What inspection should be done for the composite pipe after five years of use? Wall thickness measurement and sampling pressure test
Release date: 2026-10-22
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Direct answer: according to the use specification, the composite pipe that has been in use for more than five years enters the regular inspection stage. There are three types of projects-fixed-point measurement of wall thickness of pipelines, tracking wall thickness changes at fixed points with ultrasonic thickness gauge and other equipment; water pressure strength test of pipelines and pipe fittings according to not less than 10% of the total number of samples; use anti-corrosion leak detector to check buried pipelines, excavation or drilling sampling for leakage points. The three types of inspection cover the main concerns of the composite pipe in the buried environment: wall thickness changes, joint performance and leakage hazards.
Wall thickness fixed-point measurement
The key is "fixed point"-the first measurement is to fix the position, the method and the mark. After that, the data can be compared only when the same batch is measured. The tool uses an ultrasonic thickness gauge to take points at the accessible position of the pipe section: the outside of the elbow, the heat affected zone of the weld, and the position that has been repaired. These are the places where the wall thickness may change. Measurement records are filed by point number, and it is useful to draw trends than to look at single values. Pipe sections with a trend of thinning wall thickness, shorten the retest cycle and evaluate the replacement plan.
| Check item | object | Method | eligibility criterion |
|---|---|---|---|
| Wall thickness fixed-point measurement | Fixed point of pipeline | ultrasonic thickness measurement | No trend thinning |
| Sampling strength test | Not less than 10% of pipe fittings | Hydrostatic strength test | Pressure up to standard |
| Anti-corrosion and leak detection | Buried pipeline | Full line of leak detector | No leakage point |
| Leak point verification | Suspected location | Excavation borehole sampling | Confirm and dispose |
| Record archiving | All data | Create File by Point Number | Trend comparable |
Sampling water pressure strength test
The sampling object is pipe fittings-valves, filters, compensators and other detachable parts, the proportion of not less than 10% of the total number of pipe fittings. The method is to do hydraulic strength test after removal or isolation to verify whether the pressure bearing capacity is attenuated. Sampling should cover pipe fittings of different batches, different installation years and different working conditions, and special selection of new parts cannot explain the problem. For batches that fail the test, the same batch of pipe fittings shall be sampled with expanded sampling, and the whole with high failure rate shall be replaced. Sampling rules are written into the maintenance system and implemented according to the system every year, not by mood.
Anti-corrosion leak detection and leak point verification
- Measure the wall thickness according to the fixed point number, record and compare the historical data;
- Take not less than 10% of the pipe fittings for hydraulic strength test;
- Comprehensive inspection of buried pipeline with anti-corrosion and leak detector;
- If leakage points are found, excavation or drilling shall be sampled for inspection and confirmation;
- Confirm that the leakage point shall be handled according to the emergency repair regulations, and replace the failed pipe section;
- All inspection records shall be archived as the baseline for the next round of comparison.
How to replace the instrument
For stations without instruments, the number of excavated or drilled holes in low-lying, wet places shall be checked as an alternative. The significance of the five-year inspection is to advance the discovery of hidden dangers from "after the accident" to "within the plan"-the failure of buried pipelines is a slow process, and regular measurement is a race against time.
Relationship with maintenance system
The five-year inspection is not an isolated action, but a complete system with daily inspection and annual inspection. Patrol inspection to see the ground and operating well clues, annual inspection to see the system performance indicators, five-year inspection to see the status of the material body. Three layers of data are placed in a file, and the health of the pipeline is a complete curve. The maintenance budget is also arranged accordingly-which section should be measured and which batch should be replaced is up to the data.
Can the five-year inspection be organized by itself?
Wall thickness measurement and leak detection require equipment and operation training, which can be carried out by themselves or entrusted to professional institutions. Sampling hydraulic test involves disassembly and pressure test, and it is recommended to be carried out by an experienced team.
How many pipes should be changed if the wall thickness is reduced?
It shall be implemented according to the design documents and the manufacturer's criteria, usually based on the trend: the pipe section with obvious thinning shall be measured twice in a row, even if it is still within the allowable range, it shall be evaluated and replaced.
What should I do if I find a leak but no leak?
The same to dispose. The leakage point found in leak detection is an early signal, indicating that the anti-corrosion or sealing has failed. Excavate and replace according to the plan, and do not wait for the leakage to expand before emergency repair.
This article is organized by Luoyang wohong petrochemical equipment co., ltd. the company provides design, manufacture, installation, commissioning and operation and maintenance services for oil and gas recovery equipment, solvent recovery devices and buried composite pipe networks at gas stations, oil depots and chemical enterprises. if you need scheme configuration or on-site investigation, please contact and exchange.
