Testing of heating networks. Before putting them into operation, constructed pipelines of heating networks are tested for strength and density by water pressure (hydraulic test) or air pressure (pneumatic test).
The test checks the tightness and density of welds, pipes, flange connections, fittings and linear equipment (stuffing box expansion joints, mud traps, etc.). The heating pipe is tested twice: preliminary and final.
During preliminary testing check the strength and tightness of welds and pipeline walls before installing fittings and linear equipment. If the heat pipeline is made of pipes with a longitudinal or spiral seam, then the test is carried out before installing thermal insulation on the pipeline.
If the heat pipe is made of seamless seamless pipes, then during testing it can be isolated, with only the welded joints remaining open. The heat pipe must not be closed before the preliminary test. building structures and fall asleep.
The length of the section during preliminary testing is determined depending on local conditions, the accepted organization of work, the availability of testing means (hydraulic presses, piston pumps), construction time in individual sections, the power of the water source for filling the heat pipeline, the availability of filling means, terrain, etc.
During the final test, the construction of the heat pipeline must be completely finished according to the project. During testing, the joints of individual sections are checked (if the heat pipeline was previously tested in parts), welds, fittings and linear equipment, the density and strength of flange connections, housings of linear equipment, etc.
Hydraulic testing is performed in the following sequence: install the test installation; clean the heating pipe from the inside from scale, soil and other objects; install plugs, pressure gauges and taps; attach water supply and press; fill the pipeline with water until set pressure; inspect the pipeline and mark defective areas; eliminate detected defects; retest; disconnect the water supply and drain the water from the heating pipeline; remove plugs and pressure gauges.
To displace air from the pipes, the water supply is brought to the lowest point of the pipeline, all air valves are opened, and the drain valves are closed. There should be people on duty near the air valves who shut them off when water appears.
Spring pressure gauges used during testing must be checked and sealed by Gosstandart organizations; plugs must match technical requirements. It is not permitted to use valves to disconnect the test section from existing networks.
Test pressure is maintained for 5 minutes. The pressure gauge is checked to see if there is a drop in pressure, after which the pressure is reduced to working pressure. At operating pressure, the pipeline is inspected and the welds are tapped with a hammer with a handle no longer than 0.5 m. The weight of the hammer should not exceed 1.5 kg. The blows are applied not to the seam, but to the pipe (no closer than 100 mm from the seam).
The test results are considered satisfactory if there is no pressure drop on the pressure gauge and no leaks or sweating of the joints are detected.
At the final hydraulic test With the fittings and equipment installed, the test pressure is maintained for 15 minutes. Then the welded and flanged connections, fittings and linear equipment are inspected and then the pressure is reduced to working pressure. If the pressure drop within 2 hours does not exceed 10%, then the heat pipe is considered to have passed the test.
IN winter time hydraulic tests Heat pipelines should be carried out in short sections, and for testing it is necessary to use water heated to a temperature of 60 ° C. In addition, lowering devices are installed to ensure the drainage of water from the pipes within 1 hour.
Pneumatic testing of heat pipes carried out only in cases where a hydraulic test cannot be used. The length of the tested section is taken to be no more than 1000 m.
Pneumatic testing is carried out in the following sequence: clean and purge the pipeline; install plugs and pressure gauges; connect a compressor to the pipeline; fill the pipeline with air to a given pressure; prepare a soap solution; inspect the pipeline, lubricating the joints with soapy water, and marking defective areas; eliminate detected defects; the pipeline is tested again; disconnect the compressor and bleed air from the pipeline; remove plugs and pressure gauges.
Leaks in a pipeline are determined in several ways: by the sound of leaking air; by bubbles that form at the leak site when joints and other welded joints are covered with soapy water; by smell, if ammonia, ethyl and other gases with a pungent odor are added to the air supplied from the compressor to the pipeline. The most common method is using a soap solution, which includes water - 1 liter and laundry soap - 100 g. If during testing the outside air temperature is below 0 ° C, then the water in the soap solution is partially (up to 60%) replaced with alcohol or other non-freezing liquid , dissolving soap.
During preliminary testing, the pipeline kept under test pressure for 30 minutes, then the pressure is reduced to 3 kgf/cm2 and the pipeline is inspected. If the inspection does not reveal leaks, defects in welds, violation of the integrity of the pipeline, as well as no shift or deformation of structures fixed supports, then the pipeline is considered to have passed the preliminary pneumatic test.
Defects identified during inspection of the pipeline are eliminated after the excess pressure in it drops to zero.
During the final pneumatic test, the pressure in the pipeline is brought to the test pressure and maintained for 30 minutes. If the integrity of the pipeline is not compromised, then the pressure is reduced to 0.5 kgf/cm2 and the pipeline is maintained at this pressure for 24 hours. Then the pressure is set to 3000 mm of water. Art. and note the test start time and barometric pressure.
Hydropneumatic flushing is more effective than hydraulic flushing. In this case, air is supplied to the pipeline, the cross-section of which is not completely filled with water, by a compressor. Turbulent water movement is created in the pipes, which promotes good flushing.
The pipelines are washed until the water is completely clear.
Pipeline flushing. There may remain in the pipeline after installation various kinds contaminants: scale, stones, soil, etc. To remove them, the pipeline should be flushed with water (hydraulic flushing) or a mixture of water and air (hydropneumatic flushing).
The heating pipe is usually washed twice: the first wash is rough, the second is finishing.
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Hydraulic tests are carried out in accordance with SNiP. After their completion, a report is drawn up indicating the operability of the system.
They are performed at different stages of communications operation. Test parameters are calculated for each system separately, depending on its type.
Contents of the article
Why and when to carry out hydraulic tests?
Hydraulic testing is a type of non-destructive testing that is carried out to check the strength and tightness of pipeline systems. All operating equipment is subjected to it at different stages of operation.
In general, three cases can be distinguished in which tests must be carried out without fail, regardless of the purpose of the pipeline:
- after finishing production process for the production of equipment or parts of the pipeline system;
- after completion of pipeline installation work;
- during operation of the equipment.
Hydraulic testing is an important procedure that confirms or refutes the reliability of the operating pressure system. This is necessary to prevent accidents on highways and preserve the health of citizens.
The procedure for hydraulic testing of pipelines is being carried out in extreme conditions. The pressure under which it passes is called the test pressure. It exceeds the usual operating pressure by 1.25-1.5 times.
Features of hydraulic tests
Test pressure is supplied to the pipeline system smoothly and slowly, so as not to provoke water hammer and accidents. The pressure value is determined not by eye, but by a special formula, but in practice, as a rule, it is 25% more than the working pressure.
The water supply force is controlled on pressure gauges and measurement channels. According to SNiP, jumps in indicators are allowed, since it is possible to quickly measure the temperature of the liquid in a pipeline vessel. When filling it, be sure to monitor the accumulation of gas in different parts of the system.
This possibility should be excluded at the initial stage.
After filling the pipeline, the so-called holding time begins - a period during which the equipment under test is under increased pressure. It is important to ensure that it is at the same level during exposure. After its completion, the pressure is minimized to operating condition.
No one should be near the pipeline while the test is being carried out.
Personnel operating it must wait in a safe place, as testing the system's functionality can be explosive. After the process is completed, the results obtained are assessed in accordance with SNiP. The pipeline is inspected for metal explosions and deformations.
Hydraulic test parameters
When checking the quality of a pipeline, it is necessary to determine the indicators of the following work parameters:
- Pressure.
- Temperatures.
- Holding time.
The lower limit of the test pressure is calculated using the following formula: Ph = KhP. The upper limit should not exceed the sum of the total membrane and bending stresses, which will reach 1.7 [δ]Th. The formula is deciphered as follows:
- P – design pressure, the parameters of which are provided by the manufacturer, or operating pressure if tests are carried out after installation;
- [δ]Th – rated voltage that is allowed at test temperature Th;
- [δ]T – permissible stress at design temperature T;
- Kh is a conditional coefficient that takes different values for different objects. When checking pipelines, it is equal to 1.25.
The water temperature should not fall below 5˚C and not rise above 40˚C. The only exceptions are those cases when the temperature of the hydraulic component is indicated in the technical conditions of the object under study. Be that as it may, the air temperature during the test should not fall below the same 5˚C.
The holding time must be specified in the design documentation for the facility. It should not be less than 5 minutes. If exact parameters are not provided, then the holding time is calculated based on the thickness of the pipeline walls. For example, with a thickness of up to 50 mm, a pressure test lasts at least 10 minutes, with a thickness over 100 mm - at least 30 minutes.
Testing of fire hydrants and water supply lines
A hydrant is equipment responsible for quickly eliminating fire ignitions, so it must always be in working order. The main task of fire hydrants is to provide the optimal amount of water to fight a fire at its initial stage.
Pressure pipelines are checked in accordance with SNiP V III-3-81.
Pipes made of cast iron and asbestos are tested with a pipeline length of no more than 1 km at a time. Polyethylene water supply lines are checked in sections of 0.5 km. All other water supply systems are checked in sections of no more than 1 km. The holding time for metal water supply pipes must be at least 10 m, for polyethylene pipes - at least 30 m.
Heating system testing
Heating networks are checked immediately after their installation is completed. Heating systems are filled with water through the return pipeline, that is, from the bottom up.
With this method, liquid and air flow in the same direction, which, according to the laws of physics, promotes the removal of air masses from the system. Discharge occurs in one way: through outlet devices, a tank or heating system plungers.
If heating networks are filled too quickly, air pockets may occur due to the risers filling with water faster than the heating devices of the heating systems. pass under the lower value of the working pressure of 100 kiloPascal and the test pressure - 300 kiloPascal.
Heating networks are checked only when the boiler and expansion tank are disconnected.
Heating systems are not monitored in winter. If they have worked without breakdowns for up to about three months, then the acceptance of heating networks into operation can be carried out without hydraulic tests. When checking closed systems heating, control work must be carried out before the furrows are closed. If you plan to insulate heating networks, then do so before installing it.
According to SNiP, after testing heating systems, they are washed, and a coupling with a cross-section of 60 to 80 mm2 is mounted at their lowest point. Water drains through it. Flushing of heating networks carried out with cold water several times until it becomes transparent. Approval of heating systems occurs if within 5 minutes the test pressure in the pipeline does not change by more than 20 kiloPascal.
Hydraulic testing of heating and water supply systems (video)
Hydraulic testing of heating networks and water supply systems
After completion of hydraulic tests of heating systems in accordance with SNiP, a hydraulic test report of heating networks and water supply systems is drawn up, indicating the compliance of the pipeline parameters.
According to SNiP, its form contains the following information:
- the title of the position of the head of the enterprise providing maintenance of heating networks;
- his signature and initials, as well as the date of inspection;
- information about the chairman of the commission, as well as its members;
- information on the parameters of heating networks: length, name, etc.;
- conclusions about the control, conclusion of the commission.
Adjustment of the characteristics of heating lines is carried out by SNiP 3.05.03-85. According to the specified SNiP it the rules apply to all highways, which transport water at temperatures up to 220˚C and steam at temperatures up to 440˚C.
To document the completion of hydraulic tests of the water supply system, a report is drawn up for the external water supply system in accordance with SNiP 3.05.01-85. According to SNiP, the act contains the following information:
- name of the system;
- name of the technical supervision organization;
- data on the test pressure and test time;
- pressure drop data;
- presence or absence of signs of damage to the pipeline;
- date of inspection;
- commission withdrawal.
The report is certified by a representative of the supervisory organization.
Based on the regulatory documentation given below, a pressure testing certificate has been developed, which is one of the main documents when handing over work to the Customer at the site.
Heating networks must undergo annual hydraulic tests for strength and density (pressure testing) to identify defects after the end of the heating season and repair work. Pressure testing of pipelines accessible for inspection during operation may be performed once after completion of installation.
Hydraulic pressure testing is carried out with a test pressure of 1.25 working pressure, but not less than 1.6 MPa (16 kgf/cm2). The pipelines are maintained under test pressure for at least 5 minutes, after which the pressure is reduced to operating pressure. At operating pressure, a thorough inspection of pipelines is carried out along their entire length. The results of pressure testing are considered satisfactory if during its implementation there is no drop in pressure and no signs of rupture, leakage or fogging are found in valve bodies and seals, in flange connections, etc.
Before the start of the heating season, after completion of repairs, the heating and hot water supply systems must be subjected to hydraulic pressure testing for strength and density:
Elevator units, heaters and water heaters for heating and hot water supply - pressure 1.25 working, but not lower than 1 MPa (10 kgf/cm2);
Heating systems with cast iron heating devices– pressure 1.25 working, but not more than 0.6 MPa (6 kgf/cm2);
Panel and convector heating systems - pressure 1 MPa (10 kgf/cm2);
Hot water supply systems - pressure equal to the working pressure in the system plus 0.5 MPa (5 kgf/cm2), but not more than 1 MPa (10 kgf/cm2).
The hydraulic test must be carried out at positive outside temperatures. When the outside air temperature is below zero, checking the density is possible only in exceptional cases.
Systems are considered to have passed the test if, during testing:
No “sweating” of welds or leaks from heating devices, pipelines, fittings and other equipment were detected;
When testing water and steam heat consumption systems for 5 minutes. the pressure drop did not exceed 0.02 MPa (0.2 kgf/cm2);
When testing surface heating systems, the pressure drops within 15 minutes. did not exceed 0.01 MPa (0.1 kgf/cm2);
When testing hot water supply systems, the pressure drops within 10 minutes. did not exceed 0.05 MPa (0.5 kgf/cm2).
The results of the inspection are documented in a test certificate. If the results of pressure testing do not meet the specified conditions, it is necessary to identify and eliminate leaks, and then recheck the tightness of the system. During hydraulic testing, spring pressure gauges must be used with an accuracy class of at least 1.5, with a body diameter of at least 160 mm, a scale for a nominal pressure of about 4/3 of the measured pressure, a division value of 0.01 MPa (0.1 kgf/cm2), verified and sealed by the state verifier.
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Regulatory documentation, rules and SNiP for pressure testing of the heating system
Brief excerpts from regulatory documentation, rules and SNiP for heating pressure testing .
Analyzing the statistics of the questions you ask and understanding that many questions regarding pressure testing of the heating system for the majority of our audience remain incomprehensible to you, we decided to make a selection from the necessary points and Rules for pressure testing, approved by the Ministry of Fuel and Energy of the Russian Federation and SNiP.
All SNiPs and rules contain more than 100 pages of information, which are sometimes difficult to understand, so in order to make the task easier for you, so that you can look at and, if necessary, refer to the desired paragraph of a specific regulatory document, we have processed the applicable regulations and briefly posted on the website. Explanations to the Rules and SNiP can be found in the article: “Norms and rules for performing pressure testing of a heating system”
1. Rules for the technical operation of thermal power plants.
Developed and approved by the Ministry of Fuel and Energy Russian Federation. No. 115 dated March 24, 2003
clause 9.2 Heating, ventilation, air conditioning, hot water supply systems.
Hydraulic tests of equipment at heating points and heating systems should be carried out separately.
Heating points and heating systems must be tested at least once a year, with a test pressure equal to 1.25 working pressure at the heating network inlet, but not less than 0.2 MPa (2 kgf/cm2).9.2.11 To protect against internal corrosion, heating systems must be constantly filled with deaerated, chemically purified water.
9.2.12 Tests for the strength and density of system equipment are carried out annually after the end of the heating season to identify defects, as well as before the start heating season after the renovation is completed.
clause 9.2.13 tests for strength and density of water heating systems are carried out at test pressure, but not lower than:
— Elevator unit, water heaters for heating systems, hot water supply - 1MPa (10kgf/cm2 or 10Ati.)
- Heating systems with cast iron heating devices, stamped steel radiators - should be taken as 0.6 MPa (6 kgf/cm2 or 6Ati)
- panel and convector heating systems - 1.0 MPa (10 kgf/cm 2 or 10 Ati).
— For heaters of heating and ventilation systems - depending on the operating pressure set technical specifications manufacturer's plant.
The minimum test pressure during hydraulic testing should be 1.25 working pressure, but not less than 0.2 MPa (2 kgf/cm2 or 2Ati).
Pipeline tests are carried out in the following order and must be carried out in compliance with the following basic requirements:
"__7__" __JUNE________2000for conducting hydraulic tests for the strength and density of heating networks,
heating points and heat consumption systems,
on the balance sheet of consumers
Developer: thermal inspection
I. ^ GENERAL PART.
- In accordance with the “Rules for the operation of heat-consuming installations and heating networks of consumers” and “Safety rules for the operation of heat-consuming installations and heating networks of consumers”, annual hydraulic tests for strength and density must be carried out: heating networks, elevator units, heaters, heating and hot water supply systems that are on the balance of consumers.
- Individual tests of hot water supply, heating, ventilation systems are carried out in accordance with the requirements of SNiP 3.05.01-85 "Internal sanitary systems", heating networks - according to the instructions of SNiP 3.05.03-85 "Heat networks", technological heat-consuming installations - in accordance with the requirements of SNiP 3.05.05-84 " Technological equipment and technological pipelines."
- Work on testing the heating network, its individual elements and structures and heat consuming systems (HWS) must be carried out:
- personnel of a specialized organization licensed by Gosenergonadzor to carry out such work, at the expense of the consumer, according to a special program agreed upon with the head of the thermal inspection "Khabarovskgosenergonadzor";
- specialized consumer personnel, according to a special program approved by the chief engineer of the enterprise and agreed with the head of the thermal inspection "Khabarovskgosenergonadzor".
1.4..The test program must contain:
1.4.1. The document on the basis of which pressure testing work is carried out: an approval order signed by the chief engineer of the enterprise on whose balance sheet the tested sections of the heat supply system are located.
1.4.2. Diagram of the tested sections of heating networks and thermal units, indicating pressure tapping locations.
1.4.3. A list of names of persons conducting the tests, indicating the responsible person from the enterprise-consumer of thermal energy.
1.4.4. Layout of the location of personnel participating in the tests and means of communication between them.
1.4.5. Methodology for conducting and processing test results.
1.5. When performing hydraulic pressure testing, use spring pressure gauges of an accuracy class of at least 1.5 with a body diameter of at least 160 mm, a scale for a nominal pressure of about 4/3 of the measured pressure and a division value of at least 0.1 at (0.1 kgf/cm 2) 0, 01 MPa.
Pressure gauges must be sealed by a state verifier. The use of pressure gauges with expired seals or stamps is not allowed.
1.6. Based on the test results, a technical report is compiled, approved by the head of the thermal inspection “Khabarovskgosenergonadzor”.
1.8. Legal and individuals Those who carry out hydraulic tests for the strength and density of heating networks, heating points and heat consumption systems that are on the balance of consumers, in their activities must be guided by the requirements of this Methodology.
2. Rules for crimping heating networks,
and heat consumption systems.
A. Testing of heating networks.
2.1. Preliminary hydraulic pressure testing of underground heating pipelines is carried out in sections after they are welded and laid on permanent supports before installing equipment on them and blocking channels or backfilling trenches.
Free access to pipelines must be provided along the entire length of the tested section.
Pressure testing is carried out in the following order:
a) the tested section of the pipeline is isolated from existing networks by installing blind flanges or plugs; the use of valves to disconnect the tested section from the operating network is not allowed;
b) the supply and return pipelines, after filling with water and bleeding air, are placed under a test pressure equal to 1.25 working pressure, but not lower than 16 kgf/cm 2 and maintained under this pressure for the time necessary for a thorough inspection and tapping of the joints, but not less than 10 min. Tapping is done with a hammer with a rounded head weighing no more than 1.5 kg with a handle length of no more than 500 mm; blows must be delivered at a distance of at least 100 mm from weld.
The pressure at the lowest points should not exceed one and a half times the nominal pressure (Py) for which the pipes used to lay the network are designed.
The working pressure for supply and return pipelines of water heating networks is considered to be highest pressure water, taking into account the operation of pumping substations on the route and the terrain, which may occur during operation or shutdown of network and booster pumps.
If available online automatic regulators pressure and protective equipment ( safety valves) the operating pressure is taken to be the highest pressure in the network at the upper limit of the settings of protective and control devices.
2.2. The valves must be tested before their installation on the pipeline at the excess hydraulic pressure established for this pipeline, but not less than 16 kgf/cm 2 for valves on the supply pipeline and 12 kgf/cm 2 on the return pipeline.
Tests are carried out in two positions of the sealing rings:
a) in the open position with the valve flange plugged - to check the tightness of the stuffing box devices;
b) in the closed position - to check the tightness of the rings grinding.
The valve is considered to have passed the test if there is no pressure drop within 5 minutes.
2.3. The final hydraulic pressure testing of the entire heating pipeline is carried out together with installed equipment(valves, compensators, drain and air valves, etc.) at an excess pressure of 1.25 working pressure, but not less than 16 kgf/cm. All sectional valves and valves on branches of the network under test must be open.
The duration of the final pressure test is determined by the time required to inspect the network, but must be at least 10 minutes.
2.4. The test results are considered satisfactory if during the test there is no pressure drop on the pressure gauge and no signs of rupture, leakage or sweating are found in welds, valve bodies and seals, flange connections, etc.
Note : Testing of pipeline sections accessible for inspection during operation (laid in through channels, collectors, as well as above-ground) can be carried out once after complete installation.
2.5. When the outside air temperature is below 1°C, the pipelines are filled with water heated to 50-60°C, and pressure testing is carried out after the water temperature has dropped to 40°C. If defects are discovered that require considerable time to be eliminated, the pipeline must be emptied immediately, and it should be checked whether water remains at the lowest points of the pipeline.
2.6. At low outside temperatures or in the absence of water at the test site, in agreement with the heating network enterprise (power plants, boiler houses), hydraulic pressure testing can be replaced by pneumatic pressure testing, and the value of the test pressure must be agreed with Gosgortekhnadzor.
^B. Testing of heating points, systems
2.7. Equipment of heating points and all underground pipelines of intra-block and intra-yard networks after central heating points, as well as pipelines and equipment of heat consumption systems are subjected to hydraulic pressure testing at an excess pressure of 1.25 working, but not lower than:
a) for elevator units, air heaters for heating and ventilation systems, water heaters for heating and hot water supply systems - not less than 1 MPa (10 kgf/cm2);
b) for water heating systems with cast iron heating devices - no more than 0.6 MPa (6 kgf/cm 2);
c) for panel and convector heating systems with a pressure of 1 MPa (10 kgf/cm2);
d) for hot water supply systems with a pressure equal to the working pressure in the system plus 0.5 MPa (0.5 kgf/cm2), but not more than 1 MPa (10 kgf/cm2)
The hydraulic test must be carried out at positive outside temperatures. When the outside air temperature is below zero, checking the density is possible only in exceptional cases.
2.8. Testing of equipment at heating points, heat pipelines from central heating points and heat consumption systems is carried out in the following order:
a) after filling the pipelines or systems and completely removing air through air bleeders from all upper points, the pressure in the pipelines is brought to working pressure and maintained for the time necessary for a thorough inspection of all welded and flanged connections, equipment, fittings, etc., but at least 10 minutes;
b) if during this time no defects or leaks are detected, the pressure is brought to the test pressure (see clause 2.7).
2.9. Steam heating systems should be tested at an excess pressure at the top point of the system of 2.5 kgf/cm2, and if the operating excess pressure of the system is more than 0.7 kgf/cm2 - at a pressure equal to the operating pressure plus 1 kgf/cm2, but not less 3 kgf/cm 2 at the top point of the system.
2.10. Systems are considered to have passed the test if, during testing:
a) no “sweating” of welds or leaks from heating devices, pipelines, fittings and other equipment were detected;
b) when pressure testing water and steam heat consumption systems for 5 minutes, the pressure drop did not exceed 0.02 MPa (0.2 kgf/cm 2);
c) when testing surface heating systems, the pressure drops within 15 minutes. did not exceed 0.01 MPa (0.1 kgf/cm 2);
d) when testing hot water supply systems, the pressure drops within 10 minutes. did not exceed 0.05MPa (0.5kgf/cm2).
The results of the inspection are documented in a test certificate. If the results of pressure testing do not meet the specified conditions, it is necessary to identify and eliminate leaks, and then re-check the tightness of the system.
The Test Report is signed by the consumer and the KhabarovskGosenergonadzor inspector based on the report (see clause 1.5). The report is attached to the act. A test report without a report is invalid.
3. Safety precautions.
3.1. Before testing the heating network for design pressure, it is necessary to carefully remove air from the pipelines to be tested.
3.2. When testing a heating network for design pressure, heating points and local consumer systems must be disconnected from the network being tested.
If the density of the shut-off valves at a heating point is violated, consumers should be disconnected by valves located in the chambers connecting them to the heating network, or by valves installed at heating points.
3.3. During testing of the heating network, constant duty must be organized at heating points and in consumer systems. Special attention should be given to areas of the network in areas where pedestrians and vehicles move, areas of channelless installation, areas where there have been cases of corrosive destruction of pipes, etc.
3.4. When testing a heating network for design parameters coolant is prohibited:
a) carry out work not related to testing at test sites;
b) be in and go down into chambers, channels, tunnels;
c) located against the flange connections of pipelines and fittings;
d) eliminate identified malfunctions.
When testing a heating network for the design coolant pressure, it is PROHIBITED to sharply increase the pressure and increase it above the limit provided by the test program.
3.5. Simultaneous testing of design pressure and design temperature prohibited.
3.6. Climbing into the pipeline to inspect and clean it from foreign objects is permitted only in straight sections of no more than 150 m in length with a pipeline diameter of at least 0.8 m. in this case, free exit must be ensured from both ends of the pipeline section to be inspected and cleaned.
Branches, jumpers and connections to other pipelines located on the site must be securely disconnected.
At least 3 people must be appointed to inspect and clean the pipeline, two of whom must be at both ends of the pipeline and observe the worker.
Work in the pipeline should be in a canvas suit and gloves, boots, knee pads, goggles and a helmet. The end of the rescue rope of the safety belt must be in the hands of the observer from the side of the entrance to the pipeline. The observer from the exit side of the pipeline must have a flashlight that illuminates the entire section.
Reliability and energy efficiency of heating networks
-1. Quality of maintenance technical condition(resource) of heating networks
——1.6. CrimpingExperience in pressure testing of heating network pipelines for high pressure
Experience in crimping heating network pipelines at high blood pressure
IN . M . Lipovskikh , main engineer, Thermal networks JSC Mosenergo
Mosenergo heating networks carry out hydraulic tests of pipelines for increased pressure. Why and how did we come to this? Let me give you an example. In winter 1969, there was a major accident on a pipe with a diameter of 1200 mm on the first main line in the Kuzminki area. The factory seam burst. It cleared up within a week. They even transported patients from unheated hospitals. Then we began to wonder how to exploit heating network with diameters of 1000 mm, 1200 mm and 1400 mm, when a shutdown of any heating network affects up to 1000-1500 buildings. Today there are attempts to diagnose heating networks, but so far there is no such diagnostic that provides 100% data on the condition of a pipeline laid in a non-passage channel or without a channel. We have found that the main way to detect thinning of pipes affected by corrosion is hydraulic testing.
Methodology hydraulic tests
Previously, the Ministry of Energy issued instructions that recommended conducting tests twice and using pumps that are installed at power plants - these are second-stage pumps. At the same time, the check valve was closed, the pressure rose in both pipes, and a pipeline or heating network 20-25 kilometers long was tested. Of course, the quality of the tests was very, very low. When damage occurred, everything had to be turned off, the damage repaired, and the pressure raised again. Of course, this approach was wrong, and we abandoned these hydraulic tests.
In 1979, we began to install permanently on heating networks (in power plants and pumping stations) separate pressure testing pumps and these pumps began to carry out hydraulic tests. Specialists from VNIIST (Mingazprom Pipeline Institute) were invited; they worked with us for several years and gave the following recommendations.
When calculating and designing heating networks, the factor of repeated loading is not taken into account, although heat pipelines are constantly subject to repeated static loading. The main reason for the high damageability of heating networks is external corrosion of pipes. Failures due to corrosion account for about 95% of all failures. One of the main directions for increasing the reliability of heating networks is to improve systems for preventive testing of pipelines with internal pressure. The main purpose of the tests is to identify summer period those damages that would be potential sources of failure during operation. Tests with standard values of their parameters do not fulfill their main purpose - the rejection of weak points, which leads to failures of heat pipelines during operation. A methodology has been developed for determining the test pressure level, based on the requirement of the absence of corrosion failures during one operating cycle. It is shown that the required minimum test pressure level depends on the operating pressure, corrosion rate, pipeline diameter and tensile strength of the pipe material. From the standpoint of the proposed methodology for determining the value of test pressure, the levels of standard and increased test pressures are analyzed in terms of their ability to ensure reliable operation of heat pipelines. The possibility of testing heating networks with a frequency of more than one year has been considered. It has been shown that if only the corrosion factor is taken into account, then in principle it is possible to switch to testing pipelines with a diameter of more than 600 mm at two-year intervals. However, the adoption of such a recommendation can only be made after studying the influence on the performance of pipelines of a complex of other factors characteristic of heat pipelines. Field experimental studies were carried out on the effect of repeated loading with internal pressure of a certain level on the performance of pipelines. Sections of new pipes with a diameter of 1200 and 500 mm were tested with an internal pressure of 33 kgf/cm 2 with a number of loading cycles of up to 500. After the tests, no signs of ruptures or leaks were found in the pipe walls. Laboratory studies to determine the mechanical properties of the base metal of pipes and welded joints of cyclically tested pipes and comparison with the corresponding indicators of metal cards selected before testing showed that repeated loading at a given level of test pressure and for a given number of loading cycles had virtually no effect on the strength , plastic and viscous properties of the base metal of pipes and welded joints, and, consequently, on the performance of pipelines made from these pipes. Based on the research carried out, a draft guide has been developed for determining the parameters of internal pressure testing of heating networks for strength. The value of the test pressure during the strength test should be taken depending on the purpose of the pipeline - supply or return and its diameter: diameter 1400-900 mm, it is recommended to press the supply pipeline at 28 kgf/cm 2, return - at 20 kgf/cm 2, 800 mm - by 33 kgf/cm 2 , 700-600 mm - by 33 kgf/cm 2 , 500 mm - by 40 kgf/cm 2 and 400-150 mm - by 40 kgf/cm 2 .
Organization repairs And hydraulic tests
We received such recommendations from the institute, and we began pressing at the recommended pressures, but at the same time, a lot of ruptures were discovered from poor-quality welding of pipelines at factories, and these pipelines could function for some time, so over time, the pressing pressures were reduced. The second point: we have already started installing axial bellows expansion joints and at high pressures the guide supports could not withstand, i.e. compensators bulged, guide supports broke.
Since 1983, we have been pressing pipelines with a diameter of up to 1400 mm at a pressure of 24 kgf/cm2, return pressure - 20 kgf/cm2, pipelines with a diameter of 800-600 mm at 26 kgf/cm2 and 500 mm and below at 28-30 kgf/ cm 2.
In order to carry out hydraulic tests, it was necessary to select pumps that could be used to increase the pressure. Pumps TsNS-300, TsNS-180 and TsNS-60 were selected. TsNS-300 were installed permanently at all power plants, at pumping stations and in a number of areas in separate pavilions. The pressure they develop is 400 m, i.e. 40 kgf/cm2. And at the same time, we now have 10 mobile presses equipped with TsNS-180 pumps. The drive is a YaMZ-240 engine with a power of 300 horsepower. This engine is used on heavy duty vehicles.
Pressure testing is carried out separately for each pipe. The supply and return pipelines are pressed separately. Why is that? If we increase the pressure in two pipes simultaneously, then we end up with undesigned loads on dead (fixed) supports. And it was decided to press one pipe at a time. The networks of each district today are divided into sections up to 15-20 km long. A schedule is drawn up for each site, and starting from May 10 to August 25, each district presses these networks and carries out routine repairs.
The organization of repairs and hydraulic tests usually begins around November. Has begun heating season, and we are already starting to put together a repair schedule for next year. First of all, these schedules are coordinated with power plants. Because the stations also plan their own major repairs. After this, the schedule also provides that two districts do not simultaneously press adjacent (neighboring) networks. If there is a rupture in a large-diameter pipeline and it requires extensive repairs, then we install plugs and supply power to the consumer from the neighboring area. This schedule is agreed upon by Mosenergo, then agreed upon by the prefectures and UTEC. As a rule, we receive this approval in March. District heads transmit these schedules to administrations and prefectures, which carry out their repairs together with us. Among other things, during such hydraulic tests, since they are carried out on crowded streets where there is active traffic, it is very important to draw up a test program. The program is prepared, as a rule, by the district leadership, coordinated with the station, with the services and approved. Attached to this program is a diagram of the heating networks that are included in the pressure testing. According to this scheme, there are control points, as a rule, at the end of the highways, along which the head of the district monitors the pressure during the hydraulic test. In this case, the piezometric marks of heating networks and, taking into account the marks, the pressure in each pipeline are taken into account.
As a rule, it is prohibited to install patches on heating networks in the summer. Damages are repaired from start to finish, from good pipe to good pipe. In the summer, we accumulate about 4500-5000 such damages.
Of course, safety issues are also very important. There were very unpleasant cases when slabs were lifted, when hatches fell off due to explosions. When analyzing these cases, it turned out that air was not always vented from heating networks very carefully. Therefore, always, before turning on the pump again, the head of the district or the person responsible for pressure testing asks his people whether the vents have been blown out everywhere. When the air vents are purged, such explosions, of course, do not happen. In some cases, where hydraulic tests are carried out in particularly crowded places, as a rule, we carry out these hydraulic tests at night, so that in case of ruptures there are no accidents to people.
Prospects
Of course, hydraulic tests are not the most The best way checks. I would say the method is barbaric. Simultaneously with the ruptures, soil alluvium appears in the channels; when one section is replaced, neighboring sections begin to corrode. Now we are trying to eliminate a number of damages without waiting for hydraulic tests in advance.
We place great hopes on the pre-insulated pipelines with polyurethane foam insulation, which we have begun to operate. These pipelines have systems for monitoring the condition of thermal insulation. Of course, there is no point in pressing these pipelines, because there is no moisture and no external corrosion, and damage from internal corrosion does not always show up during hydraulic tests. But for now there are instructions that recommend that we press and prepare heating networks every year, and we act on these instructions.
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Energy saving technologies and methods go to section
Hydraulic testing of pipelines of heating networks (pressure testing) is carried out with water at a temperature not lower than + 5 ° C. Pipelines and their parts must be subjected to hydraulic testing with a test pressure equal to 1.25 working pressure, but not less than 1.57 MPa (16 kgf/cm 2 ) for supply pipes and 1.18 MPa (12 kgf/cm 2) for return pipes.
According to the rules technical operation(PTE) of heating networks and heating points of the Ministry of Housing and Communal Services of the RSFSR, water heating networks from boiler houses equipped with cast iron boilers are tested at a pressure equal to 1.25 of the working pressure in the supply manifold, but not less than 0.59 MPa (6 kgf/cm 2). Pressure must be measured using two proven pressure gauges with an accuracy class of at least 1.5.
Hydraulic testing of heating networks for ducted and ductless installations is carried out in two stages (preliminary and final). Preliminary testing is done in small areas - up to 1 km, final testing - during all construction and installation work. Both are done after the moving supports are installed and welded, the fixed supports are installed and backfilled, but before the pipes and fittings are covered with thermal insulation. When installing pipelines from seamless pipes, hydraulic testing of pipelines can be carried out after insulating the pipes, but provided that the welded joints are free from insulation, not covered with waterproofing and are located in places accessible for inspection.
If during tests with test pressure no pressure drop is detected, the pressure in the tested section of the pipeline is reduced to the working one and at this pressure the welded joints are tapped with a hammer with a rounded head weighing no more than 1.5 kg with a handle length of no more than 500 mm; blows must be applied at a distance of at least 150 mm from the weld on both sides. The test results are considered satisfactory if the pressure did not drop during the test, and no signs of rupture, leakage or sweating were found in the welded seams of the pipes.
Draining of water after testing or detection of defects should be carried out immediately with final air purging of the emptied heat pipelines, and it should be checked whether water remains at the lowest points of the pipeline.
Hydraulic testing of individual pipes is carried out in accordance with GOST 3845-75. For hydraulic testing of pipes of small diameters and lengths of sections, manual hydraulic pumps are used, and for large diameters they are used piston pumps with mechanical and electric drive.
Pneumatic testing of pipelines. According to SNiP III-30-74, testing of pipelines for strength and tightness, instead of a hydraulic test, can be carried out pneumatically at the discretion of the construction organization (heating network enterprise) if it is difficult to carry out a hydraulic test (winter time, lack of water at the test site, etc.). Pneumatic tests must be carried out in accordance with the rules SP 298-65 of the USSR State Construction Committee. According to the rules, pneumatic testing of heating network pipelines with a coolant temperature above 120 ° C, steam pipelines with a pressure above 0.098 MPa (1 kgf/cm 2) must be carried out with a test pressure equal to the working pressure with a coefficient of 1.25, but not less than 1.57 MPa (16 kgf/cm2) for supply and 0.98 MPa (10 kgf/cm2) for return pipelines.
Considering that in installation conditions it is practically impossible to create such a test pressure, and also that with such a high test pressure, air would create a great danger for personnel, and in urban conditions for the population, replacing a hydraulic test with a pneumatic one should be avoided if possible. In the absence of water, it is allowed to carry out preliminary testing of pipelines with air at a pressure of 0.59 MPa (6 kgf/cm2). The pipeline is maintained under this pressure for 30 minutes, then the pressure is reduced to 0.29 MPa (3 kgf/cm2) and the pipelines are inspected. Air leaks are detected by washing the joints, by sound, by odorization or smoke formation of the air in the pipeline. After a preliminary pneumatic test, the final test is carried out hydraulically.
