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API 6A Bolting, API 6ACRA Bolting, API 6A718 Bolting

Fasteners , Studs Bolts , Studs , Bolting , Screws , Nuts , Washer

API 6A Clouser Bolting shall be qualified, manufacture and marked in accordance with API 20E & API 20F. Bolting Levels (BSLs) are specified in the below table.

Minimum Requirement of Clouser Bolting

 API 20EAPI 20F
PSL 1BSL-1BSL-2
PSL 2BSL-1BSL-2
PSL3BSL-1BSL-2
PSL 4BSL-2 (bolt nominal diameter ≤ 2 1/2 in.)BSL-2 (bolt nominal diameter ≤ 2 1/2 in.)
PSL 4BSL-3 (bolt nominal diameter > 2 1/2 in.)BSL-3 (bolt nominal diameter > 2 1/2 in.)

API 6A Bolting Materials

Acceptable Clouser Bloating for 6B & 6BX Flanges & Studded Connections
 ProductPressure Rating MPa (psi)Nominal Size ( in .)ASTM Bolting Standard(s) and 0.2 % Offset Yield Strength
Nonexposed BoltingH2S-Exposed Bolting
A193 GR. B7 (≤ 2.5")
A320 GR. L7 (≤ 2.5")
A320 GR. L43 (≤ 4.0")
A193 GR. B7 (˃ 2.5")
A320 GR. L7 (˃ 2.5")
A13 GR. B7M (≤ 4.0")
A320 GR. L7M (≤ 2.5")
A453 GR. 660D (≤ 4. 0" )
CRA
725 MPa (105 ksi)655 MPa (95 ksi)550 MPa (80 ksi)725 MPa (105 ksi)
API 6A Studs, Bolts, and Cap Screws13.8 (2000 )All sizesNA
20.7(3000 )All sizesNA
34.5 (5000 )All sizesNA
69. 0(10,000)1 13/16, 2 1/16, 2 9/16,3 1/16NA
4 1/16NAUnacceptable
5 1/8NAUnacceptable
7 1/16NA
9, 11, 13 5/8, 18 3/4, 21 1/4NAUnacceptable
103.5(15,000 )14/5NA
2 1/16, 2 9/16,3 1/16, 4 1/16NAUnacceptable
5 1/8NA
7 1/16, 9, 11, 13 5/8NAUnacceptable
18 3/4NAUnacceptable
138.0(20,000 )1 13/16, 2 1/16, 2 9/16,3 1/16, 4 1/16, 7 1/16, 9NA
11, 13 5/8✔ Gr. L43 only✔ Gr. B7M only
API 6A NutsAll pressure ratingsAll sizesASTM A194/A194M GR.2H, 2HM, 7, 7MASTM A194/A194M GR.2HM, 7M

Allowable Clouser Bolting by Temperature Class

Temperature ClassP, S, T, UK, L
Impact testing of studs, bolts, and screws requiredNo aYes
Acceptable ASTM bolting standards and grades for studs, bolts, and screwsA193/A193M GR.B7A320/A320M GR.L7
A320/A320M GR.L7A320/A320M GR.L43
A320/A320M GR.L43A320/A320M GR.L7M
A193/A193M GR.B7MA453/A453M GR.660D
A320/A320M GR.L7MCRA
A453/A453M GR.660D-
CRA-
Acceptable ASTMs tandards and grades for nuts bASTM A194/A194MASTM A194/A194M
GR.2H, 2HM, 7, 7MGR.2H, 2HM, 7, 7M

Exposed Bolting (High Strength)

ASTM A453/A453M Grade 660D Solution- treated and age hardened bolting shall be acceptableat a hardness of HRC35 and lower, and a minimum 0% offsetyield strength of 725 MPa(105,000 psi). Environment and materials limits specified in NACE MRO175/ ISO15156 shall apply.

NOTE 1CRA materials may be used, provided they satisfy the minimum mechanical requirements of ASTM A453/A453M Grade 660D bolting, except that the maximum hardness shall meet NACE MR0175/ISO 15156 requirements.

NOTE 2NACE MR0175 provides material usage limits for H2S environments.Other forms of cracking may result from the presence of chlorides (such as seawater) and or hydrogen (such as cathodic protection ).

ASTM A453/A453M Grade 660D solution treated and age hardened bolting as stated in should not be used on pressure containing and high load bearing connectors in the following situations :
  • wet/dry offshore and coastal applications in the presence of salt air;
  • where it is routine to clean/wash equipment with untreated/raw seawater .
NOTE 1– Environmentally assisted cracking, such as s tress corrosion cracking (SCC), may result from the presence or accumulation of chlorides from deposited salt on highly stressed austenitic stainless steel bolting, such as Grade 660D.
NOTE 2 – API 6ACRA addresses alternative, higher-strength CRA materials suitable for sour exposure.

Exposed Bolting (Low Strength)

ASTM A193/A193M Grade B7M shall be acceptable at a minimum 0.2 % offset yield strength of 550 MPa (80, 000 psi) for the flanges listed in Table for NACE MR01 75/ISO 1 51 56 exposed bolting (low – strength).
ASTM A320/A320M Grade L7M shall be acceptable at a minimum 0 .2 % offset yield strength of 550 MPa (80,000 psi) for the flanges listed in Table for NACE MR01 75/ISO 1 51 56 exposed bolting (low – strength) only.
Only flanges having a bolt nominal diameter ≤ 63 .5 mm (≤ 2 .5 in.) are acceptable for this grade of bolting.

Non - Exposed Bolting

ASTM A193/A193M Grade B7 shall be acceptable for non exposed service for all flanges requiring a nominal bolt diameter ≤ 63 .5 mm (≤ 2.5 in.) and with temperature class P, S, T, and U.all bolting > 63.5 mm (> 2. 5 in.) Diameter shall require impact testing.
ASTM A320/A320M Grade L7 or L43 shall be acceptable for non exposed service for all flanges.
NOTE bolting make -up and connection capacity can be affected by miss matching the strength of the nut to the strength of the bolt. Bolting with diameters greater than38 mm (1. 50 in.) are typically affected more than smaller bolting.

Exposed Nuts

ASTM A194/A194M Grades 2HM and 7M shall be acceptable for all flange sizes and rated working pressures.
NOTE ASTM A453/A453M Grade 660D or CRA nuts may be used with NACE MR01 75/ISO 1 51 56 exposed bolting only if provisions are made to prevent galling.

API 6A Recommended Torque for All Bolting Types

Recommended Torques for Flange Bolting (SI Units)

Stud Diameter
D
in.
Threads per in.
N
1/in.
Studs with Sy = 550 MPa
Bolt Stress Equal to
275 MPa
Studs with Sy = 720 MPa
Bolt Stress Equal to
360 MPa
Studs with Sy = 655 MPa
Bolt Stress Equal to
327.5 MPa
Tension
F
kN
Torque
f = 0.07
N-m
Torque
f = 0.13
N-m
Tension
F
kN
Torque
f = 0.07
N-m
Torque
f = 0.13
N-m
Tension
F
kN
Torque
f = 0.07
N-m
Torque
f = 0.13
N-m
0.50013253661334880---
0.6251140701185392155---
0.750105912220678160270---
0.875982193328107253429---
1.0008107288488141376639---
1.1258140413706184540925---
1.25081775699812327451285---
1.375821 976113202869961727---
1.5008265991172734612972261---
1.625831 51263221 141 216532894---
1.75083691581277748420693636---
1.87584281947343356125494493---
2.00084922366418364430975476---
2.25086313375599782644187851---
2.5008788463582711032606810,828---
2.6258------1040639411 ,429
2.7508------11 46735413,168
3.0008------1375955517,1 56
3.2508------162412,1 5421 ,878
3.7508------218518,68533,766
3.8758------233820,62037,293
4.0008------249622,68341 ,057

Recommended Torques for Flange Bolting (USC Units)

Stud Diameter
D
in.
Threads per in.
N
1/in.
Studs with Sy = 80 ksi
Bolt Stress Equal to
40 ksi
Studs with Sy = 105 ksi
Bolt Stress Equal to
52.5 ksi
Studs with Sy = 95 ksi
Bolt Stress Equal to
47.5 ksi
Tension
F
lbf
Torque
f = 0.07
ft-lbf
Torque
f = 0.13
ft-lbf
Tension
F
lbf
Torque
f = 0.07
ft-lbf
Torque
f = 0.13
ft-lbf
Tension
F
lbf
Torque
f = 0.07
ft-lbf
Torque
f = 0.13
ft-lbf
0.500135676274574503559---
0.62511904052881186565115---
0.75010133789015317559118200---
0.87591876914324324241188319---
1.00082423021336131802279474---
1.12583161830552341499401686---
1.25083998842172652,484553953---
1.375849,34056397664,7597391281---
1.500859,674733127878,3229621677---
1.625870,989934163593,1 7312262146---
1.750883,28611692054109,31315342696---
1.875896,56514402539126,74118903332---
2.0008110,82517503094145,45822974061---
2.2508142,29224964436186,75832765822---
2.5008177,685342961 18233,21245008030---
2.6258------233,76547168430
2.7508------257,69454249712
3.0008------309,050704712,654
3.2508------365,070896516,136
3.7508------491,09913,78224,905
3.8758------525,52115,20827,506
4.0008------561,10816,73030,282

API 6A Stud Bolt Length

API 6A Full Thread Stud Bolt Length for 6B Flange Connectors with "R" & "RX" Gaskets

product1
Flange Size and PressureBolt Size and ThreadLength*Flange Size and PressureBolt Size and ThreadLength*
2 1/1620005/8 - 11 UNC5.0007 1/1620001 - 8 UNC7.500
2 1/1630007/8 - 9 UNC6.5007 1/1630001 1/8 - 8 UN8.500
2 1/1650007/8 - 9 UNC6.5007 1/1650001 3/8 - 8 UN11.250
2 9/1620003/4 - 10 UNC5.500920001 1/8 - 8 UN8.500
2 9/1630001 - 8 UNC7.000930001 3/8 - 8 UN9.500
2 9/1650001 - 8 UNC7.000950001 5/8 - 8 UN12.500
3 1/820003/4 - 10 UNC5.7501120001 1/4 - 8 UN9.250
3 1/830007/8 - 9 UNC6.5001130001 3/8 - 8 UN10.000
3 1/850001 1/8 - 8 UN7.7501150001 7/8 - 8 UN14.250
4 1/1620007/8 - 9 UNC6.50013 5/820001 1/4 - 8 UN9.500
4 1/1630001 1/8 - 8 UN7.50013 5/830001 3/8 - 8 UN10.750
4 1/1650001 1/4 - 8 UN8.50016 3/420001 1/2 - 8 UN10.750
5 1/820001 - 8 UNC7.25016 3/430001 5/8 - 8 UN12.250
5 1/830001 1/4 - 8 UN8.25021 1/420001 5/8 - 8 UN12.250
5 1/850001 1/2 - 8 UN10.50020 3/430002-8 UN15.000
    FOOTNOTES* Tolerance on bolt length: +0.1 25/−0 in. for lengths up to 1 2 in. +0.250/ − 0 in. for lengths over 1 2 in.

API 6A Full Thread Stud Bolt Length for 6BX Flange Connectors

product2
Flange Size and PressureBolt Size and ThreadLength *Flange Size and PressureBolt Size and ThreadLength *
1 4/510,0003/4 - 10 UNC5.5001110,0001 3/4 - 8 UN15.250
1 4/515,0007/8 - 9 UNC6.0001115,0002-8 UN19.500
1 4/520,0001 - 8 UNC7.7501120,0002 3/4 - 8 UN23.750
2 1/1610,0003/4 - 10 UNC5.50013 5/850001 5/8 - 8 UN12.750
2 1/1615,0007/8 - 9 UNC6.50013 5/810,0001 7/8 - 8 UN17.750
2 1/1620,0001 1/8 - 8 UN8.50013 5/815,0002 1/4 - 8 UN21.250
2 9/1610,0007/8 - 9 UNC6.50013 5/820,0003-8 UN29.750
2 9/1615,0001 - 8 UN7.25016 3/450001 7/8 - 8 UN14.750
2 9/1620,0001 1/4 - 8 UN9.50016 3/410,0001 7/8 - 8 UN17.750
3 1/1610,0001 - 8 UNC7.25018 3/450002-8 UN17.750
3 1/1615,0001 1/8 - 8 UN8.00018 3/410,0002 1/4 - 8 UN22.750
3 1/1620,0001 3/8 - 8 UN10.25018 3/415,0003-8 UN26.750
4 1/1610,0001 1/8 - 8 UN8.50021 1/450002-8 UN19.000
4 1/1615,0001 3/8 - 8 UN9.75021 1/410,0002 1/2 - 8 UN24.750
4 1/1620,0001 3/4 - 8UN12.50026 3/420001 3/4 - 8 UN14.250
5 1/810,0001 1/8 - 8 UN9.25026 3/430002-8 UN17.500
5 1/815,0001 1/2 - 8 UN11.5003020001 5/8 - 8 UN14.500
7 1/1610,0001 1/2 - 8 UN11.7503030001 7/8 - 8 UN17.750
7 1/1615,0001 1/2 - 8 UN13.000----
7 1/1620,0002-8 UN17.750----
910,0001 1/2 - 8 UN13.500----
915,0001 7/8 - 8 UN16.000----
920,0002 1/2 - 8UN21.750----
  • FOOTNOTES* Tolerance on tap end thread length: +0.063/ − 0 in.** Tolerance on tap end stud length: +0.1 25/− 0 in.

API 6A Tap End Stud Bolt Length for 6B Flange Connectors with "R" & "RX" Gaskets

product3
Flange Size Size and PressureBolt and ThreadTap End Length*Nut End LengthLength**
2 1/1620005/8 - 11 UNC0.7611.5633.625
2 1/1630007/8 - 9 UNC1.0422.1884.625
2 1/1650007/8 - 9 UNC1.0422.1884.625
2 9/1620003/4 - 10 UNC0.9001.8754.000
2 9/1630001 - 8 UNC1.1882.5005.125
2 9/1650001 - 8 UNC1.1882.5005.125
3 1/820003/4 - 10 UNC0.9001.8754.1 25
3 1/830007/8 - 9 UNC1.0422.1884.625
3 1/850001 1/8 - 8 UN1.3132.8135.625
4 1/1620007/8 - 9 UNC1.0422.1884.625
4 1/1630001 1/8 - 8 UN1.3132.8135.500
4 1/1650001 1/4 - 8 UN1.4383.1 256.125
5 1/820001 - 8 UNC1.1882.5005.250
5 1/830001 1/4 - 8 UN1.4383.1 256.000
5 1/850001 1/2 - 8 UN1.6883.7507.375
7 1/1620001 - 8 UNC1.1882.5005.375
7 1/1630001 1/8 - 8 UN1.3132.8135.875
7 1/1650001 3/8 - 8 UN1.5633.4387.500
920001 1/8 - 8 UN1.3132.8135.875
930001 3/8 - 8 UN1.5633.4386.750
950001 5/8 - 8 UN1.8134.0638.500
1120001 1/4 - 8 UN1.4383.1 256.500
1130001 3/8 - 8 UN1.5633.4387.000
1150001 7/8 - 8 UN2.0634.6889.625
13 5/820001 1/4 - 8 UN1.4383.1 256.625
13 5/830001 3/8 - 8 UN1.5633.4387.375
16 3/420001 1/2 - 8 UN1.6883.7507.500
16 3/430001 5/8 - 8 UN1.8134.0638.375
21 1/420001 5/8 - 8 UN1.8134.0638.375
20 3/430002-8 UN2.1885.00010.125
  • FOOTNOTES* Tolerance on tap end thread length: + 0.063/− 0 in.** Tolerance on t ap end stud length: + 0.1 25/− 0 in.

API 6A Tap End Stud Bolt Length for 6BX Studded Flange Connectors

product4
Flange Size and PressureBolt Size and ThreadTap End Length *Nut End LengthLength **Flange Size and PressureBolt Size and ThreadTap End Length *Nut End LengthLength **
1 13/1610,0003/4- 10 UNC0.9001.8753.7501110,00013/4- 8 UN1.9384.3759.750
1 13/1615,0007/8 - 9 UNC1.0422.1884.1 251115,0002-8 UN2.1885.00012.000
1 13/1620,0001 - 8 UNC1.1882.5005.1251120,00023/4- 8 UN2.9386.87515.000
2 1/1610,0003/4- 10 UNC0.9001.8753.87513 5/850001 5/8 - 8 UN1.8134.0638.375
2 1/1615,0007/8 - 9 UNC1.0422.1884.37513 5/810,0001 7/8 - 8 UN2.0634.68811.000
2 1/1620,0001 1/8 - 8 UN1.3132.8135.75013 5/815,0002 1/4 - 8 UN2.4385.62513.250
2 9/1610,0007/8 - 9 UNC1.0422.1884.37513 5/820,0003-8 UN3.1887.50018.1 25
2 9/1615,0001 - 8 UNC1.1882.5004.87516 3/450001 7/8 - 8 UN2.0634.6889.500
2 9/1620,0001 1/4 - 8 UN1.4383.1 256.25016 3/410,0001 7/8 - 8 UN2.0634.68811.000
3 1/1610,0001 - 8 UNC1.1882.5005.00018 3/450002-8 UN2.1885.00011.250
3 1/1615,0001 1/8 - 8 UN1.3132.8135.50018 3/410,0002 1/4 - 8 UN2.4385.62514.000
3 1/1620,00013/8- 8 UN1.5633.4386.75018 3/415,0003-8 UN3.1887.50016.750
4 1/1610,0001 1/8 - 8 UN1.3132.8135.75021 1/450002-8 UN2.1885.00011.750
4 1/1615,00013/8- 8 UN1.5633.4386.50021 1/410,0002 1/2- 8 UN2.6886.25015.125
4 1/1620,00013/4- 8 UN1.9384.3758.375263/4200013/4- 8 UN1.9384.3759.125
5 1/810,0001 1/8 - 8 UN1.3132.8136.000263/430002-8 UN2.1885.00011.000
5 1/815,0001 1/2- 8 UN1.6883.7507.6253020001 5/8 - 8 UN1.8134.0639.250
7 1/1610,0001 1/2- 8 UN1.6883.7507.7503030001 7/8 - 8 UN2.0634.68811.000
7 1/1615,0001 1/2- 8 UN1.6883.7508.375------
7 1/1620,0002-8 UN2.1885.00011.125------
910,0001 1/2- 8 UN1.6883.7508.500------
915,0001 7/8 - 8 UN2.0634.68810.1 25------
920,0002 1/2- 8 UN2.6886.25013.750------
    FOOTNOTES* Tolerance on bolt length: +0.1 25/−0 in. for lengths up to 1 2 in. +0.250/ − 0 in. for lengths over 1 2 in.

API 6A Full Thread Stud Bolt Length for 6B Flange Connectors with "R" Gaskets UNSC Series

product5
Flange Size and PressureBolt Size and ThreadLength*Flange Size and PressureBolt Size and ThreadLength*
2 1/1620005/8 - 11 UNC4.7507 1/1620001 - 8 UNC7.250
2 1/1630007/8 - 9 UNC6.2507 1/1630001 1/8 - 8 UN8.250
2 1/1650007/8 - 9 UNC6.2507 1/1650001 3/8 - 8 UN11.000
2 9/1620003/4 - 10 UNC5.250920001 1/8 - 8 UN8.250
2 9/1630001 - 8 UNC6.750930001 3/8 - 8 UN9.250
2 9/1650001 - 8 UNC6.750950001 5/8 - 8 UN12.250
3 1/820003/4 - 10 UNC5.5001120001 1/4 - 8 UN9.000
3 1/830007/8 - 9 UNC6.2501130001 3/8 - 8 UN9.750
3 1/850001 1/8 - 8 UN7.5001150001 7/8 - 8 UN14.000
4 1/1620007/8 - 9 UNC6.25013 5/820001 1/4 - 8 UN9.250
4 1/1630001 1/8 - 8 UN7.25013 5/830001 3/8 - 8 UN10.500
4 1/1650001 1/4 - 8 UN8.25016 3/420001 1/2 - 8 UN10.500
5 1/820001 - 8 UNC7.00016 3/430001 5/8 - 8 UN12.000
5 1/830001 1/4 - 8 UN8.00021 1/420001 5/8 - 8 UN11.750
5 1/850001 1/2 - 8 UN10.25020 3/430002-8 UN14.500
  • FOOTNOTES* Tolerance on bolt length:+0.1 25, −0 in. for lengths up to 1 2 in. +0.250, −0 in. for lengths over 1 2 in.

API 6A Tap End Stud Bolt Length for 6B Flange Connectors with "R" Gaskets UNSC Series

product6
Flange Size and PressureBolt Size and ThreadTap End Length*Nut End LengthLength**Flange Size and PressureBolt Size and ThreadTap End Length*Nut End LengthLength**
2 1/1620005/8 - 11 UNC0.7611.5633.3757 1/1620001 - 8 UNC1.1882.5005.000
21/1630007/8 - 9 UNC1.0422.1884.3757 1/1630001 1/8 - 8 UN1.3132.8135.625
2 1/1650007/8 - 9 UNC1.0422.1884.3757 1/1650001 3/8 - 8 UN1.5633.4387.250
2 9/1620003/4- 10 UNC0.9001.8753.750920001 1/8 - 8 UN1.3132.8135.625
2 9/1630001 - 8 UNC1.1882.5004.750930001 3/8 - 8 UN1.5633.4386.375
2 9/1650001 - 8 UNC1.1882.5004.750950001 5/8 - 8 UN1.8134.0638.1 25
3 1/820003/4- 10 UNC0.9001.8753.8751120001 1/4 - 8 UN1.4383.1 256.125
3 1/830007/8 - 9 UNC1.0422.1884.3751130001 3/8 - 8 UN1.5633.4386.625
3 1/850001 1/8 - 8 UN1.3132.8135.2501150001 7/8 - 8 UN2.0634.6889.250
4 1/1620007/8 - 9 UNC1.0422.1884.37513 5/820001 1/4 - 8 UN1.4383.1 256.250
41/1630001 1/8 - 8 UN1.3132.8135.12513 5/830001 3/8 - 8 UN1.5633.4387.000
4 1/1650001 1/4 - 8 UN1.4383.1 255.75016 3/420001 1/2 - 8 UN1.6883.7507.1 25
51/820001 - 8 UNC1.1882.5004.87516 3/430001 5/8 - 8 UN1.8134.0638.000
5 1/830001 1/4 - 8 UN1.4383.1 255.62521 1/420001 5/8 - 8 UN1.8134.0638.000
5 1/850001 1/2- 8 UN1.6883.7507.000203/430002-8 UN2.1885.0009.625
  • FOOTNOTES* Tolerance on tap end thread length: +0.063/− 0 in.** Tolerance on tap end stud length; +0.1 25/− 0 in.

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