torque specs 1-3/4 thread

[Hertz]

Good morning. I'm trying to determine a torque spec for some bolts we made in house. They are 4340 HTSR material and are 1.75-8 and they are 16" long with 4.5" threads on each end. They are retaining bolts holding 3" thick plates together. but I am not sure a torque I should use. Before I started here, the guys just tightened the snot of of them but I'd like to know a good ballpark of where I should be. I was trying to compare online if this would be closer to Gr5 or Gr8. They are torqued dry.

 

[memphisjed]

About 4000 ft pounds.

 

[4GSR]

Same thread size and pitch used on well head studs on a christmas tree on an oilwell. Tighten the snot out of them! Without going through the calculations determining the torque needed, 1200-2000 ft/lbs. be about right.

 

[BT Fabrication]

Good morning. I'm trying to determine a torque spec for some bolts we made in house. They are 4340 HTSR material and are 1.75-8 and they are 16" long with 4.5" threads on each end. They are retaining bolts holding 3" thick plates together. but I am not sure a torque I should use. Before I started here, the guys just tightened the snot of of them but I'd like to know a good ballpark of where I should be. I was trying to compare online if this would be closer to Gr5 or Gr8. They are torqued dry.

most will tighten to a specific rotation value, mostly till the bolt starts stretching and not any specific torque.

 

[jaguar36]

4340 HSTR is about 85ksi yield, assuming its dry it should be something like 2,400 ft-lbs. I'd bet they were nowhere close to that.

 

[gbent]

Good man with a 20# sledge.

 

[tree hugger]

I would approach this in one of two ways using the approximate relationship that Torque (Ft-Lb) = 0.2 x Dia (in) x Load (lbs) / 12. The load could be determined in one of two ways 1) the force required to hold the plates together or 2) some percentage of the proof load of the bolt. If you know the hardness of your material which I'd guess to be 28 to 32 Rc you can estimate the yield strength of the material and then calculate the proof load.

 

[Bill D]

How will you measure how much torque you are applying? I think that device's max measurable torque will be your limiting factor.
Bill D

 

[William Lynn]

The main thing is consistency of the torque, which you won't get with a sledge hammer. Best to use a torque wrench along with a torque multiplier.

 

[tree hugger]

Not a torque wrench for sure! Depending on the configuration there are hydraulic stretchers and wrenches, multipliers too as William mentioned. It's been a while so I'm not up on exactly whats out there. In a past lift we used a stretcher on some 3 or 4 in tie rods.

 

[gbent]

Torque multipliers aren't the easy answer they may seem. My big multiplier goes to 6500 ft*lb at about 6:1. That means at 6000 you are supplying 600, and the reaction arm is supplying 5400. That takes a very stout reaction arm, and a very solid place to brace it. The wind up can sometimes require more room than is available. People have been killed when the reaction arm or brace have broken.

 

[4GSR]

Here's the type of torque wrench I've seen being used.

Hydraulic Torque Wrench, Torque Repeatability ±3%

High-power hydraulic wrenches for sale, factory outlet. A hollow hydraulic torque wrench can be widely used in metallurgy, coal mine, the chemical industry, power generation, medical treatment, agriculture, machinery, oil field, and other fields. Constant torque output with a ±3% torque...

www.tool.com

 

[memphisjed]

1 1/2 bolt is north of 3000 ft lbs….

Torque Chart | ASTM A325

Because the calculations specified in the torque chart below are offered as a guide only, it is the sole responsibility of any person using them to assume all risk. There are many variables affecting the torque-tension relationship, such as human error, surface texture, and lubrication. Because...

www.a325bolts.com

At that size squish washers are used instead of torque normally. Squish washers are always the answer if you have doubt.

 

[GregSY]

I don't know the torque value, but you can bet when they assemble a split case compressor or turbine they aren't using a hammer or snot method!

 

[William Lynn]

Here's the type of torque wrench I've seen being used.

Hydraulic Torque Wrench, Torque Repeatability ±3%

High-power hydraulic wrenches for sale, factory outlet. A hollow hydraulic torque wrench can be widely used in metallurgy, coal mine, the chemical industry, power generation, medical treatment, agriculture, machinery, oil field, and other fields. Constant torque output with a ±3% torque...

www.tool.com

We had Hytork units. They worked pretty good until you try to loosen bolts after some asshat cranked the pressure all the way up when he tightened them. Then millwrights came with their gas axe and cut the heads off. Occasionally hi-collar lock washers were used and they just blew them out. Had some applications where some rigging was needed to support the reaction arm. Some guys didn't seem to mind having their face close to the head while in operation, instead of backing away. Guess they thought it was too much work to move away when multiple bolts were involved.

 

[muckalee]

most will tighten to a specific rotation value, mostly till the bolt starts stretching and not any specific torque.

Well, sounds more like studs since it is threaded on both ends. Steam turbine studs are heated to a specific value, installed in the lower case then the top nut is threaded hand tight and allowed to cool. I have installed Super nuts on studs 2 inch diameter and 18 inches long. The multi bolt nut gives options that are field installations friendly and such. The jack bolts were torqued to 150 lb ft for the 2 inch studs. I have used supernuts on studs 1 inch in diameter in an application where the nuts could not be accessed with a socket or combination wrench. These jack bolts were 5/16 inch socket head bolts and tightened by hand Allen wrench. These studs were tightened until the length of the exposed stud reached a gauge length determined to stretch the studs.

 

[Hertz]

Awesome answers guys. We have determined that because of the application it is, that we do not have to have an actual torque value, so we just tightened as much as we could. I had forgot to mention, if it matters at all, that there were 1/2" thick MS washers used as well. I originally budgeted around 2000 lbs as a baseline so this thread definitely helped out to confirm. Appreciate the responses.

 

[rbent]

I've made inhouse Supernut/jack bolt tensioners before using SHCS for similar sized hardware and they worked very well.

 

[Jhn3:16]

Sound like a good application for Superbolts they are part of the Nord-Lock group

rbent beat me to it but they are great compared to a 1"drive breaker bar with 6-8" cheater bar!

Brandon

 

[Cole2534]

Came here to suggest super-nuts or a Hy-Torc.