RO membrane element problems?

[iiiiii]

Now we've many problems with R/O membrane elements by almost time after remove them out and found the out side body(Outer Wrap) of them are cracking on axial line (Look like it was over pressure during operating period. After check back to history of operating rate pressure that it was normal condition (Under design spect.). The supply vendor has been to check but never get feed back from him. Now we're looking for the solution by self and find out the best idea and experience form every people.
Thank you for you helpful
UdomsinC "Refinery in Thailand"

 

[keeverd]

We have seen intances of this same failure while operating within the design parameters with one manufacturer's membrane element (who shall remain nameless in this public forum). Turns out it was a manufacturing defect, and is prevalent throughout the world. Contact me at keeverd@matrixwater.com for the manufacturer's name to see if you may have a bad element.

In addition to operating pressure, it is also helpful to look at the differential pressure across the element(s)(feed pressure minus concentrate discharge pressure). Generally, 10 psi per element is the maximum limit. Higher than this limit is an indication of fouling of the membrane, which can be fixed by chemical cleaning. Continued operation at higher than the recommended pressure drop can result in structural failure that you describe, and will usually be accompanied by "telescoping" of the element where the center permeate tube looks to be extended out beyond the end face of the membrane.

 

[KHAJAMM]

Let me ask you couple of questions!, Have there been frequent power failure /trip of the High Pressure Feedwater pump(s)?.
Do you have reliable feed water control valve?
The problem may be due to water hammer due to faulty shutoff valve, oversensitive flow control valve or due to poor quality of outer casing.
It is better idea to send the element to autopsy (cut open) the element and see if :
1. salt deposition is excessive (then adjust the antiscalant dosing rate).
2. Analyse the salt and see if it is Calcium Sulfate scale or carbonate. (there is a manufacturer's recommended upper limit on Calcium Sulfate Saturation Index - Adjust permate rate to operate within this limit).
3. If outer casing material which is usually fiberglass gets damaged with glass fibers in some areas missing (then it is manufacturing defect combined with high flouride in raw water).
Based on your little information, I have listed some of the problems I have experienced.