Hydraulic testing of pipelines of heating systems

Only a functioning and reliable functioning of the heating system can provide a quiet and normal life of the population during the winter season. Sometimes there are various kinds of extreme situations, in which the performance of the system can significantly differ from civilian conditions. Hydraulic testing of pipelines and crimping are necessary to prevent situations that may occur during the heating season.

Purpose of hydraulic tests

As a rule, any heating system operates in the standard mode. The working pressure of the coolant in low-rise buildings is basically 2 atm, in nine-storey buildings - 5-7 atm, in multi-storey buildings - 7-10 atm. In the heat supply system, laid underground, the pressure index can reach 12 atm.

Sometimes there are unforeseen jumps of pressure, which leads to its increase in the network. As a result, a hydraulic shock occurs . Hydraulic testing of heating pipelines is necessary to test the system not only for the ability to function under standard normal conditions, but also on its ability to overcome hydraulic shocks.

If, for some reason, the heating system has not been checked, then after a hydraulic shock serious accidents can occur that will lead to a flood of boiling water in rooms, equipment, furniture, etc.

Sequence of work

Perform hydraulic tests of pipelines in the following sequence.

• Pipeline cleaning.
• Installation of cranes, plugs and pressure gauges.
• Water and a hydraulic press are connected .
• Pipelines are filled with water to the required value.
• Inspection of pipelines and marking of places where defects were found are performed.
• Elimination of defects.
• Conducting the second test.
• Disconnection from the water supply and drainage of water from the pipelines.
• Removal of the plug and pressure gauges.

Preparatory work

Before performing hydraulic tests of pipelines of heating systems, it is necessary to check all valves, fill the glands with glands. Pipelines repair and check insulation. The heating system itself must be separated from the main pipeline by means of plugs.

After performing all the necessary manipulations, the heating system is filled with water. With the help of pumping equipment, an overpressure is created , its indicator is about 1.3-1.5 times higher than the working one. The pressure produced in the heating system must be kept for another 30 minutes. If it does not decrease, the heating system is ready for operation. Acceptance of works on hydraulic tests is carried out by inspection of heat networks.

Tests for strength and tightness

Preliminary and acceptance hydraulic testing of pipelines (SNiP 3.05.04-85) must be carried out in a certain sequence.

Strength

1. In the pipeline, the pressure is increased to the test (P _and ) by pumping water and is maintained for 10 minutes. Do not lower the pressure above 1 kgf / m ² (0.1 MPa).
2. The test pressure is reduced to the design pressure (P _p ) internal, then it is maintained by pumping water. The pipelines are inspected for defects during the time required to perform this inspection.
3. The detected defects are eliminated, then a repeated hydraulic test of the pressure pipeline is performed. Only after this, it is possible to proceed with the leak test.

Tightness

1. In the pipeline, the pressure rises to the test value for leakage (P _g ).
2. The start time of the test is fixed (T _н ), the initial level of water (h _н ) is measured in the measuring tank.
3. After that, the pressure in the pipeline is reduced.

There are three possible options for the drop in pressure, we will consider them.

First

If within 10 minutes the pressure indicator decreases by less than 2 marks of the pressure gauge scale, but also does not become lower than the calculated internal (P _p ), then you can complete the observation.

Second

If after 10 minutes the pressure drops by less than 2 marks on the pressure gauge scale, then monitoring of the pressure drop to the internal (P _p ) calculated must be continued until it falls by no less than 2 marks on the pressure gauge scale.

The duration of observation for reinforced concrete pipes should not exceed 3 hours, for cast-iron, steel and asbestos-cement pipes - 1 hour. After the specified time, the pressure should drop to the design pressure (P _p ), otherwise the water from the pipelines is dumped into the measuring tank.

The third

If within 10 minutes the pressure becomes less than the internal design pressure (P _p ), then further hydraulic testing of the heating pipes must be stopped and measures taken to eliminate the hidden defects by keeping the pipes at the internal design pressure (P _p ) until after a close inspection There will be no defects that will cause an unacceptable pressure drop in the pipeline.

Determination of additional water volume

After the observation of the drop in the pressure index for the first option and the termination of the release of the coolant in accordance with the second variant are completed, the following should be done.

• By pumping from a measuring tank of water, the pressure in the pipeline increases to the value in hydraulic tests (P _g ).
• It is necessary to remember the time when the leakproofness test (T _k ) was completed.
• Then it is necessary to measure the final water level h _k in the measuring tank.
• Determine the duration of testing of pipelines (T _k -T _n ), min.
• Calculate the amount of water pumped from the measuring tank Q (for the first option).
• Determine the difference between the volumes of water pumped out and discharged from the pipelines or the amount of additional pumped-up water Q (for the 2nd variant).
• Calculate the actual flow rate of additionally pumped water (q _n ) according to the following formula: q _n = Q / (T _k -T _n )

Drawing up an act

The certificate that all works were carried out is an act of hydraulic testing of pipelines. This document is compiled by the inspector and confirms that the work was carried out in compliance with all norms and rules, and that the heating system withstood them successfully.

Hydraulic testing of pipelines can be carried out in two main ways:

1. Manometric method - tests are performed by means of pressure gauges, devices that record the pressure indicators. During operation, these devices show the current pressure in the heating system. Conducted hydraulic testing of pipelines by means of a manometer allows the inspector to check what pressure indicator was during testing. Thus, the service engineer and the inspector check how reliable the tests are.
2. The hydrostatic method is considered to be the most efficient, it allows you to check the heating system for operation at a pressure that exceeds the average operating figure by 50%.

Different parts of the system are tested at different times, while hydraulic testing of pipelines can not last less than 10 minutes. In heating systems, an allowable pressure drop is considered to be 0.02 MPa.

The main condition for the start of the heating season is properly conducted and properly designed hydraulic testing of pipelines (SNiP 3.05.04-85), in accordance with the requirements of the current regulatory documentation.