Pump discharge line size calculation 4

[Asisraja D]

Hello professionals
Thank you for going to help me.
We have pump with capacity of
180 m3/hr , head = 45 meters.
Pump nozzle size is 100mm x 80mm
But in our plant we already installed piping for suction with 150mm inlet piping and discharge with 250mm outlet piping to the plant
(This is cooling water supply and return line both are the same size as 250mm)
So I calculated the velocity method (Q=A X V) with the known pipe size and flow rate I get 1m/s.

Few more details for your reference:

1.Pipe material is Mild steel "C" class pipe
2.Pipe length from cooling tower sump to plant supply (250mm) EOL is 80 meters.
3.Pipe length from Main header to sub-header supply (200mm) EOL is 30 meters.

My doubt is all about discharge nozzle size with discharge piping size.
Did we take wrong piping size for discharge line?
Is there any rule of thumb or design considerations for pump piping as applicable to liquid flow.

I have attached my hand sketch for more clarity.

 

[LittleInch]

That looks better.

You do need to make sure that suction line strainer doesn't get blocked or create a large pressure drop.

And don't forget NPSH is not cavitation limit. Always allow 1 to 2 m above NPSHR to make sure your pump doesn't start cavitating.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

And remember to include a min flow recirculation line. See the pump datasheet for min flow value, and also for NPSHr.
If this pump is on auto start with existing parallel pump, then the pump starting up may go out to end of curve ( EOC) during startup, since system frictional resistance will decay to zero since the active pump would be coasting down to stop - check the pump motor power is sufficient for EOC operation.

 

[Asisraja D]

LittleInch sir
We plan to install strainer after 5 meter run of the pipe but due to come space concern we installed near to suction manifold.
Thank you sir

 

[Asisraja D]

georgeverghese sir
The pump will run in manual mode and recirculation we should have planned.

check the pump motor power is sufficient for EOC operation.

Can u help me how to calculate power consumption at EOC operation?

 

[Asisraja D]

I have attached the pump suction piping.

We don't have enough space to position strainer at "y" axis so we decided to install them on "x" axis.

Does it make any increase in pressure drop ?

I know yoy are all busy professionals anyway consider my post when you have free time. Thank you all

 

[georgeverghese]

One way to find EOC motor power is to look up the Q-h curve and see what power is at 284m3/hr. However, if these pump are not configured to autostart, you can avoid EOC operation by throttling the discharge on startup, if motor power is not adequate for EOC operation.

 

[pierreick]

Hi,
Consider this booklet to support your works using centrifugal pumps.
Many more using your favorite search engine.
Pierre

 

[Asisraja D]

pierreick
thank you so much sir for sharing the booklet and your valuable time for me..