Head Scratching I think I have lost it 1

[gravitate]

The top sketch is of 3 pumps which is in the P & ID. The bottom is what is in the actual design. As far as I can see there is no difference and no advantage dissadvantage of either. Am I wrong?

 

[gravitate]

Ps this is cooling water

 

[LittleInch]

I think you're correct. The only issue is how this is converted to reality and what the distances are, but flow wise and process wise it looks identical to me.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[pennpiper]

Flow wise (pressure drop) on a pump to pump basis they are not the same.

prognosis: Lead or Lag

 

[LittleInch]

Sorry, I was looking it from the view of the bypass line (doh!)

For parallel pumping you really want the bottom version as this equalises the friction losses between the common node points ~(i.e. your red and blue arrow chevrons) for all the pumps.

If you only run one pump out of the three at anyone time the difference is likley to be negligible, but between pumps on the top diagram pump 4 has a longer inlet line and longer discharge line than pump 6 and hence is likely to pump less flow than pump 6.

The actual difference between the pumps will vary depending on the steepness of the pump curve at that point, the actual difference in pipe length etc, but as the bottom diagram has the same number of bends, tees, valves etc, then it is prefereable.

Your bypass line should also have an NRV on it as do the pumps but I guess you just left that off for speed.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[gravitate]

Thank you thats a perfect answer! Maybe I would have got it myself if I was a few years younger. Its all the alcohol from working away from home working on site that has fried my brain. There are check v/v's etc I just didnt include them. Have a great day

 

[LittleInch]

There's a button for that...

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way