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Old 05-10-2013, 02:50 PM   #1
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Watermaker: high-pressure hose vibration

Yesterday, while changing the sediment filters on my watermaker, I noticed that the green high-pressure hose (arrows) had been chafing against the back (in other words the part you can't see!) of filter housing "B" and had nearly worn all the way through the housing. I have added an extra cushion-clamp to prevent the hose from touching the filter housing. However, the root of the problem is still there: the green hose vibrates significantly when the hi-pressure pump is running despite the 4 cushion clamps holding it to the bulkhead. It is only be a matter of time before the the hose starts to wear where it passes through the clamps. Any ideas?

BTW: The hose in question is the hi-pressure supply to the membrane. The vibration is very fast and seems to be side-to-side, not axial. The hi-pressure return hose to the control valve does not vibrate.
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Old 05-10-2013, 03:00 PM   #2
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Hard pipe it from near the left side of the membrane to the inlet on the right side. Leave enough space for a short vibration reducing section of flexible HP hose that is not connected to or supported by anything else.

Why did they use such a long length of expensive hose anyway?
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Old 05-10-2013, 04:25 PM   #3
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Rick, the length of the hoses was dictated by space/acccess as I had to fit several bulky components into a relatively small engine room already occupied by two engines, mufflers, tanks, generator, batteries etc. The pic below tells the tale (membrane etc are to the right).

I want to understand what I did wrong the first time before I make changes. Is the hose vibrating because I forced it into an awkward profile? Would I have been better off if the hose were longer and followed a gentler curve?

If I go with hard (stainless?) pipes, what connection do you recommend between pipe and hose? Currently all connections are flare fittings.
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Old 05-10-2013, 04:54 PM   #4
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You didn't do anything wrong. It is the nature of a flexible hose to try and straighten out and shorten under pressure. A cyclic pressure such as that produced by a piston pump creates the mechanical movement you are experiencing. It is just the way of such machines and no mere human is going to prevent it. Those pressure pulses are capable of doing some amazing things.

If you can run hard tubing from a foot or so away from the pump, around the corner to within about a foot or so of another hard pipe connection to the membrane inlet and connect the hard pipe with flexible hose to absorb most of the vibration, you will probably quieten the whole installation a bit and eliminate the chafing problem. You can firmly fix the hard pipe with proper pipe mounts and don't let the hose touch anything.

Just use conventional JIC fittings that are available at any hydraulic supply store. Use stainless or brass.
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Old 05-12-2013, 12:48 PM   #5
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Thanks Rick. I've done some homework and several people have used refrigeration-grade copper tube for the hi-pressure feed line. This appears to be OK as it has a working pressure of around 850 psi. which is the pressure relief valve setting on my watermaker. Unlike brass and stainless, it is readily available here and I can bend and flare it myself. Probably too good to be true, so tell me the bad news - why should I not use it? If it gets your approval, are there any special do's or don'ts I should know about?
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Old 05-12-2013, 02:15 PM   #6
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Thanks Rick. I've done some homework and several people have used refrigeration-grade copper tube for the hi-pressure feed line. ... are there any special do's or don'ts I should know about?
I'm not all that keen on using copper for that application. Copper work hardens from flexing and vibration and could fracture at or near the fittings from the hose movement. But, that said, I don't see it failing very quickly and an incipient failure will show up long beforehand as a weeping crack - probably.

Try to use a straight piece and use hose for "shock absorber" where it turns around the corner at the bulkhead.
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Old 05-12-2013, 05:03 PM   #7
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Your concerns about copper are duly noted. What I have in mind is to cut the exisiting feed hose at the yellow points and connect a new copper line (pink) firmly fastened to the bulkhead. Is this roughly what you had in mind, or did I miss the point entirely?
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Old 05-12-2013, 06:35 PM   #8
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Your concerns about copper are duly noted. What I have in mind is to cut the exisiting feed hose at the yellow points and connect a new copper line (pink) firmly fastened to the bulkhead. Is this roughly what you had in mind, or did I miss the point entirely?

That looks good.
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Old 05-12-2013, 08:02 PM   #9
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When I built our watermaker I installed a pulsation damper in the high pressure feed line. It's a pressure vessel with a diaphragm in the middle and high pressure gas on one side and the fluid on the other side. The gas acts to damp out the pulsation from the high pressure pump. Similar to the accumulator in the pressure water system, just much higher pressure.

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Old 05-13-2013, 03:57 PM   #10
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When I built our watermaker I installed a pulsation damper in the high pressure feed line. It's a pressure vessel with a diaphragm in the middle and high pressure gas on one side and the fluid on the other side. The gas acts to damp out the pulsation from the high pressure pump. Similar to the accumulator in the pressure water system, just much higher pressure.

Bob
Bob, That sounds like just what I need. Who sells and how much?
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Old 05-14-2013, 11:24 AM   #11
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I kept detailed records when I built the unit which of course I cannot locate right now. The pump, pulsation damper and back pressure valve came from Catpumps (www.catpumps.com). Don't remember if I bought directly from them or a dealer.

Another great source for parts is www.wateranywhere.com.

If I can locate that folder I can give you more detailed info.

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Old 05-14-2013, 11:35 AM   #12
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Quote:
Originally Posted by Shoalwaters View Post
Your concerns about copper are duly noted. What I have in mind is to cut the exisiting feed hose at the yellow points and connect a new copper line (pink) firmly fastened to the bulkhead. Is this roughly what you had in mind, or did I miss the point entirely?
How about turning the membrane around so the high pressure "in" is on the left? It looks like you would eliminate the section of high pressure hose that you want to change to rigid tubing.
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Old 05-14-2013, 11:49 AM   #13
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Being cheap and simple mind, I would protect and wrap with cold weather pipe wrap. The webasto does the same thing so I wrapped the hose that rubs. It has worked for 10+ years.
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Old 05-14-2013, 12:47 PM   #14
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Why not move the filter bracket out a bit?
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Old 05-14-2013, 05:33 PM   #15
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Bob, Thanks, I can follow it up from there.

Larry, I will have to look long and hard at that - it may be the way to go! I didn't have vibration in mind when I planned the installation, so I put the end of the membrane with the most connections (3) nearest to where they had to go.

Phil, Cheap and simple here too! Good thought, but I would prefer to eliminate the vibration if I can rather than hiding it.

Capthead, I take it you mean space the filters a little further away from the bulkhead. There is adequate clearance for the hose behind the filters. The problem was that the last 90 degree curve had moved it away from the bulkhead to a point where it could touch the filter housing.
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Old 05-14-2013, 06:18 PM   #16
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I understand and I know nothing is easy on a boat. In fact, isn't Murphy a boater? His law seems to work well with boating.
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Old 08-18-2013, 01:29 PM   #17
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Need source of reusable hi-pressure hose fittings

I need to buy some hi-pressure re-usable brass hose fittings like the one in the picture below. I am hopeful that forum members will be able to give me a name and part number. The Gates and Aeroquip websites have me totally lost.

The brass fitting is stamped "Gates 7J-B"
It has a 3/8" female flare-nut fitting on one end
The hose is Gates Flexline 605D (or 606D?) 5/16" ID 1,500 psi
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Old 08-18-2013, 04:52 PM   #18
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go to a place that make up hydrolic lines and they can help you they are standard fittings and no big deal
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Old 08-18-2013, 08:02 PM   #19
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Jerry, nice thought, but unfortunately there is only one hydraulic hose shop here and they stock plain steel fittings - fine for excavators, but not for high pressure sea water. If I can get manufacturer and part number for the reusable (DIY) fittings, I can order online and have someone carry them down for me.
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Old 08-18-2013, 08:18 PM   #20
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Van-Tech Corp. Hoses & Fittings Van-Tech Corp. try them
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