Only proper and reliable functioning of the heating system can ensure a calm and normal life of the population in the winter season. Sometimes there are various kinds of extreme situations in which the performance of the system can differ significantly from civilian conditions. Hydraulic testing of pipelines and pressure testing are necessary to prevent situations that may arise during the heating season.
Purpose of hydraulic testing
As a rule, any heating system operates in standard mode. The working pressure of the coolant in low-rise buildings is mainly 2 atm, in nine-story buildings - 5-7 atm, in multi-storey buildings - 7-10 atm. In a heat supply system laid underground, the pressure indicator can reach 12 atm.
Sometimes unexpected surges of pressure occur, which leads to its increase in the network. The result is water hammer. A hydraulic test of heating pipelines is necessary to check the system not only for its ability to function under standard normal conditions, but also for its ability to overcome water hammer.
If for some reason the heating system has not been tested, then later hydraulic shocks can cause serious accidents that will lead to the flooding of rooms, appliances, furniture, etc.
Sequence of work
Hydraulic testing of pipelines should be carried out in the following sequence.
- Cleaning pipelines.
- Installation of taps, plugs and pressure gauges.
- Water and hydraulic press are connected.
- Pipelines are filled with water to the required level.
- Inspection of pipelines and marking of places where defects were found.
- Troubleshooting.
- Performing the second test.
- Disconnecting from the water supply and draining water from pipelines.
- Removing the plug and pressure gauges.
Preparatory work
Before performing hydraulic testing of pipelines of heating systems, it is necessary to inspect all valves, fill seals on the valves. Insulation is being repaired and checked on pipelines. The heating system itself must beseparated from the main pipeline by plugs.
After performing all the necessary manipulations, the heating system is filled with water. With the help of pumping equipment, excess pressure is created, its indicator is about 1.3-1.5 times higher than the working one. The resulting pressure in the heating system must be maintained for another 30 minutes. If it has not decreased, then the heating system is ready for operation. The acceptance of work on hydraulic testing is carried out by the inspection of thermal networks.
Strength and Leak Testing
Preliminary and acceptance hydraulic testing of pipelines (SNiP 3.05.04-85) must be carried out in a certain sequence.
Strength
- The pressure in the pipeline is increased to the test pressure (P and) by pumping water and maintained for 10 minutes. The pressure must not be allowed to drop above 1 kgf/m2 (0.1 MPa).
- The test pressure is reduced to the design (Pp) internal, then it is maintained by pumping water. Pipelines are inspected for defects for the time required to carry out this inspection.
- The detected defects are eliminated, after which a repeated hydraulic test of the pressure pipeline is performed. Only then can the leak test proceed.
Leakproof
- The pressure in the pipeline rises to the pressure test value (Pr).
- The start time of the test is fixed (Tn), the initial water level is measured in the measuring tank (hn).
- After that, a decrease in the pressure indicator in the pipeline is monitored.
There are three possible pressure drops, let's consider them.
First
If within 10 minutes the pressure indicator decreases by less than 2 marks on the pressure gauge scale, but does not fall below the calculated internal (Pp), then this can complete the observation.
Second
If, after 10 minutes, the pressure value drops by less than 2 marks on the pressure gauge scale, then in this case, monitoring the pressure drop to the internal (Pp) calculated must be continued until moment until it drops at least 2 marks on the pressure gauge.
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 decrease to the calculated one (Pp), otherwise, water is discharged from the pipelines into a measuring tank.
Third
If within 10 minutes the pressure becomes less than the internal design pressure (Pp), then further hydraulic testing of pipelines of heating systems must be suspended and measures should be taken to eliminate hidden defects by maintaining pipes under internal design pressure(Pр) until a thorough inspection reveals defects that will cause an unacceptable pressure drop in the pipeline.
Determination of additional water volume
After completing the observation of the drop in the pressure indicator according to the first option and stopping the coolant discharge according to the second option, the following should be done.
- With the help of pumping from a measuring tank of water, the pressure in the pipeline increases to the value during hydraulic tests (Pg).
- Remember the time the leak test ended (Tk).
- Next, you need to measure the final water level in the measuring tank hk.
- Determine the duration of pipeline testing (Tk-T ), min.
- Calculate the volume of water pumped from the measuring tank Q (for the 1st option).
- Determine the difference between the volumes of water pumped up and discharged from pipelines or the amount of additionally pumped water Q (for the 2nd option).
- Calculate the actual flow rate of additionally injected water (q) using the following formula: q =Q/(T k-T )
Drawing up an act
Evidence that all work has been carried out is an act of hydraulic testing of pipelines. This document is compiled by the inspector and confirms that the workwere produced 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:
- Manometric method - tests are carried out using pressure gauges, devices that record pressure indicators. During operation, these devices show the current pressure in the heating system. The ongoing hydraulic testing of pipelines using a pressure gauge allows the inspector to check what pressure was during testing. Thus, the service engineer and the inspector check how reliable the tests are.
- The hydrostatic method is considered the most efficient, it allows you to check the heating system for performance at a pressure that exceeds the average operating rate by 50%.
During different times, various elements of the system are tested, while hydraulic testing of pipelines cannot last less than 10 minutes. In heating systems, the permissible pressure drop is 0.02 MPa.
The main condition for the start of the heating season is well-conducted and properly executed hydraulic tests of pipelines (SNiP 3.05.04-85), in accordance with the requirements of the current regulatory documentation.
