Flange Bolt Torque Values Complete Reference Chart for ASME B16.5

Why Proper Flange Bolt Torque Prevents Costly Leaks

Incorrect bolt torque is a leading cause of flange joint failures. Applying correct torque ensures proper gasket compression and prevents shutdowns and safety incidents.

Target Torque Calculation Formula

ASME PCC-1 Appendix K formula: T = K x D x F / N

• T = Target torque per bolt
• K = Nut factor (thread friction)
• D = Nominal bolt diameter
• F = Total bolt load required
• N = Number of bolts

Nut Factor Values

• Unlubricated carbon steel: K = 0.20
• Moly-based lubricant: K = 0.13-0.15
• PTFE-coated studs: K = 0.10

Reference Torque Values (Lubricated Threads)

Class 150 Flanges

NPS	Bolt Size	Bolts	Torque (ft-lbs)
1/2	1/2-13	4	15
2	5/8-11	4	25
6	3/4-10	8	45
8	7/8-9	8	60
12	7/8-9	12	60

Class 300 Flanges

NPS	Bolt Size	Bolts	Torque (ft-lbs)
1/2	1/2-13	4	20
2	3/4-10	4	45
6	7/8-9	8	90
8	1-8	8	120
12	1-1/8-8	12	160

4-Pass Tightening Procedure

1. Pass 1: Star pattern at 30% torque
2. Pass 2: Star pattern at 60% torque
3. Pass 3: Star pattern at 100% torque
4. Pass 4: Circular pattern at 100% until no rotation

Common Mistakes

• No lubricant on studs
• Skipping multi-pass sequence
• Mixing bolt grades
• Reusing old gaskets

Contact Songhai Flange for torque specifications and technical documentation.

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