the values indicated in table. 2.
5.22. If unacceptable defects are detected by non-destructive testing methods, welds pipelines that are subject to the requirements of the USSR Gosgortekhnadzor Rules, a repeated quality control of the seams established by these Rules must be carried out, and in the welded seams of pipelines that are not subject to the requirements of the Rules, in a double number of joints compared to that specified in clause 5.17.
If unacceptable defects are detected during repeated inspection, all joints made by this welder must be checked.
5.23. Correction by local sampling and subsequent back-welding (without re-welding the entire joint) are subject to sections of the welded seam with unacceptable defects, if the size of the sample after removing the defective section does not exceed the values indicated in Table. 5.
Welded joints, in the seams of which, in order to correct the defective area, it is required to make a sample with dimensions greater than those allowed according to table. 5 must be completely removed.
Table 5
Sampling depth, | Length, |
St. 25 to 50 | No more than 50 |
Note. When correcting several sections in one connection, their total length may exceed that indicated in Table. 5 no more than 1.5 times at the same depth rates. |
|
5.24. Undercuts should be corrected by surfacing with thread rolls no more than 2.0 - 3.0 mm wide. Cracks must be drilled at the ends, cut out, thoroughly cleaned and welded in several layers.
5.25. All corrected sections of welded joints should be checked by external examination, radiographic or ultrasonic flaw detection.
5.26. On the executive drawing of the pipeline, drawn up in accordance with SNiP 3.01.03-84, it is necessary to indicate the distances between welded joints, as well as from wells, chambers and subscriber inputs to the nearest welded joints.
6. THERMAL INSULATION OF PIPELINES
6.1. Installation of heat-insulating structures and protective coatings must be carried out in accordance with the requirements of SNiP III-20-74 and this section.
6.2. Welded and flanged joints should not be insulated for a width of 150 mm on both sides of the joints until the pipelines are tested for strength and tightness.
6.3. Production capability insulation works on pipelines subject to registration in accordance with the Rules of the USSR Gosgortechnadzor, prior to performing tests for strength and tightness, it is necessary to agree with the local authority of the USSR Gosgortechnadzor.
6.4. When performing filling and backfill insulation during channelless laying of pipelines, the project of work must provide for temporary devices to prevent the pipeline from floating up, as well as getting into the soil insulation.
7. TRANSITIONS OF THERMAL NETWORKS THROUGH PASSAGES AND ROADS
7.1. Work at the underground (aboveground) crossing by heating networks of railway and tram tracks, highways, city passages should be carried out in accordance with the requirements of these rules, as well as SNiP III-8-76.
7.2. When puncturing, punching, horizontal drilling or other methods of trenchless laying of the cases, the assembly and tacking of the case links (pipes) must be performed using a centralizer. The ends of the links (pipes) to be welded should be perpendicular to their axes. Fractures of the axes of the links (pipes) of the cases are not allowed.
7.3. Reinforced shotcrete anticorrosive coating of cases with trenchless laying should be made in accordance with the requirements of SNiP III-15-76.
7.4. The piping within the box should be made of pipes of the maximum delivery length.
7.5. The deviation of the axis of the cases of transitions from the design position for gravity condensate pipelines should not exceed:
vertically - 0.6% of the case length, provided that the design slope of the condensate pipelines is ensured;
horizontally - 1% of the length of the case.
The deviation of the axis of the cases of transitions from the design position for the rest of the pipelines should not exceed 1% of the length of the case.
8. TEST AND FLUSHING (PURGE) OF PIPELINES
8.1. After completion of construction and installation work, pipelines must be subjected to final (acceptance) tests for strength and tightness. In addition, condensate pipelines and pipelines of water heating networks should be flushed, steam pipelines - purged with steam, and pipelines of water heating networks with an open heating system and hot water supply network - washed and disinfected.
Pipelines laid without channels and in non-passable channels are also subject to preliminary tests for strength and tightness in the course of construction and installation works.
8.2. Preliminary tests of pipelines should be carried out before installing stuffing box (bellows) expansion joints, sectioning valves, closing channels and backfilling of channelless pipelines and channels.
Preliminary tests of pipelines for strength and tightness should be carried out, as a rule, using a hydraulic method.
At negative outside temperatures and the impossibility of heating water, as well as in the absence of water, it is allowed, in accordance with the project for the production of works, to perform preliminary tests pneumatically.
It is not allowed to perform pneumatic tests of aboveground pipelines, as well as pipelines laid in the same channel (section) or in the same trench with existing utilities.
8.3. Pipelines of water heating networks should be tested with a pressure equal to 1.25 working pressure, but not less than 1.6 MPa (16 kgf / sq.cm), steam pipelines, condensate pipelines and hot water supply networks - a pressure equal to 1.25 working, unless other requirements justified by the project (working project).
8.4. Before performing tests for strength and tightness, it is necessary:
to carry out quality control of welded joints of pipelines and correction of detected defects in accordance with the requirements of Sec. 5;
disconnect the tested pipelines with plugs from the existing ones and from the first stop valves installed in the building (structure);
install plugs at the ends of the tested pipelines and instead of stuffing box (bellows) expansion joints, sectioning valves during preliminary tests;
provide access along the entire length of the tested pipelines for their external inspection and inspection of welded joints during the tests;
fully open fittings and bypass lines.
The use of shut-off valves to disconnect the tested pipelines is not allowed.
Simultaneous preliminary tests of several pipelines for strength and tightness are allowed to be carried out in cases justified by the design of the work.
8.5. Pressure measurements when testing pipelines for strength and tightness should be carried out using duly certified two (one - control) spring pressure gauges of class not less than 1.5 with a body diameter of at least 160 mm and a scale with nominal pressure 4/3 measured.
8.6. Tests of pipelines for strength and tightness (density), their purging, flushing, disinfection must be carried out according to technological schemes (agreed with the operating organizations), which regulate the technology and safety of work (including the boundaries of security zones).
8.7. On the results of testing pipelines for strength and tightness, as well as on their flushing (blowing), it is necessary to draw up acts according to the forms given in mandatory Appendices 2 and 3.
Hydraulic tests
8.8. Tests of pipelines should be carried out in compliance with the following basic requirements:
test pressure must be provided at the highest point (mark) of the pipelines;
the temperature of the water during the tests must be at least 5 degrees C;
at a negative outside temperature, the pipeline must be filled with water at a temperature not exceeding 70 degrees C and ensure the possibility of filling and emptying it within 1 hour;
when gradually filling with water, air must be completely removed from the pipelines;
the test pressure must be maintained for 10 minutes and then reduced to working pressure;
at operating pressure, the pipeline must be inspected along its entire length.
8.9. The results of hydraulic tests for the strength and tightness of the pipeline are considered satisfactory if during the tests there was no pressure drop, no signs of rupture, leakage or fogging in the welded seams, as well as leaks in the base metal, flange joints, fittings, expansion joints and other pipeline elements were found. , there are no signs of shear or deformation of pipelines and fixed supports.
Pneumatic tests
8.10. Pneumatic tests should be carried out for steel pipelines with a working pressure of no higher than 1.6 MPa (16 kgf / sq.cm) and a temperature of up to 250 degrees C, mounted from pipes and parts tested for strength and tightness (density) by manufacturers in accordance with GOST 3845-75 (in this case, the factory test pressure for pipes, fittings, equipment and other products and parts of the pipeline must be 20% higher than the test pressure adopted for the installed pipeline).
Installation of cast iron fittings (except for ductile iron valves) during the tests is not allowed.
8.11. Filling the pipeline with air and raising the pressure should be done smoothly at a rate of no more than 0.3 MPa (3 kgf / cm 2) in 1 hour. pressure equal to 0.3 test, but not more than 0.3 MPa (3 kgf / cm 2).
For the period of inspection of the route, the rise in pressure must be stopped.
When the value of the test pressure is reached, the pipeline must be held in order to equalize the air temperature along the length of the pipeline. After equalizing the air temperature, the test pressure is held for 30 minutes and then gradually decreases to 0.3 MPa (3 kgf / cm 2), but not higher than the operating pressure of the coolant; at this pressure, the pipelines are inspected with a mark of defective places.
Leaks are identified by the sound of leaking air, bubbles when soapy emulsion is applied to welded joints and other areas, and other methods are used.
Defects are eliminated only when the excess pressure drops to zero and the compressor is turned off.
8.12. The results of preliminary pneumatic tests are considered satisfactory if during the tests there was no pressure drop across the pressure gauge, no defects were found in welded seams, flange joints, pipes, equipment and other elements and products of the pipeline, there are no signs of shear or deformation of the pipeline and fixed supports.
8.13. Water pipelines in closed systems heat supply and condensate lines should, as a rule, be subjected to hydropneumatic flushing.
Hydraulic flushing with re-use of flushing water is allowed by passing it through temporary mud collectors installed along the flow of water at the ends of the supply and return pipelines.
Flushing, as a rule, should be done technical water... Flushing with potable water is allowed with justification in the project for the production of works.
8.14. The pipelines of water networks of open heat supply systems and hot water supply networks must be flushed hydropneumatically with drinking water until the flushing water is completely clarified. At the end of flushing, the pipelines must be disinfected by filling them with water containing active chlorine at a dose of 75-100 mg / l with a contact time of at least 6 hours. local authorities sanitary and epidemiological service, do not subject to chlorination and confine ourselves to rinsing with water that meets the requirements of GOST 2874-82.
After flushing, the results of laboratory analysis of flushing water samples must comply with the requirements of GOST 2874-82. A conclusion is drawn up on the results of washing (disinfection) by the sanitary-epidemiological service.
8.15. The pressure in the pipeline during flushing should not be higher than the operating pressure. Air pressure during hydropneumatic flushing should not exceed operating pressure coolant and be no higher than 0.6 MPa (6 kgf / cm2).
The water velocities during hydraulic flushing should not be lower than the design velocities of the coolant specified in the working drawings, and in the case of hydropneumatic flushing, they should exceed the design velocities by at least 0.5 m / s.
8.16. Steam lines should be purged with steam and discharged into the atmosphere through specially installed purge pipes with shut-off valves. To warm up the steam line, all start-up drains must be open before purging. The heating rate should ensure the absence of hydraulic shocks in the pipeline.
The steam velocities during blowing of each section must be not less than the operating velocities at the design parameters of the coolant.
9. ENVIRONMENTAL PROTECTION
9.1. During the construction of new, expansion and reconstruction of existing heating networks, measures to protect the environment should be taken in accordance with the requirements of SNiP 3.01.01-85 and this section.
9.2. It is not allowed without the consent of the relevant service: to carry out earthworks at a distance of less than 2 m to tree trunks and less than 1 m to bushes; movement of goods at a distance of less than 0.5 m to the crowns or tree trunks; storage of pipes and other materials at a distance of less than 2 m to tree trunks without arranging temporary enclosing (protective) structures around them.
9.3. Hydraulic pipelines should be flushed with water reused. Emptying of pipelines after flushing and disinfection should be carried out at the places indicated in the project of the work and agreed with the relevant services.
9.4. Territory construction site after completion of construction and installation work, it must be cleared of debris.
Appendix 1. ACT ON EXTENSION OF COMPENSATORS
ANNEX 1
Mandatory
________________________ "_____" _________________ 19 _____
Commission consisting of:
(surname, name, patronymic, position)
_____________________________________________________________,
1. An extension of the expansion joints listed in the table has been presented for inspection and acceptance in the section from the camera (picket, mine) No. _______ to the camera (picket, mine) No. _______.
Compensator number | Drawing number | Compensation type | Stretch value, mm | Temperature |
|
according to the drawing | design | actual | air, degrees C |
||
2. The work was carried out according to the design and estimate documentation ____________
_______________________________________________________________
COMMISSION DECISION
The work was carried out in accordance with design and estimate documentation, state standards, building codes and regulations and meet the requirements of their acceptance.
(signature)
(signature)
Appendix 2. ACT ON CONDUCTING TESTS OF PIPELINES FOR STRENGTH AND TIGHTNESS
APPENDIX 2
Mandatory
_____________________ "_____" ____________ 19 ____
Commission consisting of:
representative of the construction and installation organization _________________
_____________________________________________________________,
(surname, name, patronymic, position)
technical supervision representative of the customer _____________________
_____________________________________________________________,
(surname, name, patronymic, position)
representative of the operating agency ______________________
_____________________________________________________________
(surname, name, patronymic, position)
inspected the work performed by ___________________________
_____________________________________________________________,
(name of the construction and installation organization)
and drew up this act on the following:
1. For examination and acceptance presented ________________
_____________________________________________________________
(hydraulic or pneumatic)
pipelines tested for strength and tightness and listed in the table, in the section from the camera (picket, mine) No. ________ to the camera (picket, mine) No. _________ of the route ___________
Length __________ m.
(pipeline name)
Pipeline | Test pressure, | Duration, min | External examination at pressure, MPa (kgf / sq.cm) |
2. The work was carried out according to the design and estimate documentation __________________
_____________________________________________________________________
(name of the design organization, drawing numbers and the date of their compilation)
COMMISSION DECISION
Representative of the construction and installation organization ________________
(signature)
Customer technical supervision representative _____________________
(signature)
(signature)
Appendix 3. ACT ON RINSING (PURGE) OF PIPELINES
APPENDIX 3
Mandatory
_______________________________________ "_____" _______________ 19 _____
Commission consisting of:
representative of the construction and installation organization ________________
_____________________________________________________________,
(surname, name, patronymic, position)
technical supervision representative of the customer _____________________
_____________________________________________________________,
(surname, name, patronymic, position)
representative of the operating agency _____________________
_____________________________________________________________
(surname, name, patronymic, position)
inspected the work performed by ____________________________
_____________________________________________________________,
(name of the construction and installation organization)
and drew up this act on the following:
1. Flushing (blowing) of pipelines in the section from the camera (picket, mine) No. __________ to the camera (picket, mine) No. ______ of the route is presented for inspection and acceptance _______________________________________________________________________________
_____________________________________________________________________________________
(pipeline name)
length ___________ m.
Flushing (purging) performed ________________________________
_____________________________________________________________.
(name of medium, pressure, flow rate)
2. The work was carried out according to the design and estimate documentation _________________
____________________________________________________________________
_____________________________________________________________________.
(name of the design organization, drawing numbers and the date of their compilation)
COMMISSION DECISION
The works were performed in accordance with design estimates, standards, building codes and regulations and meet the requirements of their acceptance.
Representative of the construction and installation organization ________________
(signature)
Customer technical supervision representative _____________________
(signature)
Operating agency representative _____________________
(signature)
The text of the document is verified by:
official publication
Moscow: TsITP Gosstroy USSR, 1986