Filmtec SW-2540 RO Membrane Question

[akio.kanemoto]

Hello, just a few quick questions before I do something stupid... just to confirm:

1. The central tube in the membrane is for permeate (product freshwater) right?

2. The permeate tubes can be connected in series if using multiple pressure vessels/membranes.

3. If the end caps on the pressure vessel have permeate outlets on both ends (feed side and concentrate side of the vessel), I can collect permeate from both/either ends right? (since it collects in the central tube and is not "directional" like the feed saltwater)

4. The membrane is not directional - i.e. I can take the brine seal off, turn the membrane back to front and put the brine seal back on the other end and put it into the vessel that way (the reason that I ask is that I took the seal off one end and forgot which end it came from)

Thank you!!!!!

[Tellie]

akio, to answer questions 1,2, and 3, you've got it right. As to question 4 the membrane itself is not directional until you install the brine seal on it. First the brine seal is directional. It is shaped with a higher lip on one side. This higher lip needs to be installed facing towards the membranes product tube on the side it is installed on. The membrane is now directional so it must be installed so that the brine seal side is installed on the high pressure side of the feed line. This is because of the shape of the brine seal. As the membrane vessel is pressurized the brine seal will seal better as the pressure is against the high side. If the brine seal is either installed backwards or the high pressure line is routed to the the opposite side of the membrane vessel the high pressure salt water will eventually start to leak past the brine seal.

[akio.kanemoto]

Originally Posted by Tellie

akio, to answer questions 1,2, and 3, you've got it right. As to question 4 the membrane itself is not directional until you install the brine seal on it. First the brine seal is directional. It is shaped with a higher lip on one side. This higher lip needs to be installed facing towards the membranes product tube on the side it is installed on. The membrane is now directional so it must be installed so that the brine seal side is installed on the high pressure side of the feed line. This is because of the shape of the brine seal. As the membrane vessel is pressurized the brine seal will seal better as the pressure is against the high side. If the brine seal is either installed backwards or the high pressure line is routed to the the opposite side of the membrane vessel the high pressure salt water will eventually start to leak past the brine seal.

Hi Tellie,

Thank you very much for that - after looking through various diagrams online, I initially came to the incorrect conclusion that the central tube was for the feedwater! So I originally installed the fittings on the endcaps in reverse (i.e. pressure to the centre).. and got suspicious when I finally took the membrane out for the first time to install it and saw the brine seal etc...thankfully I stopped before I powered it up!

It's quite interesting though - that even the technical manual from Filmtec doesn't give the information that you've supplied so succinctly above.

Thanks again... now off to find just one final brass 1/2" hose to 1/4" npt fitting for the permeate (long project, losing/forgetting parts!) .. assuming all goes well, I might even get to power it up today!

[Tellie]

Good luck with it akio, and if you need any help just ask.
Tellie

[akio.kanemoto]

Originally Posted by Tellie

Good luck with it akio, and if you need any help just ask.
Tellie

Hi Tellie,

Thank you very much for that!

Now... the good news... IT WORKED!!!! WOOHOO!!! I've had these parts lying around for so long waiting to be used... it was such a journey... shipping everything from the US, then welding the engine mount, having a new crankshaft pulley etc made... it has been perhaps a 3 year journey... but well worth it!

It was quite scary at first, cranking up the pressure... I was expecting a bang or something any minute.... but all good.. the Cat Pumps regulator was a bit noisy, but so far so good. At 1600 engine rpm, I was making 2.5L/min @ 800 psi. Way cool!

One question however - I'm using a Jabsco Par-Max 4.0 Deskwash pump (with 70psi pressure cut off switch) as the feed pump.

Actually, via a 3 way valve, I use this pump for deckwash/SW dishwashing as well and the output is plumbed to the sediment filters, so I can have the benefit of filtered seawater not just for the watermaker, but also for the toilet flush, and dishwashing etc.

My issue is that after running the Jabsco pump for perhaps 30 minutes, it got REALLY hot... it didn't die yet, but I can't imagine that running at that temperature - that it will last long.

My reason for buying this pump was that it self-primes, and I have space limitations, so can't put anything beneath the WL.. and that from the Cat Pumps datasheet, it says that the input to the pump should be "flooded to 70 psi"... and this was the only pump rated that high.

Having said that - I have a vacuum/pressure gauge before the HP pump, and when I ran the HP pump/feed pump together, the gauge was reading off the scale - it maxed out at 30psi, so maybe I wasn't running the HP pump fast enough, but there certainly wasn't a vacuum!

So the question is: is it OK to keep the deckwash pump solution and let it get really hot like this and expect it to live a long time, or swap to a different pump? I really like the elegance of the pressure switch solution supplying various purposes, but if it dies after a few weeks, then perhaps not.

I've seen lots of Jabsco Water Puppies/impeller pumps used on various websites on watermakers, but again, if the HP pump isn't "drawing" that much water, won't the impeller just be spinning madly wearing itself out, trying to deliver water that isn't being used?

Thanks again!

[svloki]

You need a pump rated for "continuous duty". Your washdown pump is definitely not that type of pump. Centrifugal pumps are the most commonly used for boost.

A slight positive pressure will keep your cat happy. 70 PSI is way more than needed!

I use the Jabsco cyclone series, stainless centrifugal pump to provide boost pressure. The shaft seal will eventually go bad, but mine is working great after over 600 hours of run time.

You can also look at the magnetic drive pumps, like the March brand. No seals to wear out, but expensive.

Best luck
Bruce

[JusDreaming]

I have used a "water puppy" on ours' with no problems. It has been installed for three years now

[Minggat]

Originally Posted by akio.kanemoto

Hi Tellie,


It was quite scary at first, cranking up the pressure... I was expecting a bang or something any minute....

I commission large scale industrial desalination plants. One as big as 200 MGD (that's million gallons/day) in Saudi. The scary part dosen't easily go away when they get that big.

[Tellie]

Originally Posted by akio.kanemoto

Hi Tellie,

Thank you very much for that!

Now... the good news... IT WORKED!!!! WOOHOO!!! I've had these parts lying around for so long waiting to be used... it was such a journey... shipping everything from the US, then welding the engine mount, having a new crankshaft pulley etc made... it has been perhaps a 3 year journey... but well worth it!

It was quite scary at first, cranking up the pressure... I was expecting a bang or something any minute.... but all good.. the Cat Pumps regulator was a bit noisy, but so far so good. At 1600 engine rpm, I was making 2.5L/min @ 800 psi. Way cool!

One question however - I'm using a Jabsco Par-Max 4.0 Deskwash pump (with 70psi pressure cut off switch) as the feed pump.

Actually, via a 3 way valve, I use this pump for deckwash/SW dishwashing as well and the output is plumbed to the sediment filters, so I can have the benefit of filtered seawater not just for the watermaker, but also for the toilet flush, and dishwashing etc.

My issue is that after running the Jabsco pump for perhaps 30 minutes, it got REALLY hot... it didn't die yet, but I can't imagine that running at that temperature - that it will last long.

My reason for buying this pump was that it self-primes, and I have space limitations, so can't put anything beneath the WL.. and that from the Cat Pumps datasheet, it says that the input to the pump should be "flooded to 70 psi"... and this was the only pump rated that high.

Having said that - I have a vacuum/pressure gauge before the HP pump, and when I ran the HP pump/feed pump together, the gauge was reading off the scale - it maxed out at 30psi, so maybe I wasn't running the HP pump fast enough, but there certainly wasn't a vacuum!

So the question is: is it OK to keep the deckwash pump solution and let it get really hot like this and expect it to live a long time, or swap to a different pump? I really like the elegance of the pressure switch solution supplying various purposes, but if it dies after a few weeks, then perhaps not.

I've seen lots of Jabsco Water Puppies/impeller pumps used on various websites on watermakers, but again, if the HP pump isn't "drawing" that much water, won't the impeller just be spinning madly wearing itself out, trying to deliver water that isn't being used?

Thanks again!

Congratulations! Not many who start their own DIY watermaker make it this far. Kudos for your patience, tenacity and hard work.
A few quick points. As others have said above, you want a continuous run pump. Though I believe the Par 4 is a continous run pump it's down fall is as a proper watermaker "boost" pump is it's pressure switch and thermal protection device. It is normal for these pumps to get very hot. In a wash down application as the Par 4 is intended for it is OK for it to shut down when it gets too hot. Your high pressure pump on your watermaker cannot tolerate this from it's boost pump. A high pressure pump that is starved for water because the boost pump has shut down to cool off will soon cause itself serious damage. The only proper diaphram pumnp for this would be Spectras shurflo pumps and even they add heat sinks and cooling fans to them. As noted by others above, the cheapest solution is a Water Puppy. Also an area that needs to be understood when it comes to watermakers is pressure and flow. With a boost pump it is more important to match the flow to the high pressure pumps demands. Pressure is easy but flow is more important. You can create a 1000psi to the input of your pump but if it only delivers 1gpm and your high pressue pump requires 3gpm the 1000psi won't be worth anything and your high pressue pump will be starved and damage will surely result. This is somewhat the same principal for the membranes. 800psi is easy to obtain by restricting the pressure valve. Keeping enough flow across the membrane surface is the key to proper life expectancy of the membrane. Impeller pumps like the Water Puppy can provide more flow than needed. But then so do most impeller pumps. Even the impeller pumps on your diesel make more flow than is needed and they run for very long times. So don't worry about it over working. Just remember the proper maintenace intervals on replacing the impeller just like you do on your diesel. Also, dedicated pumps are a better way to go. Trying to make one pump do double duty is a headache waiting to happen. Keep your Par 4 for a nice wash down pump, have a proper house pressure pump for your heads and galley and have a dedicated boost pump for your watermaker. Good Luck

[akio.kanemoto]

Thank you for the replies!

OK, I will order a Water Puppy then - do I need the "commercial duty one" - or will the normal one do?

This is the normal one:

Water Puppy Flexible Impeller Pumps (Jabsco) - General-Purpose Pumps Parts

On plumbing this - I can really simplify my plumbing if I put the water puppy after the prefilters. Do you think it will be able to suck/self-prime through these ok? (I have the large 10" housings with 3/4" inlets/outlets and the water puppy is only 1/2", so it might be OK?)

Thanks again!

(can't wait to fix this so I can make water again.. there's a huge satisfaction in being able to turn seawater into drinking water!

[phorvati]

Originally Posted by akio.kanemoto

Thank you for the replies!

OK, I will order a Water Puppy then - do I need the "commercial duty one" - or will the normal one do?

This is the normal one:

Water Puppy Flexible Impeller Pumps (Jabsco) - General-Purpose Pumps Parts

On plumbing this - I can really simplify my plumbing if I put the water puppy after the prefilters. Do you think it will be able to suck/self-prime through these ok? (I have the large 10" housings with 3/4" inlets/outlets and the water puppy is only 1/2", so it might be OK?)

Thats the one I have too. It gets really hot. Prefilters, you mean the 20 or 30 and 5 micron filters. Ive had problems with suction even with feed pump installed before prefilters and everything located below waterline. My CAT pump inlet is at about 5" of vacuum. I think its because the feed pump cant keep up with the HP pump's flow demand. Next step is, to spend the $$$ and get a good one. I even took the rubber feet off and clamped the pump to a 4"x8" piece of aluminum to act as a heatsink.
What kind of pulley ratio did you put. What RPMs is the CAT pump running at? Mine is CAT290 runs at about 800-900RPMs and my brine flow is really good. CAT pump does not seem to mind the vacuum, but it does mind lack of flow. I ended up re-plumbing SW30-2540s in parallel. More product, and less salt deposits on that second membrane.

[JusDreaming]

I would not put the water puppy behind the filters, as I do not believe the pump would be able to pull the water through the filters without burning it self up.

[Tellie]

Originally Posted by JusDreaming

I would not put the water puppy behind the filters, as I do not believe the pump would be able to pull the water through the filters without burning it self up.

Agreed, it's not a good idea. Though there should be a raw water strainer just after the thru hull and before the water puppy. There's no need to filter the water before the water puppy. Anything small enough to get past the raw water strainer is far to small to be of any issue to the water puppy impeller and the pre-filter will take care of what gets past that. Also, it's pretty much becoming an accepted practice to use only a 5 Micron pre-filter.

[akio.kanemoto]

Thanks again, in that case, I'll remove the prefilters from the deckwash/sink saltwater circuit and just have them in the watermaker feed after the Water Puppy and see how I go.

So should I buy the "commercial" duty water puppy or just the normal one? Are they the same thing with different warranty or actually different products?

I'm planning on putting in a large order at WM tonight, so hopefully these will arrive in a fortnight!

Thank you!