Hi guys,
I've got a brownfield case here, an 8" pipe running straight to a centi pump suction nozzle. I put an anchor support right before pump nozzle, but still gets high loads on pump nozzle just with slight changes in temp.
Any suggestions?

Axial load = alpha*dT*E*A
A - area
dT=T1-T2
E - Elastic modulus
A - pipe cross-section area

The formula is correct and demonstrates that, theoretically, the axial load does not depend on the pipe spool length routed between nozzle and anchor support.

However, other variables should be considered when it is intended such pipe support arrangement to be analyzed: friction factor between pump base-plate and foundation plate, pump base-plate anchoring arrangement, anchor support construction (including the inherent flexibility), bolted flange joint gasket flexibility, and maybe others (depending on the real system configuration...).

A typical and simplified pipe stress model (e.g. full anchor support, pump body assimilated with rigid pipe elements fully anchored at base) cannot yield to a satisfactory/realistic solution...although I admit that I also met such EXISTING non-typical (and, maybe, non-recommended or "strange") piping routing and support arrangement nearby pump axial suction nozzle.

However, till now, I've never met a project design documentation that demonstrates satisfactorily such design solution...

My advice for "Mtm" is:

A bolted "anchor"-type support might be feasible if the pipe support shoe/dummy-leg base-plate (as applicable) has slotted holes, and no initial anchoring-bolt tightening/pre-stress is applied at installation. The slotted holes size should "compensate" the thermal expansion of the straight pipe spool enclosed by pump nozzle and "anchor" support, and the potential axial thermal movement of the pump nozzle. Therefore, the newly/modified pipework might be designed accordingly.

Another option would be to replace that "anchor-type" support with a REST + GUIDE + HOLD-DOWN support, allowing the axial thermal expansion of the pipework...

If the anchor support base-plate is welded to the foundation plate, then you have a "high-level" difficulty problem indeed...

Good luck!

Regards and A Happy New Year!

I want to make a $1,000 bet with you.

I have a vise that will exert 1e12 lbs/in. We'll stick our hands in, and we'll have someone else turn on the vise. The first one to pull his hands out pays the other.

You'd probably pull your hand out, right?
But I would know that the vise itself is only limited to about 0.001" of displacement.

Even if the vise has the ability to deliver 1e9 lbs of load, the only way it'll actually see it is if my hand is capable of delivering 1e9 lbs of load back.

The true measure of whether or not a pump fails early is the amount of distortion of the pump tearing up the bearings and/or impeller and/or casing.

However, we can't generally measure that. Why? Because we don't know the actual rigidity of the pump. What we can do is overestimate the loads at the pump nozzle as though the pump were amazingly stiff, and that's what we do in our day to day.

So, I would suggest to not qualify existing nozzles and pipe based on nozzle loads using supernaturally strong rigidity, but on supernaturally flexible pump and displacement.

If you eliminate the axial rigidity of the pump nozzle, is your pipe displacement so ridiculously low that it's not reasonable for it to cause significant pump casing distortion?

There is no listed allowable pump casing distortion, but if your total displacement can be demonstrated to be at the same order of magnitude as the relative roughness of pipe (0.0005 in), then clearly this is just a case of brown field design clashing with modern analysis techniques.

Of course, if you do this, you'll want to have good estimates of actual anchor stiffness if you go this route, and not accept CAESAR's 1e12 lb/in.

If you have my luck, though, this won't be of much help as the calculated displacement will probably be ambiguous, still.

"Brown field design often does not meet modern code requirements or current stress techniques. However, ASME B31.3 permits the continued use and replication of piping configurations with established successful life spans. Pump may incur higher than expected downtimes and maintenance costs as a result of this installation," is something I would add to my documentation.