PHE and Pump position problem 1

[simangunsong]

Hi all..

Can someone explain to me in technical/engineering, what should I consider and the effect, if :
1. I put the pumps in "parralel position" with header to inlet side of PHE.?
2. I put the pumps in "parralel position" with header to outlet side of PHE.?
3. I put one pump to one PHE and so on.?

PHE - Plate Heat Exhanger (box type)
Please see the attachment for review of the drawing..
I've asked the Generator specialist, but his answer is based his installation experienced and not based engineering answer.
And, his suggestion is no.3 one pump for one PHE in outlet side from PHE. In my other project (chiller plant), it is okay and no problem if I put the pump in "parralel position" with header to inlet side of PHE.
My consider :
1. Maintenance or exhange if one pump is not active.
2. The pump have possitive pressure.

Thank you before for your help..

 

[SAK9]

Think of this scenario if you have one pump dedicated to each PHE:
• One of the generators is on a maintenance shutdown and but its pump is in operating condition.
• Out of the remaining two generators one has a broken down pump
• In the above situation you can only operate one generator

If the all the 3 pumps are on a common header, any pump can operate with any generator and the above scenario will not result.
Now it is up to you to decide which way you want to go.
On a different note the cooling tower range seems to be high ie. 15C please check with a tower vendor if this can be achieved

 

[simangunsong]

Hi SAK9

Thank you for your reply..
Your opinion is logic and right I have only one generator operate.
I've got information from the generator specialist, the flexible rubber joint always broke because it can't handle the pressure from discharge pump (Plate Heat Exhanger actually only 6 bar) and plate heat exhanger commonly cavitate. But, I see the plate exhanger data (working pressure is 10). Is it only wrong selecting Plate heat Exhanger or flexible rubber joint or...?

 

[SAK9]

Your pressures are abnormal no wonder the flexi thingy broke open

 

[DrRTU]

Based upon your sketch, you will need to draw upon a piping expert in your office or have an outside consultant assist your design. I see numerous items which are not cost effective or not commonly undertaken . This also looks like a homework problem based upon your vague answers and odd approach conditions on the towers. Without getting into the details, I would apply the following:
1. Verify your approach condition of the towers. If you are correct on your large DT, You will need a mini flow to the sump for low ambient conditions.
2. Why the standby tower? I see this as 2 cell design. You have 2 sets of extra piping. Talk to a tower rep for a design. It should be cheaper and more eff. to oversize the cells than to have 4 cells. Look at twin fans if you concerned with reliability. VFDs on the fans may help with keeping power low during a black start. Remember all of the towers and pumps must be powered on an emg. bus.
3. Your near tower piping tells me you have not done this before. Your 200 makeup line is incorrect. Pay close attention to suction header sizing base upon NPSHa to your CW pumps. It is very common to see suction 2 -3 sizes larger than supply to towers. If you do suction basin isolation, no flex, a single motorized butterfly will do fine. Make sure you have proper drain down for low ambient protection. Indoor sump? Why the purple line? Basin equalizing is best accomplished with one big common suction.
4. Suction filtration is very important.
5. Why 4 CW pumps? Work with your preferred pump rep. I see this as a 2 -3 pump design with VFDs. You design tells be you have not seen this application before. Air control, filtration, chemical control, isolation, flow, temps, heat tracing and sequence should be on the P&ID level of plans. Pumps parallel to each other - suction from towers, supplying the plate & fames.
6. Do not use converging tees (bullhead). Utilized extended header designs.
7. It looks like you are applying coil connection details to control plate & frames. Most designs on non HVAC closed cooling allow the tower loop run as cold as the outside conditions allow, then have the ewt to the engine control the flow. Think thermostat on your car engine. Keep the controls and power simple as possible.
8. Run though how this system will start and run. How will this start w/o power.
9. You may want to shift the flow control of the plate & frames to leaving water side. Consider a tower by-pass to help with flow control.
10. Show chemical control, flex, air control, expansion tank, temperature on your engine side.