retrofit of old condenser pump: 70 meter head to 30 meter head 5

[moideen]

Dear guys,
What is the best way on following conditions?
The 13-year-old condenser centrifugal end suction pump (70-meter head (230 fthd), 1350 gpm) serving for 530-ton centrifugal chilled water system, recently found it is oversized and then we decided to retrofit with new pump. Prepared new isometric drawing with exact measurement and found the actual required head is 31 meters that gives 40-meter difference from existing. Site team had witnessed number of winding damages in past years. sure, the pump was working away from BEP. In this situation raised two opinion
First, install VFD for reducing the head and kw consumption
Second, retrofit with new pump, high energy class motor IE4 AND more efficient pump with 30-meter head and 43 kw input power
I preferred 2nd option and replaced.
Working conditioning is good and perfect, and work at BEP. Before it was drawing 186 amps, now draws only 75 amps only.
But raised some comment from some circles that if VFD fitting for old pumps can achieve the same performance. I opined that two points that
1) VFD is good if the system head and pump head intersect at BEP, then vfd is suitable
2) Being the head difference is large, then replacement is the best option
3) New motor comes with IE4 class premium efficiency instead the old pump IE1
what are your opinions. Thank you

 

[Artisi]

Moideen. Seems I misread / understood your initial post, I was thinking along the lines of installing the old pump into the lower head application.
Without the curve for the old pump but assuming the data you gave as 1350 gpm 230ft head is somewhere around mid curve / BEP it's unlikely a speed or impeller dia. reduction would be a feasible alternative to meet your lower head and the increased flow.
If you have any data for the "old" pump would be interested to see if you thoughts are valid.
As 1503-44 said, the problem appears solved with a good hydraulic selection.


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.)

 

[itsmoked]

On a different level; I'd be tempted to use a VFD just to avoid the gastly crap star-delta starter and conventional overloads. It also allows soft-starting and no lights dimming.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[moideen]

@Artisi: Flow is 1530 gpm, not the 1350. I had checked the old pump curve in the submittal file, it was missing and checked with supplier with pump serial number. But, they couldn’t to find. I attach here with old pump name plate. I checked the flow rate of old pump from balancing valve, that was 1720 gpm, difference from design 190 gpm. Ampere name plate 90 KW , but draws 186 amps it means around 110 KW above the name plate. So, it can confirm the pump is running with right side.

 

[moideen]

@1503-44: sure, now the system is working very well, and large difference in electrical consuption.

 

[Artisi]

Top marks for a nicely laid out clean pump room.
a curve would be nice - but never mind - reducing pump speed / diameter you could probably get near to the duty you want but not efficiently in terms of power running cost etc - plus outlay for VFD, anyway - your problem has been sorted.



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.)

 

[1503-44]

17 July 2021 10:59
The new pump

 

[Artisi]

I was after curve for the KSB unit

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.)

 

[1503-44]

You gonna buy the old one?