What are differences between STC, LTC and BTC in OCTG casing pipe?
Common threads of OCTG casing pipe can be divided into three kinds: STC, LTC, and BTC. STC is short for short-round thread casing, LTC long-round thread casing, BTC buttress thread casing. There are three specified lengths of API LTC casing: R-1 is 4.88 ~ 7.62m, R-2 is 7.62 ~ 10.36m, and R-3 is 10.36m to longer. The main steel grades: H-40, J-55, K-55, N-80, C-75, L-80, C-90, C-95, P-110 and Q-125. According to different well conditions and different well depth, different steel grade is selected. The corrosion resistance of the casing itself is also required in the corrosive environment. API oil casing ring parts made of steel pipe can improve material utilization, simplify manufacturing process and save material and processing time. Due to the harsh geological conditions, higher requirements are put forward for mechanical properties such as tensile properties and compressive properties of the tube body. properties testing for hydrostatic test, flattening test, sulfide stress corrosion cracking test, hardness test, tensile test, and horizontal impact test. In the complex geological conditions, the casing is also required to be resistant to extrusion.
Features of STC :
- Improve the resistance caused by scratch during screw tightening
- When screwed up, the crown clearance provides a controlled clearance for foreign particles and dirt
- The rounded crown is not sensitive to local scratches or dents.
The quality of the threaded connection directly affects the structural integrity and sealing integrity of the casing string, and the machining accuracy of the threaded connection is one of the important factors.
The thread shape of both ends of the pipe body is like long round, so it is called long round thread casing. Long round thread has the advantages of easy machining, good sealing, certain connection strength, simple field maintenance and use, cheap price, etc., and is widely used in casing connection.
Buttress thread casing pipe is named according to thread shape which is partial trapezoid, and it is one of the commonly used buckle shapes.
The advantage of BTC: improves the axial tensile and axial compression load resistance and provides leakage resistance.
IMRISTEEL can fabricate STC, LTC and BTC according to API 5CT, what’s more, our factory also can produce BT-1, BT-2 and BT-3 which can substitute for special thread, such as New VAM and VAM top.