I'm sure this discussion has been done before, but I can't seem to find it...

so what do people think about spring hangers from vertical pump nozzles...

For a pump with a top nozzle, it seems to me that from a free body diagram point of view, the weight of the water column is not really a "nozzle load" (it gets restrained at the impeller or case)...

Anyway, the one I'm looking at is fine with assuming either
1. Weight of water column is part of nozzle load
or
2. Weight of water column is not part of nozzle load...

But I'm just wondering if there is a "standard practice" for this. (yeah yeah, I know, standard practice is to just blindly take whatever the mighty computer tells you is so -- so how about a "best practice" instead).


Thanks all
Shannon

You're correct Shannon.

The weight of the liquid column, of the diameter of the pump nozzle, in the vertical riser is against the pump and not the pump nozzle for a top nozzle.

Most systems that I work on have a reducer at the nozzle and the line size increases by one or two sizes. For these cases, the weight of the liquid in that outer annulus between the reducer ID and the Line ID is against the reducer wall and that weight will be on the nozzle.

Another thing to think about is on the non-operating pump when the check valve closes or block valve is shut, the liquid column above the closed valve will be on the nozzle.

Like you said, your loads are OK either way. I generally ignore the situation except on larger lines or long risers where it makes a real difference in the loads.

Since you're into splitting hairs to get the spring loads right, let me mention a couple other things that can lead to inaccurate support and equipment loads.

1. Insulation Density - For Calcium Silicate, do you use the 11.5 lb/ft3 Caesar default value that has been around since the Asbestos Insulation days or do you use the 14-15 lbs/ft3 that is noted in modern manufacturer literature?

2. Insulated flanges and valves? - You modeled insulation, but are your flanges going to be insulated? Are the valves going to have that little fabric jacket around it that is much lighter than Cal-Sil. If so, did you turn your insulation off and on as required?

3. Does your flange and valve weights include bolts & nuts and Gear Operator on the larger valves? The nuts and bolts weight becomes significant on the larger sizes and higher flange classes.

4. Also remember that the valve weight assumed in your analysis can vary from what actually gets bought and installed.

OK, I got off track a little but those are my thoughts.

But if there is a check or other stop valve in the line some of the fluid weight is captured at least some of the time....

All in all I suggest keeping the risers short and turning horizontal as soon as possible to take the fluid column nightmare out of the equation....

Good plan John. Keeps the moment arm down too.

Also when attempting to create a model with precise weight, remember that the wall thickness and consequently pipe mass can vary by the tolerance .. which may be + /- 12.5%.

And Caesar insulation weight ignores the cladding.

And what about corrosion ? Enough !

Cheers.

What about water density differences in relation to temperature?

Density changes are usually but not always insignifcant, (my guess is that Water should not be significant,) as a matter of fact some heat transfer fluids see a 50% density change over the temperataures that they may operate at!!!!

For this calculation water density difference not significant but for humans living in cold areas and especially for fish life and death issue.

50% density change. Must remember. Thanks.