Hydraulic Bolt Tensioning Tapped Hole 3

[Gcooper79]

Hi All,

My client has a specification requiring all bolts 1” and above to be hydraulically tensioned. I have a pipe flange connecting to a compressor with a tapped hole - would you normally apply hydraulic tensioning to a tapped hole? My concern would be that the thread gets damaged during the process resulting in a replacement compressor.

Thanks.

 

[MJCronin]

What did the Compressor Vendor say when you called them ? .... Who makes the compressor and is it a common model ?

Have you called a specialty bolting services firm and asked them this question ? .... I am sure someone has asked it before ...

Can you establish the depth of the hole and the casting material ?

More information please

MJCronin
Sr. Process Engineer

 

[LittleInch]

Well the bolt will not really be subject to any more force that you would get if you tensioned the bolt using a spanner and a big hammer would it?

Hydraulic tensioners simply apply tension to the correct amount, then you tighten up the bolt and then let the tensioner relax.

They don't want to exceed yield stress in the bolt so the force on the threads should not be excessive compared to what the bolt hole was designed for. which I think is usually 75-90% yield of the bolt.

Tapped holes are usually quite a bit deeper than the equivalent nut on the other side of the flange for exactly that reason. You really don't want to strip out a casting tapped hole.

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Also: If you get a response it's polite to respond to it.

 

[GBTorpenhow]

No reason why you can't. Tensioning probably carries less risk of thread damage because you have direct control over the tension in the bolt vs just estimating the tension based on the torque applied.

Advisable to calculate or get from the vendor the required engagement depth to make sure that the bolt will yield before the threads do, and make damn sure that the studs are installed correctly to this depth.

 

[Gcooper79]

Hi All,

Thanks for the replies.

I haven’t contacted anyone yet as the requirement only arose as I finished for the day.

The casing has a full thread depth of 1.5 x bolt dia.

The compressor has a lead time of 60 - 70 weeks so I didn’t want to risk damaging it.

It sounds like hydraulic tensioning wouldn’t be a problem so long as we maintain the correct torque.

Thanks again,

Gcooper79

 

[LittleInch]

Correct torque?

Correct force more likely surely?

Are we talking about the same thing?

But 1.5 times bolt depth sounds about the minimum you want.

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Also: If you get a response it's polite to respond to it.

 

[r6155]

Hydraulic bolt tensioning works with elongation of the stud, without torque.

Regards

 

[Gcooper79]

Sorry, my mistake.

 

[hydtools]

How do you hydraulically tension a bolt, a headed fastener, that's fitted into a tapped flange? What device gets run up to retain tension in the bolt? I would understand if you had a stud and nut.

Ted

 

[r6155]

See

https://www.nord-lock.com/boltight/products/standard-bolt-tensioners/

Regards

 

[LittleInch]

You do need to order longer studs to fit into the casing though....

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Also: If you get a response it's polite to respond to it.

 

[r6155]

The stud must be longer to engage the tensioner.

Regards

 

[LittleInch]

Yup, longer on both sides of the flange.... and don't tighten the stud into the hole - use sealant and ensure it goes in the full 1.5 times the nut thickness.

But usually the compressor guys have it sorted

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Also: If you get a response it's polite to respond to it.

 

[hydtools]

@r6155 yes, but there must still be a nut that gets wound down after the bolt is tensioned from the threaded end. Implying a through hole flange, not a threaded flange as the OP mentions.

Ted

 

[r6155]

Tapped hole is on the compressor. The stud is held on it.

Regards

 

[LittleInch]

I believe the only threaded bit is the hole in the compressor casing where an flange face has been created.



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

 

[TugboatEng]

The interchangeable use of torque and tension seems to be causing some confusion. The hydraulic tensioning devices have already been mentioned but there are also hydraulic torquing devices:

https://hytorc.com/hydraulic-tools

Hydraulic tensioning is superior when the connection is designed to work with it. Hytorc works with conventional fasteners and in much smaller spaces.

 

[r6155]

Never torque. Use stud elongation with hydraulic tensioner.

Regards

 

[TugboatEng]

Well that would be ideal but it's seldom necessary and often impossible. There are a few benefits of bolts over studs, particularly in corrosive environments.

OP is going to need to explain more about their application.

 

[LittleInch]

Hydtools is the only person talking about a bolt.

The compressor has some tapped holes. Studs are inserted, generally they have a hex hole in the end to allow you to insert it to the correct depth. Then you attach the pipe flange and nut and tension up, either with hydraulic tensioner or nut torque. No bolts anywhere. [pre][/pre]

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