pipe support

[farhad2474]

Hi: Every body
We have a 24 inch pipe, according to our stress analysis it coming up from its support at a point with a force 46303 N during operation .our contractor suggested to put a clamp that permissible force is 30Kips to keep it down . Can you tell me . is this right?.Thank for your time .

farhad

 

[C2it]

Since 30kips is about 133.5kN your clamp will sustain the load. But why do you want to restrain an upward movement ? Could you not just let it move ? If you have 46kN upward there must be the same load downward somewhere else that you probably don't want ???

 

[farhad2474]

Dear friend
Thank you for your answer .this pipe is going to input of a compressor .we don’t like flange of the compressor get over stress .yes you are right .we can change piping arrangement to limit or reduce force, but it is not time to do this change for us . Would you please tell me how you calculate this stress to force? Because I check catalogue of support they give us 30kips permissible load .I know this is a stress and it is not a force.

Thank s
farhad

 

[C2it]

You need software such as Caesar II to calculate stresses and loads in your piping system. You need a stress engineer to deal with this.

30kips is a force, not a stress. 1 kip = 1000lbf.
To be consistent, stress would be in units of ksi (kips per square inch).

Are you sure that your clamp and steelwork will not distort under 46kN load ? You could be wasting your time with this approach to controlling nozzle loads.

 

[BigInch]

When you include the clamp in the stress analysis the stresses and forces will be redistributed. Find where the stresses and forces are being redistributed and what new effects the addition of that clamp will have on the piping system. It may just redistribute to another flange that won't accept such loads.

In any case, take c2it's advice and find a stress engineer. If you can't tell a stress from a force, you're wasting everybody's time looking at it.

"I'm all in favor of keeping dangerous weapons out of the hands of fools. Let's start with typewriters."
- Frank Lloyd Wright (1868-1959)

 

[JohnBreen]

Farhad2474

You have posted this same question at the end of another thread. That is not considered a "polite" practice.

You apparently have a piping geometry that results in UPLIFT on a horizontal pipe at a point where you intend to have a support. Your stated uplift force of 46,303 N (10,409 lbs force)should tell you that the support is not correctly located. Unless other issues (I cannot think of what) are involved, it would not be advisable to resist the uplift (due to expansion) force. If you model the support at issue as a +Y support the software will allow it to lift off (zero loading at operating temperature) and you will see a redistribution of the sustained weight to the immediately adjacent supports. So the support at issue will support the pipe at ambient temperature and the adjacent supports will pick up the load at temperature. The better solution would be to relocate the supports (in the area of interest) such that they will be weight bearing both at ambient temperature and at operating temperature. Again, "clamping" the pipe down (resisting the uplift force) would simply ADD that force to the weight that is transferred to the adjacent supports and would NOT be advisable. If you MUST support the pipe at the "uplift" location, consider a spring support.

Regards, John

 

[farhad2474]

Sorry I did mistake. Actually in clamp catalogue write it down 30 ksi and I wrote by mistake kpi .so this is stress unit, and just tell me please how can I calculate the clamp can bear 43000 N forces when pipe is going up. Already we did stress analysis and with this force we are not going to over stress for any place.
farhad

 

[JohnBreen]

Farhad2474,

You are welcome here.

Although the stress analysis predicts that the pipe will not be overstressed, the design will result in unnecessarily high loadings to the pipe supports and to the structures that the supports are connected to. It would be good to reassess the design.

Regarding the loadings that pipe support hardware can safely accommodate, you will find that the major manufacturers of pipe support hardware provide the LOAD RATING of ALL the hardware in their catalogs (if you want to be sure you can email the manufacturer or his representative - although they will tell you the same thing as I have about the uplift force being an "artificial" load that should be "designed away"). You CAN rely on these load ratings. So look at the catalog and you will see the load ratings for the clamps and the struts. Next you must consult with the structural engineers who has designed the structures to which the pipe supports are attached.

Regards, John.