From the editor: Until now, experts cannot come to a consensus on the issue of conducting hydraulic tests of heating networks. This issue has been repeatedly raised on the pages of the NT magazine (in particular, see NT: No. 6, 2001; No. 8, 2007; No. 7, 2008). To develop the topic, we invite you to read another opinion on this issue in the article below.

Hydraulic testing of heating networks - it's time to think about it!

A.I. Kapitanov, Honorary Mechanical Engineer of Russia,
chief project engineer of ReMoNa LLC, Kolomna, Moscow region

The essence of the proposed method

IN Russian conditions(with high-quality regulation of the heat supply system) during the heating season, the water temperature in heating networks, depending on the outside air temperature, changes more than 40 times, i.e. In winter, heating networks resemble accordion bellows: they either separate or come together.

Cyclic extensions of the length of heating network pipelines during the heating period range from 10 mm or more. The stresses created in this case cannot be compared with the elongations and stresses in heating networks during tests for strength and density, which, according to clause 6.2.13 of the Rules technical operation thermal power plants" (approved by Order of the Ministry of Energy of the Russian Federation dated March 24, 2003 No. 115) are carried out no later than two weeks after completion heating season.

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

But with the onset of the next heating season, again sleepless nights, again rush jobs to eliminate leaks in heating networks and so on ad infinitum.

The author of the article, being the head of the energy service of a reputable enterprise, experienced all these delights of life and, completely exhausted, gave the command to conduct cyclic temperature tests of heating networks at the end of the heating season, in other words, to simulate their behavior in the upcoming heating season.

As a result of the tests, instead of 3-4 traditional leaks, 34 leaks were identified.

During the summer without emergency situations, these leaks were fixed as planned, and the coming winter was, by and large, survived without the slightest disruption in the heat supply to consumers. Further, the experience gained was practiced annually.

Conclusions

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

Necessary:

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

2. Despite leaks, emergency feed the heating network, turn it on and off hot water boilers(steam-water heaters) until the pressure drop in the heating network stabilizes (this will indicate that new leaks do not appear).

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

The implementation of this seemingly insignificant event will allow:

■ provide in winter period uninterrupted heat supply to consumers;

■ prevent unproductive losses of thermal energy;

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

There are 4 types of testing of heating networks:

1. For strength and tightness (crimping). Performed at the manufacturing stage before applying insulation. When used annually.
2. On design temperature . Carried out: to check the operation of compensators and fix their working position, to determine the integrity of fixed supports (1 time every 2 years). Tests are carried out during the manufacture of networks before applying insulation.
3. Hydraulic. They are carried out with the aim of determining: the actual water consumption of consumers, the actual hydraulic characteristics of the pipeline and identifying areas with increased hydraulic resistance (once every 3-4 years).
4. Thermal tests . To determine actual heat losses (once every 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 losses 1 m of pipeline are determined according to SNiP “Thermal insulation of 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.

Instruments: 2 pressure gauges (working and control) class higher than 1.5%, pressure gauge diameter not lower than 160 mm, scale 4/3 of the test pressure.

Procedure:

1. Disconnect the test area with plugs. Replace the stuffing box expansion joints with plugs or inserts. Open all bypass lines and valves unless they can be replaced with plugs.
2. The test pressure is set = 1.25 P slave, but not more than the working pressure of the pipeline P y. Exposure 10 minutes.
3. The pressure is reduced to operating pressure, and inspection is carried out at this pressure. Leaks are monitored 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 monitored.

Pneumatic tests It is prohibited to carry out for: Overhead pipelines; When combined with other communications.

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

Instruments: 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 use = 1.25 R work.
3. The pressure rises to P tested, but not more than 0.3 MPa. Exposure 30 min.
4. Reducing pressure to P slave, inspection. Leaks are determined by the following signs: a decrease in pressure on pressure gauges, noise, bubbling of a soap solution.

Safety precautions:

• during the inspection it is prohibited to go down into the trench;
• Do not get exposed to air flow.

Design Temperature Tests

Heat networks with d ≥100mm are tested. In this case, the design temperature in the supply pipeline and in the return pipe should not exceed 100 0 C. The design temperature is maintained for 30 minutes, while the increase and decrease in temperature should not be more than 30 0 C / hour. This type of test is carried out after the networks have been pressure tested and breaks have been eliminated.

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 branches of the branch are disconnected. In this case, the decrease in temperature along the ring is caused only by heat losses of the pipelines. The test time is 2t to + (10-12 hours), t to is the travel 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 established 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 mode, at least 15 readings must be taken with an interval of 5 minutes.

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Hydraulic testing of pipelines.

Hydraulic testing of heating networks is carried out twice: first, the strength and density of the heating pipe is checked without equipment and fittings, then the entire heating pipe, which is ready for operation, with installed mud traps, valves, compensators and other equipment. Repeated testing is necessary because once the equipment and fittings are installed, it is more difficult to check the density and strength of the welds.

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

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

During the final test, the connection points of individual sections (in cases where the heat pipeline is tested in parts), welds of mud traps and stuffing box expansion joints, equipment casings, and flange connections are subject to inspection. During inspection, the seals must be sealed and the section valves must be fully open.

The need for two tests of heating pipelines is also due to the fact that in long sections it is not possible to check the entire heating pipeline at one time. The trench would have to be left open for a long time. In this regard, individual sections of heating networks are tested before backfilling, as they are prepared. The length of the tested section depends on the construction time on individual sections of the route, on the availability of manual, hydraulic or mechanized presses, filling units, piston pumps, the power of the water source (river, pond, lake, water supply system), work conditions, terrain, etc. .

When hydraulic testing heating networks, the sequence of work is as follows:
- clean heating pipes;
- install pressure gauges, plugs and taps;
- connect water and hydraulic press;
- fill the pipelines with water to the required pressure;
- inspect heat pipelines and mark places where defects are found;
- eliminate defects;
- perform a second test;
- disconnect from the water supply and drain water from the pipes;
- remove pressure gauges and plugs.

To fill the pipelines with water and ensure good removal of air from the pipes, the water supply is connected to the bottom of the heating pipe. A person on duty must be posted near each air valve. First, only air flows through the vents, then an air-water mixture, and finally only water. When only water comes out, the tap is turned off. Next, the tap is periodically opened two or three more times to completely release the remaining air from the upper points. Before filling the heating network, all vents must be opened and drains closed.

The test is carried out with a pressure equal to the working pressure with a coefficient of 1.25. By working is meant the maximum pressure that can arise in a given area during operation.

In cases where a heat pipeline is tested without equipment and fittings, the pressure is raised to the design pressure and maintained for 10 minutes, while monitoring the pressure drop, then it is reduced to the working pressure, the welded joints are inspected and the joints are tapped. The tests are considered satisfactory if there is no pressure drop, no leakage or sweating of the joints.

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

After testing, water must be completely removed from the pipes. As a rule, test water does not undergo special preparation and can reduce the quality of supply water and cause corrosion of the internal surfaces of pipes.

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

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One of which is hydraulic, necessary to identify:

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

In what cases is it necessary to carry out hydrotesting?

• Upon completion of pipeline installation work, which was carried out due to the replacement of pipes or the assembly of a new section of the heating system, before putting it into operation.
• In case of replacement or repair of components of the heating network.
• During scheduled network maintenance, which is carried out with the aim of starting the heating system for the autumn and winter period.

Cost of hydraulic testing of heating networks

What is used to measure pipeline characteristics

When carrying out activities to measure flow rates and pressures, instruments that are metrologically certified are used:

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

Stages of testing

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

• The first stage is preparation. During this period, the initial data on the network is clarified and recorded, after which a measurement program is developed and agreed upon. At this stage, preparatory actions are also underway to create testing conditions. This includes:
  • Before starting the process, you need to check whether all work on welding, installation, installation of gaskets in connections, and tightening of these connections has been completed.
  • You also need to check whether all the equipment is in order, the presence and functionality of the air drain valves.
  • Connecting the hydraulic press to the water supply and to the pressure pipe pipeline. Checking the correct connections.
  • Disconnecting the pipeline section where the test will be carried out from equipment that has not yet been fully installed or is already in use.
  • Installation of necessary instruments for testing.
• The second stage is to conduct a test under appropriate conditions. Tests must be carried out in compliance with all requirements regarding ambient temperature conditions. In case of violation, this may lead to inaccuracy of the received data.
• Prerequisites:
• The ambient temperature during events must be above zero.
• The temperature of the water used in the test should be from +5 to +40.
• Providing observation platforms for above-ground heating systems.
• Smooth increase in pressure. It should be approximately 40% higher than nominal. To increase it, the use of compressed air is prohibited.
• The test section of the pipeline must be maintained under test pressure for at least 15 minutes.
• Upon completion, the entire site must be carefully inspected and if defects are found, the measures necessary to eliminate them must be taken.
• And the last stage, this is an analysis of the results obtained and the compilation of a table indicating all the parameters. If deviations from the norm are detected, measures are taken to eliminate them, such as:
• Cleaning and flushing of the pipeline.
• Pipeline relocation.
• In case of serious problems, repairs and elimination of detected defects are carried out.

Upon completion of measures to eliminate the causes of deviations, the tests must be carried out again.

Section Contents

General provisions. Heating networks are tested for tightness (density) after completion of construction before putting them into operation, and then annually after the end of the heating period to identify defects that need to be eliminated during major repairs and after completion of repairs, before switching on putting networks into operation [2].

Newly constructed heating networks are preliminarily tested for density (pressure testing) in separate sections after welding and laying the pipelines on permanent supports before blocking the channels or backfilling the trenches. The test areas must be freely accessible for thorough inspection and tapping of sealed connections.

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

At low outside temperatures or in the absence of water on site at 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 SN 298-65.

When testing heating networks for density, spring pressure gauges of an accuracy class of at least 1.5 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 are used. Pressure gauges must be sealed by a state verifier. It is not allowed to use pressure gauges with expired seals. To tap welds at joints, use a hammer with a rounded head weighing no more than 1.5 kg and a handle no more than 500 mm long.

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

The results of the preliminary test for network tightness are considered satisfactory if no pressure drop occurred during the test, and no signs of rupture, leakage or fogging were found in the welded seams of the pipes. Before their installation on a pipeline, valves are tested under the pressure accepted for this pipeline, but not less than 16 kgf/cm2 (1.6 MPa) for valves on the supply pipeline and 12 kgf/cm2 (1.2 MPa) on the return pipeline. Valves are tested in two positions of the sealing rings: in the open position with the valve flange plugged - to check the tightness of the stuffing box devices; in the closed position - to check the tightness of the rings grinding.

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 highest point of the network). All sectional valves and valves on the branches of the network under test must be open. When the outside air temperature is below 1°C, tests are carried out with water heated to 50-60°C. To quickly remove water in order to prevent it from freezing, devices are provided that ensure its drainage from pipelines within 1 hour. The duration of the final tightness tests of the heating network is determined by the time required for its inspection and must be at least 10 minutes.

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

Pneumatic tests for tightness of newly built heating networks. Pneumatic tests are carried out on sections no longer than 1000 m. When laying a route outside populated areas, it is allowed, as an exception, to test sections 3000 m long. The test pressure during pneumatic tests is equal to the operating pressure of the network with a coefficient of 1.25, but not less than 16 kgf/cm 2 (1.6 MPa) for supply and 10 kgf/cm 2 (1.0 MPa) return pipelines.

The duration of the pipelines being under test pressure is 30 minutes, then the pressure is reduced to 3 kgf/cm2 (0.3 MPa) and the pipelines are inspected. Places of air leaks are identified by washing the joints, by sound, by odorization or smoke of the air in the pipeline. The results of preliminary tests are considered positive if a thorough inspection of the pipes does not reveal any defects in the welds, damage to the integrity of the pipelines or leaks.

The duration of preliminary tests is determined by the time required for a thorough inspection of the pipes. Defects identified during inspection are eliminated after removing excess pressure in the pipeline. Final pneumatic tests are performed after completion of installation 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 damage to 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 expiration of the exposure period, set the pressure rn, equal to 3000 mm water. Art. using a liquid pressure gauge, note the start time of the test, as well as the barometric pressure pH b mm Hg. Art.; d) after the test time, measure the pressure in the pipeline p k mm water. Art. and barometric pressure p k b mm Hg. Art.; e) the true value of the pressure drop (mm water column) in the pipeline is determined by the formula

Δp=ν(r n -r k)-13.6(r n b -r k b),

where ν is the density of the liquid pressure gauge filler (for water ν = 1 g/cm 3). When using kerosene (ν=0.87 g/cm3) in a liquid pressure gauge, 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 damage to its integrity was detected during the test, and the pressure drop does not exceed the permissible value given in Table. 5.38.

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

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

Hydraulic tests for tightness of heating networks and heat consumption systems in operation. Testing of heating 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. During testing, consumer heating points 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/cm2 (1.6 MPa). The required pressure is provided by the network pump of the heat source. One or more jumpers are first opened between the supply and return pipelines at the end of the network so that the water flow through these jumpers ensures the operation of the network pump on the descending part of its characteristic curve.

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 main at the heat source manifold before inserting (along the water flow) the make-up pipeline. When the required pressure is reached in the supply pipeline, 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 network sections in which, due to terrain profile conditions, network pumps cannot create a pressure equal to 1.25 working pressure, mobile pumping units or hydraulic presses are used.

At the initial moment of testing, the recharge of the heating network may exceed the standard value, which is explained by the compression of the air available in the network. However, with sufficient tightness (density) of the network, the amount of recharge after 10-15 minutes. decreases to the normative level and remains at this level. Exceeding the standard recharge value (0.1% of the capacity of the tested network) or a tendency to increase after 10-15 minutes. after the start of testing indicates excessive leakage and poor network tightness. In this case, the network pump is stopped and the test is stopped until the leak is located and eliminated.

To speed up checking the tightness of the network and finding the location of the leak, during the inspection period it is allowed to eliminate defects in the joints by caulking, as well as seal prefabricated and flanged connections by applying clamps on rubber gaskets. Upon completion of the network density check, the detected defects are eliminated using conventional methods. After all defects have been eliminated, the tightness of the network is re-checked. 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 leak test if, when left in place for 10 minutes. under pressure equal to 1.25 working, replenishment does not exceed the standard value. The tightness of the branches is checked after restoring water circulation in the main by establishing a pressure in them equal to the pressure in the main pipeline.

Equipment of heating points and all underground pipelines of intra-block and intra-yard networks after central heating points, as well as pipelines and equipment of heat consumption systems are subjected to hydraulic leak tests at an excess pressure of 1.25 working, 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 heating devices - 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).

Tests of equipment at heating points, heat pipelines from central heating points and heat consumption systems are carried out in the following order: a) after filling the pipelines or systems and completely removing air through air bleeders from all upper pressure points in the pipelines, bring it to working pressure and maintain it for the time required for thorough inspection of welded and flanged connections, equipment, fittings, etc., but not less than 10 minutes; b) if no defects or leaks are detected during this time, 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 heating points and the heating pipelines of yard and neighborhood networks extending from them for 10 minutes. there was no pressure drop. When testing panel heating systems, the pressure drop within 15 minutes is allowed to be no more than 0.1 kgf/cm2 (0.01 MPa).

Coloring of network water allows you to determine the location of its leakage in the communications of existing thermal power plants, boiler houses, heating networks, hot water supply heaters, identify hidden jumpers between heating networks and heat consumption systems with an independent connection scheme, detect water withdrawal from closed heating systems, as well as the content of network water in flooded ground and surface water, channels and chambers. The dye can only be used with the permission of the Chief Sanitary Doctor of the city or locality. One of the requirements for the dye is the ability to detect it at low concentrations.

As an indicator of network water leakage, pure fluorescein sodium (uranine) (C 20 H 10 Na 2 O 5) is used (TU 6-09-2281-77, produced by the Berezniki Chemical Plant. It is also allowed to use technical fluorescein (C 20 H 12 O 5). Uranine is a yellow-brown powder that dissolves in water with a yellow color and intense green fluorescence. When acidified, fluorescence disappears; when alkalized, it appears again. It is used as an adsorption or fluorescent indicator. Fluorescein is a yellowish-red or red crystalline powder that is insoluble. water, ether, chloroform, benzene. 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 preferable due to its good solubility. , Chelyabenergo uses fluorescein.

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

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

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

Water sampling from consumers, in chambers and channels of heating networks, after treatment facilities of industrial enterprises, from hot water supply systems is carried out by heating network personnel according to a specially drawn up schedule. Before taking samples from the hot water supply system, the pressure of the tap water is reduced by turning off the pumps at the heating point or partially closing 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 a special device - a source of ultraviolet rays.