How to arrange the pressure test sequence for composite pipelines at gas stations? The connection between strength, tightness, and retesting after backfilling
Release time: October 28, 2026
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The pressure test of composite pipelines is not a one-step process. Each of the three sections, strength, tightness, and retesting after backfilling, has its own tasks. Only when the sequence is arranged correctly, can the problems in each link be exposed separately and not covered up with each other.
Basic conditions before pressure testing
Before pressure testing, three things should be confirmed: the pipeline installation is completed and the appearance inspection of the joints is qualified, the pipe trench cushion layer and pipe body backfill sand are in place according to the drawings, and the pressure gauge is within the valid calibration period and the range matches. If the basic conditions are not met, pressure testing will result in meaningless data.
How to conduct strength test
Strength testing is used to verify the pressure bearing capacity of pipes and joints. Slowly increase the pressure to the test pressure and then stabilize it for observation. Pay attention to dividing the pressure increase process into sections, stabilizing each section before increasing, and giving the pipe and joint time to adapt. During the voltage stabilization period, inspect the pipeline once, focusing on whether there is any leakage or deformation in the electric fusion joint, mechanical conversion joint, and wall penetration part. After passing the strength test, release the pressure and then proceed to the tightness test.
Determination of tightness test
The pressure of the tightness test is lower than that of the strength test, and the observation time is longer, mainly depending on the pressure drop. When making judgments, temperature correction should be taken into account: for experiments that start in the morning and end in the evening, changes in ambient temperature can cause pressure drop artifacts. Record the starting and ending temperatures, and then compare the allowable pressure drop values after correction. During the observation period, do not touch valves or move pipelines, and keep the system stationary.
Arrangement for retesting after backfilling
After backfilling is completed and the ground is restored, arrange for a retest. The mechanical compaction and ground settlement during the backfilling process may affect the joint state. The pressure drop measured again should be compared with the data before backfilling to ensure that it is basically consistent before being considered as a closed loop. After passing the retest, the pressure testing work can be considered truly completed.
Key points for filling in pressure test records
Record clearly the medium, starting and ending pressure, starting and ending temperature, weather, observation duration, and conclusion, and have the executor and reviewer sign. Separate the records of the three stages of the experiment and do not merge them into one. Only when there is a problem in which stage in the future can the records be targeted.
| testing phase | Purpose | highlight |
|---|---|---|
| strength test | Test the pressure bearing capacity | Segmented boosting, no leakage at joints |
| Tightness test | Check for minor leaks | After temperature correction, the pressure drop meets the standard |
| Retest after backfilling | Confirm that the backfill is not damaged | Consistent with the data before backfilling |
Frequently Asked Questions
Should water or compressed air be used as the pressure test medium?
Execute according to the requirements of the design documents. Both media have their own applicable scenarios. Gas pressure testing should pay attention to environmental temperature compensation, while liquid pressure testing should pay attention to purging and antifreeze.
What should I do if the pressure drop during the tightness test slightly exceeds?
First, perform temperature correction. If the correction still exceeds the limit, conduct segmented leak detection, with a focus on the joints. Identify the leak points and handle them before re timing and observing.
Can retesting after backfilling be omitted?
Not recommended for province. Backfilling is one of the most vulnerable processes for pipelines to external forces, and retesting does not take much time. It is very reassuring to replace it.
What supporting services does WoHong offer?
Luoyang Wohong Petrochemical Equipment Co., Ltd. provides technical support for product matching and installation of composite pipelines for gas stations. Contact number: 13526990215, email: lixiang@vohon.cn .
