VFD vs Pressure Regulator 1

[bigtme]

Hello,
I'm desinging a pump skid that will deliver cooling water out to a piece of tooling. The skid will consist of pump, motor, heat exchanger, reservoir tank and all necessary plumbing. The pump will pull water from the tank, then push through the h/e, out to the tooling and then return the water to the tank. I only need 35 psi at the tooling but want to oversize the pump/motor for future expansion. Pump and motor will be sized for 60 psi. Should I use a pressure regulator b/t the pump skid and the tooling to limit pressure to 35psi or should I used a VFD (varible freq. drive) to slow slowdown motor to control pressure? What are the advantages/disadvantages of each?
Thank you,

 

[KiwiMace]

You didn't mention the flowrate, but I assume not a large amount in the low 10's of gpm, and a small pipe size, say 2" or less.

VFD will cost more upfront and save energy as you only run the pump at the speed you need. For low flowrates there is hardly any payback in using a vfd with pressure control.

A regulator should work equally well at less capital cost for smaller pipe sizes, provided you do not oversize your pump too much. Any additional energy you see at the pump will also be seen at the heat exchanger and increase the sizing there, but you will likely size this for the future load anyway.

 

[BigInch]

Use the valve, if you absolutely think you must have either a valve or a VFD. I'm sure at what I presume your flowrates are, you're talking about a few cents per year at best, maybe even losing more money. VFDs do not save energy all the time, and in fact are more apt to cost you more, but that depends on exactly and precisely how VFDs are used in the system and how you operate that system.

Won't extra flow simply cool the tool faster? If so, do full flow and then turn the pump off. Why not just simply use full pump flow for only the time you need to cool the tool? On/off valves and a timer are a lot less expensive and require a lot less maintenance.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[stanier]

Why not fit a smaller impeller and when the future comes around fit the larger impeller?

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[Pumpsonly]

You need to look into what is your future flow fate requirement other than just pressure. Can the pump selected meet your future flow requirement at the same RPM with a larger impeller as suggested by Stanier?