Calculation of a U-shaped compensator is to define minimum sizes compensator sufficient to compensate for temperature deformations of the pipeline. By filling out the form above, you can calculate the compensating capacity of a U-shaped compensator of given dimensions.
The algorithm of this online program is based on the method for calculating a U-shaped compensator given in the Designer’s Handbook “Design of Heat Networks” edited by A. A. Nikolaev.
- The maximum stress in the back of the compensator is recommended to be in the range from 80 to 110 MPa.
- The optimal ratio of the expansion joint overhang to the outer diameter of the pipe is recommended to be taken in the range H/Dн = (10 - 40), while the expansion joint overhang of 10DN corresponds to a DN350 pipeline, and an overhang of 40DN corresponds to a DN15 pipeline.
- The optimal ratio of the width of the compensator to its reach is recommended to be taken in the range L/H = (1 - 1.5), although other values can be accepted.
- If a compensator is needed to compensate for the calculated thermal expansions, it is too large sizes, it can be replaced with two smaller compensators.
- When calculating the thermal elongation of a pipeline, the temperature of the coolant should be taken as maximum, and the temperature of the environment surrounding the pipeline as minimum.
The following restrictions were adopted in the calculation:
- The pipeline is filled with water or steam
- The pipeline is made of steel pipe
- The maximum temperature of the working environment does not exceed 200 °C
- The maximum pressure in the pipeline does not exceed 1.6 MPa (16 bar)
- The compensator is installed on a horizontal pipeline
- The compensator is symmetrical, and its arms are the same length
- Fixed supports are considered absolutely rigid
- The pipeline does not experience wind pressure or other loads
- The resistance of frictional forces of movable supports during thermal elongation is not taken into account
- Smooth bends
- It is not recommended to place fixed supports at a distance of less than 10DN from the U-shaped compensator, since transferring the pinching moment of the support to it reduces flexibility.
- It is recommended that the pipeline sections from the fixed supports to the U-shaped compensator be of the same length. If the compensator is not located in the middle of the site, but is shifted towards one of the fixed supports, then the forces of elastic deformation and stress increase by approximately 20-40%, in relation to the values obtained for the compensator located in the middle.
- To increase the compensating ability, preliminary stretching of the compensator is used. During installation, the compensator experiences a bending load, when heated it assumes a non-stressed state, and at maximum temperature it comes into tension. Preliminary stretching of the compensator by an amount equal to half the thermal elongation of the pipeline allows you to double its compensating capacity.
Scope of application
U-shaped compensators are used to compensate for thermal expansion of pipes on long straight sections, if there is no possibility of self-compensation of the pipeline due to turns of the heating network. The absence of compensators on rigidly fixed pipelines with variable temperature of the working environment will lead to an increase in stresses that can deform and destroy the pipeline.
Flexible expansion joints are used
- For above-ground installation for all pipe diameters, regardless of coolant parameters.
- When laid in tunnels and general manifolds on pipelines from DN25 to DN200 at a coolant pressure of up to 16 bar.
- For ductless installation for pipes with diameters from DN25 to DN100.
- If the maximum operating temperature exceeds 50°C
Advantages
- High compensation capacity
- Maintenance free
- Easy to make
- Low forces transmitted to fixed supports
Flaws
- High pipe flow
- Large footprint
- High hydraulic resistance
27.02.2018
Bellows compensators (hereinafter referred to as SK) and bellows compensation devices (hereinafter referred to as SKU), designed for hermetic connection of relatively moving elements and compensation of temperature deformations of steel pipelines of water heating networks and hot water supply (hereinafter referred to as hot water supply), as well as water supply and steam pipelines of category III in all types of their gaskets and any types of thermal insulation.
To ensure the operation of the pipeline, it is necessary to correctly select the bellows compensator and install it. When choosing the type of SKU or SKU, you should be guided by the method of laying the heat pipeline, the type of its thermal insulation, as well as its compensating ability. Since the SKU and SKU are supplied in a neutral position, relative to which they can be stretched and compressed by the amplitude of the axial stroke, then in order to use the maximum working stroke (compensating capacity 2*λ- 1 =λ), the SKU and SKU must be stretched by the value ∆L installation, which depends on the outside air temperature at which installation is carried out (t installation).
The amount of preliminary stretching (installation) deformation of axial SKU and SKU is determined by the formula:
∆L mont = L λ µ *α* , mm
Where: L λ µ is the length of the section on which the SC or SKU is installed.
The installation length of the SKU or SKU is determined by the formula:
L mount =L sk + ∆L mount, mm
Where: L ск - length of the SKU or SKU as delivered (indicated in the SKU or SKU passport), mm;
An example of calculating the pre-stretching of a bellows axial expansion joint during installation
For example, consider the bellows compensator OPN-16-1000-220-2.2. According to the accepted designations, it is a device whose maximum compensating capacity is 220 mm: 110 mm for compression and 110 mm for tension.
∆L installation - the value of pre-stretching of the SKU or SKU (the required value);
t max + t min – minimum and maximum operating temperatures, °C;
t installation – outdoor air temperature at which installation is carried out;
L λ µ - length of the section on which the SC or SKU is installed;
α is the coefficient of linear expansion of the pipeline;
Example: for the Moscow region: t min = -28°С;
for the supply pipeline: t max = 150°C; t mont = 20°С;
for the reverse: t max = 90°С; t mont = 20°С;
section length: L λ µ = 163;
coefficient of linear expansion of the pipeline α = 0.0122
Pre-stretch value for supply pipeline:
∆L mounting = 163*0.0122* = 101.4 mm
Pre-stretch value for return pipeline:
∆L mounting = 163*0.0122* = 41.8 mm
For above-ground and channel installation of pipelines, tmin corresponds to the design temperature of the outside air for heating design according to SNiP 23-01-99.
The plant JSC "NPP "KOMPENSATOR" is engaged in the development, manufacture and supply of bellows expansion joints own production. Our product range includes a variety of engineered devices that are easy to install and can withstand significant loads. Compensators have IV tightness class according to OST5R.0170, retain their parameters for 30 years and are manufactured in accordance with the requirements of GOST R ISO 9001-2015 (ISO 9001:2015).
SNiP 3.05.03-85
________________
Registered by Rosstandart as SP 74.13330.2011. -
Database manufacturer's note.
BUILDING CODES AND RULES
HEATING NETWORKS
Date of introduction 1986-07-01
DEVELOPED by the Orgenergostroy Institute of the USSR Ministry of Energy (L. Ya. Mukomel - topic leader; Candidate of Technical Sciences S. S. Yakobson).
INTRODUCED by the USSR Ministry of Energy.
PREPARED FOR APPROVAL BY Glavtekhnormirovanie Gosstroy USSR (N. A. Shishov).
APPROVED by Decree of the USSR State Committee for Construction Affairs dated 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 the State Mining and Technical Supervision Committee of the USSR on April 15, 1985.
These rules apply to the construction of new, expansion and reconstruction of existing heating networks,
transporting hot water at temperature t | 200 degrees C and pressure | 2.5 MPa (25 kgf/sq.cm) |
from the source of thermal energy to heat consumers (buildings, structures).
1. GENERAL PROVISIONS
1. GENERAL PROVISIONS
1.1. When constructing new, expanding and reconstructing existing heating networks, in addition to the requirements of working drawings, work plans (WPP) and these rules, the requirements of SNiP 3.01.01-85, SNiP 3.01.03-84, SNiP III-4-80 and standards must 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 Gosgortekhnadzor (in further Rules Gosgortekhnadzor of the USSR), must be carried out in accordance with the specified Rules and the requirements of these norms and rules.
1.3. Completed construction heating networks should be put into operation in accordance with the requirements of SNiP III-3-81.
2. EARTHWORK
2.1. Excavation and foundation work must be carried out 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 trench bottom for channelless pipe laying should be equal to the distance between the outer side edges of the insulation of the outermost pipelines of heating networks (associated drainage) with an addition on each side for pipelines of a nominal diameter
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 outermost pipelines with the addition of 0.6 m on each side, the length of the pits - 1.0 m and the depth from the bottom edge of the pipeline insulation - 0.7 m, unless other requirements are justified by working drawings.
2.3. The smallest width of the trench bottom for channel laying of heating networks should be equal to the width of the channel taking into account the formwork (on monolithic areas), waterproofing, associated drainage and drainage devices, trench fastening structures with an addition of 0.2 m. In this case, the width of the trench 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 clear width between the outer edges of the canal structure and the 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 during channelless and channel laying of pipelines should be carried out after preliminary testing of pipelines for strength and tightness, complete completion of insulation and construction installation work.
Backfilling must be done in the specified technological sequence:
tamping of sinuses between pipelines of channelless laying and the base;
simultaneous uniform filling of the sinuses between the walls of the trench and pipelines during channelless installation, as well as between the walls of the trench and channel, chamber during channel installation to a height of at least 0.20 m above the pipelines, channels, chambers;
backfilling the trench 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 communications, streets, roads, driveways, squares and other structures of settlements and industrial sites should be carried out in accordance with the requirements of SNiP III-8-76.
2.5. After turning off temporary water reduction devices, channels and chambers must be visually inspected for the absence of groundwater.
3. CONSTRUCTIONS AND INSTALLATION OF BUILDING STRUCTURES
3.1. Construction and installation work building structures should be performed in accordance with the requirements of this section and the requirements of:
SNiP III-15-76 - for the construction of monolithic concrete and reinforced concrete structures foundations, supports for pipelines, chambers and other structures, as well as when grouting joints;
SNiP III-16-80 - for installation of 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 - for the protection of building structures from corrosion.
3.2. The outer surfaces of channel and chamber elements supplied to the route must be covered with a coating or adhesive waterproofing in accordance with working drawings.
The installation of channel elements (chambers) in the design position should be carried out in a technological sequence linked to the project for the installation and preliminary testing of pipelines for strength and tightness.
Support pads for sliding supports of pipelines must be installed at the distances specified in SNiP II-G. 10-73* (II-36-73*).
3.3. Monolithic fixed panel supports must be made after installation of pipelines in the panel support area.
3.4. In places where channelless pipelines are introduced into channels, chambers and buildings (structures), the cases of bushings must be put on the pipes during their installation.
At the entrances of underground pipelines into buildings, devices must be installed (in accordance with the working drawings) to prevent gas from penetrating into the buildings.
3.5. Before installing the upper trays (plates), the channels must be cleared of soil, debris and snow.
3.6. 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 no less than the minimum allowable according to SNiP II-G.10-73* (II-36-73*).
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 construction organization project and the work execution project must provide for the advanced construction of drainage pumping stations and water release devices in accordance with the working drawings.
3.8. Before laying in the trench drainage pipes must be inspected and cleared of soil and debris.
3.9. Layer-by-layer filtering of drainage pipelines (except for pipe filters) with gravel and sand must be performed using inventory separation forms.
3.10. The straightness of 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 pipe circumference 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 not more than 50 mm in each direction.
Deviation from correct form Vertical circles are not allowed.
4. INSTALLATION OF PIPELINES
4.1. Installation of pipelines must be carried out by specialized installation organizations, while the installation technology must ensure high operational reliability of pipelines.
4.2. Parts, pipeline elements (compensators, mud traps, insulated pipes, as well as pipeline units and other products) must be manufactured centrally (in factories, workshops, workshops) in accordance with the standards technical specifications and design documentation.
4.3. Laying of pipelines in a trench, channel or on above-ground structures should be carried out using the technology provided for by the work project 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 installation devices, correct placement simultaneously operating lifting machines and mechanisms.
The design of fastening mounting devices to pipes must ensure the safety of the coating and insulation of pipelines.
4.4. The 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 panel support.
4.5. Laying of pipes with a diameter of over 100 mm with a longitudinal or spiral seam should be carried out 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 thickness of the pipe wall.
Longitudinal seams must be within the upper half of the circumference of the pipes being laid.
Steeply curved and stamped pipeline bends are allowed to be welded together without a straight section.
Welding of pipes and bends into welded joints and bent elements is not allowed.
4.6. When installing pipelines, the movable supports and hangers must be shifted relative to the design position by the distance specified 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 shifted taking into account the correction for the outside air temperature during installation by the following values:
sliding supports and elements for fastening hangers to the pipe - by half the thermal elongation of the pipeline at the attachment point;
roller bearing rollers - by a quarter of thermal elongation.
4.7. When installing pipelines, spring hangers must be tightened in accordance with the working drawings.
During runtime hydraulic tests For steam pipelines with a diameter of 400 mm or more, a unloading device should be installed in spring suspensions.
4.8. Pipe fittings must be installed in a closed state. Flange and welded connections of fittings must be made without tension in the pipelines.
The deviation from the perpendicularity of the plane of the flange welded to the pipe relative to the pipe axis should not exceed 1% of the outer diameter of the flange, but be no more than 2 mm at the top of the flange.
4.9. Bellows (wavy) and stuffing box expansion joints should be installed assembled.
At underground installation heating networks, installation of compensators in the design position is allowed only after preliminary testing of pipelines for strength and tightness, backfill channelless pipelines, channels, chambers and panel 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.
Permissible deviations from the design position of the connecting pipes of compensators during their installation and welding should be no more than those specified in the technical specifications for the manufacture and supply of compensators.
4.11. When installing bellows expansion joints, they are not allowed to twist relative to the longitudinal axis and sag under the influence of their own weight and the weight of adjacent pipelines. Slinging of expansion joints should be done only by the pipes.
4.12. The installation length of bellows and stuffing box expansion joints must be taken according to the working drawings, taking into account corrections for the outside air temperature during installation.
Stretching of expansion joints to the installation length should be done using devices provided for in the design of expansion joints, or tension mounting devices.
4.13. Stretching of the U-shaped compensator should be carried out after completion of pipeline installation, quality control of welded joints (except for closing joints used for tension) and fastening of fixed support structures.
The compensator should 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.
Stretching of the compensator must be carried out simultaneously on both sides at joints located at a distance of no less than 20 and no more than 40 pipeline diameters from the axis of symmetry of the compensator, using tension devices, unless other requirements are justified by the design.
On the section of the pipeline between the joints used for stretching the compensator, there should be no preliminary displacement of supports and hangers in comparison with the design (detailed design).
4.14. Immediately before assembling and welding pipes, it is necessary to visually inspect each section to ensure that there are no foreign objects or 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 no less than the minimum allowable according to SNiP II-G.10-73* (II-36-73*).
Movable pipeline supports must be adjacent to the supporting surfaces of structures without gaps or distortion.
4.16. When performing installation work, the following types of hidden work are subject to acceptance with drawing up inspection reports in the form given in SNiP 3.01.01-85: preparation of the surface of pipes and welded joints for anti-corrosion coating; performing anti-corrosion coating of pipes and welded joints.
A report on the stretching of compensators should be drawn up in the form given in the mandatory Appendix 1.
4.17. Protection of heating networks from electrochemical corrosion must be carried out in accordance with the Instructions for the protection of heating networks from electrochemical corrosion, approved by the USSR Ministry of Energy and the Ministry of Housing and Utilities of the RSFSR and agreed with the USSR State Construction Committee.
5. ASSEMBLY, WELDING AND QUALITY CONTROL OF WELDED JOINTS
5.1. Welders are allowed to tack and weld pipelines if they have documents for the right to produce welding work in accordance with the Rules for Certification of Welders, approved by the USSR State Mining and Technical Supervision.
5.2. Before being allowed to work on welding pipeline joints, the welder must weld the permitted joint in production conditions in the following cases:
with a break in work for more than 6 months;
when welding pipelines with changes in steel group, welding materials, technology or welding equipment.
On pipes with a diameter of 529 mm or more, it is allowed to weld half the perimeter of the permissible joint; in this case, if the permissible joint is vertical and non-rotating, the ceiling and vertical sections seam
The permissible joint must be of the same type as the production joint (the definition of a joint of the same type is given in the Rules for the Certification of Welders of the USSR State Mining and Technical Supervision).
The permissible joint is subject to the same types of control that production welded joints are subjected to in accordance with the requirements of this section.
Work execution
5.3. The welder is obliged to knock out or fuse the mark 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, clean until pure metal edges and adjacent internal and external surfaces of pipes 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. Pipeline joints with a diameter of 920 mm or more, welded without a remaining backing ring, must be made with welding of the root of the seam inside the pipe. When welding inside a pipeline, the responsible person must be issued a work permit. increased danger. The issuance procedure and form of the permit must comply with the requirements of SNiP III-4-80.
5.7. When assembling and welding pipe joints without a backing ring, the displacement of the edges inside the pipe should not exceed:
for pipelines that are subject to the requirements of the USSR State Mining and Technical Supervision Rules - in accordance with these requirements;
for other pipelines - 20% of the pipe wall thickness, but not more than 3 mm.
In pipe joints assembled and welded on the remaining backing ring, the gap between the ring and inner surface pipes should not exceed 1 mm.
5.8. The assembly of pipe joints for welding should be done using mounting centering devices.
Correction of smooth dents at the ends of pipes for pipelines that 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. Sections of pipes with deeper dents or tears should be cut out. The ends of pipes with nicks or chamfers with a depth of 5 to 10 mm should be cut off or corrected by surfacing.
5.9. When assembling a joint using tacks, their number should be for pipes with a diameter 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 tacks should be evenly spaced around the perimeter of the joint. The length of one tack for pipes with a diameter of up to 100 mm is 10 - 20 mm, with a diameter over 100 to 426 mm - 20 - 40, with a diameter over 426 mm - 30 - 40 mm. The tack height should be for a wall thickness S up to 10 mm - (0.6 - 0.7) S, but not less than 3 mm, for a larger wall thickness - 5 - 8 mm.
The electrodes or welding wire used for tack welding must be of the same grade as that used for welding the main seam.
5.10. Welding of pipelines that are not subject to the requirements of the USSR State Mining and Technical Supervision Rules may be carried out without heating the welded joints:
at outside air temperatures down to minus 20 degrees C - when using pipes made of carbon steel with a carbon content of no more than 0.24% (regardless of the wall thickness of the pipes), as well as pipes made of low-alloy steel with a wall thickness of no more than 10 mm;
at outside air temperatures down to minus 10 degrees C - when using pipes made of carbon steel with a carbon content of over 0.24%, as well as pipes made of low-alloy steel with a wall thickness of over 10 mm.
At lower outside temperatures, welding should be carried out in special booths, in which the air temperature in the area of the welded joints should be maintained not lower than the specified one.
It is allowed to carry out welding work in the open air by 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 welding is completed, a gradual decrease in the temperature of the joint and the adjacent pipe area must be ensured by covering them with asbestos sheets or using another method.
Welding (at negative temperature) pipelines, which are subject to the requirements of the USSR State Mining and Technical Supervision Rules, must be carried out in compliance with the requirements of these Rules.
In rain, wind and snow, welding work 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 materials (electrodes, welding wire, fluxes, shielding gases) and pipes must be subjected to 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;
to ensure that each box or other package contains a corresponding label or tag with verification of the data on it;
for the absence of damage (damage) to the packaging or the materials themselves. If damage is detected, the question of the possibility of using these welding materials 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 weld the tacks.
Quality control
5.14. Quality control of welding work and welded joints of pipelines should be carried out by:
checking the serviceability of welding equipment and measuring instruments, quality of materials used;
operational control during the assembly and welding of pipelines;
external inspection of welded joints and measurements of seam sizes;
checking the continuity of joints using non-destructive testing methods - radiographic (X-ray or gamma rays) or ultrasonic flaw detection in accordance with the requirements of the USSR State Mining and Technical Supervision Rules, GOST 7512-82, GOST 14782-76 and other standards approved in the prescribed manner. For pipelines that are not subject to the USSR State Mining and Technical Supervision Rules, it is allowed to use magnetographic testing 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 State Mining and Technical Supervision Rules, in accordance with these Rules;
tests for strength and tightness.
5.15. During operational quality control of welded joints of steel pipelines, compliance with standards must be checked 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 welding technology and mode, the quality of welding materials, tacks and welds.
5.16. All welded joints are subject to external inspection and measurement.
Pipeline joints welded without a backing ring with weld root welding are subject to external inspection and measurement of the dimensions of the seam outside and inside the pipe, in other cases - only from the outside. Before inspection, the weld 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 inspection and measurement of 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, burns, unsealed craters and fistulas;
the dimensions and number of volumetric inclusions and depressions between the rollers do not exceed the values given in table. 1;
the dimensions of lack of penetration, concavity and excess penetration at the root of the weld of butt joints made without a remaining backing ring (if it is possible to inspect the joint from inside the pipe) do not exceed the values given in table. 2.
Joints that do not meet the listed requirements must be corrected or removed.
Table 1
Maximum allowed | Maximum |
|
Volumetric inclusion of a round or elongated shape with a nominal wall thickness of welded pipes in butt joints or smaller weld leg in corner joints, mm: | ||
St. 5.0 to 7.5 | ||
Recession (deepening) between the rollers and scaly structure of the weld surface with the nominal wall thickness of the pipes being welded in butt joints or with a smaller weld leg in corner joints, mm: | ||
Not limited |
||
Table 2
Pipelines, | Maximum permissible height (depth), % of 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% perimeter |
Do not apply | Concavity, excess penetration and lack of penetration at the root of the weld | 1/3 |
5.17. Welded joints are subjected to continuity testing using non-destructive testing methods:
pipelines that are subject to the requirements of the USSR State Mining and Technical Supervision 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), with a diameter of over 900 mm - in the volume not less than 15% (but not less than four joints) total number similar joints made by each welder;
pipelines that are not subject to the requirements of the USSR State Mining and Technical Supervision 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 over 465 mm - in a volume of 6% (but not less than three joints) of the total number of similar joints performed by each welder; in case of checking the continuity of welded joints using magnetic testing, 10% of the total number of joints subjected to control must also be checked using the radiographic method.
5.18. Non-destructive testing methods should be applied to 100% of welded joints of heating network pipelines laid in non-passable channels under roadways, in cases, tunnels or technical corridors together with other engineering communications, as well as at intersections:
railways and tram tracks - at a distance of at least 4 m, electrified railways - at least 11 m from the axis of the outermost track;
railways of the general network - at a distance of at least 3 m from the nearest roadbed structure;
highways - at a distance of at least 2 m from the edge of the roadway, reinforced shoulder strip or the bottom of the embankment;
metro - 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 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. Welds should be rejected if, when tested by non-destructive testing methods, cracks, unwelded craters, burns, fistulas, as well as lack of penetration at the root of the weld made on the backing ring are detected.
5.20. When tested by radiographic method welds pipelines that are subject to the requirements of the USSR State Mining and Technical Supervision Rules, acceptable defects are considered to be pores and inclusions, the dimensions of which do not exceed the values specified in table. 3.
Table 3
Nominal | Maximum permissible sizes of pores and inclusions, mm | Total pore length and |
|||||
individual | clusters | inclusions |
|||||
width (diameter) | width (diameter) | width (diameter) | for any 100 mm seam, mm |
||||
St. 2.0 to 3.0 | |||||||
The height (depth) of lack of penetration, concavity and excess penetration at the root of the weld of a joint made by one-sided welding without a backing ring should not exceed the values specified in table. 2.
Acceptable defects in welds according to the results of ultrasonic testing are considered to be defects, measured characteristics, the number of which does not exceed those indicated in the table. 4.
Table 4
Nominal wall thickness | Artificial size | Valid conditional | Number of defects for any 100 mm seam |
|
pipes, mm | corner reflector (“notches”), | length of an individual defect, mm | large and small in total | large |
From 4.0 to 8.0 | ||||
St. 8.0 "14.5 | ||||
Notes: 1. A defect is considered large if its nominal length exceeds 5.0 mm for a wall thickness of up to 5.5 mm and 10 mm for a wall thickness of over 5.5 mm. If the conditional length of the defect does not exceed the specified values, it is considered minor. |
||||
5.21. For pipelines that are not subject to the requirements of the USSR Gosgortekhnadzor Rules, acceptable defects in the radiographic inspection method are pores and inclusions, the dimensions of which do not exceed the maximum permissible according to GOST 23055-78 for class 7 welded joints, as well as lack of penetration, concavity and excess penetration 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 specified in table. 2.
5.22. When non-destructive testing methods are used to identify unacceptable defects in pipeline welds that are subject to the requirements of the USSR Gosgortekhnadzor Rules, repeated quality control of the seams established by these Rules must be carried out, and in pipeline welds that are not subject to the requirements of the Rules - in double the number of joints according to compared to that specified in clause 5.17.
If unacceptable defects are detected during re-inspection, all joints made by this welder must be inspected.
5.23. Sections of the weld with unacceptable defects are subject to correction by local sampling and subsequent welding (without re-welding the entire joint), if the sample size after removing the defective section does not exceed the values indicated in the table. 5.
Welded joints, in the seams of which, in order to correct the defective area, it is necessary to make a sample with dimensions larger than those allowed according to the 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 the table. 5 no more than 1.5 times at the same depth standards. |
|
5.24. Undercuts should be corrected by surfacing thread beads with a width of no more than 2.0 - 3.0 mm. Cracks must be drilled at the ends, cut out, thoroughly cleaned and welded in several layers.
5.25. All corrected areas of welded joints must be checked by external inspection, radiographic or ultrasonic flaw detection.
5.26. On the as-built drawing of the pipeline, drawn up in accordance with SNiP 3.01.03-84, the distances between welded joints, as well as from wells, chambers and customer inputs to the nearest welded joints, should be indicated.
6. THERMAL INSULATION OF PIPELINES
6.1. Installation of thermal insulation structures and protective coatings must be produced in accordance with the requirements of SNiP III-20-74 and this section.
6.2. Welded and flanged connections should not be insulated to a width of 150 mm on both sides of the connections until the pipelines are tested for strength and tightness.
6.3. The possibility of carrying out insulation work on pipelines subject to registration in accordance with the Rules of the USSR Gosgortekhnadzor, before performing strength and tightness tests, must be agreed with the local body of the USSR Gosgortekhnadzor.
6.4. When performing flooded and backfill insulation during channelless laying of pipelines, the work design must include temporary devices to prevent the pipeline from floating up, as well as soil from getting into the insulation.
7. TRANSITIONS OF HEAT NETWORKS THROUGH DRIVEWAYS AND ROADS
7.1. Work at underground (aboveground) intersections of heating networks with railways and trams, roads, city passages should be carried out in accordance with the requirements of these rules, as well as SNiP III-8-76.
7.2. When piercing, punching, horizontal drilling or other methods of trenchless laying of casings, assembly and tack of casing links (pipes) must be performed using a centralizer. The ends of the welded links (pipes) must be perpendicular to their axes. Fractures of the axes of the links (pipes) of the cases are not allowed.
7.3. Reinforced shotcrete anti-corrosion coating of cases during trenchless installation should be made in accordance with the requirements of SNiP III-15-76.
7.4. Pipelines within the casing should be made from pipes of the maximum supplied length.
7.5. The deviation of the axis of the transition cases from the design position for gravity condensate pipelines should not exceed:
vertically - 0.6% of the length of the casing, 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 transition casings from the design position for the remaining pipelines should not exceed 1% of the casing length.
8. TESTING AND WASHING (BLOWING) 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 must be washed, steam pipelines must be purged with steam, and pipelines of water heating networks with an open heating supply system and hot water supply network must be washed and disinfected.
Pipelines laid without channels and in non-passable channels are also subject to preliminary tests for strength and tightness during construction and installation work.
8.2. Preliminary tests of pipelines should be carried out before installing stuffing box (bellows) compensators, sectional valves, closing channels and backfilling of channelless pipelines and channels.
Preliminary tests of pipelines for strength and tightness should be performed, as a rule, hydraulically.
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 work plan, to perform preliminary tests using a pneumatic method.
It is not allowed to carry out pneumatic tests of above-ground 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 at a pressure equal to 1.25 working, but not less than 1.6 MPa (16 kgf/sq.cm), steam pipelines, condensate pipelines and hot water supply networks - at a pressure equal to 1.25 working, unless other requirements justified by the project (working project).
8.4. Before performing strength and tightness tests, you must:
carry out quality control of welded joints of pipelines and correction of detected defects in accordance with the requirements of Section. 5;
disconnect the tested pipelines with plugs from the existing ones and from the first shut-off valves installed in the building (structure);
install plugs at the ends of the tested pipelines and instead of stuffing box (bellows) compensators, sectional valves during preliminary tests;
provide access along the entire length of the tested pipelines for their external inspection and inspection of welds during the tests;
open the valves and bypass lines completely.
The use of shut-off valves to disconnect the pipelines under test is not permitted.
Simultaneous preliminary tests of several pipelines for strength and tightness may be carried out in cases justified by the work design.
8.5. Pressure measurements when testing pipelines for strength and tightness should be made using two duly certified (one control) spring pressure gauges of class not lower than 1.5 with a body diameter of at least 160 mm and a scale with a nominal pressure of 4/3 of the measured pressure.
8.6. Testing of pipelines for strength and tightness (density), their purging, washing, disinfection must be carried out according to technological schemes(agreed with operating organizations), regulating the technology and safety precautions for carrying out work (including the boundaries of security zones).
8.7. Reports on the results of tests of pipelines for strength and tightness, as well as on their flushing (purging) should be drawn up in the forms given in mandatory appendices 2 and 3.
Hydraulic tests
8.8. Pipeline testing should be carried out in compliance with the following basic requirements:
test pressure must be provided at the top point (mark) of the pipelines;
the water temperature during testing must be no lower than 5 degrees C;
if the outside air temperature is negative, 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 operating 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 were found in the welds, as well as leaks in the base metal, flange connections, fittings, compensators and other pipeline elements , there are no signs of shifting or deformation of pipelines and fixed supports.
Pneumatic tests
8.10. Pneumatic tests should be carried out for steel pipelines with a working pressure not 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 the 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).
The installation of cast iron fittings (except for valves made of ductile cast iron) is not allowed during testing.
8.11. Filling the pipeline with air and increasing the pressure should be done smoothly at a speed of no more than 0.3 MPa (3 kgf/sq.cm) per hour. Visual inspection of the route [entry into the security (dangerous) zone, but without descending into the trench] is allowed when pressure equal to 0.3 test, but not more than 0.3 MPa (3 kgf/sq.cm).
During the inspection of the route, the pressure rise must be stopped.
When the test pressure value is reached, the pipeline must be maintained to equalize the air temperature along the length of the pipeline. After equalizing the air temperature, the test pressure is maintained for 30 minutes and then smoothly decreases to 0.3 MPa (3 kgf/sq.cm), but not higher than the operating pressure of the coolant; At this pressure, pipelines are inspected and defective areas are marked.
Leak locations are determined by the sound of leaking air, bubbles when covering welded joints and other places with soap emulsion and the use of other methods.
Defects are eliminated only by reducing overpressure to zero and turning off the compressor.
8.12. The results of preliminary pneumatic tests are considered satisfactory if during their conduct there is no drop in pressure on the pressure gauge, no defects are found in welds, flange connections, pipes, equipment and other elements and products of the pipeline, and there are no signs of shift or deformation of the pipeline and fixed supports.
8.13. Pipelines of water networks in closed systems heating supplies and condensate pipelines should, as a rule, be subjected to hydropneumatic flushing.
Hydraulic flushing with reuse of flushing water by passing it through temporary mud traps installed along the flow of water at the ends of the supply and return pipelines is allowed.
Washing should usually be done industrial water. Washing with household and drinking water is allowed with justification in the work project.
8.14. Water network pipelines open systems heating and hot water supply networks must be flushed hydropneumatically with potable water until the flushing water is completely clarified. After 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. Pipelines with a diameter of up to 200 mm and a length of up to 1 km are permitted, in agreement with local sanitary authorities. epidemiological service, do not chlorinate and limit yourself to washing with water that meets the requirements of GOST 2874-82.
After washing, the results of laboratory analysis of wash water samples must comply with the requirements of GOST 2874-82. The sanitary and epidemiological service draws up a conclusion on the results of washing (disinfection).
8.15. The pressure in the pipeline during flushing should not be higher than the working pressure. The air pressure during hydropneumatic flushing should not exceed working pressure coolant and be no higher than 0.6 MPa (6 kgf/sq.cm).
Water velocities during hydraulic flushing must be no lower than the calculated coolant velocities indicated in the working drawings, and during hydropneumatic flushing - exceed the calculated ones by at least 0.5 m/s.
8.16. Steam lines must be purged with steam and discharged into the atmosphere through specially installed purge pipes with shut-off valves. To warm up the steam line before purging, all start-up drains must be open. The heating rate should ensure that there are no hydraulic shocks in the pipeline.
The steam velocities when blowing each section must be no 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 environment should be accepted in accordance with the requirements of SNiP 3.01.01-85 and this section.
9.2. It is not allowed without agreement with the relevant service: to produce earthworks at a distance of less than 2 m to tree trunks and less than 1 m to bushes; moving loads at a distance of less than 0.5 m to tree crowns or trunks; storing pipes and other materials at a distance of less than 2 m from tree trunks without installing temporary enclosing (protective) structures around them.
9.3. Hydraulic flushing of pipelines should be done by reusing water. Emptying of pipelines after washing and disinfection should be carried out in places specified in the work project and agreed upon 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 STRETCHING OF COMPENSATORS
APPENDIX 1
Mandatory
________________________ "_____"_________________19_____
Commission consisting of:
(last name, first name, patronymic, position)
_____________________________________________________________,
1. The extension of expansion joints listed in the table in the area from chamber (picket, shaft) No. _______ to chamber (picket, shaft) No. _______ was presented for inspection and acceptance.
Compensator number | Drawing number | Type of compensation | Stretch value, mm | Temperature |
|
according to drawing | design | actual | air, degrees C |
||
2. The work was carried out according to design estimates ____________
_______________________________________________________________
COMMISSION DECISION
The work was carried out in accordance with design and estimate documentation, state standards, building codes and rules and meet the requirements for their acceptance.
(signature)
(signature)
Appendix 2. ACT ON TESTING PIPELINES FOR STRENGTH AND TIGHTNESS
APPENDIX 2
Mandatory
_____________________ "_____"____________19____
Commission consisting of:
representative of the construction and installation organization _________________
_____________________________________________________________,
(last name, first name, patronymic, position)
representative of the customer's technical supervision _____________________
_____________________________________________________________,
(last name, first name, patronymic, position)
representative of the operating organization ______________________________
_____________________________________________________________
(last name, first name, patronymic, position)
inspected the work performed by ___________________________
_____________________________________________________________,
(name of construction and installation organization)
and drew up this act as follows:
1. ________________ are presented for inspection and acceptance
_____________________________________________________________
(hydraulic or pneumatic)
pipelines tested for strength and tightness and listed in the table, in the section from chamber (picket, shaft) No. ________ to chamber (picket, shaft) No. _________ route ___________
Length __________ m.
(name of pipeline)
Pipeline | Test pressure | Duration, min | External inspection at pressure, MPa (kgf/sq.cm) |
2. The work was carried out according to design and estimate documentation __________________
_____________________________________________________________________
(name of the design organization, drawing numbers and date of their preparation)
COMMISSION DECISION
Representative of the construction and installation organization ________________
(signature)
Representative of the customer's technical supervision _____________________
(signature)
(signature)
Appendix 3. ACT ON WASHING (BLOWING) OF PIPELINES
APPENDIX 3
Mandatory
_______________________________________ "_____"_______________19_____
Commission consisting of:
representative of the construction and installation organization ________________
_____________________________________________________________,
(last name, first name, patronymic, position)
representative of the customer's technical supervision _____________________
_____________________________________________________________,
(last name, first name, patronymic, position)
representative of the operating organization _____________________
_____________________________________________________________
(last name, first name, patronymic, position)
inspected the work performed by ____________________________
_____________________________________________________________,
(name of construction and installation organization)
and drew up this act as follows:
1. Flushing (purging) of pipelines in the section from chamber (picket, shaft) No. __________ to chamber (picket, shaft) No.______ of the route ________________________________________________________________________________ is submitted for inspection and acceptance.
_____________________________________________________________________________________
(name of pipeline)
length ___________ m.
Washing (purging) completed________________________________
_____________________________________________________________.
(name of medium, pressure, flow)
2. The work was carried out according to design estimates _________________
____________________________________________________________________
_____________________________________________________________________.
(name of the design organization, drawing numbers and date of their preparation)
COMMISSION DECISION
The work was carried out in accordance with design and estimate documentation, standards, building codes and regulations and meets the requirements for their acceptance.
Representative of the construction and installation organization ________________
(signature)
Representative of the customer's technical supervision _____________________
(signature)
Representative of the operating organization _____________________
(signature)
The text of the document is verified according to:
official publication
M.: CITP Gosstroy USSR, 1986
Before installing compensators in the designed position, it is necessary to check them by external inspection. As a rule, before final connection to the pipeline, all expansion joints must be pre-stretched or compressed by the amount specified in the design, and installed on the pipelines together with a spacer (or compression) device, which is removed only after the pipelines are finally secured to fixed supports. The amount of pre-stretching of the compensator is indicated in the drawings.
Stretching is used for “hot” pipeline lines, and compression is used for “cold” lines. The operation of stretching or compression is called cold tensioning of the pipeline and is performed in order to reduce the stress in the metal during thermal elongation of the pipeline.
For stretching of expansion joints, regardless of the method of its implementation, a report is drawn up, which indicates the construction lengths of the expansion joints before and after stretching.
U-shaped compensators, as a rule, are installed in a horizontal position and only as an exception, vertically or obliquely. When installing such compensators vertically or obliquely, at the lower points on both sides of the compensators, it is necessary to place drainage fittings to remove condensate, and at the top - air vents.
To ensure normal operation, the U-shaped compensator is installed on at least three movable supports (Fig. 5). Two supports are placed on straight sections of the pipeline connected to the compensator (the edge of the support must be at least 500 mm away from the welded joint), the third support is placed under the back of the compensator, usually on a special column.
To pre-stretch 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, spread it to the required amount. The spacer device is installed parallel to the back of the compensator. The joint at which the compensator will be stretched is indicated in the project. If there is no indication, then in order to avoid distortion, the joint cannot be used for stretching. Directly adjacent to the compensator. For this purpose, you need to leave a gap in the adjacent joint.
When lifting, expansion joints should be grasped at three points and under no circumstances by the spacer device. Only after the joints have been tacked and secured, the compensator is disconnected from the lifting equipment. It is also necessary to check the reliability of the installation of the spacer.
U-shaped compensators 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, pre-stretching of the expansion joints is replaced by tensioning the pipeline in a cold state. In this case, when installing 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 expansion value of the compensator.
Before stretching, you should make sure that all welded joints in this section of the pipeline are welded and that the fixed supports are finally secured.
When installing expansion joints without pre-stretching, for ease of pipeline installation, a pipe with a length equal to the length of the stretch is inserted into the joint intended for stretching and electrically welded to both edges of the pipeline. Sometimes ring beads are fused at the ends of the pipes being joined and temporary clamps made from corners are installed (Fig. 6). Elongated tie rods are passed through the holes in them and, by 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 slowly (without permanent gaskets) tightened with elongated studs, installing them through one and leaving holes for permanent bolts. The diameter and number of studs for tensioning pipelines in a cold state are indicated in the project.
After installing the expansion joints in the design position, welding all joints (except one) and securing the pipeline to 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 extended studs. For a flange connection, before final tightening, install the gasket provided for in the design. After the flange connection has been tightened with permanent bolts, the extended studs are removed and permanent bolts or studs are installed in their place.
When installing lens compensators, it is necessary to ensure that the drainage fittings (if any) are in the lower position, and the guide cup of the compensator is welded in the direction of movement of the product.
It is recommended to install lens compensators on pipes, assemblies or blocks before lifting them to the design position. The assembled assembly or block with lens compensators must be protected from deformation and damage during transportation, lifting and installation. For this purpose, additional stiffness is used on the compensators. After installing the units on the supports and securing them, the temporary rigidities are removed.
When installing vertical sections of pipelines, it is necessary to take measures to exclude the possibility of compression and deformation of expansion joints under the influence of gravity of the pipelines. To achieve this, three brackets are welded parallel to the expansion joints on the pipelines, which are cut off upon completion of the pipeline installation.
Lens compensators are stretched to half their compensating capacity.
The lens compensator 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 hangers of the pipelines and securing the pipelines in fixed supports.
In this case, the compensator is stretched by tightening the installation joint closest to the compensator, at which a corresponding additional gap is specially left.
The compression of the compensator is carried out after the final connection with the pipeline, but before securing it to fixed supports. To compress or stretch the lens compensator, a device is used, consisting of two clamps, fixed to the pipeline on both sides of the compensator, and elongated tie rods with nuts.
When installing several lens compensators on a pipeline line, the design must provide fixed supports behind each compensator in order to eliminate the possibility of deflection of the pipeline in a compressed state and to ensure a more uniform deformation of all compensators installed on the pipeline, since the actual rigidity of all compensators can be not the same.
For wavy expansion joints, the face-to-face length is checked before installation; using spacers and studs, establish a gap corresponding to pre-stretching.
Axial compensators are mounted in the following sequence. First, they are welded at one end to the pipeline. Check the gap between the second end and the welded pipe, equal to the value pre-stretching, stretch the compensator using the nuts and studs on it, weld the second end of the compensator to the pipeline, after which the studs and nuts are removed.
When installing hinged or universal compensators, they are welded to the pipeline at both ends in accordance with the installation diagram, without removing the bolts that fasten the cheeks of the hinges and protect the compensator from bending.
During installation, gland compensators must be installed strictly in alignment with the pipeline, without distortions, in order to avoid jamming of the moving parts and damage to the compensator packing. Pipeline guides 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 a horizontal and vertical surfaces without creating large longitudinal friction forces.
Stuffing box compensators are not subject to stretching after installation, since when the compensator is welded to the pipeline, it is moved apart by the amount specified in the design and determined by the distance between the marks marked on its body and the sleeve. In this case, a gap must be left between the thrust rings on the pipe and in the compensator body in case the temperature drops compared to the air temperature at the time of installation. The minimum gap value for a pipeline section length of 100 mm should be 30 mm at an outside air temperature at the time of installation below -5 o C, from -5 o C to +20 o C - 50 mm, above +20 o C - 60 mm. 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 tear out of the compensator body. In most cases, to do this, a rim is welded onto the sliding part of the pipe so that it does not interfere with the operation of the compensator.
4.1. The installation of pipelines must be carried out by specialized installation organizations, and the installation technology must ensure high operational reliability of the pipelines.
4.2. Parts and elements of pipelines (compensators, mud traps, insulated pipes, as well as pipeline assemblies and other products) must be manufactured centrally (in factories, workshops, workshops) in accordance with standards, technical specifications and design documentation.
4.3. The laying of pipelines in a trench, channel or on above-ground structures should be carried out using the technology provided for by the work project 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 installation devices, correct placement of simultaneously operating lifting machines and mechanisms.
The design of fastening mounting devices to pipes must ensure the safety of the coating and insulation of pipelines.
4.4. The laying of pipelines within the panel support must be carried out using pipes of the maximum delivery length. In this case, the transverse welds of the pipelines should, as a rule, be located symmetrically relative to the panel support.
4.5. Laying of pipes with a diameter of over 100 mm with a longitudinal or spiral seam should be carried out 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 thickness of the pipe wall.
Longitudinal seams must be within the upper half of the circumference of the pipes being laid.
Steeply curved and stamped pipeline bends are allowed to be welded together without a straight section.
Welding of pipes and bends into welded joints and bent elements is not allowed.
4.6. When installing pipelines, the movable supports and hangers must be shifted relative to the design position by the distance specified 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 shifted taking into account the correction for the outside air temperature during installation by the following values:
sliding supports and elements for fastening hangers to the pipe - by half the thermal elongation of the pipeline at the attachment point;
roller bearing rollers - by a quarter of thermal elongation.
4.7. When installing pipelines, spring hangers must be tightened in accordance with the working drawings.
When performing hydraulic tests of steam pipelines with a diameter of 400 mm or more, an unloading device should be installed in spring suspensions.
4.8. Pipe fittings must be installed in a closed state. Flange and welded connections of fittings must be made without tension in the pipelines.
The deviation from the perpendicularity of the plane of the flange welded to the pipe relative to the pipe axis should not exceed 1% of the outer diameter of the flange, but be no more than 2 mm at the top of the flange.
4.9. Bellows (wavy) and stuffing box expansion joints should be installed assembled.
When laying heating networks underground, installation of compensators in the design position is allowed only after preliminary testing of pipelines for strength and tightness, backfilling of channelless pipelines, channels, chambers and panel 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.
Permissible deviations from the design position of the connecting pipes of compensators during their installation and welding should be no more than those specified in the technical specifications for the manufacture and supply of compensators.
4.11. When installing bellows expansion joints, they are not allowed to twist relative to the longitudinal axis and sag under the influence of their own weight and the weight of adjacent pipelines. Slinging of expansion joints should be done only by the pipes.
4.12. The installation length of bellows and stuffing box expansion joints must be taken according to the working drawings, taking into account corrections for the outside air temperature during installation.
Stretching of expansion joints to the installation length should be done using devices provided for in the design of expansion joints, or tensioning mounting devices.
4.13. Stretching of the U-shaped compensator should be performed after completion of pipeline installation, quality control of welded joints (except for closing joints used for tension) and fastening of fixed support structures.
The compensator should 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.
Stretching of the compensator must be carried out simultaneously on both sides at joints located at a distance of no less than 20 and no more than 40 pipeline diameters from the axis of symmetry of the compensator, using tension devices, unless other requirements are justified by the design.
On the section of the pipeline between the joints used for stretching the compensator, there should be no preliminary displacement of supports and hangers in comparison with the design (detailed design).
4.14. Immediately before assembling and welding pipes, it is necessary to visually inspect each section to ensure that there are no foreign objects or debris in the pipeline.
4.15. The deviation of the pipeline slope from the design one is allowed by ± 0.0005. In this case, the actual slope must be no less than the minimum allowable according to SNiP II-G.10-73* (II-36-73*).
Movable pipeline supports must be adjacent to the supporting surfaces of structures without gaps or distortion.
4.16. When performing installation work, the following types of hidden work are subject to acceptance with drawing up inspection reports in the form given in SNiP 3.01.01-85: preparation of the surface of pipes and welded joints for anti-corrosion coating; performing anti-corrosion coating of pipes and welded joints.
A report on the stretching of compensators should be drawn up in the form given in the mandatory Appendix 1.
4.17. Protection of heating networks from electrochemical corrosion must be carried out in accordance with the Instructions for the protection of heating networks from electrochemical corrosion, approved by the USSR Ministry of Energy and the Ministry of Housing and Utilities of the RSFSR and agreed with the USSR State Construction Committee.
