Re: Desalator interconnect Bobin


 

Nick,

A couple of things:
  • There is substantial anecdotal evidence that the pickling solution is the cause of the erosion that happens with end caps, more so with the white end caps. The problem begins with a small leak which is almost never noticed and ends with chips of the end cap and a lot of saltwater flying through the engine room. See the black ones below which were victims of a hired technician who believed "more is better." I believe that you know what I mean here!.
  • The membranes operate at 50 BAR pressure and when something lets go, a sudden and without notice catastrophe can happen which will ruin most electrical devices in the engine room.
  • We wanted the TDS to always be below 285. We cruised full-time and used the watermaker for most of our freshwater. We changed membranes every 3 years, on average, or at between 300 - 350 hours.
  • The biggest part of changing membranes is the removal of the end caps.
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CW Bill Rouse Amel Owners Yacht School
720 Winnie, Galveston Island, Texas 77550 
   


On Mon, May 30, 2022 at 12:30 AM David Vogel <david.vogel@...> wrote:
When I recently replaced the interconnects at the same time as the end-cap and membranes, I received plastic interconnectors from Dessalator France - previously these were stainless steel.  I am unaware of why Dessalator changed the material.

My experience was that the black Delrin endcaps had become eroded around where the interconnector inserts, resulting in weeping, then leaking, then spraying of HP salt-water.  The only solution was not to use the watermaker - very unfortunate timing at the beginning of COVID, no spare parts available from any DESSALATOR agents I contacted, the factory in France was then closed by government decree, and then no international freight.  A lesson here about fractured supply chains, and spares holdings for remote area cruising (and I thought I was pretty well set up).

Anyway, I think that the endcap-interconnect failure occurred as a consequence of different rates of thermal expansion/contraction of stainless interconnect versus the delrin end-caps -- hot engine room, higher temps of the pressure vessels then, as the water starts to flow, the stainless steel cools and contracts quicker than the Delrin end-caps.  A slight temporary size mismatch compromised the seal of the o-rings, allowing a miniscule amount of water to seep past under pressure.  This water (and it also drying out, leaving salt crystals behind) further eroded the Delrin, the water rate increased, more erosion, and so on, leading to eventual failure - just like the shuttle SRB o-rings.

One solution would be to have the interconnector with closer thermal characteristic to the Delrin - hence (perhaps) the change from stainless steel to plastic interconnectors.

In my case, in retrospect I believe that another contributory factor was an intermittent exhaust fan (due to failing capacitor), that resulted in higher-than-normal temperatures in the engine room.  So greater temperature differentials to start with.

David
SM#396, Perigee
NZ


On 29/5/2022, 7:23 pm, "Nick Newington via groups.io" <main@AmelYachtOwners.groups.io on behalf of ngtnewington=aol.com@groups.io> wrote:


    I have a small leak from the watermaker outboard end membranes on my 160 litre per hour unit. I believe it is the stainless inter connector between the membranes.
    Had a look at Desalator website and it looks like the new one is a plastic material not stainless. This makes sense if one pickles the watermaker when not in use as “they say” that the sodium  metbisulfite  is corrosive.

    Has anyone bought one of these connectors?
    Just simple push fit right?
    Nick
    s/v Amelia
    AML54-019












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