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.

 

[hydtools]

Go back and read the original post. 'My client has a specification requiring all bolts 1” and above to be hydraulically tensioned'

Ted

 

[TugboatEng]

That's what I read as well. With fasteners above 1" it's impossible to torque by hand with a simple torque wrench. Torque multipliers add additional innacuracy. It's also very slow to draw up fasteners by hand with a multiplier. There are a lot of ways a user can screw things up with a multiplier.

 

[LittleInch]

Fair enough. I read that ss stud (bolts).

So which is it?

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

 

[desertfox]

Hi Gcooper79

When the hydraulic tensioning is done the bolt/stud is normally stretched to give a tensile force higher than the tension force required after the bolt/stud is released and the joint completed.
So you are right to be concerned, what you have to check is that at the point of the overstretching of the stud/bolt you don’t over stress the internal threads on the flange or the fastener. The reason the stud/ bolt is stretched further than it would be if you were tightening it with a torque wrench is to allow for relaxation of the joint.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[3DDave]

My client has a specification requiring all bolts 1” and above to be hydraulically tensioned.

Only bolts passing only through clearance holes with at least 1 full diameter past the seated nut can be hydraulically tensioned.

Bolts installed into tapped holes cannot be hydraulically tensioned so the threads cannot be damaged by a process that cannot be used.

 

[desertfox]

Spot on 3DDave you are perfectly correct, the only way would be if a stud was used in the tapped hole and not a hexagonal headed bolt

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[FacEngrPE]

How hydraulic bolt tensioners work. These all directly tension the body of a bolt or stud.

http://www.youtube.com/watch?v=XRjzLvySIZk

https://youtu.be/HT9XyMANR6Q

There is also Hydraulic Torque Wrench. These are functionally the same as a torque wrench, with hydraulic power added. They apply tension the body of a bolt via the inclined threads (indirect tension).

https://youtu.be/jOk6ZYggc4g

Both have their place, but not the same place.
If the hydraulic tensioner will fit and you are able to get the required thread engagement (note the above) the method can be used. Tapped holes do not concern me unless the base metal is soft - like aluminum - then more care is required with both methods.
Pay attention to tightening sequence, see below for one option.

 

[desertfox]

Hi FacEngrPE

Yes its possible to tension a bolt going through a drilled hole but how would the tensioner work with the bolt going into a tapped flange?
I guess you could use the hydraulic torque wrench but that's a slightly different process.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[r6155]

1)The blind tapped hole (see ASME VIII-1 Figure UG-40 (a-1) and (a-2)) is the same as the drilled hole when the stud is tensioned.
2)You need to calculate the elongation of the stud (mm)
3)Never use torque, it's an inaccurate system. Torque requires lubrication but not for elongation.
4)Try to use the tensioner on all the studs at the same time. Otherwise you need various sequences.

Regards

 

[desertfox]

Hi r6155

Yes agreed that a stud can tensioned in a tapped hole but I doubt that you can tension a hexagonal bolt in a tapped hole as pointed out by 3DDave.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[r6155]

Hi desertfox
I say STUD, not bolt

Regards

 

[desertfox]

Hi r6155

Yes I know you stated stud, I wasn’t sure who you were addressing your comments too,I mentioned stud in my post on the 17/06/2023 .


“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[Tmoose]

Is the flange part of a gasketed joint? Or a rigid joint made by machined metallic faces?

I believe good practice is not to fully tighten the fasteners one at a time.
I would not hesitate to use torque, at least for the intermediate stages.

Regardless it my preference to tighten the fasteners in gasketed joints ( and most joints really) in stages in a criss-cross pattern in an effort to achieve even clamping.
One time I tightened an opposed engine's cylinder head with too few steps, and created a problem when the exhaust cross over pipe was "too short" due to head "tipping."