Spectra watermaker asymmetric production

[WombatWhiskers]

Our Spectra 280C is 14 yrs old, ~2400 hours overall, though there is very little left of the original Spectra besides panel and valves.

End-Oct 2013 when I recommissioned after 6 months pickled on propylene glycol, production was slightly asymmetric 15 - 16 GPH at 85psi panel pressure. Since then performance has progressively degraded and asymmetry has increased.

Now with about 315 hours since feedpump heads were rebuilt 3-11-13, production is down to 10.0 - 12.5 GPH at panel pressure about 105psi (measured when shift begins, not shift ends).

I just uploaded a short video of the panel pressure/GPH behavior through two complete Clark pump cycles to Dropbox

https://www.dropbox.com/s/n4bfcsqxfp...production.MP4

I just completed a flow test = 2.67 GPM vs the 280C spec = 2.7 GPM. Test conditions: seachest boost pump ON (34 lpm) and 27.7 VDC at feed pumps, sea temp 68F. Also tested Water quality = 380ppm.

Any thoughts on what action to take would be appreciated!

[Dulcesuenos]

Contact JT at Halden marine survices in hollywood Fl. Or pm him here under "Tellie" he is a spectra God™

Sent from my LG-LS980 using Cruisers Sailing Forum mobile app

[WombatWhiskers]

Oops! I meant to write "Spectra 380C" not 280 C.

[senormechanico]

Originally Posted by WombatWhiskers

Any thoughts on what action to take would be appreciated!

It's pretty obvious to me the problem is on one side of the Clark pump.
Probably a leaky piston seal.
Internal leakage in the Clark pump for sure.
I'd be interested to see what Tellie says.

[WombatWhiskers]

Originally Posted by senormechanico

It's pretty obvious to me the problem is on one side of the Clark pump.

Thanks heaps -- that's my guess also. We're preparing to go offshore again in 4 weeks so I don't have time to go down a blind alley. If it is the Clark pump I will probably need to swap it for a rebuild to save time. The flow test says to me the Shurflo pump heads are still OK. I have spares but don't want to rebuild only to find just a slight improvement.

[Tellie]

Wow a video, can't be any more helpful than that. It's interesting that though this model is not made anymore, I have worked on three 380C units this week and they are all about 14 years old as yours is. Though they all needed a bit of minor work they are all now working like new. A great testament to Spectra. Your assumption and senormechanico are correct. The pump is asymmetrical. The evidence is more in the flow meter than the pressure gauge. Usually when a pump is asymmetrical you will see drop in pressure on one stroke and most of the time it is losing pressure on that cylinder. But your pressure gauge is reading well within the proper limits. What is most likely the issue is a sticking piston that is dragging. Thus what seems to be proper pressure readings but low production on the flow meter on one stroke. I agree, have the pump re-maned. Just make sure you re-pickle the membrane first before you send it off to Spectra. If time is too short you can always take advantage of their exchange program and get another re-maned pump sent right away. I'm a big fan of Spectras re-maned pumps. For all intents and purpose they are as good as a brand new pump. Once you get a fresh pump I think you will see your production back to where it is supposed to be and the TDS readings going down as well. If you need any advice while you are going through the repairs or if you need any help in the future feel free to call me anytime. J.T. Halden (aka Tellie) (954) 515-7077

[WombatWhiskers]

Thanks 10^9 for your diagnosis and advice. A couple of questions:

1. after a back flush, how many days do I have to complete reinstall at our NZ latitude before you get worried about the almost-new membrane?

2. radical change of subject: I can replace the Clark pump with a 230VAC driven CAT pump in less elapsed time, probably less $$, and get rid of all the maintenance hassles. We don't benefit from the low energy performance of the Spectra energy-recovery design - because we only make water when genset is running -> pressurizing the wingdeck level feed pumps and boosting the VDC.

Given those facts why not switch to the simple/low-tech way to pressurize the membrane?

[Tellie]

Originally Posted by WombatWhiskers

Thanks 10^9 for your diagnosis and advice. A couple of questions:

1. after a back flush, how many days do I have to complete reinstall at our NZ latitude before you get worried about the almost-new membrane?

2. radical change of subject: I can replace the Clark pump with a 230VAC driven CAT pump in less elapsed time, probably less $$, and get rid of all the maintenance hassles. We don't benefit from the low energy performance of the Spectra energy-recovery design - because we only make water when genset is running -> pressurizing the wingdeck level feed pumps and boosting the VDC.

Given those facts why not switch to the simple/low-tech way to pressurize the membrane?

1) I wouldn't go more than two weeks and in my opinion that is pushing it. Pickling solution is cheap enough to do it right.

2) A not so radical response. Unless you are well versed in watermakers I would doubt anytime saved is going to be worth it and I assure you it is going to be a lot more expensive. To convert a 380C to a Cat pump driven system is going to be a bit more complicated than just putting a Cat pump in line. First you will now need a proper boost pump that can keep up with a Cat pump, you will need a needle valve to adjust pressures, you will need a whole new set of high pressure lines and associated fittings, your plumbing is going to need to be changed out which will require new hoses, fittings and valves. Unless you have a new and good free Cat pump hanging around the pump and motor alone are going to cost you four times what a re-maned Clark pump will. The other additional parts, plus some not mentioned above, are going to cost more than a Clark pump re-build. All this and more for about six gallons more per hour. The only good way to do this to end up with a Cat stlye driven watermaker is to fix the Clark pump and make the system (Clark pump, membrane, feed pumps) operational, take it out and sell it. Spectras have the highest re-sale value of any watermaker, even this older one. Take that money and add the money you will be spending on your proposed conversion and I'll sell you a brand new AMI 230V watermaker with a warranty.
So in short...well you know what to do.

[WombatWhiskers]

Priceless good advice, thanks heaps! I had not considered the sell-buy AMI 230V watermaker strategy. Good news on the Spectra resale (though not sure who the buyer would be in NZ). I will give that some thought.

>Pickling solution is cheap enough to do it right.

Understood. Maybe there's a myth here - I thought that the Spectra chemicals reduced membrane life. Is that a non-worry? We normally use propylene glycol.

>First you will now need a proper boost pump that can keep up with a Cat pump, you will need a needle valve to adjust pressures

Needle valve understood. Boost pump - I may be about to crash land on Planet Reality. I thought our 230V seachest pump provided all the boost required as it is delivering 34 LPM to the genset and the Spectra feedpumps on the wingdeck. Adagio is a 52-ft cat, the machinery room is a meter about DWL.

I just got a quote for local Clark pump rebuild of NZD $650. I'll have a chin-wag with the OpenOcean Watermakers guy in OPUA to see what the round pump+valve costs would be. I have an idea of the HP hoses/fittings costs as I just replaced all of ours with my favorite hydraulics shop in Whangarei last October.

[Tellie]

Go ahead and use the SC-1 if that's what you have. I do prefer the PG over the SC-1 but it's not going to harm or shorten your membranes life in the short run.
Running a boost pump for a 380C is a waste of time and energy. The two feed pumps don't benefit from boost pumps. The feed pumps can be a meter above the waterline. You'll want to make sure that if you don't send the pump back to Spectra that the local guys are Spectra trained and are going to completely re-build the pump.