Recently interviewed for Pump Engineer 1

[shashankTurbomachine]

Q1. What is system curve and why it does not start from 0?
Q2. What is NPSH3 and how test it is performed?
Q3. What is preferred and allowable operating region?
Q4. How the pumps are run on parallel operation. And why 10% HRSO is advised for parallel operaration?
Q5. What are rejection criteria of pump as per API610?
Q6. How is NPSHA calculated?
Q7. What is suction specific speed?
Q8. What is the value of allowable vibration in a pump?
Q9. What is the essence of rated dia/max. dia and rated dia/min. dia.?
Q10. WHy 5% head increase with maximum impeller dia is required?

A well phrased question has answers in itself!!!

 

[shashankTurbomachine]

it would be fun to read answers to each question . Let's Start.

A well phrased question has answers in itself!!!

 

[Artisi]

After you

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.)

 

[shashankTurbomachine]

Q1. What is system curve and why it does not start from 0?
system curve indicates that the pressure developed by the pump is enough to overcome resistance offered by the system.
it doesn't start from 0 because the static head present in a system will have some head value. If there is no static lift it would start from 0.
Q2. What is NPSH3 and how test it is performed?
NPSH3 is basically 3% head dropped in total head while running the pump.
it's half answer
Q3. What is preferred and allowable operating region?
Prefferd operating range is 70-120% BEP
allowable operating range is 80-110% BEP
Q4. How the pumps are run on parallel operation. And why 10% HRSO is advised for parallel operaration?
pump when run in parallel results in double the discharge value at same head.
it's half answer
Q5. What are rejection criteria of pump as per API610?

[li]Stable head rise from rated to shutoff[/li]
[li]5% head increase with max impeller[/li]
[li]10% HRSO for parallel operation[/li]
[li]OPerating range[/li]

Q6. How is NPSHA calculated?
npSHA = hstatic+hatm+hvelocity-hfriction-vapor press
Q7. What is suction specific speed?
NSS is basically a constant which gives an idea to pump internal recircuation at higher speed.
Q8. What is the value of allowable vibration in a pump?
3mm/s
Q9. What is the essence of rated dia/max. dia and rated dia/min. dia.?
please reply
Q10. WHy 5% head increase with maximum impeller dia is required?
please reply

A well phrased question has answers in itself!!!

 

[MJCronin]

Where does the allowable vibration limit come from and how is it to be measured ???

MJCronin
Sr. Process Engineer

 

[Artisi]

Before getting too involved in a few of the question/answers, it would be interesting what position you are being interviewed for:
Plant engineer
Maintenance engineer
Application engineer
Trouble shooting engineer
Sales engineer
Pump design engineer
Etc.
Each position has different requirements and knowledge and if I were the guy interviewing I would be concentrating on specific points for the position and general points / understanding on others.


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.)

 

[LittleInch]

Q2, the other half. whilst maintaining a steady flow by controlling the outlet pressure, slowly reduce the inlet pressure by normally throttling the intake line until the differential head drops by 3%. Then increase inlet pressure, reset to a new flow and repeat until you have at least 5 points of measurement.

Normally they vary flow and measure everything.

Q3 you have the wrong way around. Preferred can't be a wider range than allowable....

Q4 Head rise to shut off I presume ( normally don't presume everyone is familiar with your abbreviations...)
Important for parallel operation to avoid the pumps "hunting" or flow getting too far away from 50/50 flow between the two pumps

Q9 and 10 are really just practical limits that many customers require. I.e. they don't want their pumps to be close to the limit of the pump diameter. Min diameter means that they can't reduce head if they've got their sums wrong and too close to max diameter because if, when tested, the pump doesn't meet the requirements, you can't just install a bigger impellor.

Many pump specs want 5 to 10% margin on max and min diameter.

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

 

[shashankTurbomachine]

Artisi

Its for Rotating Equiment & Package design engineer

A well phrased question has answers in itself!!!

 

[Artisi]

I now see why you are so concerned by the finer points of pump hydraulic understanding, it's definitely needed needed as a package design engineer.

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.)