Questions about pulsation dampeners for recip pump

[KernOily]

Guys here's a couple questions for you. These are in relation to gas-charged, bladder-type pulsation dampeners used on the suction and discharge of piston (reciprocating) pumps used in boiler feedwater service.

1) Does it make any difference if I charge the bladder with air instead of nitrogen? I say no, since the properties of the two gases (density, speed of sound, etc.) are very similar.

2) Do any of you know anybody who makes high-temperature bladders? My pumping temperature is 240° F and the bladders don't last too long in this service. We are changing them out about every month which is not acceptable. It's not possible to cool the pumpage, unfortunately.


Thanks!
Pete

 

[JJPellin]

I don't think it matters what gas you use as long as it is clean and dry. We tend to use nitrogen just because of the possibility of the gas getting into the process if the bladder ruptures. We use acccumulators manufactured by Greer and I think we use Viton (good to about 350 °F) in most services. Viton should work in BFW.

 

[electricpete]

If the pulsation damper were connected to the main fluid by a long run of uninsulated pipe, the stagnant fluid within that pipe should cool to near ambient, right?

Not sure if that would be a practical solution for you.

 

[Scipio]

Shouldn't be too hard finding an elastomer that'll handle 240°F, Viton, like JJPellin suggests, comes to mind, and should be compatible with BFW. Another option would be eliminate the bladder completely, maybe go with a teflon diaphragm damper. Another option, especially in a high vapour pressure service like this, might be a Fluid Kinetics Vapour-Dome. Those dampers don't use a bladder or mechanical interface of any kind, just a pocket of vapourized pumpage at the top of a vertical cylinder.

electricpete,

A long run of uninsulated pipe will introduce a lot of line losses between the main piping and the dampener, enough to generate too much resistance for the dampener to do its work. They should always be installed as close as possible to pump suction & discharge to minimize line losses between the pump and the damper.

 

[electricpete]

Good point. Well, let's just say you put a relatively small legnth of large-diameter uninsulated piping going straight down, then making a U-turn coming back up into an accumulator. If necessary add a pipe reducer right at the end.

The orientation below the pipe should allow the fluid to cool off and cool water will remain at the bottom.

Diamter of pipe should help address losses which limit effectiveness.

Just a thought. If there is a material out there to handle the temperature that should work as well.

 

[assco]

Good points made all around. You have no problem charging with air. You have no problem with temperature. If you are replacing bladders monthly there is something else going on.

 

[BobPE]

I agree with assco, there has to be something else going on, that replacement frequence seems too high. That is a reasonable temperature for most bladder materials so I would assume a pressure problem caused by insufficient tank volume? Give us some more info on your system, capacity, stroke setting, bladder volume and location relative to the pumps and anything else you may think of....

BobPE

 

[BRT549]

Hey BobPE - I think you're on to something with the insufficient tank volume.

 

[desertfox]

Hi 74Elsinore

One question how often does someone check the pre-charge in the pulsation dampers.
Echoing the questions of BobPE can you give us more info and include pre-charge in the dampers.


regards

desertfox

 

[stanier]

You can download dampener sizing software from Hydril to check your sizing.

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