Spectra Ventura 200T: 6.3 GPH only?

[myocean]

Before I start cleaning the membrane I like to ask the community:
My new Spectra watermaker Ventura 200T (with MPC 5000) has been in use since May, more or less daily. It has 407 hours now. We have been in a shipyard in June for 8-10 days and flushed the Spectra 2 times in between.
Now I have a low product flow since about 3 weeks. Here the details:

6.3 gph instead of about 8 gph initially.
93 psi feed pump pressure
salinity is 164 ppm
The MPC says pre-filters are good and I replace/clean them avery few days. (20 um & 5 um)
I can't find any restrictions in the flow paths.

If the membrane needs to be cleaned: Why is this? (We have been in the Med all the time in pretty clean waters)
Any suggestions?

[belizesailor]

Dont see any obvious problems from your post. I suggest a little more data gathering.

How are you measuring GPH output? Could just be a sensor issue. I would run output into a graduated container and do the math to confirm.

Get the Spectra software so you can collect data and set operating parameters. I think it is still available on their web site or tech support can hook you up with it.

The field manual for the software also lists default settings and operating ranges, like feed pump pressure, for each model...comfirm these for your unit.

I would eliminate other possibilities before assuming a dirty membrane, esp given the low hours. Could it have been contaminated with petroleum products or chlorinated water at any point? Both will quckly damage a membrane.

GPH output can vary based upon source water temp and salinity. Any changes?

Contact Spectra tech support...they are excellent.

A member here, Tellie, is a very knowledgeable Spectra rep, hopefully he will chime in soon.

[Tellie]

I would agree with Belizesailor. First check and time the product in a graduated container to make sure the 6.3gph is a real number. 93psi is just a tad bit high, 80-90psi is the normal range for your unit, but even a gauge can be off this little bit. bit. This may be indicative of some fouling in the membrane but the 164PPM is a very good reading. You mention you are in a ship yard, is/was the boat on the hard when it flushed twice or in the water? For a membrane to go from 8gph to 6.3gph in three weeks with good pressures and good PPMs would make me think something has gotten into the system. But check the amount of product made first. If you have any questions on how to do this let me know and I get you my cell number.

[myocean]

I have now checked the product flow and the 6.3 gph are real, so the MPC flow meter is right. Tellie, thank you for joining the discussion! You helped as well when I had the cracked clark pump cylinder in July. (may be you remember)
I can not say for sure that the flow went down within 3 weeks only. I have not tracked this carefully. However meanwhile it is annoying that I need to run the unit longer every day because we have some visitors on board.
By the way: I have not yet checked the supply voltage at the system itself. However the MPC is not complaining (it does when we have low battery voltage) and the battery voltage is absolutely fine.
Chlorine can not be an issue (I think) as we have the carbon filter for the flush process und we have rarely chlorinated water in the tank. We will soon have to change the carbon filter as it will be half a year old by end of October.
The time in the shipyard was in June. A few days on the hard with flushing from the tank. (slightly chlorinated tap water, passsing through the carbon filter).
We have only operated the system in the Mediterranean and not in ports. (water temp. 20...25 °C). Right now I estimate the sea water temperature to be about 24°.
By the way: What I found in the Spectra Troubleshooting Guide is that the nominal pressure should be 70-80 PSI. So the 95 I am seeing right now on my display are quite a lot I think.

[Tellie]

Sure, I do remember.
These systems are voltage sensitive. You are right, if the voltages get too low the system will go in alarm, usually around 11.5V. But first I'd let the system run for awhile and check the voltages at the screw terminals on the wiring harness and make sure you are getting proper voltages there regardless of the panels volt meter reading. How long is the electrical wiring from the power source to the watermaker and what size gauge is the wire? Also over chlorinated water would not slow down the production. If the membrane was chlorine damaged if anything you would see more production along with higher PPMs. The tech field manual calls for 80-90psi but 70-80psi works for me if production and PPMs are good. 95psi is starting to get high though and that would start to steer me away from suspecting the voltages. You just may have a membrane clogging issue. Do you have the SC-2 and SC-3?

[myocean]

I have just measured the Voltage at the Watermaker and it is 12.5 V, so I think this is ok.

Why should the membrane be clogged, what can be the reason for this?
Today the product flow is higher again (7.2 gph). This happens from time to time, its not constantly 6.3. Why? (We have now anchored in a bay with perfectly clean water, is that a reason?).
Another effect I have seen twice now is that the product flow is absolutely zero even though the flow meter seems to rotate the the MPC reports flow. (but its really zero, nothing comes out). This has happened after filter replacement, probably due to air in the system. However I think it should not report flow if there is no water.

[Tellie]

12.5V is fine. How long do you normally run the watermaker for? Membranes can clog for several reasons, it would be difficult to say from here why yours might be clogged. But gaining a gallon of product all of a sudden usually points to something other than clogging. The flow meter should always rotate whether or not your product water is diverted to your tank or over board. Is the green light "ON" or "GOOD" on the control panel when you are not getting product? Where are you checking to see if there is product water flowing? When your system first starts up it will not flow product to your tanks for a few moments allowing any stale water in the system to go over board. If the green light is "ON" on the control panel and you are not getting product flow then your diverter valve is probably dirty. You are starting to get into a lot of questions that may be interrelated or not. You might want to give me a call so we can get into this a bit deeper. I'm takeing my daughter to the airport today so after 1PM EST I'll be available.

[myocean]

Behind the flow meter there is a 3 way valve which allows me to direct the product directly into the tank or directly to an outlet. So it is very simple to check if the reported product flow is real. This zero flow thing happended only twice yet but I only noticed that there is now product flow after 1 or 2 hours of operation because the tank gauge did not move. So I went to check and found zero product flow while the MPC was reporting all ok. I assume this has been cause by air - somehow.

However - this is not my current problem. I have this low flow high pressure, nothing else looks wrong.
Its difficult to call you, Tellie, at the moment, we just have a prepaid mobile phone and calling the US would not work for long... However I can deliver all kinds of facts.

(from tomorrow we are on a passage, back in the internet world not before Friday)

[myocean]

I am back. This issue has still not been solved. (and I have not yet received the offshore kit which may be comprises the cleaning stuff SC-2 and SC-3). Right now I am close to Gibraltar and see 108 ppm (and green 'good' light is always on) on my display and 102 PSI feed pressure (it has run now for 3 hours). (pre-filters changed yesterday).
Typically we run the watermaker 3-5 hours a day.
Production is close to 7 gph at the moment. Any thoughts?

The zero production issue came back yesterday and I realized that the product diversion valve had not switched even though ppm were low as always, so all the good water has been put into the sea again. (this was again very annoying because I realized this only after 5 hours of production and we have currently 9 people on board, so we need the water). I think it would be a good idea to have the flow meter only in the 'to tank' line and not prior to the diversion valve.

[medicrene]

If this was a new membrane, you need to expect that there will be some reduction from basic use. I have a different watermaker and when I noticed the small increase in salinity and decreased output, I called the manufacturer. He stated that was normal. He uses the same system in his boat, he is a trusted friend and I believed his answer. He would have gladly sold me cleaning supplies and such, but insted told me the truth. If you are getting output, keep going.

[belizesailor]

Originally Posted by myocean

...

The zero production issue came back yesterday and I realized that the product diversion valve had not switched even though ppm were low as always, so all the good water has been put into the sea again. (this was again very annoying because I realized this only after 5 hours of production and we have currently 9 people on board, so we need the water). I think it would be a good idea to have the flow meter only in the 'to tank' line and not prior to the diversion valve.

The diversion valve is a simple solenoid which may be having problems. Pretty easy to plumb around until you can replace.Your water quality is good, so you could just remove the solenoid...a small amount of higher PPM water at the start of the run will go to your tank, but by the time it is diluted with existing water in the tank and new product water it wont matter.

[donradcliffe]

I've had problems with the diversion valve (different system) in the past--usually solved by taking it all apart and cleaning crud/corrosion out. You might check the electrical connections to the valve also.

[myocean]

Originally Posted by medicrene

I noticed the small increase in salinity and decreased output, I called the manufacturer. He stated that was normal.

I am seeing at the moment salinities lower than ever and feed pump pressures higher than ever. At the same time the product flow is too low (usually <6.5 instead of 8 fpm)

[myocean]

Hi together - I have not worked on this since the last post. There were many other things to do and we are not sailing at the moment.
Yesterday a guy here in the marina who has done technical jobs on many boats said that a lot of watermakers need in fact to be operated much more than people think. Otherwise the membrane clogs more and more and production goes down. He said to be sure a watermaker needed to run about 30% of the time. Rising back pressure and decreasing product flow would be typical, he said. And the manufacturers specifications about need for flushing and running times would be far too optimistic.
What do you think about this?

[Tellie]

Originally Posted by myocean

Hi together - I have not worked on this since the last post. There were many other things to do and we are not sailing at the moment.
Yesterday a guy here in the marina who has done technical jobs on many boats said that a lot of watermakers need in fact to be operated much more than people think. Otherwise the membrane clogs more and more and production goes down. He said to be sure a watermaker needed to run about 30% of the time. Rising back pressure and decreasing product flow would be typical, he said. And the manufacturers specifications about need for flushing and running times would be far too optimistic.
What do you think about this?

Not sure what's meant by running 30% of the time but the marina guy is correct for the most part. Sometimes watermakers are not run long enough and shorter run periods are detrimental to membranes. This gets into that grey area where debates start among the watermaker guys on how long a run time is good for a watermaker. My usual statement to my customers is that it is better to run your watermaker every third day for three hours than to run it everyday for one hour. I like to use the ten to one ratio to explain the reasons for this. This is only for easy math every watermaker is different for many different reasons. It basically takes ten gallons of salt water to make one gallon of fresh product water. One gallon of fresh goes to your tank and the other nine gallons go overboard as brine. This nine gallons is important to the process. Membranes are cross flow filters not barrier filters. The nine gallons basically flush and wash the surfaces of the memembrane to keep it clean. If the membrane were a barrier filter (like fuels filters) it would clog within minutes. The longer the system runs the better flushing action the membrane gets. Short run times may not allow the membrane to receive a good flushing thus having a cumulative effect of build up of material on the input of the membrane causing higher pressures and lower product output. This also happens when an owner likes to crank up the pressure on their unit to the max to squeeze out that last 1-2gph. As far as the fresh water flush, go with what the manufacture of your watermaker recommends. The big manufacturers have done A LOT more research and have gone through a lot of headaches to get this right, don't always try to be smarter than the guy who builds it. This is also just some part of why sizing a watermaker to you and your boats needs is not a simple one two three decision or what works for your buddy and his boat will work for you and your boat. You can get too small a watermaker and too large a one as well. All that being said membranes are finicky things. They have gotten better over the years, but no two membranes are alike. For the most part these differences won't be noticed or be an issue for boat based watermakers. This is not the fault of the watermaker manufacture but of the way membranes are made. No two membranes are alike and unfortunately some will fail sooner than the next one, even though operated and cared for in the exact same way. It's rare but I've had brand new fresh ones fail straight out of the bag. I've seen them last for 12 years (which is extremely rare as well) and others last only two years. On average and for the most part, 5-8 years is a good life expectancy for a membrane on a properly taken care of watermaker.