Hydraulic testing of pipelines

Hydraulic testing of heating networks are needed to test pipelines, constituent elements, seams, for strength and their density. This is done due to the fact that over time, even with good maintenance, equipment can wear out and, as a result, fail. And to prevent emergencies, to timely find defects that can cause an irreversible process, a number of activities are carried out, consisting of testing and testing the network.

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One of which is hydraulic, required to identify:

  • actual consumption of water by consumers;
  • determination of pipeline hydraulic characteristics;
  • to find areas with increased hydraulic resistance;
  • testing for strength and tightness.

When is hydrotesting required?

  • At the end of the installation work of the pipeline, which was carried out due to the replacement of pipes or the assembly of a new section of the heating system, before putting it into operation.
  • In case of replacement or repair of the components of the heating network.
  • During the execution of scheduled maintenance of the network, which is carried out in order to start the heating system for the autumn and winter periods.

The cost of hydraulic testing of heating networks

What is used to measure the characteristics of the pipeline

When carrying out activities for measuring flow rates and pressures, devices are used that are metrologically certified:

  • One of them is a deformation manometer or pressure sensors, which have an accuracy class of at least 0.4. These instruments are used to measure pressure.
  • When measuring water flow, regular devices are used that are installed on a heat source and with the help of flow meters that are part of the accounting unit. In the absence of one of the listed devices, an ultrasonic flow meter is used, the sensors of which are attached. The value of its error should be no more than 2.5 percent.

Test steps

Activities consist of preparation, direct verification and analysis of indicators obtained as a result of tests.

  • The first stage is preparation. During this period, the initial data on the network are clarified and recorded, after which the measurement program is developed and agreed upon. At this stage, preparatory actions are also underway to create conditions for testing. This includes:
    • Before starting the process, you need to check whether all welding, installation, installation of gaskets in joints, tightening of these joints have been completed.
    • You also need to check whether all the equipment is in order, the presence and operability of the drain with air valves.
    • Connecting the hydraulic press to the water supply and to the pressure pipe pipeline. Performing a connection check.
    • Disconnecting the section of the pipeline where the test will be carried out from equipment that has not yet been fully installed or is already in use.
    • Installation of the necessary devices for testing.
  • The second stage is the verification under appropriate conditions. Tests must be carried out in compliance with all requirements relating to the temperature regime of the environment. In case of violation, this may lead to inaccurate data received.
  • The necessary conditions:
    • The ambient temperature during the events should be above zero.
    • The temperature of the water used in the test should be from +5 to +40.
    • Provision of viewing platforms, with an above-ground location of the heating system.
    • Smoothness of pressure increase. It should be higher than the nominal by about 40%. To increase it, the use of compressed air is prohibited.
    • It is necessary to maintain the test section of the pipeline under test pressure for at least 15 minutes.
    • Upon completion, the entire area must be carefully examined 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:
    • Pipeline cleaning and flushing.
    • Pipeline relocation.
    • In case of serious problems, repairs and elimination of detected defects are carried out.

At the end of the measures to eliminate the causes due to which deviations occur, the tests must be carried out again.

Hydraulic testing of pipelines of heating networks (pressure testing) is carried out with water with a temperature not lower than + 5 ° C. Pipelines and their parts must be subjected to a hydraulic test 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 for Technical Operation (PTE) of heating networks and heating points of the MZHKH RSFSR, water heating networks from boiler houses equipped with cast-iron boilers are tested with a pressure equal to 1.25 working pressure in the supply manifold, but not less than 0.59 MPa (6 kgf / cm 2 ). The pressure must be measured using two tested pressure gauges with an accuracy class of at least 1.5.

Hydraulic tests of heat networks with channel and channelless laying are carried out in two stages (preliminary and final). A preliminary test is done in small areas - up to 1 km, the final one - when performing all construction and installation work. Both are carried out after the installation and welding of the movable supports, installation and backfilling of the fixed supports, but before the pipes and fittings are covered with thermal insulation. When installing pipelines from seamless pipes, hydraulic testing of pipelines can also be carried out after the pipes are insulated, but on condition that the welded joints are free from insulation, not covered with waterproofing and located in places accessible for inspection.

If no pressure drop is detected during the test pressure tests, 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 during the test the pressure did not decrease, and no signs of rupture, leakage or sweating were found in the pipe welds.

Drainage of water after testing or detection of defects should be carried out immediately with a final air purge of the emptied heat pipelines, and it should be checked whether water has remained 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, piston pumps with a mechanical and electric drive are used.

Pneumatic testing of pipelines. According to SNiP III-30-74, testing of pipelines for strength and tightness instead of the hydraulic method can be carried out pneumatically at the discretion of the building organization (heating network enterprises) if it is difficult to conduct a hydraulic test (winter time, lack of water at the test site, etc.). Pneumatic tests must be carried out in accordance with the rules of SP 298-65 of the Gosstroy of the USSR. According to the rules, pneumatic testing of pipelines of heating networks with a coolant temperature above 120 ° C, steam pipelines with a pressure above 0.098 MPa (1 kgf / cm 2) should 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 / cm 2) for supply and 0.98 MPa (10 kgf / cm 2) for return pipelines.

Considering that it is practically impossible to create such a test pressure under installation conditions, and also that with such a high test pressure air would create a great danger for personnel, and in urban conditions for the population, the replacement of a hydraulic test with a pneumatic one should be avoided if possible. In the absence of water, it is allowed to carry out a preliminary test of pipelines with air pressure of 0.59 MPa (6 kgf / cm 2). Under this pressure, the pipeline is maintained for 30 minutes, then the pressure is reduced to 0.29 MPa (3 kgf / cm 2) and the pipelines are inspected. Air leakage is detected by soaping the joints, by sound, odorization or smoke in the air in the pipeline. After the preliminary pneumatic test, the final test is carried out hydraulically.

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Hydraulic testing of pipelines.


Hydraulic testing of heating networks is carried out twice: first, the strength and density of the heat pipeline are checked without equipment and fittings, after the entire heat pipeline, which is ready for operation, with installed mud collectors, valves, compensators and other equipment. A re-check is necessary because it is more difficult to check the density and strength of welds when the equipment and fittings are installed.

In cases where, when testing heat pipelines without equipment and fittings, there is a pressure drop across the instruments, it means that the existing welds are loose (naturally, if there are no fistulas, cracks, etc. in the pipes themselves). The pressure drop during testing of pipelines with installed equipment and valves may indicate that, in addition to joints, gland seals or flange connections are also defective.

During the preliminary test, not only welds, but also the walls of pipelines are checked for density and strength. it happens that the pipes have cracks, fistulas and other factory defects. Tests of the installed pipeline must be carried out before the installation of thermal insulation. In addition, the pipeline should not be backfilled or closed by engineering structures. When the pipeline is welded from seamless seamless pipes, it may be submitted for testing already insulated, but only with open welded joints.

During the final test, the junction points of individual sections (in cases of testing the heat pipe in parts), welded seams of mud collectors and stuffing box compensators, equipment cases, flange connections are subject to verification. During the test, the glands must be sealed and the sectional valves fully open.

The need for two tests of heating mains is also caused by the fact that in long sections it is not possible to check the entire heat pipeline at a time. It would take a long time to leave the trench open. In this regard, individual sections of heating networks are tested before backfilling, as they are prepared. The length of the test section depends on the timing of construction on individual sections of the route, on the availability of manual, hydraulic or mechanized presses, filling units, piston pumps, the power of the water source (river, pond, lake, water supply), working conditions, terrain, etc. .

During hydraulic testing of heating networks, the sequence of work is as follows:
- carry out cleaning of heat pipelines;
- install pressure gauges, plugs and taps;
- connect water and hydraulic press;
- fill the pipelines with water to the required pressure;
- conduct an inspection of heat pipelines and mark the places where defects are found;
- eliminate defects;
- make a second test;
- disconnect from the water supply and drain the water from the pipes;
- remove gauges and plugs.

To fill the pipelines with water and to remove air from the pipes, the water supply is connected to the bottom of the heat pipe. Near each air crane it is necessary to put a duty officer. First, only air enters through the air vents, then the air-water mixture and, finally, only water. When the outlet is only water, the valve is closed. Then the tap is periodically opened two or three more times to completely release the remaining part of the air from the upper points. Before filling the heating network, all air vents must be opened and drains closed.

The test is carried out with a pressure equal to the working pressure with a factor of 1.25. Under the working understand the maximum pressure that can occur in this area during operation.

In cases of testing a heat pipeline without equipment and fittings, the pressure is raised to the calculated one and maintained for 10 minutes, while controlling the pressure drop, after which it is reduced to the working one, the welded joints are inspected and the joints are tapped. The tests are considered satisfactory if there is no pressure drop, no leakage and no sweating of the joints.

Tests with installed equipment and fittings are carried out with a holding time of 15 minutes, flange and welded joints, fittings and equipment, gland seals are inspected, after which the pressure is reduced to working pressure. The tests are considered satisfactory if the pressure drop does not exceed 10% within 2 hours. The test pressure checks not only the tightness, but also the strength of the equipment and pipeline.

After the test, the water must be completely removed from the pipes. As a rule, the test water is not specially treated and can reduce the quality of the network water and cause corrosion of the internal surfaces of the pipes.

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heat loss tests to determine actual heat losses by heat pipelines depending on the type of building and insulating structures, service life, condition and operating conditions;

Hydraulic loss tests to obtain the hydraulic characteristics of pipelines;

Tests for the potentials of stray currents (electrical measurements to determine the corrosiveness of soils and the dangerous effect of stray currents on pipelines of underground heating networks).

All types of tests must be carried out separately. The combination of two types of tests in time is not allowed.

6.83. For each test, a special team is organized, headed by the test leader, who is appointed by the chief engineer.

To conduct tests of heat networks for thermal and hydraulic losses and for the presence of potentials of stray currents, at the discretion of the management of the organization, specialized organizations with appropriate licenses may be involved.

The test manager must determine in advance the necessary activities that must be performed in the process of preparing the network for testing. These activities include:

Insert fittings for manometers and sleeves for thermometers;

Insertion of circulation jumpers and bypass lines;

Selection of measuring instruments (pressure gauges, thermometers, flow meters, etc.) for each measurement point in accordance with the expected limits of the measured parameters in each test mode, taking into account the terrain, etc.

6.84. For each type of test, a work program must be drawn up, which is approved by the chief engineer of the OETS.

When receiving thermal energy from a heat source belonging to another organization, the work program is agreed with the chief engineer of this organization.

Two days before the start of the tests, the approved program is transferred to the OETS dispatcher and the head of the heat source to prepare the equipment and establish the required network operation mode.

The work program of the test must contain the following data:

Tasks and main provisions of the test methodology;

List of preparatory, organizational and technological measures;

The sequence of individual steps and operations during the test;

Modes of operation of the equipment of the heat source and the heating network (flow rate and parameters of the heat carrier during each stage of the test);

Schemes of operation of the pumping and heating plant of the heat source in each test mode;

Schemes of inclusion and switching in a heat network;

The timing of each individual stage or test mode;

Observation points, object of observation, number of observers at each point;

Operational means of communication and transport;

Safety precautions during testing;

List of persons responsible for the implementation of certain activities.

6.85. Before the start of the test, the Test Director must:

Check the implementation of all preparatory measures;

Organize verification of the technical and metrological condition of measuring instruments in accordance with regulatory and technical documentation;

Check the shutdown of the branches and heating points provided for by the program;

Brief all members of the team and shift personnel on their duties during each individual stage of the test, as well as measures to ensure the safety of direct participants in the test and those around them.

6.86. A hydraulic test for the strength and density of heating networks in operation should be carried out after a major overhaul before the start of the heating period. The test is carried out on separate mains leaving the heat source with the water heating installations of the heat source turned off, heat consumption systems turned off, with open air vents at consumer heat points. The mains are tested in whole or in parts, depending on the technical feasibility of providing the required parameters, as well as the availability of operational means of communication between the OETS dispatcher, the heat source personnel and the team conducting the test, the number of personnel, and the availability of transport.

6.87. Each section of the heating network must be tested with a test pressure, the minimum value of which should be 1.25 working pressure. The value of the working pressure is set by the technical manager of the OETS in accordance with the requirements of the Rules for the Design and Safe Operation of Steam and Hot Water Pipelines.

The maximum value of the test pressure is set in accordance with the specified Rules and taking into account the maximum loads that the fixed supports can take on.

In each case, the value of the test pressure is set by the technical manager of the OETS within the allowable limits indicated above.

6.88. During a hydraulic test for strength and density, the pressure at the highest points of the heating network is brought to the test pressure value due to the pressure developed by the heat source network pump or a special pump from the pressure test station.

When testing sections of the heating network in which, according to the conditions of the terrain profile, network and stationary pressure testing pumps cannot create a pressure equal to the test one, mobile pumping units and hydraulic presses are used.

6.89. The duration of test pressure tests is set by the chief engineer of the OETS, but must be at least 10 minutes. from the moment the make-up water flow is established at the calculated level. Inspection is carried out after the test pressure is reduced to the working one.

The heat network is considered to have passed the hydraulic test for strength and density if, when it is located for 10 minutes. under a given test pressure, the recharge value did not exceed the calculated one.

6.90. The water temperature in pipelines during strength and density tests should not exceed 40 degrees. C.

6.91. The frequency of testing the heat network for the maximum temperature of the coolant (hereinafter referred to as temperature tests) is determined by the head of the OETS.

The entire network from the heat source to the heat points of heat consumption systems should be subjected to temperature tests.

Temperature tests should be carried out at stable daily positive temperatures of the outside air.

The maximum achievable temperature of the network water should be taken as the maximum temperature in accordance with the approved temperature schedule for regulating heat supply at the source.

6.92. Temperature tests of heating networks that have been in operation for a long time and have unreliable sections should be carried out after repair and preliminary testing of these networks for strength and density, but no later than 3 weeks before the start of the heating period.

6.93. The water temperature in the return pipeline during temperature tests should not exceed 90 degrees. C. Ingress of high-temperature coolant into the return pipeline is not allowed in order to avoid disrupting the normal operation of network pumps and the operating conditions of compensating devices.

6.94. To reduce the temperature of the water entering the return pipeline, tests are carried out with heating systems turned on, connected through mixing devices (elevators, mixing pumps) and water heaters, as well as with hot water supply systems turned on, connected in a closed circuit and equipped with automatic temperature controllers.

6.95. For the period of temperature tests, the following must be disconnected from the heating network:

Heating systems for children's and medical institutions;

Non-automated hot water systems connected in a closed circuit;

Hot water supply systems connected according to an open scheme;

Heating systems connected through elevators with underestimated, in comparison with the calculated, mixing ratios;

Heating systems with direct connection scheme;

Calorific installations.

The shutdown of heat points and heat consumption systems is carried out by the first valves on the side of the heating network installed on the supply and return pipelines of heat points, and in case of leakage of these valves - by valves in the chambers on branches to heat points. In places where valves do not provide shutdown tightness, it is necessary to install plugs.

6.96. Tests to determine heat losses in heat networks should be carried out once every five years on the mains characteristic of a given heat network in terms of the type of building and insulation structures, service life and operating conditions, in order to develop standard indicators and normalize operational heat losses, as well as assess technical condition of heating networks. The test schedule is approved by the technical manager of the OETS.

6.97. Tests to determine hydraulic losses in water heating networks should be carried out once every five years on the mains that are typical for a given heating network in terms of terms and conditions of operation in order to determine the operational hydraulic characteristics for the development of hydraulic modes, as well as assess the condition of the internal surface of pipelines. The test schedule is established by the technical manager of the OETS.

6.98. Tests of heat networks for heat and hydraulic losses are carried out with disconnected branches of heat points of heat consumption systems.

6.99. When conducting any tests, subscribers must be warned three days before the start of the tests about the time of the tests and the deadline for shutting down heat consumption systems, indicating the necessary security measures. The warning is handed against receipt to the responsible person of the consumer.

From the Editor: Until now, experts cannot come to a consensus on the issue of hydraulic testing of heating networks. This issue has been repeatedly raised on the pages of the NT journal (in particular, see NT: No. 6, 2001; No. 8, 2007; No. 7, 2008). In the development of the topic, we suggest that you familiarize yourself with another opinion on this issue in the article below.

Hydraulic tests of thermal networks - it's time to think!

A.I. Kapitanov, Honorary Mechanical Engineer of Russia,
Chief Project Engineer, ReMoNa LLC, Kolomna, Moscow Region

The essence of the proposed method

In Russian conditions (with a quality regulation of the heat supply system) during the heating season, the water temperature in heating networks, depending on the outdoor temperature, changes more than 40 times, i.e. heating networks in winter resemble accordion furs: they will disperse, then they will converge.

Cyclic elongation of the length of pipelines of heating networks during the heating period is from 10 mm or more. The stresses created in this case cannot be compared with elongations and stresses in thermal networks during strength and density tests, which, according to clause 6.2.13 of the "Rules for the technical operation of thermal power plants" (approved by Order of the Ministry of Energy of the Russian Federation of 03.24.2003 No. 115) are held no later than two weeks after the end of the heating season.

Thermal power engineers conscientiously carry out the specified test procedure, detect thinness in pipes, eliminate them in the summer, and before the start of the heating season they cheerfully report to all authorities about the readiness of heating networks for the upcoming winter.

But with the onset of the next heating season, again sleepless nights, again rush to fix 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 tests, instead of 3-4 traditional leaks, 34 leaks were detected.

During the summer, without emergency work, these leaks were planned to be eliminated, and the coming winter was, by and large, experienced without the slightest disruption in the heat supply to consumers. Further, the experience gained was practiced annually.

findings

It's time to stop entertaining yourself with the thought: “At the end of the heating season, I carried out hydraulic tests of heating networks. Over the summer, I eliminated 3-4 identified leaks and everything will be fine for me in the upcoming heating season.” This is a clear self-deception!

Necessary:

1. At the end of the heating season, prepare and during at least one work shift 5-6 times sharply (by 30-40 ° C) at operating pressure and water circulation, raise and lower the temperature of the water in the heating network.

2. Regardless of leaks, emergency feed the heating network, turn 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 fix the leaks.

The execution of this seemingly insignificant event will allow:

■ ensure uninterrupted heat supply to consumers in winter;

■ prevent unproductive losses of thermal energy;

■ improve the social climate in the team servicing boiler plants and heating networks.

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