ammonia pump oversized

[luissandoval]

Whats happen if an ammonia pump(liquid overfeed system) is oversized for example:

My system needs
Q = 50 m^3/h
Total Head = 35 m

The pump was selected for work in the system

Q = 50 m^3/h
Total head = 50 m

will i have any problem?

[Peter_1]

It will consume more but I don't think it will give you specific problems.
Perhaps a small bypass or a VFD can be a solution.

[US Iceman]

As Peter said, it should work OK based on the information provided. However, I would caution you to verify the NPSHR of the pump and make sure you have adequate NPSH on top of the pump at that operating condition to make sure it works OK.

[smpsmp45]

We had similar experience with over sized pumps( as the ratio was 10:1 defined by plate freezer manufacturer). The excess liquid is bypassed when you adjust the glow rates through each equipment( like freezer, coil). We had suggested to use VFD to minimize the power consumption.

[luissandoval]

smpsmp45:

what is VFD?????? and does you have any drawing where i can see the bypass that you say me???


Best Regards.

[US Iceman]

VFD = variable frequency drive; used to control the Hertz for the purpose of speed control

The bypass valves mentioned is in the pump discharge line. As solenoid valves close, the pump discharge pressure will increase slightly. The bypass valve allows the pressure in the liquid line to bypass back into the tank.

[luissandoval]

thanks guys. their comments are very important for me.

if i don't have the solenoid valve, i could do the same if i close a little the discharge valve of the pump.

[US Iceman]

...i could do the same if i close a little the discharge valve of the pump.


Yes, that is one way.

However, the VFD works very well also. When you slow down the pump to control the discharge pressure the NPSHR reduces rapidly, which helps to reduce cavitation issues.

[smpsmp45]

US ICeman has answered it rightly

[tomireland]

Hi Guys, in my experience, the discharge side of the pump will have an adjustable pressire relief valve for venting to the top of the separator in case of "dead heading", the oversizing of the pump is not an issue if it is a centrifigual hermetic type pump, the inlet of the freezer will have a regulating valve for throttling the flow for the correct duty required.

[Segei]

Whats happen if an ammonia pump(liquid overfeed system) is oversized for example:

My system needs
Q = 50 m^3/h
Total Head = 35 m

The pump was selected for work in the system

Q = 50 m^3/h
Total head = 50 m

will i have any problem?
This isn't oversized pump. Just head is greater than at design conditions. Adjustment of coil hand expansion valves will solve this diffrence.