Direct steam injection into cooling water line at pump suction

[Amanda123]

Currently there is an operation scenario at one of our plant which directly injecting steam into cooling water line at pump suction in order to generate hot water at 60 deg C for circulation, by doing this its generate vapor at pump suction and lead to cavitation which ultimately damage pump and mechanical seals. Please advise better solution to this rather than installing a heat exchanger.

 

[EdStainless]

Posting once is enough, please don't post in multiple forums

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P.E. Metallurgy, Plymouth Tube

 

[JJPellin]

Inject the steam into the pump discharge rather than the suction.

Johnny Pellin

 

[JJPellin]

We routinely inject steam into cooling water to use it for heating. This is most common to heat up oil in a lube oil system prior to start-up in winter. It would never be advisable to inject the steam upstream of a cooling water pump. Surely the steam pressure is higher than the cooling water pressure and this injection can happen downstream of the pump. If someone thinks that the pump is needed for mixing, they are mistaken.

Johnny Pellin

 

[Amanda123]

Dear Johnny,

Thank you for the reply. There is another latest update, i have find out there is condensate tank nearby which most of condensate being send to drain. If i replace the steam injection with this condensate from condensate tank at pump suction to get hot water at 60 deg c, is that it will solve the problem since there will be no steam bubble? or still need to relocate the injection point to pump discharge?

 

[EdStainless]

You will have to do some homework.
If the inlet pressure to the pump is too low then while it may work with cold water you may have issues with hot water.
If you have the pressure in the line then inject after the pump just to be safe.

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P.E. Metallurgy, Plymouth Tube

 

[Amanda123]

Dear guys,

Thank you for the feedback. The pump suction pressure is 1 barg and and steam injection pressure is 3 barg, hence steam pressure is definitely higher than pump suction pressure.

 

[EdStainless]

Do you have enough pressure in the condensate line to inject it after the pump?
The hot water has a higher vapor pressure and could push the limits of NPSH on your pump.

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P.E. Metallurgy, Plymouth Tube

 

[Amanda123]

Dear Ed,


I dont think so the pressure is enough, because the condensate tank operating at ATM condition and pump suction pressure is 1 barg. That mean the condensate pressure is lesser that pump suction pressure. Unless i put new pump for condensate injection which become costly.

 

[gerhardl]

Hi there,

Suggestion: Pump, free straight pipelength x 3-5 pumplengths, checkvalve, steam inlet, 5-10 pipe diameter straight free length, temperature control???