How is the pressure testing and flushing of glass fiber reinforced pipe operated?
In order to minimize the temporary piping added during the blowing process, save time on pressure testing and blowing, and improve the pass rate of pressure testing and blowing, the pipeline pressure testing and blowing operations are carried out according to systems, areas, and pressure grades. It is necessary to develop a plan and guide construction before pressure testing and blowing.
② For pipeline pressure testing, clean water is used. When conducting experiments and flushing on stainless steel pipelines, the chloride ion content in the water must not exceed 25×10^(-6) (25ppm). The pipeline pressure testing and flushing procedures are to be carried out according to the contractor's specifications.
During pressure tests, unauthorized personnel are not allowed to enter. No repairs should be made on the pipes after the pressure test is completed.
④ Prior conditions should be met before the pressure test:
The pipeline installation project within the experimental scope has been completed according to the planned drawings, excluding painting and insulation, with the installation quality meeting the relevant regulations.
b. Weld seams and other areas awaiting inspection have not been painted or insulated.
The expansion joints on the pipeline have been fitted with temporary restraint devices.
d. The pressure gauges used for testing have been calibrated and must maintain an accuracy of no less than 1.5 levels within the cycle. The full scale value of the gauge should be 1.5 to 2 times the measured pressure, and there must be at least two pressure gauges.
e. Liquids or gases meeting the pressure test requirements are ready.
The pipeline has been reinforced in accordance with the experimental requirements.
The test pipeline has been isolated from unrelated systems using blind flanges or other methods.
The safety valves and external components on the pipeline under test have now been removed or isolated.
The experimental plan has been approved and technical briefings have been conducted.
Hydraulic tests should adhere to the following rules:
Prior to the experiment, ensure all air is expelled when injecting the liquid.
b. During experiments, the ambient temperature should not be lower than 5°C. When the ambient temperature falls below 5°C, anti-freezing measures must be adopted.
The pipeline experimental pressure is 1.5 times the planned pressure.
When the planned temperature of the pipeline is higher than the experimental temperature, the experimental pressure is calculated as follows:
　　Ps=1.5P[σ]1[σ]2
Ps----Experimental Pressure (Gauge Pressure) (MPa)
P--- Planning Pressure (Gauge Pressure) (MPa)
σ1----Allowable stress (MPa) of the pipe material under experimental temperature.
[σ]2 -- Allowable stress of piping materials at the planned temperature (MPa).
When [σ]1[σ]2 exceeds 6.5, use 6.5.
When the pipeline and equipment are tested as a system, the test pressure of the pipeline should be used for the test if it is equal to or less than the test pressure of the equipment. If the test pressure of the pipeline exceeds the test pressure of the equipment, and the test pressure of the equipment is not less than 1.15 times the planned pressure of the pipeline, the test can be conducted at the test pressure of the equipment with the consent of the construction unit.
For pipelines with significant offsets, the static pressure of the experimental medium should be included in the experimental pressure. The experimental pressure for liquid pipelines is based on the higher point, but the pressure at the lower point must not exceed the load-bearing capacity of the pipeline components.
Hydraulic test pressure should be increased slowly. After reaching the test pressure, maintain it for 10 minutes before reducing the test pressure to the planned pressure. Hold the pressure for 30 minutes, and it is considered合格 if the pressure does not drop and there are no leaks.
After the experiment, the blind plates and expansion joint restraint devices should be removed promptly, and the accumulated fluid should be drained completely. When draining, avoid creating a vacuum and do not discharge it on the ground.
i. When leaks are discovered during the experiment, they must not be handled under pressure. After eliminating the defects, the experiment should be re-conducted.
⑥ It is necessary to conduct a leakage test for pipelines transporting toxic fluids, with air (i.e., airtightness test) being the chosen medium for the leakage test. The airtightness test is conducted according to the following rules:
a. The airtightness test pressure is the planned pressure.
b. Key points of the airtightness test include inspecting valve stuffing boxes, flange or threaded joints, vent valves, exhaust valves, drain valves, etc.
c. The airtightness test is conducted by applying soap solution or other foaming agents, and is deemed passable if no leaks are detected.
After the pipeline passes the pressure test, the pipeline should be arranged for blowing or cleaning operations according to the blowing plan.