How To Distinguish The Thread Of Oil Pipeline?

Oil pipe thread, which is the most common tools, is a part that difficult to distinguish. Thread is very important to the tool division or supervisor. If a tool division is unaware pipeline thread, it is difficult to work from preparation to direct operations. Here we recognize some common tubing joint on the market, each of them has their own advantages and each have their own usefulness.

Common tubing thread

Tubing thread is commonly divided into EU, NU and NewVam. The EU and NU, which is a triangular joint type, is difficult to distinguish from the joint appearance. But from the whole string can be easily distinguished that EU means external upset and NU means no external upset. New Vam is actually a buttress thread connections and it is not external upset, so it is very easy to distinguish.

EU(External upset)

EU is a kind of external upset oil pipe joint,  there are three biano logos related to EU. EUE (External Upset End) represents outside the thick end, EUB (External Upset Pin) denotes an outer thickened pin thread, EUB (External Upset Box) indicates external upset box thread. In addition to the use of pin and box represent the male thread and female thread, the other said male thread: 1 external thread 2 male 3 male thread; female thread:1. female buckle 2 internal thread 3 box 4 box thread.

NU(Non-upset)

NU is a kind of non-upset oil pipe joint, in addition to no external upset, NU is usually 10 threads per inch and EU is 8 threads per inch. NUE represents a non thickening end or end thickening

New VAM

This thread is substantially rectangular-shaped cross section, equal pitch intervals, little taper and no external upset. The VAM with excellent performance, high connecting strength and good sealing effectcan meet requirements of different service conditions. This thread is widely used in all kinds of special thread and it belongs to the high quality special thread. VAM follow the thread specification of API, thus inherits the advantages of high bonding strength. It improved Screw seal form in order to overcome the poor sealing performance.

Common drill connection

REG(Regular Style Connection)

This type of drill pipe joint thread was used to connect the inner upset drill pipe so that drill pipe diameter is smaller than the inner diameter of the thickened and the inner diameter of the thickened is smaller than the diameter of the inner tube diameter. The main purpose of API design regular style connection is applied to the bit connection. Since the drill bit is located in the end of drill string, the stress concentration phenomenon of thread is not relevant, so API retained their all specifications.

IF(Internal-flush style connection)

This type of tool joint thread connects EUE or inside and outside thickened drill pipe, forming the inner diameter of the drill pipe joints, tube inner diameter and thick pipe inner diameter is equal to the inner diameter or approximate size. All specifications are used thread V-0.065 flat top and bottom triangular tooth type, which width is 0.065 inches (1.651mm). Because of this type easily lead to stress concentration, API has gradually replaced it.

FH(Full-hole style connection)

This type of joint screw connects inside and outside thickened drill pipe, forming the inner diameter of the drill pipe joint is equal to thickened end diameter and they are smaller than the inner diameter of the pipe. Although the thread specification is not much, but it has three models named V-0.065、V-0.05 and V-0.040 so that it has been widely used in kelly, drill pipe, drill collars and drill.

API thread specification

API Round Thread

There are short round thread casing and the long round thread casing points. There are some advantages about round thread casing as follows:

• Improve the abrasion caused by resistance when the thread tightening
• Tighten the screw, the tooth tip provides a reasonable space for foreign particles and dirt
• The circular arc tooth is not sensitive to local scratch or dent damage

Round thread due to its easy processing, good sealing performance and low price, is widely used in casing connection. In addition, it’s simple in site maintenance and use. In the test of different specifications of the round thread casing, use appropriate specifications of the thread gauge to test, when necessary carries on corresponding processing to the data

Buttress Thread

In oil field tubing, buttress thread is a pipe thread form designed to provide a tight hydraulic seal. The thread form is similar to that of Acme thread the force is transmitted almost parallel to the axis and thread is about the same strength as standard v threads.

The advantages of buttress thread:

• Buttress thread can withstand large tensile or compressive load, especially having sufficient tensile strength.
• The design of the thread parameters are optimized to ensure that at least there is a tight fit around the thread, there is no gap, so that the sealing capacity of the terminal is greatly improved.