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condensate pump noise

condensate pump noise

condensate pump noise

(OP)
we have a LP condensate flash drum. The flashed steam passes through fin fan cooler, and return of fin fan cooler goes back in the drum. The return line is submerged in the tank below the normal level. Pressure in the drum is maintained by venting in the atmosphere or putting nitrogen in the fin fan outlet line (split range control valves).The condensate pump makes a lots of noise. Is it possible that N2 is entrained in the liquid and going to pump. what may be the possible reasons for the pump noise? cavitation, Gas entrainment, recirculation? Is it ok with fin fan outlet line submerged in the liquid?

RE: condensate pump noise

What is your NPSHa to NPSHr margin?

RE: condensate pump noise

(OP)
NPSHA=9m
NPSHR=3.5m

RE: condensate pump noise

Have you considered a two phase flow?

RE: condensate pump noise

Are You sure that NPSH Available is always 9m and never goes below under any operating circumstance?

 

Best Regards
Qalander(Chem)

RE: condensate pump noise

You probably have vortexing which is bringing entrained gasses into the flash drum and depositing them under the level where the condensate pump is picking them up.

rmw

RE: condensate pump noise

(OP)
Is it ok to have fin fan outlet line submerged in the tank? What purpose does it solve?

RE: condensate pump noise

I have doubts on this pipeline's health and integrity over longer life periods and
may be susceptible to leakages;
consequently some leaked steam might agitate the condensate/ get trapped and cause the "Pump in question's vapor/gas locking" thus noise.

Best Regards
Qalander(Chem)

RE: condensate pump noise

Some sort of Vortex arresting system at pump suction may be helpful
Additionally the incoming pipeline may be so positioned below the liquid surface as stirring and agitation gets minimized;
may be a baffle plate slanted 45 degrees to receive the direct inlet material(if installable in earliest opportunity may prove useful).
Other learned colleagues may correct/guide better.

Best Regards
Qalander(Chem)

RE: condensate pump noise

1) It is normal if your fluid contain lighter component than its design.
2) Can you try with following suggestion
-Trottle pump discharge
-Spray water at your drum to gain sub cool liquid.
-check pump vent line already release before pump start. if in doubt, just stop the pump for a while then venting all line to clear vapor lock.
-If pump has minimum flow line try to operate in manual to check if noise still generate in diffrent flow.

RE: condensate pump noise

I agree that vortexing may be the culprit. Does the vessel have a vortex breaker at the pump nozzle?

RE: condensate pump noise

(OP)
ya pump has a vortex breaker around inlet nozzle.

RE: condensate pump noise

What elevation difference do you have between the pump and tank level?  You mention NPSHA of 9 Meters, which would indicate 9 Meters(18 feet) of elevation.

Also, what pressure range do you have for the split range control on N2 and vent?  A large pressure swing could cause vapor bubbles to form in the pump suction.

RE: condensate pump noise

(OP)
tank (2.2 meter ID) is at around 4.2 m above ground level. Tank level is maintained around 70%. Pressure at pump suction is 1.25 kg/cm2 (g). Pressure range is 0-1.6 kg/cm2 (g). Pump suction temperature is around 109 deg C.

RE: condensate pump noise

what is the velocity in the suction pipe? Does the suction pipe have at least 5 diameters of straight run (bigger line size) to the pump and a reducer right at the pump suction nozzle?

RE: condensate pump noise

(OP)
there is one blockvalve and one strainer in the horizontal line to pump suction. can this be a problem? I think valve and strainer should be in vertical line prior to horizontal suction line.

RE: condensate pump noise

What is the velocity and diameter of the suction line? Include any minflow that might be being used in the velocity calc. I think these problems start at the drum outlet nozzle- not neccessarily vortexing in the conventional sense, but this is the critical point in the system where there may be very little liquid head to supress cavitation in the nozzle. Where as the pump may calculate plenty of NPSHa, the calc implies clear liquid all the way to the pump. In reality, the nozzle static pressure drop may be higher than expected (you may have even ignored it in the calculation)- any vapor formation in the nozzle can cavitate the pump and make your NPSHa very much less than calculated.

Try running the drum level as high as possible, and if using a fixed rate minflow (spillback via orifice) try an alternative minflow protection to minimizes suction line velocity.

best wishes,
sshep

RE: condensate pump noise

Can the OP clarify..

Pressure at the Pump Suction is 0-1.6kg/cm2 @ 109oC

0???!!! Definitely an NPSH problem

 

RE: condensate pump noise

That's what the very first response's spirit from me.(3-1-09)  

Best Regards
Qalander(Chem)

RE: condensate pump noise

(OP)
Pressure at the pump suction is 1.6 kg/cm2 g and range of pic is 0-1.6.

RE: condensate pump noise

(OP)
I am sorrry for mistyping in the earlier post. The range of the PT which is used for the pressure control in the drum is 0-1.6 kg/cm2 (G). The pump suction pressure is currently 1.25 kg/cm2 (g).
More over pump discharge flow is 45 m3/h. pump has a suction reducer of 8"*3". so suction vel in 8" line is 1.27 ft/sec and in 3" reducer 8.58 ft/sec.

RE: condensate pump noise

Condensate is a pain to handle. If there is any pressure drop between the drum and the pump inlet you are going to flash some vapour. Our condensate is let down in stages, HP to MP, MP to LP and LP to atmospheric. The atmospheric is then quenched with cold boiler feed water to give a few degrees of subcooling. The subcooled condensate is then pumped back to the deaerator.

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