Pressure Gauge Readings at Pump Suction and Discharge?

[David3625]

Hi all,

I am fairly new to this forum and need your help to clear my confusion surrounding the pressure gauges reading at pump suction and discharge?

1. How can I determine what would be the pressure gauge reading at pump discharge?

2. Is the pressure gauge reading at pump suction equals to NPSHa?

3. Can I determine TDH using gauge readings?

Appreciate any help.

 

[TenPenny]

1...install a pressure gauge (but that's probably not the answer you were looking for)
Or, Pdischarge = Psuction + pump tdh, so you can figure it from there.

2 No. Not even close.

3 Yes : Pdischarge - Psuction = tdh if the pump is running (don't forget to resolve units of measure)

 

[David3625]

Thank for reply.

I actually would like to calculate the pressure reading at the pump discharge by having following info:

- flow
- pump centerline elevation - Hp
- discharge pipe elevation - Hd
- Friction loss on discharge pipe - HLd

Can I say:

Pressure reading at pump discharge = (Hd - Hp) + HLd

Should I add velocity head too?

 

[BigInch]

Pressure reading at pump discharge =

Suction Pressure
+ Pump Head added at a given flowrate,
convert to pressure
(see your pump curve)

Usually ignoring velocity head isn't a problem.

Now go have a look at

http://www.mcnallyinstitute.com

There's tons of "how to" info on the pages there.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[sheiko]

@david3625,

Don't forget to add the destination pressure to (Hd - Hp) + HLd.

"We don't believe things because they are true, things are true because we believe them."

 

[BigInch]

I actually would like to calculate the pressure reading at the pump discharge by having following info:

That info gives you the system head, not a "pressure reading at pump discharge", and that only if there is no outlet head and the pipeline is flat.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[rmw]

Be careful about the physical location of any gages that you are using. Sometimes gages are mounted so that their location is not at the reference point; example being a gage mounted on a pigtail on top of (or below) a pipe when the reference for the gage reading is at the pipe centerline. If that is the case you have to correct the gage reading for the difference in elevation to the reference point.

rmw