From the editor: Until now, experts cannot come to a consensus on the issue of conducting hydraulic tests of heating networks. This issue has been repeatedly raised on the pages of the NT magazine (in particular, see NT: No. 6, 2001; No. 8, 2007; No. 7, 2008). To develop the topic, we invite you to read another opinion on this issue in the article below.
Hydraulic tests heating networks - it's time to think!
A.I. Kapitanov, Honorary Mechanical Engineer of Russia,
chief project engineer of ReMoNa LLC, Kolomna, Moscow region
The essence of the proposed method
In Russian conditions (with quality regulation heat supply systems) during the heating season, the water temperature in heating networks, depending on the outside air temperature, changes more than 40 times, i.e. heating network In winter they resemble accordion bellows: sometimes they separate, sometimes they come together.
Cyclic extension of the length of heating network pipelines in heating season range from 10 mm or more. The stresses created in this case cannot be compared with the elongations and stresses in heating networks during tests for strength and density, which, according to clause 6.2.13 of the Rules technical operation thermal power plants" (approved by Order of the Ministry of Energy of the Russian Federation dated March 24, 2003 No. 115) are carried out no later than two weeks after completion heating season.
Thermal power engineers conscientiously carry out the specified test procedure, detect defects in the pipes, fix them in the summer, and before the start of the heating season cheerfully report to all authorities about the readiness of heating networks for the coming winter.
But with the onset of the next heating season, again sleepless nights, again rushes to eliminate leaks in heating networks, and so on ad infinitum.
The author of the article, being the head of the energy service of a reputable enterprise, experienced all these delights of life and, completely exhausted, gave the command to conduct cyclic temperature tests of heating networks at the end of the heating season, in other words, to simulate their behavior in the upcoming heating season.
As a result of the tests, instead of 3-4 traditional leaks, 34 leaks were identified.
During the summer without emergency situations, these leaks were fixed as planned, and the coming winter was, by and large, survived without the slightest disruption in the heat supply to consumers. Further, the experience gained was practiced annually.
conclusions
It’s time to stop flattering yourself with the thought: “At the end of the heating season, I carried out hydraulic tests of heating networks. Over the summer I fixed 3-4 identified leaks and everything will be fine for me in the upcoming heating season.” This is obvious self-deception!
Necessary:
1. At the end of the heating season, prepare and during at least one work shift sharply (by 30-40 °C) 5-6 times at operating pressure and water circulation to raise and lower the temperature of the water in the heating network.
2. Despite leaks, emergency feed the heating network, turn it on and off hot water boilers(steam-water heaters) until the pressure drop in the heating network stabilizes (this will indicate that new leaks do not appear).
3. At the same time, bypass the heating network and record leaks.
The implementation of this seemingly insignificant event will allow:
■ provide in winter period uninterrupted heat supply to consumers;
■ prevent unproductive losses of thermal energy;
■ improve the social climate in the team servicing boiler plants and heating networks.
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 density 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 equipment (hydraulic presses, piston pumps), timing of construction in individual areas, capacity of the water source for filling the heating pipeline, 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 connection points of individual sections are checked (if the heat pipe was previously tested in parts), welds, fittings and linear equipment, density and strength of flange connections, linear equipment housings, 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 of heating 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 that 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 on the different areas systems.
This possibility should be excluded at the initial stage.
After filling the pipeline, the so-called holding time begins - the period during which the equipment under test is under high blood 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 voltage 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 technical conditions 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 indicated in project documentation to the object. 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.
Conducting hydraulic tests of heating networks needed for testing pipelines, components, seams, for strength and their density. This is done due to the fact that over time, even with good maintenance, the equipment can wear out and, as a result, fail. And to prevent emergency situations, to timely find defects that can cause an irreversible process, a number of activities are carried out, consisting of testing and network testing.
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Video of the company "PROMSTROY"
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One of which is hydraulic, necessary to identify:
- actual water consumption by consumers;
- determination of pipeline hydraulic characteristics;
- to find areas with increased hydraulic resistance;
- testing for strength and tightness.
In what cases is it necessary to carry out hydrotesting?
- Upon completion installation work pipelines that were carried out due to the replacement of pipes or the assembly of a new section heating system, before putting it into operation.
- In case of replacement or repair of components of the heating network.
- During scheduled network maintenance, which is carried out with the aim of starting the heating system for the autumn and winter period.
Cost of hydraulic testing of heating networks
What is used to measure pipeline characteristics
When carrying out activities to measure flow rates and pressures, instruments that are metrologically certified are used:
- One of them is a deformation pressure gauge or pressure sensors, which have an accuracy class of at least 0.4. These devices are used to measure pressure.
- When measuring water flow, standard instruments are used that are installed on the heat source and with the help of flow meters, which are part of the metering unit. In the absence of one of the listed devices, an ultrasonic flow meter is used, the sensors of which are overhead. The magnitude of its error should be no more than 2.5 percent.
Stages of testing
Activities consist of preparation, direct testing and analysis of indicators obtained as a result of tests.
- The first stage is preparation. During this period, the initial data on the network is clarified and recorded, after which the measurement program is developed and agreed upon. At this stage, preparatory actions are also underway to create testing conditions. This includes:
- Before starting the process, you need to check whether all work on welding, installation, installation of gaskets in connections, and tightening of these connections has been completed.
- You also need to check whether all the equipment is in order, the presence and functionality of the air drain valves.
- Connecting the hydraulic press to the water supply and to the pressure pipe pipeline. Checking the correct connections.
- Disconnecting the pipeline section where the test will be carried out from equipment that has not yet been fully installed or is already in use.
- Installation of necessary instruments for testing.
- The second stage is to conduct a test under appropriate conditions. Tests must be carried out in compliance with all requirements regarding temperature regime environment. In case of violation, this may lead to inaccuracy of the received data.
- The necessary conditions:
- The ambient temperature during events must be above zero.
- The temperature of the water used in the test should be from +5 to +40.
- Providing observation platforms for above-ground heating systems.
- Smooth increase in pressure. It should be approximately 40% higher than nominal. To increase it, the use of compressed air is prohibited.
- The test section of the pipeline must be maintained under test pressure for at least 15 minutes.
- Upon completion, the entire site must be carefully inspected and if defects are found, the measures necessary to eliminate them must be taken.
- And the last stage, this is an analysis of the results obtained and the compilation of a table indicating all the parameters. If deviations from the norm are detected, measures are taken to eliminate them, such as:
- Cleaning and flushing of the pipeline.
- Pipeline relocation.
- In case of serious problems, repairs and elimination of detected defects are carried out.
Upon completion of measures to eliminate the causes of deviations, the tests must be carried out again.
General information
Based on the Rules for the Technical Operation of Thermal Power Installations (approved by Order of the Ministry of Energy of the Russian Federation dated March 24, 2003 N 115), when operating heating network systems, heating network enterprises must ensure the reliability of heat supply to consumers, the supply of coolants (water and steam) with flow rates and parameters in accordance With temperature chart regulation and inlet pressure drop.
During operation, all existing heating networks must be tested for strength and density to identify defects no later than two weeks after the end of the heating season.
Hydraulic tests of pipelines of water heating networks in order to check strength and density should be carried out by test pressure with the results entered into the report.
Test pressure is the excess pressure at which hydraulic testing of thermal power plants and networks for strength and density should be carried out.
The minimum test pressure during hydraulic testing is 1.25 working pressure, but not less than 0.2 MPa (2 kgf/cm2).
The maximum value of the test pressure is established by strength calculations according to regulatory and technical documentation agreed with the Gosgortekhnadzor of Russia. The test pressure value is selected by the manufacturer (design organization) within the range between the minimum and maximum values.
Hydraulic tests are carried out by the person responsible for safe operation heating networks together with personnel authorized to operate heating networks.
Hydraulic tests
When conducting hydraulic tests for the strength and density of heating networks, the equipment of the heating networks (stuffing box, bellows compensators, etc.), as well as sections of pipelines and connected heat-consuming power plants not involved in the tests, should be disconnected with plugs.
Strength and density tests are carried out in the following order:
disconnect the tested section of the pipeline from existing networks;
at the highest point of the section of the pipeline under test (after filling it with water and bleeding air), set the test pressure (control using a pressure gauge);
the pressure in the pipeline should be increased gradually;
the rate of pressure rise must be indicated in the regulatory and technical documentation (NTD) for the pipeline.
Tests for strength and density are carried out in compliance with the following basic requirements: pressure measurement during testing should be carried out using two certified spring pressure gauges (one control) of class not lower than 1.5 with a body diameter of at least 160 mm. The pressure gauge must be selected from the condition that the measured pressure value is within 2/3 of the scale of the device; test pressure must be provided at the top point (mark) of the pipelines; the water temperature must be no lower than 5 °C and no higher than 40 °C; when filling with water, air must be completely removed from the pipelines; the test pressure must be maintained for at least 10 minutes and then reduced to working pressure; at operating pressure, a thorough inspection of pipelines is carried out along their entire length.
The test results are considered satisfactory if during the tests there was no drop in pressure and no signs of rupture, leakage or fogging were found in the welds, as well as leaks in the base metal, in the housings and seals of the valves, during flange connections and other pipeline elements. In addition, there should be no signs of movement or deformation of pipelines and fixed supports.
A report of the established form is drawn up on the results of testing pipelines for strength and density.
The results of hydraulic testing of a pipeline for strength and tightness are considered satisfactory if during the testing there was no pressure drop, no signs of rupture, leakage or fogging were found in welds, as well as leaks in the base metal, flange connections, fittings, compensators and other pipeline elements , there are no signs of shift or deformation of the pipeline and fixed supports.
