The need for Standby pumps when VSD is avialable
The need for Standby pumps when VSD is avialable
(OP)
Hi
I was wondering whether standby pumps are required when the lead pump is coupled with a Variable Speed Drive (Sometimes also called Variable Frequency Drive).
Say I have a design flow rate of 12.5 m³/hr at 30 m Head (55 GPM at 98.43 ft).
There is a pump with a Variable Speeed Drive that can provide that flow at the required head along with a reasonable efficiency.
Would there be a benefit from splitting that flow over 3 pumps (33% each) with Approx 4.17 m³/hr at 30m Head, also each coupled with VSD?
Or since I have VSD would it be better to go with a (one duty and one alternate) arrangement? As in the pumps take turns in serving the demand.
In Summary, which is the overall better of the two arrangements:
Best Regards
I was wondering whether standby pumps are required when the lead pump is coupled with a Variable Speed Drive (Sometimes also called Variable Frequency Drive).
Say I have a design flow rate of 12.5 m³/hr at 30 m Head (55 GPM at 98.43 ft).
There is a pump with a Variable Speeed Drive that can provide that flow at the required head along with a reasonable efficiency.
Would there be a benefit from splitting that flow over 3 pumps (33% each) with Approx 4.17 m³/hr at 30m Head, also each coupled with VSD?
Or since I have VSD would it be better to go with a (one duty and one alternate) arrangement? As in the pumps take turns in serving the demand.
In Summary, which is the overall better of the two arrangements:
- 3 pumps 4.17 m³/hr at 30m (18.4 GPM at 98.43 ft) each c/w VSD (1nos duty and 2nos standby)
- 2 pumps 12.5 m³/hr at 30 m Head (55 GPM at 98.43 ft) c/w VSD (1nos duty and 1nos alternate)
Best Regards





RE: The need for Standby pumps when VSD is avialable
With 2 pumps there will be more holes in the range, and lesser reliability.
There's a lot of reliability, standby and capacity games you can play. You might go for 3 pumps, 6 m3/h each, 2 running, one on standby, if reliability is critical. That'll give you 12 pretty easily all the time.
If you can do with partial flow when one pump is down for maintenance, 3 pumps, 4 m3/h ea, 1 on standby will give you reasonably good reliability for an 8 m3/h flow, but a bit less for 12 m3/h.
Independent events are seldomly independent.
RE: The need for Standby pumps when VSD is avialable
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: The need for Standby pumps when VSD is avialable
“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
http://waterhammer.hopout.com.au/