Installation of thermal networks. Bellows axial compensator. Calculation of pre-stretching during installation Pre-stretching of the U-shaped compensator
Instead of SNiP III-30-74
These rules apply to the construction of new, expansion and reconstruction of existing heating networks that transport hot water at temperature and pressure and steam at temperature and pressure from the source of thermal energy to heat consumers (buildings, structures).
1. General Provisions
1.1. When building new, expanding and reconstructing existing heating networks, in addition to the requirements of working drawings, work plans (PPR) and these rules, the requirements of SNiP 3.01.01-85, SNiP 3.01.03-84, SNiP III-4-80 and standards .
1.2. Works on the manufacture and installation of pipelines, which are subject to the requirements of the Rules for the Arrangement and Safe Operation of Steam and Hot Water Pipelines of the USSR Gosgortechnadzor (hereinafter referred to as the Rules of the USSR Gosgortekhnadzor), must be carried out in accordance with the indicated 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. Earthworks
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 trench bottom width for channelless pipe laying should be equal to the distance between the outer side edges of the insulation of the extreme pipelines of heat networks (associated drainage) with the addition on each side for pipelines with a nominal diameter of up to 250 mm - 0.30 m, over 250 to 500 mm - 0 .40 m, over 500 to 1000 mm - 0.50 m; the width of the pits in the trench for welding and insulating pipe joints during channelless laying of pipelines should be taken equal to the distance between the outer side faces of the insulation of the outermost pipelines with the addition of 0.6 m on each side, the length of the pits is 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 bottom of the trench in the case of channel laying of heat networks should be equal to the width of the channel, taking into account the formwork (in monolithic sections), waterproofing, associated drainage and drainage devices, the trench fastening structure with the addition of 0.2 m. In this case, the width of the trench should be at least 1 .0 m
If it is necessary for people to work between the outer edges of the channel structure and the walls or slopes of the trench, the clear width between the outer edges of the channel 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, full implementation insulating and building installation work.
Backfilling must be done within the specified technological sequence:
padding of sinuses between pipelines of channelless laying and the base;
simultaneous uniform backfilling of the sinuses between the walls of the trench and pipelines with channelless laying, as well as between the walls of the trench and channel, chamber with channel laying to a height of at least 0.20 m above pipelines, channels, chambers;
backfilling of the trench to design marks.
Backfilling of trenches (pits) to which additional external loads (except for the own weight of the soil) are not transferred, as well as trenches (pits) at intersections with existing underground utilities, 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 the temporary dewatering devices, the channels and chambers must be visually inspected for the absence of groundwater in them.
3. Structures and installation of building structures
3.1. Production of construction and installation works building structures should be performed in accordance with the requirements of this section and the requirements of:
SNiP III-15-76 - during the construction of monolithic concrete and reinforced concrete structures of foundations, supports for pipelines, chambers and other structures, as well as when monolithic joints;
SNiP III-16-80 - when installing prefabricated concrete and reinforced concrete structures;
SNiP III-18-75 - during installation metal structures supports, span structures 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 coated with a coating or pasting waterproofing in accordance with working drawings.
The installation of channel elements (chambers) in the design position should be carried out in the 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 provided for in SNiP II-G.10-73* (II-36-73*).
3.3. Monolithic fixed shield supports must be made after the installation of pipelines in the shield support section.
3.4. In places where pipelines of channelless laying enter channels, chambers and buildings (structures), cases of bushings 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 (plates), the channels must be cleared of soil, debris and snow.
3.6. The deviation of the slopes of the bottom of the channel of the heat network and drainage pipelines from the design is allowed by the value, while the actual slope must be at least the minimum allowable 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 construction organization project and the work execution project should provide for the advanced construction of drainage pumping stations and water outlet 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 carried out using inventory separating forms.
3.10. The straightness of the sections of drainage pipelines between adjacent wells should be checked by looking at the light with 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 circumference should be no more than 0.25 of the pipe diameter, but no more than 50 mm in each direction.
Deviation from correct form vertical circles are not allowed.
4. Installation of pipelines
4.1. The installation of pipelines must be carried out by specialized installation organizations, while the installation technology must ensure high operational reliability of the pipelines.
4.2. Details, elements of pipelines (compensators, mud collectors, insulated pipes, as well as pipeline units 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, channel or on above-ground structures should be carried out according to the technology provided for by the project for the production of works and excluding the occurrence of residual deformations in pipelines, violation of the integrity of the anti-corrosion coating and thermal insulation by using appropriate mounting devices, correct placement of simultaneously operating hoisting 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 shield support must be carried out using pipes of the maximum delivery length. In this case, the welded transverse seams of the pipelines should, as a rule, be located symmetrically with respect to the shield support.
4.5. Laying pipes with a diameter of more than 100 mm with a longitudinal or spiral seam should be carried out with a displacement of these seams by at least 100 mm. When laying pipes with a diameter of less than 100 mm, the offset of the joints must be at least three times the thickness of the pipe wall.
Longitudinal seams must be located within the upper half of the circumference of the pipes to be laid.
Steeply bent and stamped pipe bends may be welded together without a straight section.
Welding of branch pipes and bends into welded joints and bent elements is not allowed.
4.6. When installing pipelines, movable supports and suspensions must 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 outdoor temperature during installation, by the following values:
sliding supports and fastening elements of hangers to the pipe - by half of the thermal elongation of the pipeline at the point of fastening;
rollers of roller bearings - by a quarter of thermal elongation.
4.7. Spring hangers during installation of pipelines must be tightened in accordance with the working drawings.
During hydraulic testing of steam pipelines with a diameter of 400 mm or more, an unloading device should be installed in spring hangers.
4.8. Pipe fittings must be installed closed. Flanged and welded fittings must be made without interference of pipelines.
The deviation from perpendicularity of the plane of the flange welded to the pipe with respect to the axis of the pipe 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 mounted assembled.
At underground laying 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 pipelines without channel laying, channels, chambers and shield supports.
4.10. Axial bellows and stuffing box compensators should be installed on pipelines without breaking the compensator axes and pipeline axes.
Permissible deviations from the design position of the connecting pipes of expansion joints during their installation and welding should not exceed those specified in the technical specifications for the manufacture and supply of expansion joints.
4.11. When mounting bellows compensators, their twisting relative to the longitudinal axis and sagging under the action of their own weight and the weight of adjacent pipelines are not allowed. Slinging expansion joints should be done only by the branch pipes.
4.12. The installation length of bellows and stuffing box expansion joints must be taken from the working drawings, taking into account the correction for the outside air temperature during installation.
Stretching expansion joints to the installation length should be carried out using the devices provided for by the design of the expansion joints, or tension mounting devices.
4.13. Stretching of the U-shaped compensator should be performed after the completion of the installation of the pipeline, quality control of welded joints (except for the closing joints used for tension) and fixing the structures of fixed supports.
The expansion joint must be stretched to the value specified 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 pipeline diameters from the axis of symmetry of the expansion joint, 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, it is not necessary to carry out preliminary displacement of supports and hangers 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 garbage.
4.15. The deviation of the slope of pipelines from the design is allowed by the value. In this case, the actual slope must be at least the minimum allowable according to SNiP II-G.10-73* (II-36-73*).
The movable supports of the pipelines must be adjacent to the supporting surfaces of the structures without gap and distortion.
4.16. When performing installation work, the following types are subject to acceptance with the preparation of survey reports in the form given in SNiP 3.01.01-85 hidden works: preparation of the surface of pipes and welded joints for anti-corrosion coating; implementation of anticorrosive coating of pipes and welded joints.
An act should be drawn up on the stretching of compensators in the form given in the mandatory Appendix 1.
4.17. Protection of heat networks from electrochemical corrosion must be carried out in accordance with the Instructions for the protection of heat networks from 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 joints
General provisions
5.1. Welders are allowed to tack and weld pipelines if they have documents for the right to carry out welding work in accordance with the Rules for the certification of welders approved by the USSR Gosgortekhnadzor.
5.2. Before being allowed to work on welding joints of pipelines, the welder must weld a tolerance joint under production conditions in the following cases:
with a break in work for more than 6 months;
when welding pipelines with a change in the group of steel, welding consumables, technology or welding equipment.
On pipes with a diameter of 529 mm or more, it is allowed to weld half the perimeter of the tolerance joint; at the same time, if the tolerance joint is a vertical fixed joint, the ceiling and vertical sections of the seam should be welded.
The tolerance joint must be of the same type with the production one (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 subject to the same types of control that are subject to production welded joints in accordance with the requirements of this section.
Manufacturing jobs
5.3. The welder is obliged to knock out or build up a brand at a distance of 30 - 50 mm from the joint from the side accessible for inspection.
5.4. Before assembly and welding, it is necessary to remove the end caps, clean the edges and the inner and outer surfaces of the pipes adjacent to them 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. Joints of pipelines with a diameter of 920 mm or more, welded without the remaining backing ring, must be made with welding of the weld root inside the pipe. When welding inside the pipeline, the responsible contractor must be issued a work permit for the performance of high-risk work. 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 that are subject to the requirements of the Rules of the USSR Gosgortekhnadzor - in accordance with these requirements;
for other pipelines - 20% of the pipe wall thickness, but not more than 3 mm.
At 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 centering devices.
Straightening 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 of up to 100 mm - 1 - 2, with a diameter of more than 100 to 426 mm - 3 - 4. For pipes with a diameter of more than 426 mm, tacks should be placed every 300-400 mm around the circumference.
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 - 10 - 20 mm, a diameter of more than 100 to 426 mm - 20 - 40, a diameter of more than 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 tacks must be of the same grade as for welding the main seam.
5.10. Welding of pipelines, which are not subject to the requirements of the Rules of the USSR Gosgortekhnadzor, is allowed to be carried out without heating the welded joints:
at an outdoor temperature of up to minus 20 ° 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 outdoor temperature of up to minus 10°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 more than 10 mm.
At a lower outdoor temperature, welding should be carried out in special booths, in which the air temperature in the area of the welded joints must be maintained not lower than the specified one.
It is allowed to carry out welding work on outdoors when heating the pipe ends to be welded over a length of at least 200 mm from the joint to a temperature of at least 200°C. After welding is completed, a gradual decrease in the temperature of the joint and the adjacent pipe zone should be ensured by covering them with an asbestos sheet or using another method.
Welding (at a negative temperature) of pipelines that are subject to the requirements of the Rules of the USSR Gosgortekhnadzor must be carried out in compliance with the requirements of these Rules.
In case of rain, wind and snowfall, welding work may 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 incoming inspection:
for the presence of a certificate with verification of the completeness of the data given in it and their compliance with the requirements of state standards or technical specifications;
for the presence on each box or other packaging of an appropriate label or tag with verification of the data given on it;
for the absence of damage (damage) to the packaging or the materials themselves. If damage is found, the question of the possibility of using these welding consumables must be decided by the organization performing the welding;
on the technological properties of the electrodes in accordance with GOST 9466-75 or departmental regulations approved in accordance with SNiP 1.01.02-83.
5.13. When applying the main seam, it is necessary to completely cover and digest the potholders.
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 inspection of welded joints and measurements of weld dimensions;
checking the continuity of joints by non-destructive control methods - radiographic (X-ray or gamma rays) or ultrasonic flaw detection in accordance with the requirements of the Rules of the USSR Gosgortekhnadzor, GOST 7512-82, GOST 14782-76 and other standards approved in in due course. For pipelines that are not subject to the USSR Gosgortekhnadzor 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 Rules of the Gosgortekhnadzor of the USSR, in accordance with these Rules;
strength and tightness tests.
5.15. During the operational quality control 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 weld seam.
5.16. All welded joints are subject to external inspection and measurement.
Joints of pipelines welded without backing ring with welding of the root of the seam are subjected to external inspection and measurement of the dimensions of the seam outside and inside the pipe, in other cases - only outside. Before inspection, the weld 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 weld).
The results of an 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, burns, unwelded craters and fistulas;
the size and number of volumetric inclusions and recessions 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 the 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 are subject to correction or removal.
Table 1
table 2
5.17. Welded joints are subjected to continuity testing by non-destructive testing methods:
pipelines that are subject to the requirements of the USSR Gosgortekhnadzor Rules, with an outer diameter of up to 465 mm - in the amount provided for by these Rules, with a diameter of more than 465 to 900 mm - in the amount of at least 10% (but not less than four joints), with a diameter of more than 900 mm - in volume of at least 15% (but not less than four joints) total number the same type of 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 the amount of at least 3% (but not less than two joints), with a diameter of more than 465 mm - in the amount of 6% (but not less than three joints) of the total number of the same type joints made 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 must be checked, in addition, by radiographic method.
5.18. 100% of welded joints of pipelines of heat networks laid in impassable channels under the carriageway, in cases, tunnels or technical corridors together with other engineering communications, as well as at intersections should be subjected to non-destructive control methods:
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 subgrade structure;
motorways - at a distance of at least 2 m from the edge of the carriageway, the reinforced roadside strip or the sole of the embankment;
underground - at a distance of at least 8 m from the 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. Welded seams should be rejected if cracks, non-welded craters, burns, fistulas, as well as lack of penetration at the root of the weld made on the backing ring are found during testing by non-destructive testing methods.
5.20. When checking by radiographic method the welds of pipelines, which are subject to the requirements of the Rules of the Gosgortekhnadzor of the USSR, pores and inclusions, the dimensions of which do not exceed the values \u200b\u200bspecified in Table 3, are considered acceptable defects.
Table 3
The height (depth) of lack of penetration, concavity and excess penetration at the root of the joint weld, made by one-sided welding without a backing ring, should not exceed the values \u200b\u200bspecified in Table. 2.
Permissible 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 Table. 4.
Table 4
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 more than 5.5 mm. If the conditional length of the defect does not exceed the specified values, it is considered small.
2. In electric arc welding without a backing ring with one-sided access to the seam, the total conditional length of defects located at the root of the seam is allowed up to 1/3 of the pipe perimeter.
3. The amplitude level of the echo signal from the measured defect should not exceed the amplitude level of the echo signal from the corresponding artificial corner reflector ("notch") or an equivalent segmental reflector.
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5.21. For pipelines that are not subject to the requirements of the USSR Gosgortekhnadzor Rules, pores and inclusions whose dimensions do not exceed the maximum allowable in accordance with GOST 23055-78 for welded joints of the 7th class, as well as lack of fusion, concavity and excess penetration are considered acceptable defects in the radiographic method of control at the root of a seam made on one side arc welding without a backing ring, the height (depth) of which should not exceed the values \u200b\u200bspecified in Table 2.
5.22. When non-destructive testing methods reveal unacceptable defects in the welds of pipelines that are subject to the requirements of the USSR Gosgortekhnadzor Rules, a repeated quality control of the welds established by these Rules should be carried out, and in the welds of pipelines that are not subject to the requirements of the Rules - in twice the number of joints according to compared with that specified in clause 5.17.
If unacceptable defects are detected during the re-inspection, all joints made by this welder should be checked.
5.23. Correction by local sampling and subsequent welding (without re-welding the entire joint) is subject to sections of the weld with unacceptable defects, if the dimensions of the sample after removing the defective section do not exceed the values \u200b\u200bspecified 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 sizes larger than those allowed in Table 5, must be completely removed.
Table 5
5.24. Undercuts should be corrected by surfacing thread rollers with a width of not more than 2.0 - 3.0 mm. Cracks must be drilled at the ends, cut down, carefully cleaned and welded in several layers.
5.25. All repaired areas of welded joints should be checked by visual inspection, radiographic or ultrasonic inspection.
5.26. On the executive 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 subscriber 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 joints should not be insulated to a width of 150 mm on both sides of the joints before testing pipelines for strength and tightness.
6.3. The possibility of performing insulation work on pipelines subject to registration in accordance with the Rules of the USSR Gosgortechnadzor must be agreed with the local authority of the USSR Gosgortekhnadzor before performing tests for strength and tightness.
6.4. When performing filling and backfill insulation during channelless laying of pipelines, it is necessary to provide for temporary devices in the project for the production of works to prevent the pipeline from surfacing, as well as from getting into the soil insulation.
7. Transitions of heating networks through driveways and roads
7.1. The performance of work at the underground (above-ground) crossing of railway and tram tracks, roads, city passages by heating networks 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 cases, the assembly and tacking of the sections (pipes) of the case 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-concrete anti-corrosion coating of cases during their trenchless laying should be made in accordance with the requirements of SNiP III-15-76.
7.4. Pipelines within the case should be made of pipes of the maximum delivery length.
7.5. The deviation of the axis of transition cases from the design position for gravity condensate pipelines should not exceed:
vertically - 0.6% of the length of the case, provided that the design slope of the condensate pipelines is ensured;
horizontally - 1% of the length of the case.
The deviation of the transition case axis from the design position for the remaining pipelines should not exceed 1% of the case length.
8. Testing and flushing (purging) of pipelines
General provisions
8.1. After completion of construction and installation works, 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 - purged with steam, and pipelines of water heating networks with an open heat supply system and hot water supply networks - washed and disinfected.
Pipelines laid without channels and in impassable channels are also subject to preliminary tests for strength and tightness in the course of construction and installation works.
8.2. Preliminary testing of pipelines should be carried out before installing stuffing box (bellows) compensators, sectional valves, closing channels and backfilling pipelines without channel laying and channels.
Preliminary testing of pipelines for strength and tightness should be carried out, as a rule, in a hydraulic way.
At negative temperatures of the outside air 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 by pneumatic means.
It is not allowed to perform 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 heat networks should be tested with a pressure equal to 1.25 working pressure, but not less than 1.6 MPa (16), steam pipelines, condensate pipelines and hot water supply networks - with a pressure equal to 1.25 working pressure, unless other requirements are justified by the project (working draft ).
8.4. Before performing tests for strength and tightness, it is necessary:
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 from the existing ones and from the first stop valves installed in the building (structure) with plugs;
install plugs at the ends of the tested pipelines and instead of stuffing box (bellows) compensators, sectional valves during preliminary tests;
provide access throughout the tested pipelines for their external inspection and inspection of welds for the duration of 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 work design.
8.5. Pressure measurements when testing pipelines for strength and tightness should be carried out using two duly certified (one - control) spring pressure gauges of class at least 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) that regulate the technology and safety of work (including the boundaries of protected zones).
8.7. On the results of testing pipelines for strength and tightness, as well as on their flushing (purging), acts should be drawn up in the forms given in mandatory appendices 2 and 3.
Hydraulic tests
8.8. Piping tests 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 should not be lower than 5 ° C;
at a negative outside temperature, the pipeline must be filled with water at a temperature not exceeding 70 ° C and it must be possible to fill and empty 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 their implementation there was no pressure drop, no signs of rupture, leakage or fogging in welds, as well as leaks in the base metal, flange joints, fittings, compensators and other elements of pipelines , there are no signs of shift or deformation of pipelines and fixed supports.
Pneumatic tests
8.10. Pneumatic tests should be performed for steel pipelines with a working pressure of not more than 1.6 MPa (16) and a temperature of up to 250 ° C, mounted from pipes and parts tested for strength and tightness (density) by manufacturers in accordance with GOST 3845- 75 (at the same time, 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 ductile iron valves) is not allowed for the duration of the test.
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) per 1 hour. 3 test, but not more than 0.3 MPa (3).
For the period of inspection of the route, the pressure increase must be stopped.
When the test pressure is reached, the pipeline must be held 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 gradually decreases to 0.3 MPa (3), but not higher than the working pressure of the coolant; at this pressure, pipelines are inspected with a mark of defective places.
Leaks are identified by the sound of escaping air, by bubbling when welding joints and other areas are covered with soapy emulsion, and by other methods.
Defects are eliminated only when the excess pressure is reduced to zero and the compressor is turned off.
8.12. The results of preliminary pneumatic tests are considered satisfactory if during their conduct there was no pressure drop on the pressure gauge, no defects were found in welds, 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. Pipelines of water networks in closed heat supply systems and condensate pipelines should, as a rule, be subjected to hydropneumatic flushing.
Hydraulic flushing is allowed with reuse of flushing water by passing it through temporary sumps installed in the direction of water movement at the ends of the supply and return pipelines.
Flushing, as a rule, should be carried out with process water. Flushing with utility and drinking water is allowed with justification in the project for the production of works.
8.14. Pipelines of water networks of open heat supply systems and hot water supply networks must be flushed hydropneumatically with drinking-quality water until the flushing water is completely clarified. Upon completion 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. Pipelines with a diameter of up to 200 mm and a length of up to 1 km are allowed, in agreement with the local sanitary authorities. epidemiological service, do not expose to chlorination and limit yourself to washing with water that meets the requirements of GOST 2874-82.
After washing, the results of laboratory analysis of samples of wash water must comply with the requirements of GOST 2874-82. A conclusion is drawn up on the results of washing (disinfection) by the sanitary and epidemiological service.
8.15. The pressure in the pipeline during flushing should not be higher than the working one. The air pressure during hydropneumatic flushing should not exceed the working pressure of the coolant and be no higher than 0.6 MPa (6).
Water velocities during hydraulic flushing must not be 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 pipelines must be purged with steam and vented to the atmosphere through specially installed purge pipes with shutoff valves. To warm up the steam pipeline, 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 the blowing of each section must be at least the operating velocities for the design parameters of the coolant.
9. Environmental protection
9.1. During the construction of new, expansion and reconstruction of existing heating networks, environmental protection measures should be taken 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 carry out excavation at a distance of less than 2 m to tree trunks and less than 1 m to shrubs; movement of goods at a distance of less than 0.5 m to crowns or tree trunks; storage of pipes and other materials at a distance of less than 2 m to tree trunks without the installation of temporary enclosing (protective) structures around them.
9.3. Flushing of pipelines in a hydraulic way should be carried out with the reuse of water. Emptying of pipelines after washing and disinfection should be carried out at the places indicated in the project for the production of works and agreed with the relevant services.
9.4. Territory construction site after completion of construction and installation works, it must be cleaned of debris.
Annex 1
Mandatory
Act
about stretching compensators
____________________________ "_____" _________________ 19_____
Commission consisting of:
(last name, first name, patronymic, position)
inspected the work performed by ________________________________
________________________________________________________________________,
1. Stretching presented for inspection and acceptance
compensators listed in the table, in the area from the chamber (picket,
mine) N_______ to the camera (picket, mine) N_______.
───────────────────┬─────────┬────────┬─────────────────────┬───────────┐
Compensator number │ Number │ Type │ Value │Temperature│
according to the drawing │ drawing │ compen-│ extensions, mm │external │
│ │ sator ├──────────┬───────────┤air, °С│
│ │ │design│actual│ │
│ │ │ │ │ │
───────────────────┼─────────┼────────┼─────────┼───────────┼───────────┤
│ │ │ │ │ │
───────────────────┴─────────┴────────┴─────────┴───────────┴───────────┘
_________________________________________________________________________
drafting)
Commission decision
The work was carried out in accordance with design and estimate documentation, state standards, building codes and regulations and meet the requirements for their acceptance.
(signature)
(signature)
Annex 2
Mandatory
Act
on testing pipelines for strength and tightness
Commission consisting of:
representative of the construction and installation organization ____________________
________________________________________________________________________,
(last name, first name, patronymic, position)
representative of the technical supervision of the customer _______________________
________________________________________________________________________,
(last name, first name, patronymic, position)
_________________________________________________________________________
(last name, first name, patronymic, position)
________________________________________________________________________,
(name of construction and installation organization)
and drew up this act as follows:
1. _____________________ were presented for examination and acceptance
_________________________________________________________________________
(hydraulic or pneumatic)
pipelines tested for strength and tightness and listed in
table, in the section from the camera (picket, mine) N_______ to the camera
(picket, mines) N_________ routes ___________
Length __________ m.
(pipeline name)
─────────────────┬─────────────────┬─────────────────────┬──────────────┐
Pipeline │ Test │ Duration, │ Outdoor │
│ pressure, MPa │ min │ inspection at │
│ (kgf/sq.cm) │ │ pressure, MPa│
│ │ │ (kgf/sq.cm) │
─────────────────┼─────────────────┼─────────────────────┼──────────────┤
─────────────────┴─────────────────┴─────────────────────┴──────────────┘
2. The work was carried out according to the design and estimate documentation _______________
_________________________________________________________________________
________________________________________________________________________.
(Name design organization, numbers of drawings and their date
drafting)
Commission decision
Representative of the construction and installation organization _____________________
(signature)
Representative of the technical supervision of the customer _____________________
(signature)
(signature)
Appendix 3
Mandatory
Act
on flushing (purging) pipelines
_____________________ "_____" ____________ 19____
Commission consisting of:
representative of the construction and installation organization ____________________
________________________________________________________________________,
(last name, first name, patronymic, position)
representative of the technical supervision of the customer _______________________
________________________________________________________________________,
(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) is presented for inspection and acceptance
pipelines in the section from the chamber (picket, mine) N__________ to the chamber
(picket, mines) N______ routes __________________________________________
_________________________________________________________________________
(pipeline name)
length ___________ m.
Flushing (purging) was carried out by _____________________________________________
________________________________________________________________________.
(medium name, pressure, flow rate)
2. The work was carried out according to the design and estimate documentation _______________
_________________________________________________________________________
________________________________________________________________________.
(name of design organization, drawing numbers and date
drafting)
Commission decision
The works were performed in accordance with the design estimates, standards, building codes and regulations and meet the requirements for their acceptance.
Representative of the construction and installation organization _____________________
(signature)
Representative of the technical supervision of the customer _____________________
(signature)
Representative of the operating organization _____________________
The calculation of the pre-stretching of the expansion joint during installation is necessary for the maximum use of the compensating capacity of the bellows expansion joint for its intended purpose.
Compensating capacity of the compensator
First, let's define what a compensating ability is. As a rule, the compensating capacity is expressed in negative (-) and positive (+) values in its marking. For example, KSO 200-16-80, where 80 is the value of the maximum compensating ability. It means that the KSO compensator has k.s. 80mm (i.e. +/-40) +40mm in tension and -40mm in compression.
The maximum values of expansion (narrowing) of pipelines depend on the largest and the smallest values temperature working environment.
Here is a way to install a bellows expansion joint in a cold state, determining the installation length of the bellows expansion joint, in order to use its compensating ability to the maximum:
|
∆.(E set - T min) |
|||||||||
|
T max - T min |
Determination of the total length of the stretched expansion joint:
L=L 0 +H [mm], where:
Δ
- total expansion of the pipeline [mm]
L0- free length of compensator [mm]
L- installation length of the compensator (length of the expanded compensator) [mm]
T max- maximum working temperature[°C]
T min- minimum operating temperature [°C]
T mouth- mounting temperature [°C]
The axial expansion joint must be mounted in a cold state, the direction of movement is installed in this cold state. The amount of pre-stretch depends on the set temperature.
The minimum operating temperature of the pipeline is 0 o C, and the maximum is 100 o C. Thus, the difference is 100 o C. Let's take the length of the heating main 90 m. Calculating the maximum elongation of pipes, we get ∆L=100mm, i.e. a suitable compensator would be a CSR with a compensating capacity of +/-50mm.
Now let's determine the nature of the compensator operation at an installation temperature of 20 ° C.:
- at 0 o C CSR is stretched by 50mm;
- at 100 o C CSR is compressed by 50 mm;
- at 20 ° C, the CSR is stretched by 30 mm;
- at 50 ° C, no forces act on the CSR.
Therefore, if you pre-stretch the KSO compensator with a compensating capacity of +/-50 mm at an installation temperature of 20 ° C, then it will show maximum efficiency on a pipeline section 90 m long. If the temperature of the working medium rises to 50 ° C, the compensator will assume an unstressed state. When the temperature of the pipeline reaches 100 ° C, the compensator bellows will be stretched by 50 mm (maximum operating condition).
Rules for the installation and installation of compensators.
1. Bellows, lens and gland expansion joints should be mounted assembled.
2. Axial bellows, lens and gland expansion joints should be installed coaxially with pipelines.
Permissible deviations from the design position of the connecting pipes of expansion joints during their installation and welding should not exceed those specified in the technical specifications for the manufacture and supply of expansion joints.
3. When installing lens, corrugated and gland expansion joints, as well as fittings, the direction of the arrow on their body must coincide with the direction of movement of the substance in the pipeline.
4. When installing bellows and lens compensators, torsional loads relative to the longitudinal axis and sagging under the action of their own weight and the weight of adjacent pipelines should be excluded, and the flexible element should be protected from mechanical damage and sparks during welding.
5. The installation length of bellows, lens and gland expansion joints must be taken from the working drawings, taking into account the correction for the outdoor temperature during installation.
6. To compensate for temperature deformations of pipelines during installation, U-shaped, bellows, lens and gland expansion joints must be installed with tension (compression) by the value specified in the project. If the air temperature at the time of installation differs from that adopted in the project, then the expansion (compression) value of the compensator should be increased (if the project specifies extension) or reduced (if compression is specified) by the value (mm):
v=aL(t p +t m)
a - temperature coefficient of linear expansion of the pipeline metal, ° С -1, taken for carbon and low alloy steels 0.012 and high alloy steels - 0.017;
L is the estimated length of the pipeline section, m;
t p - air temperature adopted in the project at the time of installation, ° С;
t m - actual air temperature at the time of installation, ° С.
7. When installing stuffing box compensators, free movement of moving parts and safety of the packing must be ensured.
8. Installation of single-section axial bellows, lens, stuffing box and U-shaped compensators with tensile devices is carried out in the following sequence (Fig. 1, a):
Expansion of compensators to the installation length should be carried out using the devices provided for by the design of the compensator or tensioning mounting devices.
Damn.1. Sequence of operations (1-5) when installing compensators:
A - U-shaped, axial bellows single-section, lens and gland with a device for stretching;
b - the same without a device for stretching;
c - U-shaped compensator for group laying.
a) one side of the compensator is welded or flanged to the pipeline;
b) a section of the pipeline with an attached compensator is installed in guides and sliding supports and fixed in a fixed support.
Note.
Depending on the installation conditions (for example, for U-shaped compensators), the pipeline can first be installed in guides and sliding supports and fixed in a fixed support, and then connected to this section of the compensator;
c) with the help of spacers, the compensator is subjected to tension by the design value. It is allowed to pre-stretch the compensator before it is connected to the pipeline;
d) the section of the pipeline on the other side, lying freely in the guides and sliding supports, is pulled up to the free joint of the compensator and joined to it by welding or on the flange;
e) the connected section of the pipeline is fixed in another fixed support;
f) the device for pre-stretching is removed from the compensator.
11. The installation of axial bellows expansion joints without a stretching device is carried out in the following sequence (see drawing 15, b):
a) a section of the pipeline on one side of the compensator is installed in guides and sliding supports and fixed in a fixed support;
b) the pipeline section on the other side of the compensator is installed so that the distance between the ends of the pipeline sections is equal to the installation length of the compensator, and is fixed in another fixed support. The installation length of the compensator must be equal to its construction length (the compensator is unloaded) plus the preload (compression)
c) the compensator is connected to one of the sections of the pipeline;
d) with the help of mounting devices, the compensator is stretched and attached to another section of the pipeline;
e) Mounting devices are removed.
12. With a group arrangement of U-shaped expansion joints (see Fig. 15, c) parallel pipelines, expansion joints should be stretched by stretching the pipeline in a cold state. In this case, stretching of the U-shaped compensator should be performed after the installation of the pipeline is completed, quality control of welded joints (except for the closing one used for tension) and fixing the pipeline in fixed supports.
- The welded joint, at which the expansion joint should be stretched, is indicated in the project. If there is no such indication, then in order to avoid a decrease in the compensating ability of the compensator and its distortion, a joint located at a distance of at least 20 days from the axis of the compensator should be used.
- Removable or welded clamps with mounting elongated studs and nuts are used as a tightening device for tensioning.
- With a group arrangement of U-shaped compensators, the installation sequence is as follows:
a) sections of the pipeline and the U-shaped compensator are installed on supports. A wooden spacer with a width equal to the stretching value is inserted into the gap left for joint tension;
b) the expansion joint is connected by welding on both sides to the corresponding sections of the pipeline;
c) the pipeline section is fixed in fixed supports;
d) the spacer is removed, the compensator is pretensioned, the joint is connected by welding;
e) Mounting aids are removed.
- For pipelines of heating networks, in accordance with the requirements of SNiP 3.05.03-85, expansion joint tension should be performed simultaneously from both sides at joints located at a distance of at least 20 days and not more than 40 days from the axis of symmetry of the compensator
- An act must be drawn up on the expansion (compression) of the compensator in the form of Appendix 6 of SNiP 3.01.01-85.
- U-shaped compensators should be installed in compliance with the general slope of the pipeline specified in the project.
- Lens, corrugated and stuffing box expansion joints are recommended to be installed in units and blocks of pipelines during their assembly, while applying additional stiffness to protect the expansion joints from deformation and damage during transportation, lifting and installation. At the end of the installation, the temporarily installed stiffnesses are removed.
- When installing vertical sections of pipelines, it is necessary to exclude the possibility of compression of compensators under the action of mass vertical section pipeline. To do this, parallel to the compensators on the pipelines, three brackets should be welded, which are cut off at the end of the installation.
- To determine the correct position of the fittings installed on the pipeline, it is necessary to be guided by the instructions of the catalogs, specifications and working drawings. The position of the axes of the handwheels is determined by the project.
- Pipe fittings must be installed in a closed state. Flanged and welded fittings must be made without straining the pipeline. During welding of welded fittings, its shutter should be opened to failure in order to prevent it from jamming when the body is heated.
Compensation devices in heating networks they serve to eliminate (or significantly reduce) the forces arising from thermal elongation of pipes. As a result, the stresses in the pipe walls and the forces acting on the equipment and supporting 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 of the wall, 0 C; t m - installation temperature, 0 C.
To compensate for the elongation of pipes, special devices are used - compensators, and they also use the flexibility of pipes at bends in the heating network route (natural compensation).
According to the principle of operation, compensators are divided into axial and radial. Axial compensators are installed on straight sections of the heat pipeline, as they are designed to compensate for the forces arising only as a result of axial elongations. Radial expansion joints are installed on heating systems of any configuration, as 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 thermal networks, axial compensators of two types are used: stuffing box and lens. In stuffing box compensators (Fig. 29.3), temperature deformations of the pipes lead to the movement of the glass 1 inside the body 5, between which the gland packing 3 is placed for sealing. The packing is clamped between the thrust ring 4 and the bottom box 2 with the help of bolts 6.
Figure 19.3 Gland expansion joints
a - unilateral; b - double-sided: 1 - glass, 2 - grundbuksa, 3 - gland packing,
4 - thrust ring, 5 - housing, 6 - tightening bolts
As a gland packing, an asbestos graphic 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 compensators are placed in the chambers.
Connection of compensators with pipelines is carried out by welding. During installation, it is necessary to leave a gap between the sleeve shoulder and the body thrust ring, which excludes the possibility of tensile forces in the pipelines in case the temperature drops below the installation temperature, and also carefully align the center line to avoid distortions and jamming of the glass in the body.
Gland expansion joints are made one-sided and two-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 pipe sections, the elongations 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 for underground installation. In this case, they are installed at d y \u003d 100 mm or more, with above-ground laying - at d y \u003d 300 mm or more.
In lens compensators (Fig. 19.4), during temperature elongation of pipes, special elastic lenses (waves) are compressed. This ensures complete tightness in the system and does not require maintenance of compensators.
Lenses are made from sheet steel or stamped half-lenses with a wall thickness of 2.5 to 4 mm by gas welding. To reduce hydraulic resistance inside the compensator, a smooth pipe (jacket) is inserted along the waves.
Lens compensators have a relatively small compensating ability and a large axial reaction. In this regard, to compensate for temperature deformations of pipelines of heating networks, big number waves or produce a preliminary stretch. They are usually used up to pressures of about 0.5 MPa, since at high pressures waves can swell, and an increase in the rigidity of the waves by increasing the wall thickness leads to a decrease in their compensating ability and an increase in the axial reaction.
Ryas. 19.4. Lens three-wave compensator
natural compensation temperature deformation occurs as a result of pipeline bending. Bent sections (turns) increase the flexibility of the pipeline and increase its compensating capacity.
With natural compensation at the turns of the route, temperature deformations of pipelines lead to transverse displacements of the sections (Fig. 19.5). The displacement value depends on the location of the fixed supports: the longer the section, the greater its elongation. This requires an increase in the width of the channels and complicates the operation of movable supports, and also makes it impossible to use modern channelless laying at the turns of the route. The maximum bending stresses occur 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 pipeline
A- with the same length of the shoulders; b- different shoulder lengths
TO radial expansion joints used in heating networks are flexible And wavy hinge type. In flexible compensators, temperature deformations of pipelines are eliminated by means of bending and torsion of specially bent or welded sections of pipes different configuration: U- and S-shaped, lyre-shaped, omega-shaped, etc. The most widely used in practice due to ease of manufacture are U-shaped compensators (Fig. 19.6, a). Their compensating capacity is determined by the sum of deformations along the axis of each of the sections of pipelines ∆ l= ∆l/2+∆l/2. In this case, the maximum bending stresses occur in the segment most remote from the axis of the pipeline - the back of the compensator. The latter, bending, is displaced by the value 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 pre-stretching; b- pre-stretched
To increase the compensating ability of the compensator or reduce the amount of displacement, it is installed with preliminary (mounting) stretching (Fig. 19.6, b). In this case, the back of the compensator in the non-working state is bent inward and experiences bending stresses. When the pipes are elongated, the compensator first comes to an unstressed state, and then the back bends outward and bending stresses of the opposite sign appear in it. If in the extreme positions, i.e., with preliminary stretching and in working condition, the maximum allowable stresses, then the compensating ability of the compensator is doubled compared to 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 move outward and, therefore, the dimensions of the compensatory niche will decrease. The work of flexible compensators of other configurations occurs in approximately the same way.
pendants
Suspensions of pipelines (Fig. 19.7) are carried out using rods 3, connected directly to pipes 4 (Fig. 19.7, A) or with traverse 7 , to which on collars 6 a 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. Guide cups 9 spring blocks, welded to the support plates 10, allow you to eliminate the transverse deflection of the springs. Suspension tension is provided by nuts.
Rice. 19.7 Pendants:
A- traction; b- collar; V- spring; 1 - support beam; 2, 5 - hinges; 3 - traction;
4 - pipe; 6 - collar; 7 - traverse; 8 – spring suspension; 9 - glasses; 10 – plates
3.4 Ways to isolate heat networks.
Mastic isolation
Mastic insulation is used only when repairing heating networks laid either indoors or in through channels.
Mastic insulation is applied in layers of 10-15 mm on a hot pipeline as the previous layers dry. Mastic insulation cannot be done by industrial methods. Therefore, the specified insulating structure for new pipelines is not applicable.
Sovelite, asbestos tripel and vulcanite are used for mastic insulation. The thickness of the thermal insulation layer is determined on the basis of technical and economic calculations or according to current standards.
The temperature on the surface of the insulating structure of pipelines in the passage channels and chambers should not exceed 60 ° C.
The durability of the heat-insulating structure depends on the mode of operation of the heat pipelines.
block isolation
Prefabricated block insulation from preformed products (bricks, blocks, peat slabs, etc.) is arranged on hot and cold surfaces. Products with dressing of seams in rows are laid on asbozurite mastic grease, the thermal conductivity coefficient of which is close to that of the insulation itself; lubrication has minimal shrinkage and good mechanical strength. Peat products (peat slabs) and corks are laid on bitumen or iditol glue.
to flat and curved surfaces heat-insulating products are fixed with steel studs, pre-welded 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.
During installation, the products are adjusted to each other, mark and drill holes for the studs. Mounted elements are fixed with studs or wire twists.
With multilayer insulation, each subsequent layer is laid after leveling and fixing the previous one with overlapping of longitudinal and transverse seams. The last layer, fixed with a frame or a metal mesh, is leveled with mastic under the rail and after that plaster is applied with a thickness of 10 mm. Pasting and painting is carried out 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 - mnogosovnost and complexity of installation.
backfill insulation
On the horizontal and vertical surfaces of building structures, backfill thermal insulation is used.
When installing thermal insulation on horizontal surfaces (non-attic roofs, ceilings above the basement), the insulating material is mainly expanded clay or perlite.
On vertical surfaces, backfill insulation is made of glass or mineral wool, diatomaceous earth, perlite sand, etc. To do this, the parallel insulated surface is fenced with bricks, blocks or meshes, and insulating material is poured (or stuffed) into the resulting space. With mesh fencing, the mesh is attached to studs pre-installed in a checkerboard pattern with a height corresponding to a given insulation thickness (with an allowance of 30 ... 35 mm). A metal woven mesh with a cell of 15x15 mm is pulled over them. Loose material is poured into the resulting space in layers from the bottom up with light tamping.
After backfilling, the entire surface of the grid is covered with a protective layer of plaster.
Backfill thermal insulation is quite effective and easy to use. However, it is not resistant to vibration and is characterized by low mechanical strength.
Cast insulation
As insulating material mainly foam concrete is used, which is prepared by mixing cement mortar with foam mass in a special mixer. The heat-insulating layer is laid in two ways: by the usual methods of concreting the space between the formwork and the insulated surface or shotcrete.
With the first method 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 matting to ensure normal conditions for foam concrete hardening.
shotcrete method cast insulation is applied over mesh reinforcement of 3-5 mm wire with cells of 100-100 mm. The applied shotcrete layer adheres tightly to the insulated surface, does not have cracks, pits and other defects. Gunning 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. Disadvantages of cast insulation - long duration devices and the inability to work at low temperatures.
1.1. Products are allowed to be used in construction areas with a design outdoor temperature for designing heating systems not lower than minus 40°С. The seismicity of construction areas is not more than nine points on the Richter scale.
1.2. Products are allowed to be used when the content of chlorides in the network water is not more than 250 mg/kg.
1.3. Products must be installed on straight sections of pipelines, limited by fixed supports. Only one product is allowed between fixed supports.
A deviation from straightness in plan and profile is allowed with the obligatory installation of guide supports in the same places at least two in front of each compensating device.
1.4. Way of accession to the pipeline - welding.
1.5. For any method of laying pipelines, except for underground channelless, the installation of compensating devices should be provided, as a rule, at one of the fixed supports.
1.6. On channelless underground heating networks, the product should be placed in the middle of the pipeline section, limited by fixed supports.
1.7. Before and after the compensating device, it is necessary to install guide supports, which exclude the movement of pipelines in the radial direction.
When channelless laying of the pipeline, the installation of guide supports is not required.
Examples of layouts for the bellows compensating device, guides and fixed supports are shown in the figure:
6.8. On sections of pipelines with bellows compensating devices, the use of suspension supports is not allowed.
6.9. When choosing fixed supports, the following factors should be considered:
Spacer force of the compensator;
Compensator stiffness force;
Friction in guides and sliding bearings;
The magnitude of the centrifugal force that occurs when the pipeline is bent.
The calculation of loads on the end and intermediate fixed supports for various installation methods of bellows compensating devices is carried out at the stage of designing a heat network and is given in special literature.
6.10. The maximum distance between the fixed supports of the pipeline is determined by the formula:
where 0.9 is the safety factor, taking into account calculation inaccuracies and errors
installation features;
Compensating capacity of the compensator, mm
a - average coefficient of linear expansion of pipe steel at
heating from 0°С to t°С, mm/m°С;
t - design temperature of network water in the supply pipeline, °С;
t RO - calculated outdoor temperature for system design
heating, taken equal to the average air temperature of the most
colder than the five-day period according to the chapter SNiP "Construction climatology
and geophysics”, °C.
1.8. The products do not require maintenance during operation and belong to the class of non-repairable products; they do not require the construction of special chambers, and when laying on the ground - maintenance platforms.
Installation instructions.
2.1. Installation of products is carried out in accordance with the design of the pipeline, executed by the design organization.
2.2. Before installation, the products must be checked for compliance with their technical characteristics of the heating network project, as well as for the absence of mechanical damage.
2.3. When moving compensating devices during the installation period, measures must be taken to protect the product from shocks, shocks and exclude pollution or flooding. groundwater its internal cavity.
2.4. When performing welding work, the ends of the insulation of the compensating device should be protected with detachable tin screens 0.8 ... 1 mm thick to prevent its ignition.
Installation of products is allowed to be carried out at an air temperature of at least minus 30 ° C.
2.5. Before welding the product to the pipeline, the deviations of the connections between the product and the pipeline are checked, which should not exceed following values: nozzle alignment tolerance - 2 mm;
the tolerance of parallelism of the ends of the connecting pipes and connected pipes is 3 mm.
The maximum welding gap between the branch pipe and the pipeline is 2 mm.
2.6. The product should be installed on heat pipelines so that the direction of the arrow (if any) on the body of the compensating device coincides with the direction of movement of the coolant.
2.7. Products are mounted on the pipeline with preliminary stretching.
The length of the compensator during installation Lmount., mm is determined by the formula:
L builds.- building length of the compensator in the state of delivery, mm;
Compensating capacity of the compensator, mm;
A- coefficient of linear expansion of pipe steel,
removable 0.012 mm/m °С;
t hire. - the lowest air temperature during operation, °С;
L- the length of the compensator section between the fixed supports,
on which the compensator is mounted, m.
The mounting length of the compensating device is set by the installer.
The sections of the pipeline before and after the compensating device must be mounted and fixed in fixed supports so that the distance between the ends of the pipes at the installation site of the product corresponds to the installation length L mont. at ambient temperature at the moment of fixing the pipeline in the second fixed support; the ambient air temperature and the distance between the ends of the fixed pipes must be recorded in an act;
The compensating device is welded to one of the sections of the pipeline;
A universal mounting device is installed on the free connecting pipe of the product and the free end of the pipeline, with the help of which the compensator of the product is stretched to the junction with the pipeline, and the joint is welded;
Remove the mounting fixture from the product.
When expanding the compensator, it is necessary to ensure the same movement of the connecting pipes relative to the ends of the product.
If it is impossible to install the product in the middle of the straight section of the heat pipeline between the fixed supports, it is allowed to install it anywhere in the straight section of the heat pipeline. To do this, when the compensator is stretched, it is necessary to ensure the movement of the connecting pipes relative to the ends of the compensating device by inversely proportional lengths of the sections of the heat pipe between the product and the fixed supports.
2.9. Connection of conductors-indicators of the product with a common signal system must be carried out after completion of welding work before insulating the joints of the connecting pipes with the heat pipe. Indicator conductors should not touch the metal of the pipes anywhere.
| bellows compensating device | |
| end fixed support | |
