Thread connection is the most common basic knowledge in tools, and it is also a difficult part to distinguish. The thread connection is very important to the field engineer. If you do not know the thread connections, there will be many problems in material, preparation and operation command, which may affect the progress of field operation and cause unnecessary losses.
1. Type of oil casing thread connection
API thread types include: BTC (partial ladder thread), LTC (long round thread), STC (short round thread), NU (TBG unthickening tubing thread), EUE (external thickening tubing thread), XC (direct casing thread), IJ (integral joint tubing thread) and other types of API thread.
VAM series thread: NEW VAM, VAM TOP (VAM TOP HT, VAM TOP HC) VAM MUST, VAM ACE, DINO VAM, VAM FJL, VAM TM, VAMSLIJ-II, etc
JFE Series: JFE FOX, JFE BEAR
Tenaris Series: Tenaris NK3SB, Tenaris ER
Hunting series: Hunting Seal Lock Boss, Hunting Seal Lock HT, Hunting Seal Lock APEX
Baosteel series products: BGT1, BGC
Other patent thread: Tiangang, WSP-1T, WSP-2T, NSCC, NSCT, etc
2, tubing commonly used thread connection
- 1) NewVAM
This type of buckle is characterizing by a rectangular section, equal spacing of pitch, small taper, no external thickening. Seen at the end of the production slip sleeve in the workshop.
- 2) EU(External upset) is getting thicker
The EU connection is an externally thickening tubing connection. In the process of recognizing the variable buckle joint on the shop shelf, three other signs related to EU will be found. EUE(External Upset End) indicates the thickened end, EUP(External Upset Pin) indicates the thickened male buckle, and EUB(External Upset Box) indicates the thickened female buckle.
- 3)NU(Non-upset) is not thickening externally
NU indicates a tubing connection without external thickening. In addition to the lack of thickening, there is another difference between NU and EU. Nu is usually 10 buttons per inch and EU is usually 8 buttons per inch. Where NUE represents the non-thickening end or the end is not thickening. Again, E means End.
3. Common thread connection of drill pipe
REG and IF buckles are commonly found in drill pipe. Others such as FH are not found in the tool shop.
According to experience:
REG buckle and IF buckle are generally 5 buckle /in and 4 buckle /in, but greater than 4-1/2 “even 4 buckle /in is REG buckle, that is to say greater than 4-1/2” are generally REG buckle, less than 4-1/2 “IF buckle more.
- 1) REG(API Regular Thread) Regular threads in the API standard
In other words,Thread used in regular drill pipe joints. This type of thread has been using to connect the internal thickened drill pipe to form the diameter of the joint of the drill pipe is less than the internal diameter of the thickened end of the drill pipe, and the diameter of the thickening end of the drill pipe is less than the internal diameter of the drill pipe. REG buckle is more delicate, IF the buckle is rough, the reason is that the buckle density per unit length is different.
- 2) IF(API Internal Flush) Indicates the API internal flush type
The thread used for the internal flat drill pipe joint. This type of thread is using to connect the externally thickened or externally thickening drill pipe to form the inside diameter of the drill pipe joint. The inside diameter of the thickened end of the drill pipe is equal to or similar to the inside diameter of the drill pipe pipe.
- 3) FH(API Full Hole)API standard in the hole button type
As the name suggests, it is as big as an eye. What about that eye? Refers to the bore diameter of drill pipe joint and the bore diameter of the thickened end of drill pipe. Not the bore diameter of the drill pipe, which is usually smaller than that of the drill pipe.
Summary of steel grade of oil casing
Oil casing is usually composing of two parts, one is the pipe body and the other is the collar. There are many kinds of oil casing steel grades. For the convenience of field use and differentiation, they are usually distinguishing by color. Some commonly using colors are listing below. See the table below for details:
| steel grade | Coupling color | Tube body strip color |
| H-40 | black | Nothing |
| J-55 | green | 1green |
| K-55 | green | 3green |
| N-80 | red | red |
| C-75 | blue | blue |
| C-75,9Cr | blue+2yellow | blue+2 yellow |
| C-75，13Cr | blue+1yellow | blue+1 yellow |
| L-80，9Cr | red+2yellow | red+brown+yellow |
| C-90 | Purple | Purple |
| C-95 | Brown | Brown |
| T-95 | Prink | Prink |
| P-110 | white | white |
| P-125 | orange | orange |
Where the steel grade numbers represent 1000Psi, for example N-80 indicates a minimum yield strength equal to 80,00psi equal to approximately 55.16MPa.
Common flush Thread Types are the HYDRILL CS, HYDRILL 511, TSWP, and FL-4S available in 2-7/8 “and 4”.
- 1. The HYDRILL CS is 1.9 “and externally thickened, the HYDRILL 511 is 2-7/8” and thin to thick, and the TSWP is 4 “and sealed for double shoulders.
- 2. FL-CS are sharing with 2-7/8 “and 4” flusher.
- 3. In addition, milling shoes and other tools also have TSWP buckle.
- Screen tube, blind tube Thread Types
BTC, for the side ladder buckle, the common size is 5-1/2 “, 6-5/8 “, 7 “and so on.
STC, short round grain, common sizes are 4-1/2 “, 5-1/2 “, 6-5/8 “, 7 “, 7-5/8 “, etc.
LTC, long round buckle, common sizes are 4 “, 4-1/2 “, 5-1/2 “, 7 “and so on.
