Only proper and reliable functioning of the heating system is able to 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.
Hydraulic test purpose
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 high-rise buildings - 7-10 atm. In a heating system laid underground, the pressure indicator can reach 12 atm.
Sometimes unforeseen pressure surges occur, which leads to its increase in the network. The result is a water hammer. Hydraulic testing of heating pipelines is necessary to test the system not only for the ability to function in standard normal conditions, but also for its ability to overcome hydraulic shocks.
If, for any reason, the heating system has not been tested, then subsequently serious hydraulic accidents can occur that can result in boiling water in rooms, equipment, furniture, etc.
Work sequence
Hydraulic testing of pipelines should be carried out in the following sequence.
- Pipeline cleaning.
- Installation of taps, plugs and manometers.
- Water and hydraulic press are connected .
- Pipelines are filled with water to the required value.
- Inspection of pipelines and marking of places where defects were detected.
- Elimination of defects.
- The second test.
- Disconnection from the water supply system and drainage of water from pipelines.
- Removing plugs and manometers.
Preparatory work
Before performing hydraulic tests of pipelines of heating systems, it is necessary to revise all valves, fill the glands with valves. Pipelines are repaired and checked for insulation. The heating system itself must be separated from the main pipeline by means of plugs.
After performing all necessary manipulations, the heating system is filled with water. With the help of pumping equipment, excess pressure is created ; its indicator is approximately 1.3-1.5 times higher than the working one. The pressure obtained in the heating system must be maintained for another 30 minutes. If it has not decreased, then the heating system is ready for operation. Acceptance of work on hydraulic tests is carried out by inspection of heating networks.
Strength and Leak Testing
Preliminary and acceptance hydraulic testing of pipelines (SNiP 3.05.04-85) must be performed in a certain sequence.
Strength
- In the pipeline, the pressure rises to the test (P and ) by pumping water and is maintained for 10 minutes. Pressure drops must not be allowed to exceed 1 kgf / m 2 (0.1 MPa).
- The test pressure is reduced to the calculated (P r ) internal, then it is maintained by pumping water. Pipelines are inspected for defects over the time required to complete this inspection.
- The detected defects are eliminated, after which a repeated hydraulic test of the pressure pipe is performed. Only then can the leak test be started.
Tightness
- In the pipeline, the pressure rises to the indicator of the leak test (P g ).
- The test start time is recorded (T n ), the initial water level (h n ) is measured in the measuring tank.
- After that, a decrease in the pressure indicator in the pipeline is monitored.
There are three options for the pressure drop, consider them.
First
If within 10 minutes the pressure indicator decreases by less than 2 marks on the gauge scale, but does not fall below the calculated internal (P p ), then this can be completed observation.
Second
If after 10 minutes the pressure decreases by less than 2 marks on the gauge scale, then in this case, monitoring the pressure drop to the internal (P p ) calculated must be continued until it drops by at least 2 marks on the 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 decrease to the calculated (P r ), otherwise, water is discharged from the pipelines into the measuring tank.
Third
If within 10 minutes the pressure becomes less than the internal design pressure (P r ), then further hydraulic tests of the pipelines of the heating systems must be suspended and measures taken to eliminate hidden defects by maintaining the pipes under the internal design pressure (P r ) until the moment of careful inspection defects will not be detected that will cause an unacceptable pressure drop in the pipeline.
Determination of additional water volume
After observing the drop in the pressure indicator in the first embodiment and stopping the coolant discharge in the second embodiment, the following should be done.
- By pumping from a measured water tank, the pressure in the pipeline increases to the value during hydraulic tests (P g ).
- Remember the time when the leak test (T k ) has ended.
- Next, you need to measure the final water level h k in the measuring tank.
- Determine the duration of the testing of pipelines (T k -T n ), min.
- Calculate the volume of water Q pumped up from the measuring tank (for option 1).
- Determine the difference between the volumes of water pumped and discharged from pipelines or the amount of additional water pumped Q (for the 2nd option).
- 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 work has been 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:
- Gauge method - tests are carried out by means of pressure gauges, devices that record pressure indicators. During operation, these devices show the current pressure in the heating system. Ongoing hydraulic testing of pipelines using a manometer allows the inspector to check what pressure indicator was during testing. Thus, the operating engineer and inspector check how reliable the tests are.
- The hydrostatic method is considered the most effective, it allows you to check the heating system for operability at a pressure that exceeds the average operating indicator by 50%.
Various elements of the system are tested for different times, while hydraulic tests of pipelines cannot 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 the properly conducted and properly executed hydraulic testing of pipelines (SNiP 3.05.04-85), in accordance with the requirements of the current regulatory documentation.