When to replace your membrane

[new2maple]

I have a h20 membrane which I sent back to cdl to be cleaned at the end of the year. It was 88% before they washed and only 92% after they washed. The previous year it went from 105% to 120%. Now only improving 4% after a wash I am wondering when its not worth washing and should just replace it?

[mountainvan]

If your operation depends on the ro like mine does, it can't hurt to have a backup if you can afford it. It really sucks to have lots of sap and a membrane on its last pass. Been there done that.

[maple flats]

Those numbers sound low for sure. My question is, how was the reading last year 105% and 120%? How can they remove water and pass no sugar to get the 105 or the 120%? the 105 and 120% are as compared to what? I fail to understand those numbers.
Getting back to this year's numbers, I have a spare set of membranes just in case, and I think everyone should be prepared with spares in case of a failure. I would not use the old ones. How old are they? To go from 120% after cleaning one year to 92% the next seems to indicate an issue you may need to address.

[Russell Lampron]

I too am wondering what they are comparing it too to come up with 105% and 120% flow rates. It should be 100% if it is perfectly clean. It looks like you've lost 28 points off of the best flow but are they using same bench mark for comparison? Ether way it looks like you should get a spare membrane for when this one slows down too much.

[claytski]

This might help to explain the over 100% flow rates. When a membrane is manufactured the flows are plus or minus 20% from the published flows. Thats just how they are manufactured. When I have my membranes manufactured they send a list of serial numbers and the flows for that individual membrane. CDL just took the spec sheet number and compared the flows to that. Thats why they are over 100%. What they should have done is take the actual flow for that membrane and compare the flows.

[new2maple]

They explained the reason for being over 100% the same as you did. With last year being late and all at once they said I must have pushed it harder than the previous year. It was only the second year on that membrane. I guess I will have to try to wash and rinse more often if I can this year.

[bowhunter]

I would agree, try to wash more often this season. I would rinse it thoroughly after each run and use all the permeate. No reason to run any fresh permeate to the sewer or on the ground when you can get some cleaning value out of it. The membranes really foul quickly at the end of the cycle as you push the pressure higher. I would get another membrane as a backup, but I still think you probably have useful life in the old membrane. They should last 4-5 years in this service.