Why conduct hydraulic tests of thermal networks. Strength and tightness tests

Reliable and economical operation of heat networks, which are one of the links in the heat supply system, largely depends on the rational organization of their operation.

Organizations of the service of operation of thermal networks perform the following works:

maintenance, testing and repair of heating network equipment;

adjustment of heat supply systems and assistance to heat consumers in adjusting heat consumption systems;

development and operational management of thermal and hydraulic mode;

control for rational use heat and metering of heat consumption by consumers;

participation in development long-term plans development of city heat supply;

consideration and approval of projects for new heating networks and schemes for connection to heating networks, issuance of technical specifications and permits for connections.

All heating networks before being put into permanent operation must be subjected to:

1) crimping- to determine the density and mechanical strength pipelines and fittings;

2) hydraulic testing - to determine the hydraulic characteristics of pipelines;

3) thermal tests - to determine the actual heat losses of the network;

4) testing for design temperature- in order to check the operation of the compensating devices of the network and fix their normal position.

Upon acceptance, the operating organization receives the following documentation from the builders: 1) a heat pipeline passport in the form established by Gosgortechnadzor, 2) executive drawings, 3) technical certification, hydraulic and temperature tests.

The installed equipment of heating points is also tested before being put into operation: elevators - for the calculated mixing ratio; water heaters - for the calculated heat transfer coefficient and hydraulic losses corresponding to the project; automatic regulators - on settlement modes.

Heating networks in operation must be subjected to control tests within the following periods:

1) crimping - annually after completion heating period to identify defects to be eliminated during a major overhaul, as well as after the completion of the repair, before putting the network into operation;

2) hydraulic and thermal tests - once every three to four years and design temperature tests - once every two years.

Let's consider the main types of tests of thermal networks.

Hydraulic tests for strength and tightness. Tests for strength and tightness are carried out as separate sections and throughout the network as a whole. When carrying out such tests, subscriber installations must be reliably disconnected, the tests of which must be carried out separately.

When testing the strength and tightness of sections of newly installed pipelines, together with fittings, a test pressure is created that exceeds the working pressure by 25%.

The trial pressure is maintained for a short period of time (usually 15 minutes) and then reduced to the operating pressure. The test results are considered satisfactory if, after establishing the working pressure, its decrease does not exceed 10% in 2 hours.

Determination of hydraulic resistance. The main purpose of these tests is to determine the actual hydraulic resistance s individual sections of the heating network and water-heating installations of CHP.

Thermal testing to the maximum temperature.The main task of these tests is to check the operation of devices that compensate thermal deformations heat pipeline. These tests are usually carried out with the installations of heat consumers turned off, but jumpers are switched on for those consumers that provide water circulation in the branches. The duration of the test is determined from the condition of maintaining the maximum water temperature at the end sections of the network for a period = 30 min = 1800 with.

Heat Loss Test. The main purpose of such tests is to check the effectiveness of thermal insulation of heat pipelines and to establish baseline indicators for calculating the heat losses of the network.

Heat loss tests should be carried out under steady state thermal conditions. Therefore, it is advisable to carry out them immediately after the end of the heating season, when the soil near the heat pipeline is warmed up, thereby reducing the duration of the tests. If before testing the heating network did not work for a long time, then it is necessary to first bring it to a steady thermal regime by means of long-term (until heat loss stabilization) maintenance of the temperature planned for testing.

test questions

1. Describe the main types of external corrosion of pipelines of water heating networks and methods for protecting heat pipelines.

2. Give ways to combat internal corrosion and scale formation in STS.

3. Formulate the main tasks of the heat network operation service.

4. Specify the main types of hydraulic and thermal tests of thermal networks.

5. What is the methodology for conducting thermal tests of networks for maximum temperature and for heat losses?

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, for the timely detection of defects that can cause an irreversible process, a number of activities are carried out, consisting of network testing and testing.

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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 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 to work.
• 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 measures 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, standard devices are used, which are installed on 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 regarding temperature regime environment. In case of violation, this can 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 must be between +5 and +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 step, 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.

On the basis of the normative documentation given below, a pressure test report was developed, which is one of the main documents when the work is handed over to the Customer at the facility.

Heat networks must be subjected to annual hydraulic tests for strength and density (pressure tests) to detect defects after completion heating season and holding repair work. Pressure testing of pipelines available for inspection during operation is allowed to be carried out 1 time after installation is completed.

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). Pipelines are kept under test pressure for at least 5 minutes, after which the pressure is reduced to working pressure. At operating pressure, a thorough inspection of pipelines along their entire length is carried out. The results of pressure testing are considered satisfactory if during its implementation there was no pressure drop and no signs of rupture, leakage or fogging were found in valve bodies and stuffing boxes, in flange connections, etc.

Before the beginning of the heating season, after the completion of the repair, 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 - with a pressure of 1.25 working pressure, but not lower than 1 MPa (10 kgf / cm2);

Heating systems with cast iron heating appliances- pressure 1.25 working, but not more than 0.6 MPa (6 kgf / cm2);

Panel and convector heating systems - with a pressure of 1 MPa (10 kgf / cm2);

Hot water supply systems - with a pressure equal to the operating pressure in the system plus 0.5 MPa (5 kgf / cm2), but not more than 1 MPa (10 kgf / cm2).

Hydraulic testing should be carried out at positive outside temperatures. At outside temperatures below zero, a density test is only possible in exceptional cases.

Systems are considered to have passed the test if, during their implementation:

No “sweating” of welds or leaks from heating devices, pipelines, fittings and other equipment was found;

When pressing water and steam systems heat consumption for 5 min. the pressure drop did not exceed 0.02 MPa (0.2 kgf/cm2);

When pressing systems panel heating pressure drop within 15 min. did not exceed 0.01 MPa (0.1 kgf/cm2);

When pressure testing hot water systems, the pressure drop for 10 minutes. did not exceed 0.05 MPa (0.5 kgf/cm2).

The results of the check are documented in an act of pressure testing. If the pressure test results do not meet the specified conditions, it is necessary to identify and eliminate leaks, and then re-check the tightness of the system. During hydraulic testing, spring pressure gauges of an accuracy class of at least 1.5 should be used, with a body diameter of at least 160 mm, a scale for a nominal pressure of about 4/3 of the measured one, with a division value of 0.01 MPa (0.1 kgf / cm2), verified and sealed by the sovereign.

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Normative documentation, rules and SNiP for pressure testing of the heating system

Brief excerpts from normative documentation, rules and SNiP for pressure testing of heating .

Analyzing the statistics of the questions you ask and realizing that many questions on 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 the Crimping Rules, approved by the Ministry Fuel and Energy of the Russian Federation and SNiP.

All SNiPs and rules contain information on more than 100 pages, which are sometimes difficult to understand, therefore, in order to make it easier for you, so that you can see, and if necessary, refer to the desired paragraph of a particular regulatory document, we have processed the applicable regulations and in summary posted on the site. Explanations to the Rules and SNiP can be found in the article: "Norms and rules for pressure testing of the heating system"

1. Rules for the technical operation of thermal power plants.

Designed and approved by the Ministry of Fuel and Energy Russian Federation. No. 115 dated March 24, 2003

p. 9.2 Heating, ventilation, air conditioning, hot water systems.

Hydraulic tests of the equipment of heat points and heating systems should be carried out separately.
Heating points and heating systems should 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 / cm 2).

9.2.11 To protect against internal corrosion, heating systems must be constantly filled with deaerated, chemically treated water.

9.2.12 Tests for the strength and density of the system equipment are carried out annually after the end of the heating season to identify defects, as well as before the start of the heating period after the repair is completed.

Clause 9.2.13 strength and density tests of water heating systems are carried out with test pressure, but not lower than:

- Elevator unit, water heaters for heating systems, hot water supply - 1MPa (10kgf / cm 2 or 10Ati.)

- Heating systems with cast-iron heaters, stamped steel radiators - should be taken 0.6 MPa (6 kgf / cm 2 or 6 Ati)

- 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 specifications manufacturer's plant.

The minimum value of the test pressure during a hydraulic test should be 1.25 working pressure, but not less than 0.2 MPa (2 kgf / cm 2 or 2 Atm).
Piping tests are carried out in next order must comply with the following basic requirements:

"__7__" __JUNE________2000

on hydraulic testing for strength and density of heating networks,

heat points and heat consumption systems,

on the balance sheet of consumers

Developer: Thermal Inspection

I. ^ GENERAL PART.

1. Annual hydraulic tests strength and density: heat networks, elevator nodes, heaters, heating systems and hot water supply, which are on the balance of consumers.
2. Individual tests of hot water, 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.
3. Work on testing the heating network, its individual elements and structures and heat-consuming systems (HPS) should be carried out:

• personnel of a specialized organization licensed by the State Energy Supervision Authority for the right to carry out such work, at the expense of the consumer under a special program agreed with the head of the thermal inspection "Khabarovskgosenergonadzor";
• specialized personnel of the consumer, according to a special program approved by the chief engineer of the enterprise and agreed with the head of the thermal inspection of Khabarovskgosenergonadzor.

1.4.. The test program should contain:

1.4.1. The document on the basis of which the work on pressure testing is carried out: a work permit signed by the chief engineer of the enterprise, on the balance sheet of which the tested sections of the heat supply system are located.

1.4.2. Scheme of the tested sections of heating networks and heating units with indication of pressure tapping points.

1.4.3. Surname list of persons conducting tests, indicating responsible person from the enterprise-consumer of thermal energy.

1.4.4. The layout of the personnel involved in the tests and the means of communication between them.

1.4.5. Methodology for conducting and processing test results.

1.5. For hydraulic pressure testing, use spring pressure gauges 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 and a division value of at least 0.1 atm (0.1 kgf / cm 2) 0, 01 MPa.

The pressure gauges must be sealed by the state verifier. The use of pressure gauges with expired seals, stamps is not allowed.

1.6. Based on the test results, a technical report is drawn up, approved by the head of the thermal inspection of Khabarovskgosenergonadzor.

1.8. Legal and individuals, carrying out hydraulic tests for the strength and density of heat networks, heat points and heat consumption systems that are on the balance of consumers, in their activities should be guided by the requirements of this Methodology.

2. Rules for pressure testing of heating networks,

and heating systems.

A. Testing of thermal networks.

2.1. Preliminary hydraulic pressure testing of underground heat 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.

The entire length of the test section shall be provided with free access to pipelines.

Pressurization is carried out in the following order:

a) the tested section of the pipeline is isolated from the existing networks by installing blind flanges or plugs; the use of valves to disconnect the test section from the existing network is not allowed;

b) the supply and return pipelines, after being filled with water and vented, 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 performed 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 100 mm from the weld.

The pressure at the lower points should not exceed one and a half times the nominal pressure (P y), for which the pipes used for laying the network are designed.

The working pressure for the supply and return pipelines of water heating networks is considered to be the highest water pressure, 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 means of protection ( safety valves) the highest pressure in the network according to the upper limit of the setting of protective and control devices is taken as the working pressure.

2.2. Gate valves must be tested before they are installed on the pipeline at the excess hydraulic pressure set 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 with two positions of the sealing rings:

a) in the open position with a plugged valve flange - to check the tightness of stuffing boxes;

b) in the closed position - to check the tightness of the grinding of the rings.

The valve is considered to have passed the test if no pressure drop occurs within 5 minutes.

2.3. The final hydraulic pressure test of the entire heat pipeline is carried out together with installed equipment(gate valves, compensators, drain and air cocks, etc.) at an overpressure of 1.25 working pressure, but not less than 16 kgf/cm. All sectional valves and branch valves on 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 was no pressure drop on the pressure gauge and no signs of rupture, leakage or sweating were found in welds, valve bodies and glands, in flanged joints, 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 1 time after the installation is completed.

2.5. When the outside air temperature is below 1С, the pipelines are filled with water heated to 50-60С, and pressure testing is performed after the water temperature drops to 40С. In the event of defects that require considerable time to eliminate, the pipeline must be immediately emptied, and it should be checked whether water has remained at the lowest points of the pipeline.

2.6. At low temperatures outside air 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, while the test pressure value must be agreed with Gosgortekhnadzor.
^

B. Testing of heating points, systems

2.7. The equipment of heating points and all underground pipelines of intra-quarter 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 overpressure of 1.25 working pressure, but not lower than:

a) for elevator units, heaters for heating and ventilation systems, water heaters for heating and hot water supply systems - not less than 1 MPa (10 kgf / cm 2);

b) for water heating systems with cast iron heaters - 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 / cm 2);

d) for hot water supply systems with a pressure equal to the operating pressure in the system plus 0.5 MPa (0.5 kgf / cm 2), but not more than 1 MPa (10 kgf / cm 2)

Hydraulic testing should be carried out at positive outside temperatures. At outside temperatures below zero, a density test is only possible in exceptional cases.

2.8. Testing of equipment of heat points, heat pipelines from central heat points and heat consumption systems is carried out in the following order:

a) after filling pipelines or systems and completely removing air through air vents from all top points the pressure in the pipelines is brought to the working pressure and maintained for the time necessary for a thorough inspection of all welded and flanged joints, equipment, fittings, etc., but not less than 10 minutes;

b) if during this time no defects or leaks are found, the pressure is brought to the test pressure (see clause 2.7).

2.9. Steam heating systems should be tested at an overpressure at the top point of the system of 2.5 kgf / cm 2, and if the operating overpressure systems more than 0.7 kgf / cm 2 - at a pressure equal to the working pressure plus 1 kgf / cm 2, but not less than 3 kgf / cm 2 at the top point of the system.

2.10. Systems are considered to have passed the test if, during their implementation:

a) no “sweating” of welds or leaks from heating devices, pipelines, fittings and other equipment was found;

b) during pressure testing of water and steam heat consumption systems for 5 minutes, the pressure drop did not exceed 0.02 MPa (0.2 kgf / cm 2);

c) during pressure testing of surface heating systems, the pressure drop for 15 minutes. did not exceed 0.01 MPa (0.1 kgf / cm 2);

d) during pressure testing of hot water supply systems, pressure drop for 10 minutes. did not exceed 0.05 MPa (0.5 kgf / cm 2).

The results of the check are documented in an act of pressure testing. If the test results 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 on the basis of 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. Prior to testing the heating network for design pressure, it is necessary to carefully remove air from the pipelines to be tested.

3.2. During the test of the heat network for design pressure, heat points and local consumer systems must be disconnected from the network under test.

In case of violation of the density of the shut-off fittings at the heating point, consumers should be turned off by valves located in the chambers for connecting them to the heating network, or by valves installed at heating points.

3.3. During the testing of the heating network, constant duty should be organized at heating points and in consumer systems. Special attention should be given to sections of the network in places where pedestrians and vehicles are moving, sections of channelless laying, sections where there were cases of corrosive destruction of pipes, etc.

3.4. When testing the heat network for the design parameters of the coolant, it is prohibited:

a) to perform work on the test sites that is not related to the test;

b) stay and descend into chambers, channels, tunnels;

c) be located against flange connections of pipelines and fittings;

d) to eliminate the identified malfunctions.

When testing the heat network for the design pressure of the coolant, it is PROHIBITED to sharply raise the pressure and increase it above the limit provided for by the test program.

3.5. Simultaneous testing for design pressure and design temperature is prohibited.

3.6. Climbing into the pipeline for inspection and cleaning it from foreign objects is allowed only in straight sections with a length of not more than 150 m and a pipeline diameter of at least 0.8 m. at the same time, a free exit from both ends of the pipeline section to be inspected and cleaned must be provided.

Branches, jumpers and connections to other pipelines available on the site must be securely disconnected.

At least 3 people must be appointed to inspect and clean the pipeline, of which two 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 lantern that illuminates the entire section of the pipeline.

Reliability and energy efficiency of heating networks

-one. Maintenance quality technical condition(resource) of heating networks
——1.6. Crimping

Experience in pressure testing of pipelines of heating networks for increased pressure

Experience in pressure testing of pipelines of heating networks for increased pressure

AT . M . Lipovsky , main engineer, Thermal networks JSC Mosenergo

Thermal networks of Mosenergo carry out hydraulic tests of pipelines for increased pressure. Why and how did we arrive at this? I'll give you an example. In 1969, the winter was major accident on a pipe with a diameter of 1200 mm on the first highway in the Kuzminok area. Broken factory seam. She cleared up within a week. Even patients were taken out of unheated hospitals. Then we began to wonder how to operate heat networks with diameters of 1000 mm, 1200 mm and 1400 mm, when the shutdown of any heat network affects up to 1000-1500 buildings. Today there are attempts to diagnose heating networks, but so far there is no such diagnostics that gives 100% data on the condition of a pipeline laid in an impassable channel or channelless. We came to the conclusion that the main way to detect thinning of pipes affected by corrosion is hydraulic testing.

Methodology hydraulic tests

Earlier, the Ministry of Energy issued instructions that recommended testing 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 trials was very, very low. When damage occurred, it was necessary to turn off everything, repair this damage and raise the pressure again. Of course, this approach was wrong, and we abandoned these hydraulic tests.

In 1979, we began to install permanently in heating networks (at power plants and at pumping stations) separate pressure testing pumps and these pumps began to carry out hydraulic tests. Specialists from VNIIST (Pipeline Institute of Mingazprom) were invited, they worked with us for several years and gave the following recommendations.

When calculating and designing heat networks, the factor of repeated loading is not taken into account, although heat pipelines are constantly under conditions of repeated static loading. The main reason for the high damage of heating networks is the external corrosion of pipes. Failures due to corrosion account for about 95% of all failures. One of the main directions for improving the reliability of heat networks is the improvement of preventive testing systems for pipelines with internal pressure. The main purpose of testing is to identify summer period those damages that would be potential foci of failure during the operation period. Tests at standard values ​​of their parameters do not fulfill their main purpose - rejection of weak points, which leads to failures of heat pipelines during operation. A technique has been developed for determining the level of test pressure, based on the requirement that there are no failures of a corrosive nature during one operation cycle. It is shown that the required minimum level of test pressure depends on the working pressure, corrosion rate, pipeline diameter and tensile strength of the pipe material. From the standpoint of the proposed methodology for determining the magnitude of the test pressure, the levels of standard and increased test pressures are analyzed according to their ability to provide reliable operation heat pipelines. The possibility of testing heat networks with a frequency of more than one year is considered. It is 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 with a two-year interval. However, the adoption of such a recommendation can be carried out only after studying the effect on the performance of pipelines of a complex of other factors characteristic of heat pipelines. Conducted polygon experimental studies the influence of repeated loading by 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 up to 500. After the tests, there were no signs of ruptures and leaks in the walls of the pipes. 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 maps selected before testing showed that repeated loading at a given level of test pressure and for a given number of loading cycles had practically no effect on strength , plastic and viscous properties of the base metal of pipes and welded joints, and, consequently, on the performance of pipelines from these pipes. On the basis of the conducted studies, a draft guideline was developed for determining the parameters for testing thermal networks by internal pressure for strength. The value of the test pressure during strength testing 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 by 28 kgf / cm 2, return - by 20 kgf / cm 2, 800 mm - by 33 kgf / cm 2, 700-600 mm - by 33 kgf / cm 2, 500 mm - up to 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 started testing at the recommended pressures, but at the same time, a lot of ruptures were found from poor-quality welding of pipelines at factories, and these pipelines could function for some time, therefore, over time, pressure testing was reduced. The second point: we have already begun to install axial bellows expansion joints and, at high pressures, we could not withstand the guide supports, 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 / cm 2, a return pressure of 20 kgf / cm 2, pipelines with a diameter of 800-600 mm by 26 kgf / cm 2 and 500 mm and lower by 28-30 kgf / cm 2.

In order to carry out hydraulic tests, it was necessary to select pumps that can raise the pressure. The pumps TsNS-300, TsNS-180 and TsNS-60 were selected. CNS-300 were permanently installed at all our power plants, at pumping stations and in a number of areas in separate pavilions. The head they develop is 400 m, i.e. 40 kgf / cm 2. And at the same time, we have now made 10 mobile presses, where the TsNS-180 pumps are installed. The drive is the YaMZ-240 engine with a power of 300 Horse power. This engine is used in heavy vehicles.

Pressure testing is carried out separately for each pipe. The supply and return pipelines are pressed separately. Why is that? If we raise the pressure simultaneously in two pipes, then we get off-design loads on the dead (fixed) supports. And it was decided to press one pipe at a time. Networks of each district today are divided into sections up to 15-20 km long. A schedule is drawn up for each section, and starting from May 10 to August 25, each district presses these networks and carries out current repairs.

The organization of repairs and hydraulic tests begins, basically, already somewhere in November. The heating season has begun, and we are already starting to draw up a schedule of repairs for next year. First of all, these schedules are coordinated with power plants. Because the stations are also planning their overhauls. After that, we also provide in the schedule that two districts do not simultaneously press adjacent (neighboring) networks. If there is a break in a large-diameter pipeline, and it requires a large repair, then we put plugs and power the consumer from the neighboring area. This schedule is coordinated in Mosenergo, then coordinated in the prefectures, in UTEKH. As a rule, we receive this approval in March. The heads of the districts forward these schedules to the councils, prefectures, which carry out their repairs together with us. Among other things, with such hydraulic tests, since they are carried out on crowded streets where there is an active movement of cars, it is very important to draw up a test program. The program is prepared, as a rule, by the leadership of the districts, coordinated with the station, with the services and approved. Attached to this program is a scheme of heat networks that are included in the pressure test. According to this scheme, there are control points, as a rule, these are on the final highways, along which the head of the district monitors the pressure during a hydraulic test. This takes into account the piezometric marks of heating networks and, taking into account the marks, the pressure in each pipeline.

As a rule, it is forbidden to put patches on heating networks in summer. Damage is repaired from start to finish, from good pipe to good pipe. Such damages we gain in the summer somewhere up to 4500-5000.

Of course, safety issues are also very important. There were very unpleasant cases when the slabs were lifted, when hatches flew off during breaks. When analyzing these cases, it turned out that air is not always very carefully released from heating networks. 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 air vents have been blown everywhere. When the air vents are blown out, 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 there are no accidents with people during breaks.

prospects

Of course, hydraulic testing is not the most The best way checks. I would say the way is barbaric. Simultaneously with the breaks, 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 pre-insulated pipelines in polyurethane foam insulation which we have started to use. These pipelines have systems for monitoring the state of thermal insulation. Of course, it makes no sense to press 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 so far there are instructions that recommend us to press and prepare heating networks annually, and we act according to this instruction.

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Section content

General provisions. Heat networks are tested for tightness (density) after construction is completed before they are put into operation, and then annually after the end of the heating period to identify defects that must be eliminated during major repairs and after repairs are completed, before switching on networks into operation [2].

Newly built heating networks are preliminarily tested for density (pressurized) in separate sections after welding and laying pipelines on permanent supports before closing the channels or backfilling the trenches. The test areas should have free access for a thorough inspection and tapping of tight joints.

The final hydraulic tests of the entire pipeline are carried out together with the installed equipment (gate valves, compensators, drain and air valves, etc.). When laying a heating network above ground, as well as laying in through channels or collectors that provide access and inspection of pipelines during operation, the test is carried out once after complete completion installation. Gate valves are tested before they are installed on the pipeline.

At low outdoor temperatures or in the absence of water on site, on newly commissioned heating networks (in agreement with the operating organization), instead of hydraulic tests for density, pneumatic tests are carried out in accordance with the rules of SN 298-65.

When testing heat networks for density, spring pressure gauges of an accuracy class of at least 1.5 are used with a body diameter of at least 150 mm, a scale for a nominal pressure of about 4/3 of the measured pressure and a division value of 0.1 kgf / cm 2. The pressure gauges must be sealed by the state verifier. It is not allowed to use pressure gauges with expired seals. For tapping welds at the joints, a hammer with a rounded head weighing no more than 1.5 kg and a handle no more than 500 mm long is used.

Hydraulic tightness tests of newly constructed heating networks. A preliminary check of the tightness of individual sections of the heating network after they are welded and laid on permanent supports is carried out in the following order. The tested section of the pipeline is isolated from the existing networks with blind flanges or plugs. The use of valves to disconnect the test section from the existing network is not allowed. The supply and return pipelines, after being filled with water and vented, are placed under a test overpressure of 16 kgf / cm 2 (1.6 MPa) at the highest point of the laying. In this case, the excess pressure at the lower point (with a large difference in terrain marks) should not exceed 24 kgf / cm 2 (2.4 MPa). Otherwise, the length of the test sections should be reduced. Pipelines withstand test pressure during the time necessary for a thorough inspection and tapping of the joints, but not less than 10 minutes. When tapping, blows should be applied at a distance of at least 150 mm from the weld.

The results of the preliminary network tightness test are considered satisfactory if during the test there was no pressure drop, and no signs of rupture, leakage or fogging were found in the pipe welds. Valves before being installed on the pipeline are tested under the pressure adopted for this pipeline, but not less than 16 kgf / cm 2 (1.6 MPa) for valves on the supply and 12 kgf / cm 2 (1.2 MPa) on the return pipelines. Gate valves are tested in two positions of the sealing rings: in the open position with a plugged gate valve flange - to check the tightness of stuffing boxes; in the closed position - to check the tightness of the grinding of the rings.

The final check of the tightness (density) of heating networks before putting them into operation is carried out under a pressure of 1.25 working, but not less than 16 kgf / cm 2 (1.6 MPa) in the supply and 12 kgf / cm 2 (1.2 MPa) in return pipelines (at the top point of the network). All sectional valves and valves on the branches of the network under test must be open. At an outside air temperature below 1°C, tests are carried out with water heated to 50-60°C. For quick removal water in order to prevent its freezing, devices are provided that ensure its drainage from pipelines for 1 hour. The duration of the final tests of the heating system for tightness is determined by the time required for its inspection, and should be at least 10 minutes.

If defects are found that require considerable time to eliminate them, the tests are stopped, and at an outside air temperature below 1 ° C, the pipeline is immediately emptied and the water is checked to see if there is water left at the lower points. The test results are considered satisfactory if during the test there was no pressure drop on the pressure gauge and no signs of rupture, leakage or wetting of welds, valve bodies and stuffing boxes, flange connections, etc. were found.

Pneumatic tightness tests of newly built heating networks. Pneumatic tests are carried out on sections with a length of not more than 1000 m. When laying a route outside settlements, it is allowed, as an exception, to test sections with a length of 3000 m. 2 (1.6 MPa) for supply and 10 kgf / cm 2 (1.0 MPa) return pipelines.

The duration of the pipelines under test pressure is 30 minutes, then the pressure is reduced to 3 kgf / cm 2 (0.3 MPa) and the pipelines are inspected. Air leaks are detected by soaping the joints, by sound, odorization or smoke in the air in the pipeline. The results of preliminary tests are considered positive if a thorough examination of the pipes does not reveal any defects in the welds, violations of the integrity of the pipelines and leaks.

The duration of preliminary tests is determined by the time required for a thorough inspection of the pipes. Defects identified during the inspection are eliminated after removing the excess pressure in the pipeline. The final pneumatic test is performed after the installation is completed in the following sequence: a) the pressure in the pipeline is brought to the test pressure and maintained for 30 minutes; b) in the absence of signs of violation of the integrity of the pipeline, the pressure is reduced to 0.5 kgf / cm 2 (0.05 MPa), at which it is maintained for 24 hours; c) after the exposure period, set the pressure r n, equal to 3000 mm of water. Art. on a liquid manometer, note the start time of the test, as well as the barometric pressure p n b mm Hg. Art.; d) after the test time, the pressure in the pipeline p to mm of water is measured. Art. and barometric pressure p to b mm Hg. Art.; e) the true value of the pressure drop (mm water column) in the pipeline is determined by the formula

Δp \u003d ν (r n -r c) -13.6 (r n b -r c b),

where ν is the density of the liquid manometer filler (for water ν=1 g/cm3). When used in liquid manometer kerosene (ν \u003d 0.87 g / cm 3), the height of the column at the beginning of the test should be 3450 mm.

The pipeline is considered to have passed the final pneumatic test if no violation of its integrity was detected during the test, and the pressure drop does not exceed the allowable value given in Table. 5.38.

Table 5.38. Test duration and allowable pressure drop per 1000 m of pipeline length

Note. With different pipeline diameters in the test section, the total duration of the test and the allowable pressure drop are proportional to the length of the pipes of each diameter.

Hydraulic tests for tightness of heating networks and heat consumption systems in operation. Testing of heat networks for tightness (density) is carried out along separate lines extending from the heat source. These lines are tested in whole or in parts, depending on the availability of operational means of transport and communication between the duty personnel of the heat source and the team conducting the tests, as well as their number. When tested heat points consumers and water heating installations of the heat source are turned off. The water temperature in the pipelines during this period should not exceed 40 ° C, and the pressure should be equal to the working pressure with a coefficient of 1.25, but not lower than 16 kgf / cm 2 (1.6 MPa). The required pressure is provided by the heat source's mains pump. One or more jumpers between the supply and return pipelines at the end of the network are preliminarily opened so that the water flow through these jumpers ensures the operation of the network pump on the descending part of its characteristic.

After turning on the network pump and creating circulation, the pressure in the network is increased by gradually closing the valve on the return pipeline of the tested line at the heat source collector to the tie-in (along the water flow) of the make-up pipeline. When the required pressure in the supply pipeline is reached, the valve on the return pipeline is closed until the pressure difference between the supply and return pipelines in the heat source reaches 1-3 kgf / cm 2 (0.1-0.3 MPa). When testing sections of the network in which, according to the conditions of the terrain profile, network pumps cannot create a pressure equal to 1.25 working pressure, mobile pumps are used. pumping units or hydraulic presses.

At the initial moment of the test, the replenishment of the heating network may exceed the standard value, which is explained by the compression of the air present in the network. However, with sufficient tightness (density) of the network, the amount of recharge after 10-15 minutes. reduced to the standard and kept at this level. Exceeding the standard value of recharge (0.1% of the capacity of the tested network) or a tendency to increase it after 10-15 minutes. after the start of the tests, it indicates an excess leakage and poor tightness of the network. In this case network pump is stopped and the test is stopped until a leak is found and repaired.

To speed up the network tightness check and find the leak during the test period, it is allowed to eliminate defects in the joints by chasing, as well as seal prefabricated and flanged connections by applying clamps to rubber gaskets. Upon completion of the network density check, the detected defects are eliminated by conventional methods. After all defects are eliminated, the network is retested for tightness. The duration of control tests for tightness (density) is determined by the time required to inspect the network. The network is considered to have passed the tightness test if, when it is located for 10 minutes. under pressure equal to 1.25 working pressure, make-up does not exceed the standard value. The tightness of the branches is checked after the restoration of water circulation in the main by establishing a pressure in them equal to the pressure in the main pipeline.

The equipment of heating points and all underground pipelines of intra-quarter and intra-yard networks after central heating points, as well as pipelines and equipment of heat consumption systems, are subjected to hydraulic leak tests at an overpressure of 1.25 working pressure, but not lower: a) for elevator units and water heaters of heating systems and hot water supply - 10 kgf / cm 2 (1 MPa); b) for underground pipelines after heating points - 12 kgf / cm 2 (1.2 MPa); c) for water heating systems with cast iron heaters - 7.5 kgf / cm 2 (0.75 MPa) at the lowest point of the system, and for panel and convector systems - 10 kgf / cm 2 (1.0 MPa); d) for heaters of heating and ventilation systems - 9 kgf / cm 2 (0.9 MPa); e) for hot water supply systems connected to open heating networks - 7.5 kgf / cm 2 (0.75 MPa).

Testing of equipment of heat points, heat pipelines from central heat points and heat consumption systems is carried out in the following order: thorough inspection of welded and flanged joints, equipment, fittings, etc., but not less than 10 minutes; b) if during this time no defects or leaks are found, the pressure is brought to the test pressure.

The results of hydraulic tests are considered satisfactory if during their conduct: a) no signs of rupture, leakage or sweating are found in the welds of pipes, flange joints, valve bodies, etc.; b) when testing the equipment of heat points and the heat pipelines of yard and block networks extending from them for 10 minutes. there was no pressure drop. When testing panel heating systems, a pressure drop within 15 minutes is allowed no more than 0.1 kgf / cm 2 (0.01 MPa).

Coloring network water allows you to determine the places of its leakage in the communications of existing CHPPs, boiler houses, heating networks, hot water heaters, to identify hidden jumpers between heating networks and heat consumption systems when independent scheme connections, detect drawdown from closed systems heat supply, as well as the content of network water in flooded ground and surface waters channels and cameras. You can use the dye only with the permission of the Chief Sanitary Doctor of the city or locality. One of the requirements for the dye is the possibility of its detection at a low concentration.

Pure fluorescein-sodium (uranine) (C 20 H 10 Na 2 O 5) (TU 6-09-2281-77, produced by the Berezniki Chemical Plant) is used as an indicator of network water leakage. It is also allowed to use technical fluorescein (C 20 H 12 O 5).Uranine is a yellow-brown powder, soluble in water with a yellow color and intense green fluorescence. Fluorescence disappears upon acidification and reappears upon alkalinization. Used as an adsorption or fluorescent indicator. Fluorescein is a yellowish-red or red crystalline powder insoluble in water, ether, chloroform, benzene. It dissolves when heated in alcohol, acetone, acetic acid. It dissolves well in caustic alkalis, forms a yellow-red solution with intense green fluorescence in ultraviolet rays. The use of uranine is preferred due to its good solubility. Mosenergo and Chelyabenergo systems use fluorescein.

To prepare a water-soluble salt of fluorescein, it is necessary to take 20 liters of a 42% alkali solution (12.5 kg of 100% NaOH) and 250 liters of water per 100 kg of fluorescein.

The working solution is injected into the make-up water line in front of the deaerator or into the make-up water tank of the heating system. The required dosing time is determined from the condition of uniform distribution of fluorescein in network water, taking into account the length main pipelines. The amount of fluorescein is calculated based on the volume of water in the pipelines of the heating system, taking into account the consumption of make-up water during the testing period.

The working concentration of fluorescein in network water is 1.0-1.5 g/m 3 and it should be maintained for 2-5 days, necessary to check all possible places of leakage of network water. The dosing rate and flow rate of the fluorescein solution is controlled using a flow meter (rotameter) or by changing the level in the tank of the working fluorescein solution.

Water sampling from consumers, in chambers and channels of heating networks, after treatment facilities industrial enterprises, from hot water supply systems is carried out by the personnel of the heating network according to a specially drawn up schedule. Before sampling from the hot water supply system, the pressure is reduced tap water, for which they turn off the pumps at the heating point or partially close the valves. The presence of fluorescein in samples is determined by the visible color of the water or (for low concentrations of the indicator) using special device- a source of ultraviolet rays.

Tests of thermal networks are starting and operational. Start-up tests are carried out after the construction of new networks or overhaul. They are intended to determine the suitability of the structure for operation. During operation, sludge accumulates in pipes and equipment, pipelines corrode, protective properties thermal insulation change. The allowable change in the various characteristics of the structure is periodically checked by performance tests. Launchers and performance tests are divided into pressure testing, hydraulic and thermal tests and tests for the maximum temperature of the coolant.

Crimping designed to determine the density and mechanical strength of pipelines, fittings and equipment. Starting pressure testing of channelless networks and in impassable channels is carried out in two stages: preliminary and final. Preliminary pressure testing is carried out as the work is completed in short sections before the installation of stuffing box compensators, valves on the pipelines and before closing the channels or backfilling the trenches. The purpose of pressure testing is to check the strength of welding under a test overpressure of 1.6 MPa during the time necessary for inspection and tapping of the joints. Tapping is carried out with hammers weighing 1.5 kg on a handle 500 mm long, blows are applied on both sides of the seam at a distance of about 150 mm from the joint.

Final pressure testing is done after completion of all work and installation of all equipment elements on pipelines, but before thermal insulation is applied. When installing networks from seamless pipes, it is allowed thermal insulation before the test, but leaving the welded joints free of insulation. The overpressure pressure is brought to 1.25 R slave (R slave - working pressure), but not less than 1.6 MPa in the supply pipelines and 1.2 MPa in the return pipelines. The duration of crimping is determined by the time required to inspect the networks.

Pressure testing of equipment of substations, heating points, together with local systems, is carried out in two steps. Equipment and pipelines disconnected from the networks are filled with water from the city water supply, required pressure testing is created by the pressure of pressure testing pumps with a manual or mechanical drive. Initially, the system is pressurized with working pressure to check the tightness of welded and flanged joints of equipment, fittings and pipelines. Then the excess pressure is brought to 1.25 of the working one, but not lower than the norms established for each type of equipment necessary for strength testing. The duration of the test of heat points and pipelines extending from them is taken at least 10 minutes.

The results of testing networks and heating points at each stage are considered satisfactory if during their implementation a pressure drop above the established limits is not detected, and there are no breaks, water leaks and fogging in welds, flange joints and fittings. If breaks and other damage are found, the water is drained (from the networks in no more than 1 hour); defective seams are cut down and digested; leaks are eliminated by tightening the bolts, changing the packing. Then the pressing is repeated. Existing heating networks are pressure tested annually at the end of the heating season to identify defects and after major repairs.

Hydraulic tests are designed to determine the actual hydraulic characteristics of the new network and equipment of points or changes in these characteristics during operation. During hydraulic tests, the pressure, flow rate and temperature of the coolant are simultaneously measured at characteristic points (places of change in diameters, water flow rates, network jumpers) of the network. At control points, exemplary pressure gauges, mercury thermometers with a division value of 1 ° C and normal measuring diaphragms are installed. The tests are carried out with the heat points turned off at maximum and reduced to 80% of maximum expenses water. Water circulation in networks and branches is ensured by the inclusion of end jumpers.

The pressure loss in the investigated sections of the supply and return pipelines is calculated by the formula:

where P1, P2- pressure gauge readings at the beginning and end of the section, Pa;

z 1 , z 2- geodetic marks at the points of location of pressure gauges, m;

is the heat carrier density at the corresponding temperature, kg/m 3 .

According to the pressure measurements in the supply and return pipelines, a real piezometric graph is built, and the estimated pressure graph is determined from the water flow rates in the sections. By comparison, the deviations of the actual and calculated piezometric graphs are established.

Thermal testing carried out in order to determine actual losses heat in the networks and comparing them with the calculated and normative values. The need for thermal testing is dictated by the natural destruction of thermal insulation, its replacement in certain areas, as well as structural changes. Tests are carried out at the end of the heating season, when the entire structure of the heat pipeline and the adjacent soil are warmed up fairly evenly. Before testing, the destroyed insulation is restored, the chambers and channels are drained, and the operation is checked. drainage devices, thermal points of consumers are turned off, water is circulated through jumpers.

During the tests, the flow rates and temperatures of the coolant are measured at the beginning and end of the investigated section of the supply and return pipelines. A stable circulation mode is established, in which several readings are taken after 10 minutes.

The actual specific heat loss is determined by the formulas

; (14.3)

, (14.4)

where q f1 , q f2- actual specific heat losses in the supply and return pipelines, kW/m; G 1 , G p–. average consumption of network water, respectively, in the supply pipeline and make-up water, kg / h; τ 11 , τ 12- average water temperatures at the beginning and end of the supply pipeline, °С; τ 21 , τ 22- the same, the return pipeline; l- section length, m.

By comparing the actual heat losses with the calculated ones, the quality of the insulation is established. To compare with the standard losses, the actual heat losses are recalculated according to the average annual water temperatures in the supply and return pipelines and the average annual ambient temperature. Heat loss steam pipelines are determined by the change in enthalpy, steam humidity and the amount of condensate. Thermal and hydraulic tests of networks are carried out after 3-4 years.

Tests for maximum coolant temperature carried out in order to control the reliability of the structure, the operation of compensators, the displacement of supports, to determine the actual stresses and deformations of the most loaded network elements. Tests are carried out every two years at the end of the heating season with disconnected consumers with the circulation of the coolant through the end bridges.

During the test period, the temperature of the coolant rises at a rate of 30 ° C per hour, at the end points of the network Maximum temperature held for at least 30 minutes.

As the pipelines heat up, at certain time intervals, the movements of fixed points on the pipes, U-shaped arms and sleeves of stuffing box expansion joints are measured. The actual displacements of the network elements are compared with the calculated ones and the actual stresses at the characteristic points are established from them. If the difference between the calculated and actual elongations of pipelines exceeds 25% of the calculated elongation, then searches should be made for places of pipe pinching, subsidence or shear fixed supports and other reasons for this difference.