According to SY/T6194-96 regulations, the casing length of China is not fixed, and its range is 8-13m. The casing with length not less than 6m can be supplied, and its quantity should not exceed 20%.
The inside and outside surfaces of the casing should not be folded, striped, separated, cracked, rolled and scarred. These defects should be completely removed and the removal depth should not exceed 12.5% of nominal wall thickness. The outer surface of the coupling shall not be folded, striped, separated, cracked, rolled, and scarred.
The surface of casing and coupling threads should be smooth, and no burrs, tearing. No other defects are allowed to interrupt the thread, affect the strength and tighten the connection.
Common specifications of casing are as follows.