In order to ensure the basic quality requirements of tubing and casing, the general principles stated below should be followed in selecting the tubing and casing plant and ordering its products.
casing and tubing facturies should obtain GB/T 19001 system certification and the right to use API. Pipes manufactured according to API Spec 5CT shall be marked with appropriate markings and meet API Spec 5CT, API Spec 5B and order supplementary technical requirements.
When ordering, the user should determine the ordering manufacturer and its products according to SY/T 5539, and give priority to the manufacturer and its products which conform to the first-class products according to SY/T 5539 product quality evaluation and inspection, while the manufacturer whose product quality evaluation and inspection is the fourth-class products should stop ordering.
All inspections and full-scale evaluation tests should be carried out for the first order of the manufacturer’s products or for the new products.
Inspections and full-scale evaluation tests should be conducted when ordering casing and tubing with non-API Spec 5CT specifications, or different yield strength and tensile strength from API Spec 5CT.
For ordering new products, products from new suppliers and various special uses or non-API Spec 5CT casing and tubing, the inspection method of merchandise which combines the onsite supervision of users with the inspection of incoming merchants should be carried out. Onsite supervision should be conducted by users or the third party inspection organizations entrusted by users.