membrain passing sugar?

[jgrenier]

I used my new to me 600 R/O for he first time last night it has the NF270 membrain. is it normal for them to pass about a 10th percent sugar?

[sugarman3]

No!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!,should not be passing any sugar

[Sunday Rock Maple]

No, not normal but first wash the hydrometer and test cup in hot water and test it with distilled water --- it could be off a little, or you could have sugar residue from them not being clean.

[DrTimPerkins]

is it normal for them to pass about a 10th percent sugar?

How are you measuring passage (in permeate I assume)? What sort of instrument and process....hydrometer, refractometer, conductivity, boiling it down? Some of these things have errors of +/- 0.1 to 0.2 brix associated with them. First step would be to determine whether you are truly getting a reading of 0.1 brix. If you are, then there are some possible remediation measures you might take.

[not_for_sale]

How are you measuring passage (in permeate I assume)? What sort of instrument and process....hydrometer, refractometer, conductivity, boiling it down? Some of these things have errors of +/- 0.1 to 0.2 brix associated with them. First step would be to determine whether you are truly getting a reading of 0.1 brix. If you are, then there are some possible remediation measures you might take.

I second that. With the digital instruments out there people think its accurate to the last digit. It couldn't be further from me truth.

[DrTimPerkins]

I second that. With the digital instruments out there people think its accurate to the last digit. It couldn't be further from me truth.

Not just the digital instruments....analog instruments also have certain errors. For example, a brand-new standard off-the-shelf vacuum gauge used in the maple industry has a rated accuracy of +/- 2% FS (full scale), or 0.6" Hg in each direction....before adding in any other sources of error. Measurements of syrup density with a hydrometer has sources of error from the hydrometer, the temperature measurement, and human error factors. Calibration and proper technique can greatly reduce these types of error.

[DrTimPerkins]

So back to the original question. Should membranes pass sugar? Some membranes do pass a little....it is a tradeoff between throughput and rejection rate. In most cases though, they shouldn't pass much of any. If you are really trying to push to high concentration levels....try backing off a bit and see what happens. How did they benchmark when you first started it up this season? Was it processing much more slowly than it should? If so, it might just be time for a new membrane, or at least a really good cleaning cycle.

To verify whether or not it is passing sugar, take some permeate and boil it down. Reduce it by about 5:1 or 10:1 if you can. If you do that, you should get a much higher reading on your hydrometer or refractometer. If the reading doesn't go up, it was probably just instrument or measurement limitations or error. If the reading does go up, did you take your membrane out for cleaning? If so, the seals may not have seated properly when you put it back together. If that is OK, then contact the RO or membrane supplier. Sometimes (not always) you can "tighten" the membranes a little through a conditioning process, which is somewhat specific to the membrane.

[Russell Lampron]

Short answer Yes an NF 270 will pass a little sugar at higher pressures and concentration levels. It's not as tight as other membranes and most sugarmakers shy away from them for that reason. The NF90, Mark 1 and XLE are much tighter and shouldn't pass any sugar. The NF 270 is a faster flowing membrane so it would be a trade off. Faster concentration times with less syrup produced or slower concentration times with no sugar passage.

[PerryFamily]

I too have a nf270 ( yet to be used) membrane. I recently learned of the downfall if this membrane. I was told from a cdl rep they can pass up to 50% mineral at higher pressure or over 8% concentration. I assume it will pass sugar as well?
My plan is 6-8% Max and replace it next year.