condensate pump noise

[amar122amar]

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?

 

[amar122amar]

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

 

[amar122amar]

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.

 

[SeanB]

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.