OCTG pipe refers to Oil Country Tubular Goods,a collection of rolled metal products, more commonly known as Drill pipe, Casing and Tubing which are manufactured according to API Specification and are used both onshore and offshore in petroleum industry. This severe corrosion environment requires the pipe with high corrosion resistance and crush resistance especially for geological complex areas, the performance of coating has higher requirements. According to the specific application of anti-corrosion coating and the different corrosion environment, it can be divided into drilling pipe internal coating, oil casing internal coating and interrnal/outside coating of oil transport pipe.
The high temperature and high pressure resistance test of petroleum casing pipe coating is a standard laboratory method developed with reference to the standard NACE TM 0185, which can be used to test the quality of coating on steel pipe. This experiment is carried out in the autoclave under certain corrosive medium, temperature and pressure conditions. It is suggested to select special oil-casing coating test devices such as autoclave, booster equipment, autoclave heating device, autoclave safety system and comprehensive control system. The test procedures and methods are as follows:
1. Prepare liquid or gas-phase corrosive medium;
2. Open the cover of the autoclave and put the sample in. If the autoclave volume allows, several sample tests can be carried out at the same time and a certain distance can be ensured between each sample;
3. Slowly pour liquid phase medium into the kettle, then tighten its cover, input gas-phase corrosive medium, slowly boost pressure, and heat the kettle body; Note that during the heating process, decompress the kettle body, so that the test pressure cannot exceed the maximum pressure of the test conditions;
4. Keep the pressure and temperature in the kettle under the specified test conditions, and heat the coating sample test time at least 16h;
5. After the test, cooled the autoclave body below 93℃ ,then relieved and reduced the pressure to normal within 15min~30min at even speed, drained out the corrosive medium and taken out the samples;
6.Check the outer coating immediately for swelling and softening, and then cool it to room temperature for comparison with untested samples.