Gauges are thread detection things, different thread types, different sizes are to use different gauges. Therefore, thread processing plant needs to be equipped with a lot of gauges, and gauges are consumable, when it is not qualified by the higher level of gauge test should be scrapped.
There are different grades of gauges, thread mills should generally be equipped with working gauges and proofreading gauges. Working rules are used to check the steel pipe thread, and checking rules are used to check working rules.
API thread
Oil casing is a deep machining product with high demand and large consumption in oil drilling and production engineering. A single casing is threaded together into a long string thousands of meters long and capable of accepting hundreds of atmospheres of pressure -- a tubular high-pressure vessel. In 1924 API drew up the specification for oil well tubing, casing joint threads were V-shaped with 10 and 8 teeth per inch, but were later adopted by API 8 teeth round thread and partial ladder thread replacement, and in use today. API SPEC
The 5B specification specifies that the common casing threads are round (CSG) and partial trapezoidal (BCSG). These two kinds of thread joints are generally used in Chinese oil and gas fields. With the exploration and development of oil and gas in our country, especially deep well, super deep well, high pressure gas well, directional well, and hydrogen sulfide bearing the increase of Wells, putting forward a higher requirement for the application performance of oil casing joint. There is no habit of requiring gas tightness, cohesion strength, corrosion resistance of API circular thread and partial step thread, so the joint arises at the historic moment.
1)API round thread
The casing thread has the casing short round thread (CSG/STC) and the casing long round thread (LCSG/LTC).
Tubing round thread has unthickened tubing thread (TBG/NUE) and externally thickened tubing thread (UPTBG/EUE).
API pipe connection with round thread
2)API offset ladder thread
This thread is in order to improve the resistance to axial tensile or compressive load capacity, and supply anti-leakage and planning, English abbreviation BCSG/BTC, no shoulder taper pipe thread, need to have a collar connection, tooth type for partial trapezoid, flat top flat bottom.
