pump suction gauge is ZERO,DISCHARGE 40 PSIG.
pump suction gauge is ZERO,DISCHARGE 40 PSIG.
(OP)
As I visit the air cooled chilled water plant, found the chilled water pump suction gauge is zero; the discharge pressure is 40psig.as far as I know, if there is no sufficient suction will cause the cavitations. But I was told there is not much any problem on this system.
THANKS
THANKS





RE: pump suction gauge is ZERO,DISCHARGE 40 PSIG.
If it is reading zero, either fit a new gauge or have the existing gauge checked.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: pump suction gauge is ZERO,DISCHARGE 40 PSIG.
However operating at this pressure might draw air into the system and if the water become hot might create vapour bubbles.
There are a few explanations:
1) Your system works fine at pressures lower than 0 psig, but you guage is only good for positive pressures. As artisi says, fit a guage which can read pressures below atmospheric.
2) Your guage is isolated or broken
3) Your pressurizing system isn't working and you need to add water to pump it back to what it should be
4) Your expansion tank is broken or not pressurized correctly
Learn more about how your system is designed to work and then you will be able to work out if it's not working correctly.
PS Please don't use CAPITALS in your post - this is seen as SHOUTING and is not allowed.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: pump suction gauge is ZERO,DISCHARGE 40 PSIG.
First rule of maintenance: if it ain't broke, don't fix it.
RE: pump suction gauge is ZERO,DISCHARGE 40 PSIG.
RE: pump suction gauge is ZERO,DISCHARGE 40 PSIG.
I suspect your system needs a bit of "pumping up", but how much you need to work out from the operating manual.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: pump suction gauge is ZERO,DISCHARGE 40 PSIG.
If it is a pressure gauge, then if the inlet is at negative pressure the gauge will read zero. You need to fit a compound or a vacuum gauge to establish what condition the inlet to the pump is operating under.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: pump suction gauge is ZERO,DISCHARGE 40 PSIG.
RE: pump suction gauge is ZERO,DISCHARGE 40 PSIG.
discharge gauge
RE: pump suction gauge is ZERO,DISCHARGE 40 PSIG.
RE: pump suction gauge is ZERO,DISCHARGE 40 PSIG.
I can see one in the background on a different gauge that is obviously a valve. Assume if that's what it is- that the valve is open.
As a chem eng/metallurgist the first part of any answer I give starts with "It Depends"
RE: pump suction gauge is ZERO,DISCHARGE 40 PSIG.
This is a quite interesting observation and denotes your knowledge on theory.
1. We should note that some specific pumps can work with very low NPSHReq, most of the fire pumps fall within this category (Please have a look at NFPA Standards). Your pump seems to be within those with capability of very low NPSHReq.
2. Assuming that your pressure gauge is good, we have to find the reason of why the equipment is operating properly. One explanation might be because the NPSHAvailable is higher than the NPSHReq. So, please, check the NPSHAv, the pump might be sucking from one tank, read the pressure reading at the tank in this case. By calculating the NPSHAv using the standard formula that we are used to apply, you can calculate it easily. Check your P&ID to have a more accurate calculation result. Then, go to the pump specification, and have from the supplier the NPSHReq by this specific pump. If al is OK I mean NPSHAv > NPSHReq + 20%, you can go to the next step.
3. As BigInch said NPSH is an absolute pressure reading PSI(a) while your manometer reading as it can be seen from the photo is a gauge reading PSI(g). That means if from your calculation, you find a NPSHa of about 5m, then at the gauge you should have
PSI(g) = PSI(a)- ATM
PSI(g) = 5 - 10 m
PSI(g) = -5m
And here is the secret: In this specific case, it will be more interesting to have a compound pressure gauge which can read negative value of pressure (or if you want, vacuum) instead of simple pressure gauge which cannot read negative values. And you wil see that your needle will move in the CounterClockWise direction!
This will be helpful troubleshooting the system in the future in case there will be some issue.
Hope this help.
Good Lick.
Martial.