Bolt Tightening Procedure

on 10 January 2016. Posted in Pipe Flange

bolt circle 1 Bolt tightening procedures are typically specific to the application and the type of bolt being used. However, there are some general guidelines that can be followed:

Use the correct torque specifications provided by the manufacturer for the particular bolt and application.
Lubricate the threads and the contact surface of the bolt and nut with an appropriate lubricant.
Tighten the bolts in a star pattern, tightening each bolt a little at a time to ensure that the load is evenly distributed.
Use a calibrated torque wrench or tensioning device to achieve the correct level of bolt tension.
Verify the torque or tension after a specified time has elapsed or after a specified number of cycles.

It is important to note that these general guidelines may not be sufficient for all applications, and that specific bolt tightening procedures should be followed for each application. Additionally, it is important to consider the environment and any safety factors that may be relevant to the application.

Start the tightening procedure by lubricating the nuts and bolts. Then hand tighten till they are snug against the flanges. If an air wrench is used make sure the pressure is set to the minimum. When tightening, always use the correct sequential bolt order for the flange.

4 and 8 Bolt Flanges

First round - 30% of final torque (flange sequential order)
Second round- 60% of final torque (flange sequential order)
Third round - 100% of final torque (flange sequential order)
One final time - clockwise or counter clockwise sequentially around the flange.

12 Bolt Flanges and More

First round - 20% of final torque (flange sequential order)
Second round - 40% of final torque (flange sequential order)
Third round - 80% of final torque (flange sequential order)
Fourth round - 100% of final torque (sequential order)
One final time - clockwise or counter clockwise sequentially around the flange.

Article Links

Bolt Standards

ASME Standards

ASME PCC-1 - Guidelines for Pressure Boundary Bolted Flange Joint Assembly

ISO Standards

ISO 4162 - Hexagon bolts with flange - Small series - Product grade A with driving feature of product grade B
ISO 15071 - Hexagon bolts with flange - Small series - Product grade A
ISO 15072 - Hexagon bolts with flange with metric fine pitch thread - Small series - Product grade A
ISO 21670 - Fasteners - Hexagon weld nuts with flange

ANSI Class Torque Factor
Pipe Size (NPS)	150# (ft-lbs)	300# (ft-lbs)	400# (ft-lbs)	600# (ft-lbs)	900# (ft-lbs)	1500# (ft-lbs)	2500# (ft-lbs)
1/2	45	45	45	45	150	150	-
3/4	45	90	90	90	150	150	-
1	45	90	90	90	240	240	-
1 1/4	-	-	-	-	-	-	-
1 1/2	45	150	150	150	368	368	-
2	90	90	90	90	240	240	-
2 1/2	90	150	150	150	368	368	-
3	90	150	150	150	240	533	-
3 1/2	-	-	-	-	-	-	-
4	90	150	240	240	533	750	-
5	150	150	240	368	750	1200	-
6	150	150	240	368	533	1020	-
8	150	240	368	533	1020	1650	-
10	240	368	533	750	1020	3000	-
12	240	533	750	750	1020	3300	-
14	368	533	750	1020	1020	4770	-
16	368	750	1020	1020	1650	6600	-
18	533	750	1020	1650	3000	8800	-
20	533	750	1200	1650	3300	11580	-
22	-	-	-	-	-	-	-
24	750	1200	2250	3000	6600	-	-

Four Bolt Tightening Sequence

Sequential Order: 1-2, 3-4
Rotation Order: 1, 3, 2, 4

Eight Bolt Tightening Sequence

Sequential Order: 1-2, 3-4, 5-6, 7-8
Rotation Order: 1, 5, 3, 7, 2, 6, 4, 8

Twelve Bolt Tightening Sequence

Sequential Order: 1-2, 3-4, 5-6, 7-8, 9-10, 11-12
Rotation Order: 1, 5, 9, 3, 7, 11, 2, 6, 10, 4, 8, 12

sixteen Bolt Tightening Sequence

Sequential Order: 1-2, 3-4, 5-6, 7-8, 9-10, 11-12, 13-14, 15-16
Rotation Order: 1, 9, 5, 13, 3, 11, 7, 15, 2, 10, 6, 14, 4, 12, 8, 16

Twenty Bolt Tightening Sequence

Sequential Order: 1-2, 3-4, 5-6, 7-8, 9-10, 11-12, 13-14, 15-16, 17-18, 19-20
Rotation Order: 1, 9, 5, 13, 3, 11, 7, 15, 2, 10, 6, 14, 4, 12, 8, 16

Twenty Four Bolt Tightening Sequence

Sequential Order: 1-2, 3-4, 5-6, 7-8, 9-10, 11-12, 13-14, 15-16, 17-18, 19-20, 21-22, 23-24
Rotation Order: 1, 9, 17, 5, 13, 21, 3, 11, 19, 7, 15, 23, 2, 10, 18, 6, 14, 22, 20, 8, 16, 24