Can FCV replace Frequency drive
Can FCV replace Frequency drive
(OP)
Helow there,
Some one please advise the consequences if the SWRO high pressure pumps is controlled by a Flow control valve instead of VFD.
A quick comparison with pros/cons would help complete my ongoing study
Thanks'
Niss
Some one please advise the consequences if the SWRO high pressure pumps is controlled by a Flow control valve instead of VFD.
A quick comparison with pros/cons would help complete my ongoing study
Thanks'
Niss





RE: Can FCV replace Frequency drive
RE: Can FCV replace Frequency drive
Yes, This is Seawater RO plant where the feed RO high pressure pump pressure ranges 70 - 78 bar-g at discharge. The energy is recovered with Isobaric PX-ERD devices. I have never seen a SWRO desal plant with an auto FCV on pump discharge side, however would like to know WHAT IF and the pros and cons
Thanks
Niss'
RE: Can FCV replace Frequency drive
RE: Can FCV replace Frequency drive
For a feed pump sized for the maximum expected membrane pressure requirement, feed pressure control can be achieved by two methods:
Use a feed throttle valve to reduce pump discharge pressure as required by the membrane.
Or use a VFD to vary the frequency of the power to the feed pump motor. Varying pump speed allows the pump to vary discharge pressure with minimal energy loss. The VFD also allows a gradual increase in pressure (slower ramp up) which minimizes electrical starting load and reduces stress on the instrumentation and membranes. However, if the expected feed pressure variation is less than 4-5 bar then a solid-state soft-start motor starter may be a more economical solution. Typical VFDs have a 3% loss of electrical energy. Significant energy savings on RO systems is also not going to happen if the pump is properly sized.
VFDs are suitable to 600 kW. For larger RO systems, at higher power levels, medium voltage equipment is generally used, making VFDs extremely expensive. Other means of feed pressure control are available such as the high pressure hydraulic energy management integration (HP-HEMI) energy recovery device (ERD) that centralizes brine hydraulic energy recovery, feed pressure and flow control and brine pressure and flow control into one compact and fully integrated unit.
If PD pumps are used to provide feed pressure control, VFD or a feed throttle valve are not necessary.
It is more cost effective to properly size the feed pump than to try to optimize operations with a VFD or FCV. The size of the RO system also has an impact on the method of pressure control that is selected.
RE: Can FCV replace Frequency drive
RE: Can FCV replace Frequency drive
The file I have attached has a presentation given to ASME, Engineers Australia and the Institution of Mechanical Engineers.
ôThe beautiful thing about learning is that no one can take it away from you.ö
---B.B. King
http://waterhammer.hopout.com.au/
RE: Can FCV replace Frequency drive
Flow will be varying up to 20% from design, to meet some unusual cases
Further, the RO HP pump is rated approx. 2 MW which is 4.16 kV medium voltage connection
Also advise, is soft starters adequate to ramp up/ramp down without VFD and with FCV
Thanks'
Niss
RE: Can FCV replace Frequency drive
RE: Can FCV replace Frequency drive
"Whom the gods would destroy, they first make mad "