peremate flow rate vs maxium feed flow rate

[chrisnjake9]

I have a home built ro that I have been using for three years. I am currently using a fluid tech 330 gph pump I am thinking about replacing it with a 660 gph fluid tech but don't want to exceed the membrane capacity the permeate flow rate says 2600 gpd but maxium feed is 14 gpm ? can some one explain this and will the bigger pump work and process the sap faster without hurting membrane

[TunbridgeDave]

That's seems easy to answer. The feed rate is 14 gpm or 840 gph so the bigger pump would not be a problem. However if the rated permeate capacity is 2600gpd or 1.8gpm you don't want to crank the pressure up and exceed that amount on the permeate flow meter or you may blow out the membrane. A 330 gph pump should handle 3 4x40 membranes. How many do you have and what are you getting for benchmarks with your current pump? Also are you putting a bigger motor on there to drive the bigger pump?

[SWEETER CREATIONS]

My belief is that 2600 gallon per day is for an 8 hour day or 5.33 gallons per minute , so if my thinking is correct buying a bigger pump WIll have adverse effects on the membranes. Not sure if this is correct, only my 2 cents. Mike

[chrisnjake9]

yes bigger 2.5 hp motor up from 1.5 hp. im running 2 xle 4040s flow rates depend on my pressures I can process 500 gallons of sap in about 2 hrs with pressures around 250 to 300 or let it run all night while sleeping at around 125-150

[BreezyHill]

The feed rate is so you don't cavitate the pump. Under the 14 gpm you could starve the pump and eat her up. This is typically done by having a filter that gets plugged or is simply undersized from the start. My unit has that pressure gauge on the filter so I can see if it starts plugging. If I remember right if it goes past 65 PSI it was time to change the filter. The alarm is at 70 psi and 10 psi alarm on the inlet of the high pressure pump. Unit shuts down if you ignore the alarm for 2 minutes. I remember we ate one pump when the alarm failed to sound and unit cavitated. That was when dad added the sap screener & filter system to the releaser and put a bigger filter on the RO.

[TunbridgeDave]

That's sounds pretty impressive . I've got 2 xle4040 also, but only a 240gph procon pump with a 3/4 hp motor. The best I've done is around 210 gph after 20 minutes or so of operation with freshly cleaned membranes and running at 300 psi, so obviously the bigger pump is working for you. I think the 2600 gpd rating from Dow's product sheet is what they recommend when sizing water filtration systems for a home or business etc. I don't think it's the actual maximum flow that the membrane can handle. The max pressure of 600psi would be more critical. If you do get the bigger pump I'd be curious how you make out though. My guess is it would be a little overkill since you have a 50% bigger pump and twice as big a motor as I do now but are not getting that same percentage increase in production.

[TunbridgeDave]

I think there was some confusion, Breezy, the 14gpm is the max flow for the membrane so you have to keep it under that. I never understood why they don't give a minimum flow for the membranes on that data sheet, but generally I've heard you want to keep the flow rate for each 4x40 at 100 gph or more to keep them from clogging. That's a good point about the pump cavitating though. If you got that bigger pump you may have trouble in that respect without upgrading the feed pump.

[chrisnjake9]

dave I have kicked breaker on my motor a few times I cant believe the 3/4 is working for u I thought I was over working the 1.5 hp motor now im thinking it was an electrical issue I can wire it for 220 I might try that

[TunbridgeDave]

Mine is set for 110v right now and I thought the same thing about going to 220 but it's not feasible atm. The only way I can stall the motor is if I crank the pressure up over 400 and that would probably trip the breaker, however the motor never get more than warm to the touch. The 3/4 hp motor is the original motor from the mid 80's when the rig was made, and I know hp ratings are different than they used to be. For example, we had to replace a motor on the gutter cleaner in the barn. The old one was a 3hp and to get a new motor with the same power we had to go to a 5hp. I think the amperage gives a better idea of how powerful a motor is along with it's efficiency rating. Mine draws 11 amps at 110 volts. Hope you get it figured out :)

[mellondome]

I think there was some confusion, Breezy, the 14gpm is the max flow for the membrane so you have to keep it under that. I never understood why they don't give a minimum flow for the membranes on that data sheet, but generally I've heard you want to keep the flow rate for each 4x40 at 100 gph or more to keep them from clogging. That's a good point about the pump cavitating though. If you got that bigger pump you may have trouble in that respect without upgrading the feed pump.

The 14 gpm is flow across the membrane surface. Only truely applies if you are recirculating like commercial units do or if you have a pump so big that you are letting that much flow through the concentrate side to keep from exceeding the max pressure rating of your housing. @ 300 psi, you should be getting closer to 100-120 gal/hr on a 4x40 that is used for maple. (XLE...NF270...). Of this... half is concentrate. . 1 gal/min. So you can push an additional 12gal /min past on concentrate before membrane failure.