Is pressure thrust accounted for in API 610 with use of unrestrained joint

[AgsMyDude]

I see that 9.3.10.4 of API 610 states that thrust restraints are required for expansion joints installed at pump discharge for VS1 and VS2 pumps but what about the suction side or other pump types? Are API 610 pump casings designed to transmit axial pressure thrust force to the support structure and if so, how much? I understand that it is typical to include tie rods to restrain this force but I am curious about suction side expansion joints without tie rods or cases in which the piping on the other side of the discharge expansion joint is anchored. I am not sure if allowable nozzle loads are relevant here since the axial thrust due to an unrestrained expansion joint occurs in the pump casing which transmits it to support structure.

Thanks in advance

 

[bimr]

Pumps are not generally designed to provide thrust restraints on piping as there is no way that the pump manufacturer can predict or anticipate the thrust. Properly designed piping supports will include anchoring of piping before and after a pump which eliminates the need for expansion joints.

 

[AgsMyDude]

Thanks for the response bimr. I do disagree with your second statement. Tied expansion joints are often required to accommodate thermal pipe growth/contraction and prevent exceedances of allowable pump nozzle loads in properly designed systems. In fact, anchoring the pipe on either side of the pump would likely necessitate an expansion joint between the pump and anchor; otherwise your pump nozzle(s) and anchor loads are going to be quite high. Let me know if I am misunderstanding.

 

[bimr]

Thanks for the response bimr. I do disagree with your second statement. Tied expansion joints are often required to accommodate thermal pipe growth/contraction and prevent exceedances of allowable pump nozzle loads in properly designed systems. In fact, anchoring the pipe on either side of the pump would likely necessitate an expansion joint between the pump and anchor; otherwise your pump nozzle(s) and anchor loads are going to be quite high. Let me know if I am misunderstanding.

Expansion joints may be of great benefit in a pumping system when used properly. They are, however, only needed when pipe strain is present. In addition, the correct installation of an expansion joint is also important.

It is not simply a matter of bolting expansion joints onto the pipeline. This method of installation may transfer the strain through the joint and onto the pump casing, which will ultimately cause pump seal and bearing failure. In order to protect the pump from such problems with the use of expansion joints, it is necessary to independently anchor and secure the end of the expansion joint closest to the pump. This will allow the expansion joint to absorb the entire strain coming from the pipeline as well as protecting the pump.

Many engineers consider expansion joints a weak point in the piping system:

Link

 

[quadtracker]

Pipe expansion bends and or spring loaded pipe hangers or supports will generally accomodate thermal growth which might help with your concerns.