How to torque a 2" grade 8 fastener 7

[richardl63]

I need to torque a 2"-4.5 pitch nut on a grade 8 threaded rod. I usually don't work with fasteners this large, so don't know what tools may be available. Advised Lubricated torque on a 2-4.5 fastener is 5,621 ft-lbs, and dry advised torque is 7,495 ft-lbs. I know the recommendations vary depending on the source, regardless, it's a lot of torque. I know there are some very expensive torque multipliers and hydraulic wrenches, but this is a one time job. Is there a low cost tool do to this. A 20' long cheater bar seems ridiculous, but I have not found an economical tool in my searches.

Richard Lee, PE
Lee Engineering Inc.
richardl@leeengineeringinc.com

http://www.leeengineeringinc.com

Richard Lee, PE
Lee Engineering Inc

http://www.leeengineeringinc.com

 

[MacGyverS2000]

Define "economical"...

https://hytorc.com/avanti

The Avanti 50/80 fits the bill. But this isn't something you can pick up at your local AutoZone as a loaner tool.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[JohnRBaker]

You may need to look to Archimedes for some inspiration as to what a solution might look like:

"Give me a lever long enough and a fulcrum on which to place it, and I shall move the world."

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[racookpe1978]

Please define the "economical" cost of your set of 2 inch diameter grade 8 bolts failing in service.

What steps are you going to take to torque it? You CANNOT torque it up in one step from hand-tight to full torque! How many 2 inch studs must be fastened and what is their configuration?

 

[thebard3]

As with most operations, there's not a single right or wrong way to do it, but maybe you can rent a bolt tensioner like this one. I couldn't find anything that wasn't proprietary.

Link

 

[chicopee]

About hiring an outside firm that provides services with hydraulic equipment. For example, pressure safety valves of high pressure boilers found in power plants are hydraulically tested by specialized companies that I came in contact when in my former days when I did internal inspections as an authorized NB inspector.

 

[JStephen]

Consider identifying the non-economical equipment you need, find the local supplier, call them up and find out who owns that equipment locally- hire them to come out and do it.

The 20' cheater bar might be a solution, but you'd still need the wrench to handle the torque and some way to measure that torque. (I'm thinking oversized fish-scale on the end of the cheater bar).

Would using finer thread reduce the torque requirement?

Long ago, far away- the shop where I was working had in their inventory a 60" long pipe wrench and it was BENT. They had bought it to use to tighten/untighten the screw end on hydraulic cylinders and tried to rotate it with a track-hoe; it was bent to the side.

 

[Compositepro]

one option:

http://www.nord-lock.com/superbolt/multi-jackbolt-tensioners/

 

[hydtools]

A slugging wrench may be economical.

http://www.protoindustrial.com/en/i...lugging-Wrenches-Super-Heavy-Duty---12-Point/

Ted

 

[JJPellin]

I agree with Hydtools. Perform the calculations to determine the nut rotation needed to get the same stress level that would be achieved with the specified torque. Mark the nut and stud and hammer it to the proper rotation angle using a slug wrench. In one regard, this is actually better than torque. It removes the variable of lubricant. A given rotation angle gives a known stretch which gives a known stress. At that point, use the slickest lube you can get (Moly Paste) and hammer away.

Johnny Pellin

 

[LittleInch]

Isn't it rotation required to get the correct bolt stress? not torque?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[JJPellin]

We typically select a torque value in order to target a particular stress level (perhaps 50 percent of yield). We can target that same stress using nut rotation and get a more accurate result, depending on the length of the faster that is being stretched.

Johnny Pellin

 

[richardl63]

Thanks everyone for the suggestions regarding the question about tools. The hydraulic tensioning method looks great. I think I'll check into finding one to borrow or hire, or buy. The slugging method might also be OK if used in combination with a load indicating washer or turn of the nut method.

Richard Lee, PE
Lee Engineering Inc

http://www.leeengineeringinc.com

 

[dvd]

Enerpac offers on-site torquing services with their equipment, or it can be leased.

https://www.enerpac.com/en/enerpac-bolting-service

 

[hydtools]

Jeez, a $300.00 wrench, a heavy hammer, and maybe 2 to 3 hours of labor. One time job, but we don't know how many nuts to tighten so labor is a guess. The job could have been finished by now.

Ted

 

[dvd]

Be reasonable - do it my way.

 

[Retiredat46]

Have you considered using a planetary gear torque multiplier?

 

[EngineerTex]

I have used the Supernut in the past that was suggested by CompositePro. Highly recommended.

The worst way to verify preload (least accurate and hardest to do) is by using torque. Do not use a 20-foot cheater bar.

If you don't want to go to the Supernut, then the easiest way to verify bolt preload is by the turn-of-the-nut method. Use this:

http://www.accurate-supply.com/product/hammer-wrench-bw-5200-2-stud/

and verify number of turns of the nut for correct fastener preload/elongation. The hammer wrench is ubiquitous in the oil industry where flanges and bolts are made up and broken down over and over again. Turn-of-the-nut is accurate and unaffected by the use of anti-sieze (also highly recommended).

If you already have ultrasonic inspection equipment on hand, then calculate elongation required and translate that into fastener preheat. Get the fastener to the correct temperature, put it into the joint, slip the nut on to hand-tight and let it cool. Verify preload with your UT equipment.

There are lots of ways to do this. Torque should be your last resort.

[EDIT] I skimmed through the responses and didn't see that hydtools and jjpellin already said what I said on the hammer wrench. Mea culpa. I agree with them.

Engineering is not the science behind building. It is the science behind not building.

 

[hydtools]

dvd, no, it just seemed to meet OP's economical request.

Ted

 

[JStephen]

Go to about 3:45 in this video:

https://www.youtube.com/watch?v=mEhzOYzvrq0