GOST 633-80 Tubing and Couplings

Tubing is used for oil and gas production. Tubing shall be made seamless, plain or upset and coupling with high-seal connections. Coupling-free connections are possible.

This standard applies to seamless steel tubing smooth and couplings, with upset ends and couplings are smooth vysokogermetichnye and couplings, as well as flush-joint pipe with upset ends, used for the exploitation of oil and gas wells.

  • GOST 633-80 D (Casing and Tubing) = API 5CT H-40
  • GOST 633-80 D (Casing and Tubing)= API 5CT J-55
  • GOST 633-80 D (Casing and Tubing) = API 5CT K-55
  • GOST 633-80 E (Casing and Tubing)= API 5CT N-80
  • GOST 633-80 E (Casing and Tubing) = API 5CT L-80
  • GOST 633-80 L (Casing and Tubing)= API 5CT C-90
  • GOST 633-80 L (Casing and Tubing)= API 5CT C-95
  • GOST 633-80 M (Casing and Tubing)= API 5CT P-110

Tubing to this standard shall be manufactured in two grades B and A depending on accuracy and quality level.

Size range of tubing, types of connections for the two grades are given in Table 1.

Table 1 size range of tubing grades A & B
size range of tubing grade A&B
Limit dimensional and mass tolerance are given below:
Limit dimensinal and mass tolerance
Technical requirements:
Outside and inside tube surface shall be free of cracks, laps, discountinuities, cavities and inclusions.
Small indentations, scratches on insignificant scale of production origin are permissible if they leave the wall thickness wihtin specified limits.
The run-out sections from upset part to tube body shall be smooth and gradual; wall thickness shall be within the specifed limits. Up set part of 85 mm length from the ends shall be free of defects.
Chemical composition of steel is not specified except that phosphorus and sulphur contents shall not exceed 0.045% each.
Mechanical properties of tubing and coupling metal are give in table 2.
Mechanical properties of tubing and coupling metal Table 2
Mechanical properties

Surfaces of threads and sealing shall be zinc-coated or phosphate-treated. All tubing except grade TBO shall be delivered with coupling (power-tight makeup) and anti-corrosion and sealing compounds applied. For transportation tubing and couplings shall be pointed for corrosion protection. Special internal coationgs on tubing grade A shall be applied on request.

Thread profile for plain and upset-end tubing is shown in Figure 1.

Fig. 1. Round thread profile for tubing.
Round thread dimensions for grades B and A are given below. Round thread dimensions
Thread sizes are give in Table 3, 4, 5 and 6.
Table 3 Sizes, mm of round thread for plain-end tubing grades B and A


Symbols for table 3

Limit tolerances for nominal sizes are given below. Pitch, mm:
- on 25,4 mm length ±0,75
- on full-profiled thread ±0,120
Taper, mm on 100 mm thread length:
pipe body (+0,66) - (0,22)
coupling (+0,22) - (0,36)
Table 4 Size, mm of round thread for external-upset tubing grades B and A
external-upset tubing
Symbols for table 4
Symbols for table 4

High-seal thread connections type NKM.

Thread profile for tubing.

Thread profile for nominal bore 60 to 102 mm is shown in Fig.2; for nominal bore 114mm see Fig. 3. Thread dimension are given in Table 5.

Fig.2. Thread profile (type NKM 60-102)
a- coupling; upset end;
b - tube; nipple.
Fig.3. Thread profile (type NKM 114)
a - coupling;
b - tube.
Bevel C can be replaced by rounding to 0.2 mm radius.

For dimensions of connectiong parts, see Fig. 4 and Table 6.
Fig.4. Thread ty NKM.
Limit thread tolerances are given in Table 7.

Thread interference measured as the distnace from the reference plane of the thread gauge to tube end shall be 20-1.2 mm for nominal bore 60 to 102 mm and 24-2.5 mm for nminal bore 114 mm.

Thread interference for galvanized or phosphate-treated coupling measured by a thread gauge shall be 5.0-1.2 mm for nomianl bore 60 to 102 mm and 6.0-2.5 mm for nominal bore 114 mm.

For power make-up of tubing and galvanized or phosphate-treated coupling thread interferences are given below:
Power Make-up
Power make-up of tubing and couplings shall guarantee complete contact of tube end and the thrust surface of the coupling. Tubing grade B may have a gap of 0.5mm between the above suraces.

Table 5 Thread dimensions for tubing with high-seal type NKM and pup type NKB connections of grades B and A
Table 5

Table 6 Dimensions of high-seal thread connections for tubing

Table 6
Symbols for table 6

Pup joints.

For thread profile and dimensions see Fig.2 and Table 5; details of dimensions are given in Fig.5 and Table 8. For limit tolerances, see Talbe 7.

Thread interference for the male and measured by using respective thread gauges haveing complete and incomplete thread profiles shall be 18+1.2 mm.

Fig. 5. Thread type NKB.
Table 7 Limit tolerances for thread types NKM and NKB, mm
Table 7
Thread interference for the gemale end measured by repective thread gauge shall be 5-1.2 mm.

Table 8 Size of tubing with pup joints grades B and A, mm
Table 8
Symbols for Table 8
Wall thickness variation of both male and female ends shall not exceed 1.0 mm.
Symbols for table 8

Thrust belt width shall be sa given below:

Threads of couplings shall be coaxial within 0.75 mm in the end plane and within 3 mm on one meter legnth. Plain end coaxiality may be increased to 1.0 mm if this parameter on one meter legnth is 2.0 mm.

Thread sufaces, thrust belts on tubes and couplings shall be free from burrs, pits, discountinuities and other defects affecting strength and sealing properties.

Thread surface roughness shall not exceed 20 m.
Wall thickness variation of couplings and threaded tube ends grade NKB shall not exceed 0.1 mm for nominal bores 27 to GOST 17410-78.
Grade D and K shall be supplied without non-destuctive examination on special agreement.

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Seamless pipe Specification, standard and identification

Seamless pipes are extensively applied for the nuclear device, gas, petrochemical, ship building and boiler industries. Seamless pipes dominates 65% of market share in Chinese boiler industry.