Free engineerin' tool
Flange Bolt Torque Calculator
Get y'all a startin' bolt torque for a flanged joint. Pick your flange class and size (the bolt count and diameter come straight off the Texas Flange bolt and stud chart) or punch in any inch bolt. Then set your bolt grade, target stress and lube. The calculator runs the standard short-form torque formula, T = K × D × F, and shows y'all the torque per bolt, the preload and a three-pass tightenin' sequence.
Lotta procedures shoot for 40 to 70% of minimum yield. Kept between 10 and 90%.
4″ Class 150: 8 studs, 5/8-11 UNC
124 ft-lb per bolt
168 N·m per bolt
- Tensile stress area
- 0.2260 in²
- Bolt yield (min.)
- 105,000 psi
- Target bolt stress
- 52,500 psi (50% of yield)
- Preload per bolt
- 11,865 lbf
- Total bolt load (8 studs)
- 94,921 lbf
Tightenin' passes (star pattern)
- Pass 137ft-lb
- Pass 274ft-lb
- Pass 3124ft-lb
Then go 'round once more at full torque till dem nuts quit turnin'.
Torque-to-preload rides mighty heavy on lube, thread condition and washers. Make sure the bolt stress suits your gasket (too little and she leaks, too much and you can crush it) and follow the gasket maker’s and your site’s boltin’ procedure.
This here's a reference tool for plannin' and quotin'. Check it against your purchase spec and your site's procedures before y'all go usin' it.
Get y'all a flange quote
Questions Folks Ask Us
How do y'all figure bolt torque?
A common short-form formula is T = K × D × F, where K is the nut factor ('bout 0.20 for dry steel, 0.16 with moly anti-seize), D is the nominal bolt diameter in inches and F is the target preload in pounds. Divide by 12 and you got your ft-lb, cher.
What preload oughta flange bolts get tightened to?
A whole lotta procedures shoot for roughly 40 to 70 percent of the bolt's minimum yield strength. The right number depends on the gasket and the joint, so y'all check what the gasket maker recommends and what your site procedure says.
How come lube changes the torque?
Most of the torque you put on gets eaten up by friction in the threads and under the nut. Good lube cuts that friction down, so the same preload takes less torque. Run a dry-bolt torque on lubed bolts and I tell you what, you can over-stress 'em.
What's the tightenin' sequence for a flange?
Tighten 'em in a star (cross) pattern over a few passes, say 30, 60 and 100 percent of final torque, then go 'round in a circle at full torque till dem nuts quit turnin'.
What bolts go on ASME B16.5 flanges?
Alloy steel studs to ASTM A193 B7 with A194 2H heavy hex nuts are what most folks run on carbon steel flanges. Cold service usually gets A320 L7, and stainless systems mostly get B8 or B8M.
