RO Unit

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offshoresnipe
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RO Unit

Postby offshoresnipe » Mon Jul 05, 2010 4:24 am

The vessel that I am sailing on has both a evap. and a RO system. For the past 12 weeks the RO system has been working fine. I would flush with fresh water when I shut it down and chem. cleaned it when needed. Last week it just went to hell. The water went from 450 PPM to well over 900 PPM to 1.35.
I have changed 3 of the 5 membranes and replaced suspect o-rings, took apart each cell, inspected it all. Have read the very poor service book at least 3 times. I have the system back up and running, 3 of the 5 cells are doing good getting 280 PPM to 450PPM. The other two just do not want to make good water. One of the cells has a new membrane and I replaced the other one with one of the other used ones that had the better of the two readings.

The good thing about all this is the days are going by fast, getting lots of OT and am getting paid to teach myself all about RO's.

Any input would be great.

I am thinking about starting a company that would go around and test service manuals for company's.
Show up, give me the book and let me see how well and fast I can work the problem on there equipment, then I would let the company know if the manual is any good and submit my bill.
The Chief said I should show up after 48 hours of no sleep and hung over, do it in the dark, in a cramped position with a weak flashlight, that would give it a real engineer test.



Thanks again for all you input and help!!!!

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offshoresnipe
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Re: RO Unit

Postby offshoresnipe » Tue Jul 06, 2010 4:53 am

UPDATE!!!

I pulled one of the membranes today and changed the direction of it and also have found that the small o-rings in the heads can get crushed very easy when putting the heads back on. These are the o-rings that separate the feed water under 800+ psi from the product being produced in the membranes. I also been adjusting the feed water and membrane discharge press. a little. Found a small change can make a world of difference at the product water end. The water is getting better. 310 PPM
In my spare time I am writing the new service manual for the next guy, with drawings and all.

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JK
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Re: RO Unit

Postby JK » Tue Jul 06, 2010 6:45 am

What is the temperature of your inlet SW?

I have found that cooler SW temperature means a better salinity reading for the output, but your production went down; as the SW temperature goes up, the salinity and production also go up.
No great surprise there.
On an icebreaker, when you are keeping your seabay temperatures up around 25*C to keep them clear, it does get problematic.

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The Dieselduck
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Re: RO Unit

Postby The Dieselduck » Tue Jul 06, 2010 9:32 pm

You know, now that you mentioned it. I do remember having issues with Orings as well. I cant remember much problems with these system though (I worked with a very small units - a few 60 gal day, also with a 2000 l/day, and also a 350 ton a day unit) didn't really have much problems that I can recall with most of them. But that was mostly because I wasn't directly responsible for it, and it was kinda of a "scary piece of equipment" apparently, so it was only used when really needed. But when it was running I did not experience many problems.

I don't remember much, but I though we were getting much lower salinity readings, something like 50 ppm or the likes. 300 sounds still a bit high. And yes I do remember cursing the manuals and their lack of clear explanations. Mmmm. strange how these problems keeps on living in this day and age.
Martin Leduc
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Martin's Marine Engineering Page
http://www.dieselduck.net

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Big Pete
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Re: RO Unit

Postby Big Pete » Wed Jul 07, 2010 9:49 am

You have to be very careful with O rings, lube them with something, but if you are making potable water it should be a food grade lubricant. Don't freak out,vegetable oil/ cooking oil will do at a pinch.
The design always appeared flawed to me, a single O ring between high pressure salt water and low pressure Pot water!!!!!!

Shouldn't this be 2 O rings with a tell tale drain between them to tell you when one has failed???

BP
It is always better to ask a stupid question than to do a stupid thing.

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offshoresnipe
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Re: RO Unit

Postby offshoresnipe » Thu Jul 08, 2010 6:19 am

I have the unit running much better now. I think that it was o-rings, one rolled brine seal and fouled membranes. It is now making water in the 200 PPM range.
I am sure that the o-rings have been the number one problem. I too think it is a very poor design, I like the your thought BP, having a drain line that would tell you if you had leakage past the o-rings.
Now that the unit is making good water the ship has made a port call for a few days. I did not want to shut it down. Flushed the system with fresh water, pulled the 5 and 20 micro filters. Will have to see how it acts when I start it back up in two days.
Thanks for the input.


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