Watermaker Pressure Vessel

[cat man do]

Originally Posted by 44'cruisingcat

CAMP WATERMAKER

Now that is a handy toy, pressureblast the bottom and fill up the drinking water on a few buck's of fuel.

Fit's in with the Multihullers rule of nothing on board unless it does at least 2 job's.

Thank's for the link.

Dave

[bobs]

Originally Posted by 44'cruisingcat

10 Gph sounds very small. Are you sure of this figure? That's less than a litre a minute? I would have thought 100 gph would be closer to the mark for even a small pressure cleaner. Using a 10 gph pump for watermaking would result in a very small freshwater production.

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Right you are,..it should be close to 100 GPH .
But dont you also think it might work ?
When I get my hands on a suitable membrane/vessel i will be giving it a try.
Anyone else who gave it a shot ??

Greetz

[GordMay]

Pressure washers are generally rated in gallons per minute. The smaller domestic units deliver about 1.5 to 2 GPM, or 90 - 120 gallons per hour.

[44'cruisingcat]

Originally Posted by bobs

-------


Right you are,..it should be close to 100 GPH .
But dont you also think it might work ?
When I get my hands on a suitable membrane/vessel i will be giving it a try.
Anyone else who gave it a shot ??

Greetz

I can't see why it wouldn't work. The only real worry would be the life expectancy of the pump. But they are so cheap if you got a year out of one it would be worth it, as long as you had it set up so it was easy enough to replace. My little Karcher is rated at 1250psi, and watermakers tend to run around 800psi, so the pump would do it easily. They also come with high pressure cut-offs built in.

[44'cruisingcat]

Originally Posted by cat man do

Now that is a handy toy, pressureblast the bottom and fill up the drinking water on a few buck's of fuel.

Fit's in with the Multihullers rule of nothing on board unless it does at least 2 job's.

Thank's for the link.

Dave

I'm very interested in one of these too Dave. They were selling them at Sanctuary Cove boat show for $3500.

I had previously been thinking about building a watermaker using a Karcher pressure washer pump etc, but that also involved needing a 2000 watt invertor, and enough solar panels and batteries to feed it.

With one of these (with a larger membrane or two to increase the production rate - 120 litres/hour would be nice if possible) I could do pretty nicely by just running it for two or so hours per week. (a couple of litres of petrol) I wouldn't need as big a solar array, probably a less expensive solar regulator, a smaller invertor, less batteries - the thing would almost pay for itself! AND I can beach the boat and give the hulls a good wash, AND it will jump start the motors if the batteries run flat!

[EngNate]

A couple of thoughts, from a Factory Authorized Village Marine Tec sales & service center:

Many watermakers have been home and factory built with the industrial CAT pumps, which can be purchased at a relatively reasonable price (one source online is McMaster-Carr, a large industrial supply chain. McMaster-Carr . The bronze head pumps are almost a waste of money, the SS heads are pretty hardy, and not really hard to rebuild (either one). McMaster can also sell you the parts, or a complete head assembly. This is a big plus if you're cruising in US waters. A phone call and a credit card should get you what you need in 2-3 days no matter where you are in the continental US.

The one thing I'd be wary of using a pressure washer pump is the possibility (probability) of small amounts of its crankcase oil getting into the feedwater. If this is the case, you'll have steadily decreasing production, and the chemical cleaning process will be of limited help. The cost savings in the pump will ultimately be consumed by the need to replace membranes. On top of that, these pumps are not at all designed for salt water, and you'll probably replace it on a regular basis. Corrosion by-products will be passed to your membranes and that won't be good. Much worse, they will get into your high pressure regulator and that will be bad.

If you're designing your own system, one very important thing is insuring that there is enough discharge flow relative to the product output, about 10:1, as a rule of thumb. That means for every gallon of fresh water that comes out, 10 gallons of seawater is dumped back overboard, about 10% saltier than when it came in. This all has to be supplied by the HP pump. You can get about 7 gallons per hour of product for each 1 gallon per minute of pump capacity at operating pressure. The actual performance of the pump will be significantly different with the typical booster pump supply pressure of 10-15 psi, compared to the 40-50 psi from a household water supply. Insufficient flow will give you problems with mineral scale buildup in the membranes. Again, the chemical cleaning process won't keep up with it, and you'll be replacing membranes. If you buy a CAT pump, you can go by the manufacturer's specs, and their tech dept (if you don't find the info in the full specs) can tell you how much flow you'll get at a particular operating and feed pressure, and you can select your membranes accordingly. You cannot go by the specs that come with your pressure washer. They give you two totally separate ratings, max. pressure at 0 flow, and max flow at 0 pressure. You'll have to set it up and test, with the booster pump, HP regulator and a flowmeter, before you can determine the actual capacity and select an appropriate membrane.

OK, now I'll have to insert the 'plug' for what I sell. Village Marine HP pumps have titanium wetted parts, and the head, called the 'manifold assembly' is warranteed for life. If you take nominally good care of it, you will likely never see the day you replace or repair it.

On double duty as a pressure washer, you must keep the hose run very short, or you will have dissapointing results. I've seen it done.

[phorvati]

Hi since this thread mentioned the PV and damage from rupturing at 1000psi or more, I though I should post my experinece.
Amazing thing happened the other day. As I was making water, I heard a lound bang from the lazarrete, and the pressure gauge dropped to 0 psi.

One of the nylon screws that holds the carbon clamps of the pressure vessel end-caps broke and the end fitting blew out. Thank god it only hit the bulkhead about 3-4" away and besides that nothing realy bad happened. I replaced the tiny nylon screws (#8-32), with the brass screwes, which luckily I happen to have. In about half hour I was making water again but this time I was afraid to go too high on the psi, so I kept the pressure just under 800psi. It could have been that debree cloged the needle valve for a bit and caused the pressure to rise. Its weird that it could happen because I do have a relief valve set at 1000psi which I tested once about a year ago and it did work.
But in any event, the bang was loud but no serious damage. I am glad I was not in front of the cap when it happened.

[MoonlightSailor]

Does anyone have advice on using glycerin lubricant, or any other lubricant on the o-rings when assembling the pressure vessel caps?

[Cheechako]

"If the pressure vessel is full of room temperature water there is NO expansion of the pressurized fluid (for all practical purposes). Because water is so incompressable even ...." Having spent over 20 years testing, using and designing vessels for high pressure water forming of aircraft components, you are techinically correct about the incompressibility of water. However, depending on the modulus of elasticity of the vessel material, the vessel expands under pressure and relax's when the pressure is relieved. There is a little stored energy involved, but not a lot. However, as Gord says, if the vessel turns to shrapnel, those pieces could fly pretty fast from little energy....especially if there is any trapped air involved. . However, in 20 years of forming up to 10,000 psi with water, I really haven't seen anything other than a sharp stream of water from a fracture... On another note, it seems when I replaced my vessels on my boat, the vessel was probably the best bargain among all the other componants out there! BUY IT!

[Tellie]

Originally Posted by MoonlightSailor

Does anyone have advice on using glycerin lubricant, or any other lubricant on the o-rings when assembling the pressure vessel caps?

Use GLY grease on your O-rings and membrane brine seal. But very very little. A little goes a long way. Put a small dab between your index finger and thumb and run any O-rings through your fingers just barely coating them. Use GLY on all your O-rings to help keep them supple. GLY comes in a small tub which should last you as long as you own the boat.

[goboatingnow]

You can get good high pressure washer pumps from the like of Interpump UK - High Pressure Pumps Pressure Washers Motor Pumps Interpump Accessories
the experience of many including my self is that brass pumps last reasonably well as long as you religiously fresh flush after each use, ie never let the pump sit in salt water for too long.

The best pumps are actually not CAT, but Wanner, Hydra-cell, no pulsation. but quite expensive.

Watermakers manufacturers tend to hype "the magic and mystery", but its not that difficult. You can go wrong but at least youll know the end result like nothing else.

Do get good high pressure hoses with stainless or bronze ends made professionally, I found these are the things that give trouble, a good hose shop should be able to terminate in NPT fittings, rather then metric as I never found a source of metric membranes. ( nor a european source of pressure vessels).

Ive just finished an automated controller for mine.


To be honest, Id give up on the pressure washer, the speeds, pressures and flow rates are different. just focus on one thing at a time!!.

BTW, the easiest way to make pressure vessels, would be to hold the end caps with long threaded rods, like some hydraulic rams ,etc

Dave

[akio.kanemoto]

Originally Posted by Tellie

Use GLY grease on your O-rings and membrane brine seal. But very very little. A little goes a long way. Put a small dab between your index finger and thumb and run any O-rings through your fingers just barely coating them. Use GLY on all your O-rings to help keep them supple. GLY comes in a small tub which should last you as long as you own the boat.

Howdy,

On this note, I've just finally started working on installing my various bits and pieces for the watermaker and tried a test fit of the end caps and DAMN it's hard to get them in past the o-rings!

I note your comment on GLY lubricant - I have a tub of silicon grease for o-rings, can I use this? Or is the GLY stuff special to the application?

[MoonlightSailor]

OK, can someone tell me of an online source that sells that stuff in a small quantity? Having a hard time finding some in a small quantity.

[MoonlightSailor]

Glycerine, that is. :-)

[akio.kanemoto]

Originally Posted by MoonlightSailor

Glycerine, that is. :-)

I have a feeling that Tellie is reffering to the brand "GLY" - there is something called "GLY 92 Microlube" or somesuch which looks not too inappropriate...

Tellie?