Carrying out hydraulic tests of pipelines of the heating network. TTC

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

AT Russian conditions(at quality regulation heating systems) for heating season The water temperature in heating networks varies more than 40 times depending on the outdoor temperature, 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 heat networks during strength and density tests, which, according to clause 6.2.13 of the Rules technical operation thermal power plants” (approved by the Order of the Ministry of Energy of the Russian Federation of March 24, 2003 No. 115) are carried out 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 it on and off hot water boilers(steam-water heaters) until the pressure drop in the heating network stabilizes (this will indicate that no new leaks appear).

3. At the same time, bypass the heating network and fix the leaks.

The execution of this seemingly insignificant event will allow:

■ provide in winter period uninterrupted supply of heat to consumers;

■ prevent unproductive losses of thermal energy;

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

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 should be subjected to annual hydraulic tests for strength and density (pressure tests) to identify defects after the end of the heating season and carry out 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 results of the pressure test 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.

profsantenik.by

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 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. In accordance with the "Rules for the operation of heat-consuming installations and heat networks of consumers" and the "Safety regulations for the operation of heat-consuming installations and heat networks of consumers", annual hydraulic tests for strength and density should be carried out: 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 their performance 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 upper points, the pressure in the pipelines is brought to working pressure and maintained for the time necessary for a thorough inspection of all welded and flanged joints, equipment, fittings, etc., but at least 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 overpressure in top point system 2.5 kgf / cm 2, and if working 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 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.

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 of movement of pedestrians and vehicles, 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 heating 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 with 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 repetition of 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 method for determining the level 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 test pressure level depends on the operating pressure, corrosion rate, pipeline diameter and tensile strength of the pipe material. From the standpoint of the proposed methodology for determining the magnitude of the test pressure, the levels of standard and increased test pressures are analyzed in terms of 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 chosen. 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 also plan their own 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 especially 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 replacing one section, 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 are acting according to this instruction.

Please leave your comments and suggestions on the forum go. To read the document, select the section you are interested in.

Energy saving technologies and methods go to section

There are 4 types of heat network tests:

1. For strength and tightness (crimping). It is carried out at the manufacturing stage before applying insulation. When used annually.
2. at design temperature. Carried out: in order to check the operation of compensators and fix their working position, to determine the integrity fixed supports(1 ruble in 2 years). Tests are carried out during the manufacture of networks before applying insulation.
3. hydraulic. They are carried out in order to determine: the actual consumption of water by consumers, the actual hydraulic characteristics of the pipeline and the identification of areas with increased hydraulic resistance (1 time in 3-4 years).
4. Thermal testing . To determine the actual heat loss (1 time in 3-4 years). Tests are carried out according to the following dependence:

Q = cG(t 1 - t 2) £ Q norms = q l *l,

where q l - heat loss 1m pipeline, determined by SNiP " Thermal insulation pipelines and equipment”.

Heat losses are determined by the temperature at the end of the section.

Strength and tightness tests.

There are 2 types of tests:

1. hydraulic.
2. Pneumatic. Checked at t n<0 и невозможности подогрева воды и при её отсутствии.

Hydraulic tests.

Devices: 2 manometers (working and control) class above 1.5%, manometer diameter not less than 160mm, scale 4/3 of the test pressure.

Order of conduct:

1. Shut off the test area with plugs. Replace gland compensators with plugs or inserts. Open all bypass lines and valves if they cannot be replaced with plugs.
2. The test pressure is set = 1.25R slave, but not more than the working pressure of the pipeline P y. Exposure 10 minutes.
3. The pressure is reduced to the working pressure, at which the inspection is carried out. Leaks are controlled by: pressure drop on the pressure gauge, obvious leaks, characteristic noise, fogging of the pipe. At the same time, the position of the pipelines on the supports is controlled.

Pneumatic tests it is forbidden to carry out for: Above-ground pipelines; When combined with laying with other communications.

When testing, it is forbidden to test cast iron fittings. It is allowed to test ductile iron fittings at low pressures.

Devices: 2 pressure gauges, pressure source - compressor.

1. Filling at a rate of 0.3 MPa/hour.
2. Visual inspection at pressure P ≤ 0.3P tested. , but not more than 0.3 MPa. R isp \u003d 1.25R work.
3. The pressure rises to P tested, but not more than 0.3 MPa. Exposure 30 min.
4. Reduction of pressure to P slave, inspection. Leaks are determined by signs: a decrease in pressure on pressure gauges, noise, bubbling of a soap solution.

Safety precautions:

• during the inspection it is forbidden to go down into the trench;
• do not get exposed to the air stream.

Design Temperature Tests

Thermal networks with d ≥100mm are tested. At the same time, the design temperature in the supply pipeline and in the return must not exceed 100 0 С. The design temperature is maintained for 30 minutes, while the increase and decrease in temperature should not exceed 30 0 С/hour. This type of test is carried out after pressure testing of networks and elimination of gusts.

Tests to determine thermal and hydraulic losses

This test is carried out on a circulation circuit consisting of supply and return lines and a jumper between them, all branch subscribers are disconnected. In this case, the decrease in temperature along the movement along the ring is caused only by the heat losses of the pipelines. The test time is 2t to + (10-12 hours), t to - the run time of the temperature wave along the ring. Temperature wave - an increase in temperature by 10-20 0 C above the test temperature along the entire length of the temperature ring, is set by observers and the temperature change is recorded.

The test for hydraulic losses is carried out in two modes: at maximum flow and 80% of the maximum. For each of the modes, at least 15 readings should be taken with an interval of 5 minutes.

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 regime;

control over the rational use of heat and accounting for heat consumption by consumers;

participation in the development of long-term plans for the development of the city's 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 of 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 Gosgortekhnadzor, 2) as-built drawings, 3) certificates of technical examination, 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) pressure testing - annually after the end of the heating period to identify defects that must be eliminated during a major overhaul, as well as after the repair is completed, 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. Strength and tightness tests are carried out both in individual sections and on the entire 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 (typically 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 at maximum temperature.The main task of these tests is to check the operation of devices that compensate for thermal deformations of the heat pipe. 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 the maximum temperature and for heat losses?

After completion of construction and installation works, heating networks are tested for strength and tightness by water pressure (hydrostatic method) or air (manometric method) before putting them into operation. During the test, the tightness and strength of welds, pipes, flange connections, fittings and linear equipment (stuffing expansion joints, mud collectors, etc.) are checked.

Before testing pipelines, it is necessary to perform the following auxiliary work and organizational measures:

• check the validity period of the approvals of the technological scheme for testing pipelines and, if necessary, re-coordinate the project for the production of works with the operational services and make payment for the supply of heating or drinking water to fill the pipelines;
• check the design position of the movable supports;
• securely fix the fixed supports and fill them with soil;
• disconnect the test pipelines with plugs from existing or already put into operation and from the first stop valves installed in the building;
• install plugs at the ends of the tested pipelines, and instead of stuffing box compensators and sectional valves, temporarily install "coils";
• connect the press and pipeline to the water supply and install pressure gauges;
• provide access for the entire length of the tested pipelines for external inspection and inspection of welds for the duration of the tests;
• fully open fittings and bypass lines.

For testing by the hydrostatic method, hydraulic presses, piston pumps with a mechanical or electric drive are used. When performing tests for strength and tightness, the pressure is measured using certified and sealed spring pressure gauges (at least two - one control) of a class of at least 1.5 with a body diameter of at least 160 mm and a scale with a nominal pressure equal to 4/3 measured.

Testing of water heating networks by the hydrostatic method is carried out by a test pressure equal to 1.25 working pressure, but not less than 1.6 MPa. The working pressure is determined by the pressure of the heat carrier on the supply pipeline of the CHP or boiler house. With a steep profile of the tested network, the excess pressure at the lower points should not exceed 2.4 MPa. Otherwise, the test must be carried out in separate sections. Testing by the hydrostatic method of pipelines laid in a trench with impassable channels is carried out in two stages: preliminary and final.

During the preliminary test, the strength and tightness of the welds and the walls of the pipeline are checked before the installation of fittings and linear equipment. Until the preliminary test, the heat pipeline must not be covered with building structures and covered. Preliminary testing of heat pipelines by the hydrostatic method is carried out in small sections no more than 1 km long, as well as when laying in cases and sleeves.

If the heat pipeline is made of pipes with a longitudinal or spiral seam, then the tests are carried out before the device on the thermal insulation pipeline. If the heat pipeline is welded from seamless seamless pipes, then its testing can be carried out after the installation of thermal insulation, provided that the welding joints are free from insulation and are in places accessible for inspection.

During the final test, the construction of the heat pipeline must be completely completed in accordance with the project. During testing, they check the junctions of individual sections (if the heat pipeline was previously tested in parts), welds of fittings and linear equipment, tightness of flange connections, cases of linear equipment.

When filling the pipelines with water and when draining water after the test, the air valves installed at the highest points of the pipeline profile must be fully open, and the drain valves that allow the water to drain in no more than an hour are closed. To force air out of the pipes, the water supply is brought to the lowest point of the pipeline.

The test pressure during the test by the hydrostatic method is maintained for the time necessary for visual inspection of the joints, but not more than 10 minutes. If during the test pressure test no pressure drop, leaks and fogging of welds are detected by the pressure gauge, then the pressure in the tested section of the pipeline is reduced to the working one, and the pipeline is re-examined. The test results are considered satisfactory if during the entire time of the test there is no pressure drop on the pressure gauge, leaks and fogging of welds, ruptures, signs of shear or deformation of the structures of fixed supports. If leaks appear in the seams during testing by the hydrostatic method, their correction by chasing is prohibited. Detected defective places are cut down, cleaned and welded again, after which a second test is performed.

Pneumatic test. At low outdoor temperatures and the absence of heated water for testing pipelines, the construction and installation organization can, in agreement with the customer and the operators, conduct a test using the pneumatic method. The pneumatic test is carried out in the following sequence: clean and purge the pipeline; install plugs and pressure gauges; attach the compressor to the pipeline; fill the pipeline with air to a predetermined pressure, prepare a soap solution; inspect the pipeline, coat the joints with soapy water and mark defective places; eliminate detected defects; retest the pipeline; release air from the pipeline; disconnect the compressor from the pipeline and remove the plugs and pressure gauges.

Leaks in the pipeline are determined by the sound of air leaking, by the bubbles that form at the leak site, if the joints and other welded joints are covered with a soapy solution, or by smell, if ammonia is added to the air supplied from the compressor to the pipeline, methyl mercaptan and other gases with a pungent odor.

The most widely used method is to check the non-tightness of a pipeline when it is tested by a pneumatic method using a soap solution (100 g of laundry soap is dissolved in 1 liter of water). In urban conditions, pneumatic testing of pipelines is carried out on a section no longer than 1000 m.

Outside settlements, as an exception, it is allowed to test heating mains in sections up to 3000 m long. The pipeline is filled with air smoothly, with a pressure rise of no more than 0.3 MPa per hour. Upon reaching a test pressure equal to 1.25 working pressure, but not lower than 1.6 MPa, the heat conductor is held for some time to equalize the air temperature along the length of the section.

If during the inspection no leaks, defects in welds, violation of the integrity of the pipeline, and no shift or deformation of the structures of fixed supports are found, then the pipeline is considered to have passed the preliminary test. The duration of the preliminary tests is determined by the time required for holding and thoroughly inspecting the pipelines.

If the specified test is used as the final one, after the completion of all installation and welding work, the pressure in the heat pipe is smoothly brought to the test pressure and maintained for 30 minutes. If at the same time there are no signs of violation of the integrity of the pipeline, then the pressure drops to 0.3 MPa, and the heat pipeline is kept under this pressure for 24 hours. at low temperatures - with the use of heated water. An appropriate act is drawn up on the test results in accordance with SNiP 41-02-2003.

Flushing of pipelines. Pipelines of water heating networks in closed heat supply systems, as a rule, are subjected to hydropneumatic flushing, i.e. mixture of water and air. The purpose of flushing is to clean the inner surface of the pipes from construction debris, sand, dirt, rust, scale, etc., that accidentally got into the pipes. It is advisable to start flushing immediately after testing the pipes in order to use the water already filled in. The drain and air valves required for flushing should be installed on the pipes before testing the pipelines.

High-quality washing of pipes of large diameter and long length requires the creation of high speeds of water movement, which is achieved by mixing compressed air with a pressure of 0.3-0.6 MPa into the washed water. On the washed section of the heat pipeline in several places at low points (through drain valves), air is supplied from compressors. Compressed air mixes with water rust, scale, sand and dirt that have settled in the lower part of the pipes, and an increased speed helps to eject them from the heat pipeline with water.

Pipelines of water heating networks of open heat supply systems must be flushed hydropneumatically with drinking-quality water until the flushing water is completely clarified. Upon completion of flushing, pipelines must be disinfected by filling them with water containing active chlorine at a dose of 75-100 mg / l with a contact time of at least 6 hours. Pipelines with a diameter of up to 200 mm and a length of up to 1 km are allowed by agreement with local bodies of the sanitary and epidemiological service, do not subject to chlorination and limit yourself to washing with drinking water.

Flushing of supply and return heat pipelines, depending on their length, is carried out in parallel or sequentially by sections or entire highways. Usually, a jumper between the supply and return lines is arranged to flush the return pipeline. Diameters of branch pipes for water discharge, fittings for compressed air and jumpers are determined by the project or are selected from reference literature depending on the diameter of the pipeline.

The discharge of water from the drains during flushing is controlled and regulated by a representative of the operating organization in terms of the amount of make-up water and the pressure in the return line to the CHP or boiler house. The quality and clarification of water is preliminarily determined visually, and finally - by laboratory analysis.

Based on the results of pipeline flushing, the construction and installation organization draws up an act in the form of Appendix 3 of SNiP 3.05.03-85 with the participation of representatives of technical supervision and the operating organization.