Maximum Torque on a Jackscrew

[McDermott1711]

I'm going to calculate (or analyze via FEM) maximum stress in a jackscrew which is used to make space for removing a valve sandwiched between two flages. I know tightening torque on that machine bolt is at first low but it will increase as far as isolating space is increased.
So, how can I calculate maximum torque which will be applied on this jackscrew?

Nothing is more fairly distributed than common sense: no one thinks he needs more of it than he already has. Rene Descartes

 

[r6155]

See ASME PCC-1

Regards

 

[McDermott1711]

See ASME PCC-1

I searched for it, but found nothing.

Nothing is more fairly distributed than common sense: no one thinks he needs more of it than he already has. Rene Descartes

 

[LittleInch]

I'm not sure that you can.

The force required to separate the flanges is almost certainly not linear and the start force to get any movement is highly variable, from negative (i.e. the pipe springs a part a bit) to high, especially if the pipe temperature is higher than the installed temperature.

Flexibility of the piping either side is very variable and difficult to get a figure for to move the pipe what 5mm? 10 mm?

Friction between the end of the jack screw and the flange is very difficult to estimate.

Only way to get close is to try it and measure the torque. Even then the next time will be different.

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

 

[McDermott1711]

Only way to get close is to try it and measure the torque.

So, how they size these bolts (considering risk of fracture within threaded area)?

Nothing is more fairly distributed than common sense: no one thinks he needs more of it than he already has. Rene Descartes

 

[LittleInch]

The biggest one they can get in the flange.

You can also use flange spreaders, but normally you design it so that you have an elbow somewhere that allows movement.

Got any more info?

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

 

[Heaviside1925]

OP,
I would consider looking at this from the opposite direction, being that, wouldn't you want your threads to fracture before you applied enough force to damage the flange body? That maybe what R6155 was point to, that is, what is the maximum force you can apply to the flange body without damage?

 

[mfgenggear]

OP
Do you have an standard operating procedure .
SOP, may be that should be the question.
Heaviside makes an excellent statement.
Review free body diagram of a standard screw automobile jack. It's amazing how is supports an automobile.
But we have no idea how you are designing
A screw jack or what size it is.

 

[McDermott1711]

Thanks a lot for all the above answers.

Nothing is more fairly distributed than common sense: no one thinks he needs more of it than he already has. Rene Descartes