General information

Based on the Rules technical operation thermal power plants (approved by order of the Ministry of Energy of the Russian Federation dated March 24, 2003 N 115), when operating heating network systems, heating network enterprises must ensure the reliability of heat supply to consumers, the supply of coolants (water and steam) with flow rates and parameters in accordance with temperature chart regulation and inlet pressure drop.

During operation, all existing heating networks must be tested for strength and density to identify defects no later than two weeks after the end of the heating season.

Hydraulic testing of pipelines of water heating networks in order to check strength and density should be carried out test pressure with the results included in the act.

Test pressure is the excess pressure at which hydraulic testing of thermal power plants and networks should be carried out for strength and density.

The minimum value of test pressure during hydraulic testing is 1.25 working pressure, but not less than 0.2 MPa (2 kgf/cm2).

The maximum value of the test pressure is established by strength calculations according to the normative and technical documentation agreed with the State Mining and Technical Supervision Authority of Russia. The test pressure value is chosen by the manufacturer ( design organization) between the minimum and maximum values.

Hydraulic tests are carried out by the person responsible for the safe operation of heating networks together with personnel authorized to operate heating networks.

Hydraulic tests

When conducting hydraulic tests for the strength and density of heating networks, the equipment of heating networks (stuffing box, bellows compensators, etc.), as well as sections of pipelines and connected heat-consuming power plants not involved in the tests, should be disconnected with plugs.

Strength and density tests are carried out in the following order:

disconnect the tested section of the pipeline from existing networks;

at the highest point of the section of the pipeline under test (after filling it with water and bleeding air), set the test pressure (control using a pressure gauge);

the pressure in the pipeline should be increased gradually;

the rate of pressure rise must be indicated in the regulatory and technical documentation (NTD) for the pipeline.

Tests for strength and density are carried out in compliance with the following basic requirements: pressure measurements during testing should be carried out using two certified spring pressure gauges (one control) of class not lower than 1.5 with a body diameter of at least 160 mm. The pressure gauge must be selected from the condition that the measured pressure value is within 2/3 of the instrument scale; test pressure must be provided at the top point (mark) of the pipelines; the water temperature must be no lower than 5 °C and no higher than 40 °C; when filling with water, air must be completely removed from the pipelines; the test pressure must be maintained for at least 10 minutes and then reduced to working pressure; at operating pressure, a thorough inspection of pipelines is carried out along their entire length.

The test results are considered satisfactory if during the test there was no drop in pressure and no signs of rupture, leakage or fogging were found in the welds, as well as leaks in the base metal, in valve bodies and seals, in flange connections and other pipeline elements. In addition, there should be no signs of movement or deformation of pipelines and fixed supports.

A report of the established form is drawn up on the results of testing pipelines for strength and density.

The results of hydraulic tests of the pipeline for strength and tightness are considered satisfactory if during their conduct there was no drop in pressure, no signs of rupture, leakage or fogging were found in welds, as well as leaks in the base metal, flange connections, fittings, compensators and other pipeline elements , there are no signs of shift or deformation of the pipeline and fixed supports.

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

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

• check the validity periods of approvals technological scheme pipeline testing and, if necessary, re-agreed the work project with operational services and make payment for the supply of heating or drinking water for filling pipelines;
• check the design position of the moving supports;
• securely secure the fixed supports and fill them with soil;
• disconnect the tested pipelines with plugs from existing or already put into operation and from the first shut-off valves installed in the building;
• install plugs at the ends of the pipelines being tested, and instead of stuffing box expansion joints and sectional valves, temporarily install “coils”;
• connect the press and pipeline to the water supply source and install pressure gauges;
• provide access for the entire length of the pipelines being tested external examination and inspection of welds during testing;
• open the valves and bypass lines completely.

For testing by the hydrostatic method, hydraulic presses and piston pumps with mechanical or electric drive are used. When performing tests for strength and tightness, pressure is measured using certified and sealed spring pressure gauges (at least two - one control) of class no lower than 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 using the hydrostatic method is carried out with a test pressure equal to 1.25 working pressure, but not less than 1.6 MPa. Working pressure is determined by the coolant pressure in the supply pipeline of a thermal power plant or boiler house. If the profile of the tested network is steep, the excess pressure at the lowest points should not exceed 2.4 MPa. Otherwise, the test must be carried out in separate areas. Hydrostatic testing of pipelines laid in a trench with impassable channels is carried out in two steps: preliminary and final.

During preliminary testing, the strength and tightness of welds and pipeline walls are checked before installing fittings and linear equipment. Before the preliminary test, the heat pipeline cannot be covered with building structures and filled up. Preliminary testing of heat pipelines using the hydrostatic method is carried out on small sections no more than 1 km long, as well as when laid in cases and sleeves.

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

At the final test, the construction of the heat pipeline must be completely completed in accordance with the design. During testing, the joints of individual sections are checked (if the heat pipeline was previously tested in parts), welds of fittings and linear equipment, the tightness of flange connections, and housings of linear equipment.

When filling pipelines with water and when draining water after testing, air valves installed in highest points pipeline profile, must be completely open, and the drain valves, which ensure the release of water in no more than an hour, must be closed. To displace air from the pipes, water supply is brought to the lowest point of the pipeline.

Test pressure during testing using 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 the pressure gauge does not detect a drop in pressure, leaks or fogging of the welds, then the pressure in the tested section of the pipeline is reduced to operating pressure, and the pipeline is re-inspected. The test results are considered satisfactory if during the entire test period there is no pressure drop on the pressure gauge, leakage or fogging of welds, ruptures, signs of shift or deformation of fixed support structures. If leaks appear in the seams during testing using the hydrostatic method, correcting them by hammering is prohibited. Defective areas found are cut out, cleaned and welded again, after which the test is repeated.

Pneumatic test. At low temperatures external air and the absence of heated water for testing pipelines, the construction and installation organization can, in agreement with the customer and operators, conduct testing using the pneumatic method. Testing using the pneumatic method is carried out in the following sequence: clean and blow through the pipeline; install plugs and pressure gauges; connect the compressor to the pipeline; fill the pipeline with air to a given pressure, prepare a soap solution; inspect the pipeline, coat the joints with soapy water and mark defective areas; eliminate detected defects; retest the pipeline; bleed 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 leaking air, by bubbles formed at the leak site if 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 for checking the leakage of a pipeline when testing it using a pneumatic method using soap solution(100 g laundry soap dissolve in 1 liter of water). In urban conditions, testing of pipelines using the pneumatic method is carried out on a section no more than 1000 m long.

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. When a test pressure is reached equal to 1.25 working pressure, but not lower than 1.6 MPa, the heat wire is maintained for some time to equalize the air temperature along the length of the section.

If the inspection does not reveal leaks, defects in welds, violation of the integrity of the pipeline, and there is no shift or deformation of the fixed support structures, then the pipeline is considered to have passed the preliminary test. The duration of preliminary tests is determined by the time required to maintain and thoroughly inspect the pipelines.

If the specified test is used as a final test, after 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 there are no signs of damage to the integrity of the pipeline, then the pressure is reduced to 0.3 MPa, and the heat pipeline is maintained under this pressure for 24 hours. After all construction and installation work is completed, the final test of the heat pipelines is carried out using the hydrostatic method in the warm season, and at low temperatures - using heated water. A corresponding report 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. a mixture of water and air. The purpose of flushing is to clean inner surface pipes from construction debris, sand, dirt, rust, scale, etc., accidentally falling into the pipes. It is advisable to start flushing immediately after testing the pipes in order to use the already filled water. The drain and air taps necessary for flushing must 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 to the washed water. On the section of the heat pipeline being washed, air from compressors is supplied in several places at low points (through drain valves). Compressed air mixes with water the rust, scale, sand and dirt that has settled in the lower part of the pipes, and increased speed promotes their ejection by water from the heat pipeline.

Pipelines of water heating networks open systems Heat supplies must be flushed hydropneumatically with potable quality water until the flushing water is completely clarified. Upon completion of flushing, the pipelines must be disinfected by filling them with water containing active chlorine in 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 permitted by agreement with local sanitary and epidemiological service authorities, do not chlorinate and limit yourself to rinsing with drinking water.

Flushing of supply and return heat pipelines, depending on their length, is carried out in parallel or sequentially in sections or entire lines. Usually, to flush the return pipeline, a jumper is installed between the supply and return lines. The diameters of water discharge pipes, fittings for compressed air and jumpers are determined by the project or 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 based on the amount of make-up water and the pressure on the return line at the thermal power plant or boiler house. The quality and clarification of water is preliminarily determined visually, and finally - by laboratory analysis.

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

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 to determine: the actual water consumption of consumers, the actual hydraulic characteristics of the pipeline and to identify 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.

During 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.

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 using 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 its 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, this 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 network tightness 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/cm2 (0.75 MPa) at the lowest point of the system, and for panel and convector systems - 10 kgf/cm2 (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.

Hydraulic testing of pipelines of heating networks (pressure testing) is carried out with water at a temperature not lower than + 5 ° C. Pipelines and their parts must be subjected to hydraulic testing with a test pressure equal to 1.25 working pressure, but not less than 1.57 MPa (16 kgf/cm 2 ) for supply pipes and 1.18 MPa (12 kgf/cm 2) for return pipes.

According to the Rules for Technical Operation (RTE) of heating networks and heating points of the Ministry of Housing and Communal Services of the RSFSR, water heating networks from boiler houses equipped with cast iron boilers are tested at a pressure equal to 1.25 of the working pressure in the supply manifold, but not less than 0.59 MPa (6 kgf/cm 2 ). Pressure must be measured using two proven pressure gauges with an accuracy class of at least 1.5.

Hydraulic testing of heating networks for ducted and ductless installations is carried out in two stages (preliminary and final). Preliminary testing is done in small areas - up to 1 km, final testing - during all construction and installation work. Both are done after installing and welding the movable supports, installing and backfilling the fixed supports, but before covering the pipes and fittings with thermal insulation. When installing pipelines from seamless pipes, hydraulic testing of pipelines can be carried out after insulating the pipes, but provided that the welded joints are free from insulation, not covered with waterproofing and are located in places accessible for inspection.

If during tests with test pressure no pressure drop is detected, the pressure in the tested section of the pipeline is reduced to the working one and at this pressure the welded joints are tapped with a hammer with a rounded head weighing no more than 1.5 kg with a handle length of no more than 500 mm; blows must be applied at a distance of at least 150 mm from the weld on both sides. The test results are considered satisfactory if the pressure did not decrease during the test, and no signs of rupture, leakage or sweating were found in the welded seams of the pipes.

Draining of water after testing or detection of defects should be carried out immediately with final air purging of the emptied heat pipelines, and it should be checked whether there is any water remaining at the lowest points of the pipeline.

Hydraulic testing of individual pipes is carried out in accordance with GOST 3845-75. For hydraulic testing of pipes of small diameters and lengths of sections, manual hydraulic pumps are used, and for large diameters, piston pumps with mechanical and electrical drives are used.

Pneumatic testing of pipelines. According to SNiP III-30-74, testing of pipelines for strength and tightness, instead of a hydraulic test, can be carried out pneumatically at the discretion of the construction organization (heating network enterprise) if it is difficult to carry out a hydraulic test (winter time, lack of water at the test site, etc.). Pneumatic tests must be carried out in accordance with the rules SP 298-65 of the USSR State Construction Committee. According to the rules, pneumatic testing of heating network pipelines with a coolant temperature above 120 ° C, steam pipelines with a pressure above 0.098 MPa (1 kgf/cm2) must be carried out with a test pressure equal to the working pressure with a coefficient of 1.25, but not less than 1.57 MPa (16 kgf/cm2) for supply and 0.98 MPa (10 kgf/cm2) for return pipelines.

Considering that in installation conditions it is practically impossible to create such a test pressure, and also that such a high test pressure with air would create a great danger for personnel, and in urban conditions for the population, replacing a hydraulic test with a pneumatic one should be avoided if possible. In the absence of water, it is allowed to carry out preliminary testing of pipelines with air at a pressure of 0.59 MPa (6 kgf/cm2). The pipeline is maintained under this pressure for 30 minutes, then the pressure is reduced to 0.29 MPa (3 kgf/cm2) and the pipelines are inspected. Air leaks are detected by washing the joints, by sound, by odorization or smoke formation of the air in the pipeline. After a preliminary pneumatic test, the final test is carried out hydraulically.