What are the three tests to be conducted after the construction of composite pipes? Static conductivity, strength, and tightness

What are the three tests to be conducted after the construction of composite pipes? Direct answer: Conducting static electricity test, only for the main pipeline, to verify the static electricity discharge ability of the conductive layer; Strength testing is conducted on both the inner and outer layers, with a pressure of five atmospheres and a holding time of thirty minutes; Tightness test, covering both the inner and outer layers, holding at one atmosphere for 60 minutes, and checking all connections with soap solution. Only when all three items are qualified can the pipeline be considered as passing the construction acceptance. In terms of sequence, static electricity leads to pressure, and any item that does not meet the standard shall not enter the backfilling process.

Static electricity test

This only applies to the main pipeline. The conductive layer of the composite pipe is responsible for dissipating the static electricity generated by liquid flow. When it fails, it will accumulate charges in the pipe section, which is a clear hidden danger for oil storage and transportation. The test verifies the continuity of the conductive layer to see if the resistance value is within the required range. The testing points are selected at both ends of the pipe section, and the results are recorded in the acceptance record. Damage to the conductive layer during construction - such as excessive heating, improper cutting, and inadequate handling of connections - will all be exposed in this area.

Strength testing and tightness testing

Both are pressure tests, using dry air or nitrogen as the medium, with differences in pressure and holding time. The strength test pressure is high and the time is short, holding at five atmospheres for thirty minutes, testing the pressure bearing capacity of the pipe and joint; The tightness test pressure is low and the time is long, holding at one atmosphere for 60 minutes, testing the sealing performance of the system. Both items must cover the inner and outer tubes - any failure of either layer in the double-layer structure is an accident. During the pressure holding period, if the pressure drops beyond the limit, use soap solution to check all connections, and the bubble point is the leakage point.

Test steps and criteria

1. Confirm that the installation is complete, the bracket is fixed in place, and the port sealing is reliable;
2. First, conduct a static conductivity test on the main pipeline and record the resistance value;
3. Inner tube strength test: Increase the pressure to five atmospheres and hold for thirty minutes;
4. Outer tube strength test: same pressure and time;
5. Tightness test: hold at one atmosphere for 60 minutes;
6. Check all connections with soap solution, bubbles are leaking;
7. Three items of data shall be recorded in the acceptance record, and can only be backfilled if they are qualified.

Boosting and operational safety

The pressure should be gradually increased in stages, with each stage stabilizing for a moment before increasing again to avoid pressure shock. During the testing period, personnel are not allowed to stand facing the ports and connections. If leakage is found, release the pressure first and then deal with it. It is strictly prohibited to tighten under pressure - operating under pressure is not only a safety issue, but also can cause the seal to deteriorate the tighter it is tightened.

Common mistakes

It is common to simplify the three tests for pressure testing of composite pipes into one - only performing pressure testing without conducting static electricity, which brings the hidden dangers of the conductive layer into operation. Insufficient holding time is the second type - from thirty minutes to ten minutes, slow leakage cannot be detected. The soap solution inspection process is the third type - only visible joints are inspected, regardless of the buried layer and ports. Not all test records are of the fourth type - data is verbally reported, but there is no evidence to trace back afterwards. Acceptance is the cheapest link in the entire lifecycle of a pipeline, and saving it is the least cost-effective.

Can water be used as a medium for testing?

Select the medium according to the design documents for pressure testing, and gradually increase the pressure for gas testing in stages; The specific medium and parameters shall be subject to the design documents and product installation manual.

How to deal with leakage?

Release pressure before handling, and it is strictly prohibited to tighten under pressure; Find the leakage point, replace the seal or remake the joint, and then go through the complete testing process again after treatment.

Do test records need to be saved?

I need it. The three test data are the core evidence of acceptance, which are archived together with the concealed engineering records, and subsequent maintenance and traceability rely on them.

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.