I have an 8" line running at 150°F. This line connects to the discharge of a pump and comes off the top of the pump and then elbows oover about 4' above. I ran this line with the pipe sitting on a +Y restraint. This configuration did not pass API 610 so I changed the +Y restraint to a hanger and the line passed API 610 with flying colors! My only problem with this is that there is only 0.04" of movement at the hanger (vertical and horizontal). Isn't this amount of movement similar to letting the pipe rest on a rigid support? So why does my model pass with a hanger that moves 0.04" and not a rigid support?
Thanks

Because 0.04" is enough to lift the pipe off the support, thus adding weight to the next support in each direction. Lift-off has been discussed here many times, you can search for the threads.

Is 0.04" of movement at a spring enough to cause the stress (forces and moments)at the pump nozzle to double?

My designers do not want to install a spring if there is 0.04" of movement in the spring.

I believe 0.04" of movement is very small.If you can play with the support location where gravity load balances the thermal force, you could get rid of the spring support. Other option will be to add more flexibility in the pipe around the pump discharge nozzle to get rid of spring support.

Hope it will help.

Cheers
Saneh

Dear Ronevich

One of my senior advised me that if less than 2mm vertical displacement on the first support of the pump or column piping, no need to go for a spring.
Because 1mm displacement will be cleared by

1.After some period of time
2.some dust particle will be accumulated in between the gap

Finally the load will be tranferrefd to the support (not to the pump nozzle). But for calculation purpose , you consider the spring.

If any one has comments on this matter, please share with us

regards

Sha..

If your piping cofiguration in pump relays much on that support then it should be considered as a spring. Many documents they say that prove such small amount of displacement in real application would be neglegible "BUT" what proof can I have when I only got code, caesar and company standard beside me that doesnt take resposibility on that decision??

For me It will be a spring and my job or resting support?

My opinions...

Regards!

Hello,

One thing that is normally missed on pipe supports near nozzles is the actuall location of the support.

CAESAR II considers the support at the centerline of the pipe, and not at the exact location which is the bottom of pipe.

Pipes also expand from the centerline outwards. Try modelling your first support from the nozzle at the bottom of pipe, this may help.

Good luck!

See this previous discussion providing advice for the EXACT SAME SUBJECT.

The search option will save regurgitating excellent info that has already been chewed on before.

http://www.coade.com/ubbthreads/ubbthrea...=true#Post11941

Dear Bob

I gone through the thread mentioned by you. But there is no solid information(either Spring can be neglected or to be considered if the displacement is even less that 2mm.).

Please share your expereince on that...

regards

Sha..

as mention above.. "If there is spring in your calculation, there must be spring at the site".
transfer of load doesnt mean seeing big lift-off or etc. If your pump fail's during that case, then you should install spring but when lift-off occurs and seeing no failure then, whats the use?

Regards..

Dear Serzed...

I agree your statement for theoritical.But you should think about how it is practically followed.I still remember that one of the revamping project i worked,I modelled the same configuration of piping(in caesar) for the centrifugal pumps of 4" size(discharge side and the temp also around 140 deg c). As per API 610 it is failing.Because the existing first support is rigid restraint.But if I use spring in the first support for the discharge line, it is passing.I am 100%sure about the inputs are in line with existing condition.However the pump is running since more than 12 years without failure.

This is where we have to think about the practical experience and confidence on taking decision.

One of my seniors also advised the same one( ie if the vertical displace ment is less than 2mm , normally spring support not necessarily to be provided.Only for calculation purpose you can consider as a spring).

Even instead of using normal resting support, rigid tie rod support can be used. Because during vertical lifts, the length of tie rod will absorb the displacement to some extent( it means that one or two millimeter)by bending.this muy guess and I request the expert to share if any comments

I am expecting some experts can share and guiding to the juniors on this issue. Because, this will help them surely to save the cost by avoiding spring in some location where it is not at all needed....


Sharing information is always good for each other

Sha.

However, I would caution that "meeting standards or codes" and "not failing" are not the same thing. (grin)

SLH

typical theory vs. practice.
We assume the supports are fully rigid (if the supporting construction is not modelled) which it isn't. Most probably the nozzle will carry more weight than your calculation says cause of the flexibility of the support itself.
If the stress is at 100.1 % of the maximum allowable it's not according to the code. Will it break? No, most probably not.

Only thing you can do is to trust on your experience and instinct. Try to eliminate as much variables as possible: thermal setting of pumps discharge, flexibility of support and such. Check your code stress comparison and maybe considering your case 105% is allowable. If you're not sure do the analysis again and again until everything passes the code requirements.
Moving the second support from the discharge nozzle further away will be a good start I guess (if the lines runs in 1 straight line for a while).