Can I add a second Membrane to my Spectra Cape Horn Watermaker?

[SV THIRD DAY]

Originally Posted by Pizzazz

I understand that a blanket statement that you can always increase output by adding a membrane threw you off

Wrong statements that will confuse people and lead them astray tend to do that....didnt throw me off...was just wrong. Again...correctly illustrating the danger of internet advice. It's exactly why I felt a responsibility to correct your incorrect blanket statements or you would have led others into adding membranes to units that could not support them. Maybe now you're seeing the problem I'm trying to prevent here. People take comments that aren't correct and then people in the water maker field or left dealing with those for years as the thread is viewed by others without the detailed understanding.

My response isn't based out of emotion it's based out of responsibility. A responsibility to not make incomplete generalizations that are going to send people down a wrong and incorrect path. As I've said a hundred times it's not that I'm smarter than anyone else (I'm a self described cruising bozo) it's just that I've learned you can't make broad generalizations and as you call it blanket statements and post it online or you're going to hose people. Selling water makers and more importantly water maker parts, I've seen it all. I've seen all the mistakes, I've seen the misinterpretations from the broad generalizations posted on chat forums that's why they're dangerous and with no personal animus towards anyone I have a responsibility to call them out and correct them as I've done here.

You still appear to be confusing, as I've commented before, the common water maker design with a pressure regulating valve downstream of, for example a piston pump, and an energy recovery pump like the Clark pump. Tellie tried to explain that to people to prevent them from making costly mistakes, but for folks who don't want to listen, I have pressure vessels for sale....there just is a no return policy when it won't work....

[Frode]

Originally Posted by SV THIRD DAY

...I've seen the misinterpretations from the broad generalizations posted on chat forums that's why they're dangerous and with no personal animus towards anyone I have a responsibility to call them out and correct them as I've done here

Thanks for your efforts, Rich. The personal reason I've had for hanging out on this specific site for years is that people here will take the time to explain, and to complete a discussion, even when something has been said seemingly hundreds of times before. Your efforts are by no means wasted.

People like you and Tellie, who share willingly from your observations and knowledge, is why people like me hang out here, to learn. As long as the discussions continue to provide solid information, I don't believe anyone is going to drop in and just get the wrong idea (quite a few people attempted to do that on the topic of LiFePO4 batteries, where few people had the tenacity to read through the 6,000 or so posts, but they were quickly told to go read up more).

I'll gladly profess not to have a full understanding of the workings of the Clark device, but I'm getting close. When I feel I have enough information, I intend to purchase one, and modify my existing system to make full use of it.

For now, I'm comparing the documentation from Spectra on the pressures, flow rates, etc. between the Cape Horn and the Newport 700/1000. I feel I'm close to having the required info to present numbers to support how one would successfully add an additional membrane to the Cape Horn.

Thanks to all of you who participate to make this a lively and useful discussion.

[SV THIRD DAY]

Thanks Frode....No problem. I know I need a little work at times on toning down my irreverent and sometimes smart ass web writing style...hey...but as I tell my wife, stick with what you are good at...ha ha ha
When I have time I enjoy going into the deep technical weeds.
There still is a misunderstanding of how the Clarke pump works with the assumption that recovery rate works the same as one of my units. But I'm not going to get back on that horse...it's been bead enough in this thread.

Ah....the famous LiFePO4 thread...that's a Gem.
Being in the boat yard now, I just turned off my solar and set my battery charger/inverter at 13.4v for Bulk, Absorption, and Float and guess what...my batteries are remaining at 13.4v or 80% SOC according to my battery monitor without overcharging and killing them. Funny how the internet experts on that thread said that was impossible and my batteries would fry. Show again where real life trumps theory. I'm half tempted to go post about it over there but you know...then that will suck me down from the work I should be doing in the boat yard...ha ha ha

[Pizzazz]

I think we are in agreement and I will try to learn from my mistakes. As I have said before, I think Rich's watermakers are the most cost effective solutions there. At the same time, I think it is really positive to encourage newbies like me to propose new ideas and help reduce the outrageous costs of most marine equipment. It could get tiring for the old timers - point noted. I was trying to get to the bottom of this and read a bit more on energy recovery watermakers vs. the brute force approach. I think I have a better understanding now and it seems that adding the second membrane to the Cape Horn is more problematic than it seems.

1) Conventional watermakers such as those that Rich sells and virtually everyone else's except for Spectra and Schenker, feed high pressure seawater through the membrane and aim to achieve around 25-30% recovery. It is efficient, somewhat heavy on the membranes but it allows 3-4 amps/gallon efficiency (clearly depends a lot on salinity, temperature and host of other factors). They are quite simple to build and inexpensive. Many conventional watermaker designs recover only 10-15% and for those, you can easily add additional membranes to increase the product rate at little cost. Eventually, once you go above 30-35% recovery the salt rejection capability of the membrane will be below target and the quality of the water will suffer. This was Rich's argument and I think it is now settled.

2) The energy recovery watermakers that use the Clark pump, take feed at, say 120 psi, and intensify it to, say 800 psi, by using a piston pump that is fed with the brine utilizing the pressure remaining in the brine. It appears that the Clark pump is optimized for certain recovery ratio's (fixed by the relative diameters of the piston and the outlet opening). So, if you have a 10% recovery Clark pump, it is optimized for 10% recovery meaning that it uses the pressure differential from the inlet to the outlet of the membrane to help intensify the pressure by 6-7 times. If you add a second membrane to the energy recovery watermaker, the recovery will go up but the pressure drop will be larger, which means that the Clark pump may not be able to boost the pressure 6-7 times but may be half that. This in turn means that the intensifier will not be able to achieve 800 psi but only 400-500 psi which is not enough for reverse osmosis. You can correct for that by adding a larger low pressure pump (to feed 200 psi pressure for example) but this will stress the intensifier beyond its design and the amperage will go up. It is almost certain that the efficiency of this setup will be lower that the optimal manufacturer design. So you will produce more water but likely it will be less efficient than just running the original design for longer. So, there is limited advantage to add more membranes.

I still think that my original statement that you can add more membranes as long as you can maintain the pressure is valid but it appears that maintaining the pressure is not straightforward. There is a research paper cited below that summarizes a setup with a variable high pressure pump parallel to the Clark pump that achieves what the OP wanted to do but I think it looks like a lot of effort. It does however, increase the output of a Spectra Watermaker three-fold while keeping the same power efficiency. Check it out if you want to pursue that design.

https://www.researchgate.net/figure/...ectrical-power

[Frode]

Fabulously informative article - thanks for posting the link, Pizzazz!

[SV THIRD DAY]

Originally Posted by Pizzazz

I think I have a better understanding now and it seems that adding the second membrane to the Cape Horn is more problematic than it seems.

Pulling teeth can be messy, but I promise to use more Novocain next time.

As stated by Tellie and me several times, the understanding flaw comes in the false assumption that water makers with the Clarke Pump vs Piston pump are operating under the same control and design criteria and throwing out % recovery rates as if that's all that matters.

So we went from absolutely it will work and anyone that says otherwise is shilling for Spectra to keep the little man down to "is more problematic than it seems".

We will get there and if we are lucky without causing a cruiser to Blow thousands of dollars on internet education while damaging their Clarke pump in the process.

[Frode]

After analyzing the data from Spectra, and gaining a better idea of how the Clark pump works, I wanted to share my findings. I figure there are more people out there who are as interested in numbers as I am.

If it weren't already obvious, the 7, 10, 15, and 20 percent designations for the Clark models refer to their maximum product recovery rates. This is the information I was missing when claiming it would be possible to increase the rate with an additional element. You can increase the throughput from the Cape Horn model, but not simply by adding an extra element.

Since the Clark device is a pressure intensifier, those numbers also provide an insight into the output pressures, by providing you with the pressure multiplier (feed pressure times multiplier equals output pressure) for each model:

7% : 14.2
10% : 10.0
15% : 6.7
20% : 5.0

The input pressure for the Ventura 150 (7% pump) is listed as 60-70, resulting in a high pressure of roughly 850-1,000. The Newport 1000 (20% pump) lists input pressure (on HI) as 200, resulting in a high pressure of 1,000. The Cape Horn, when running both feed pumps, provides feed pressure of 90-100, resulting in high pressure of 900-1,000 PSI (vs. 600-800 when operating on a single feed pump). DOW lists max operating pressure of 1,000 PSI for these membranes, and all of these units stay within those parameters.

Spectra has configured their units to use a 20" membrane with the 7%; a 40" with the 10%; 2x40" with the 15%; and 3x40" with the 20%. Product recovery rate (averaged out), per 40" membrane, would be 300 GPD for the 7%, up to 400 GPD for the 10%, 350 GPD for the 15%, and 333 GPD for the 20%. All well within DOW's specified max permeate flow rate of 600 GPD.

With a max 10% recovery rate from the Clark pump included with the Cape Horn system, it would take a feed flow rate of 4.1 GPM to max out the system (600 GPD). Anything beyond that would require more than one membrane.

Finally, DOW specifies a max recovery rate of 13% per element (SW30-2540), which is why the large Newport models require more than one element. It seems the Newport 1000 could have been operated with just two elements, but Spectra probably saw it as prudent to go to three.

[SV THIRD DAY]

Frist Dow does NOT specify a maximum recovery rate of 13% per element...sheesh....

Originally Posted by Frode

The input pressure for the Ventura 150 (7% pump) is listed as 60-70, resulting in a high pressure of roughly 850-1,000. The Newport 1000 (20% pump) lists input pressure (on HI) as 200, resulting in a high pressure of 1,000. The Cape Horn, when running both feed pumps, provides feed pressure of 90-100, resulting in high pressure of 900-1,000 PSI (vs. 600-800 when operating on a single feed pump). DOW lists max operating pressure of 1,000 PSI for these membranes, and all of these units stay within those parameters.

More wrong data posted as fact....why do I even try....

There is no such animal as a water maker running at near or at 1000psi.

Why is it people GUESSING don't come out and say it's a guess but rather feel the need to state guesses as if they are Facts with some scientific standing behind them? It's maddening....but it's also the internet...beware those promising diamonds and delivering coal and then telling you it has the same chemical elements.

Folks...please do not take this guess data and use it...or you could damage your system. Because what other piece of info is our good friend missing?

Originally Posted by Frode

This is the information I was missing when claiming it would be possible to increase the rate with an additional element. .

Not even a "Thanks Rich, you were right...."

Of course if I wouldn't have pushed the issue just how many other completely Bogus "facts" and internet cruise rumors would have been started by this thread sending how many folks astray? Yet the lessons seem not to be learned...that's the saddest part in all this. You have people telling you they are right then sha-zam they admit they were wrong and just as adamantly publish more incorrect information.

It's not the fact that people want to learn and figure things out that is the problem, it's the publishing of Rumors and Guesses, Stated as Facts that is the problem. Those bogus facts then cause EVERYONE in the water maker industry heartache and we spend hours on the phone and email troubleshooting with cruisers who screwed up their system because someone on the internet told them to do something. The best ever was a bloke that pickled his water maker with Urine...yes PEE. Why? Because he told me he read on the internet that Urine is sterile and good for pickling water makers. This is for real folks and people posting technical advice on the internet need to take more responsibility for what they are posting because it can be damaging to others that hear what they want to believe.

Quick...someone ban me from the internet because I can't take it anymore...Tellie...you were right....I should have ran and ran fast....

[Frode]

Originally Posted by SV THIRD DAY

Frist Dow does NOT specify a maximum recovery rate of 13% per element...sheesh....



More wrong data posted as fact....why do I even try....

There is no such animal as a water maker running at near or at 1000psi.

Why is it people GUESSING don't come out and say it's a guess but rather feel the need to state guesses as if they are Facts with some scientific standing behind them? It's maddening....but it's also the internet...beware those promising diamonds and delivering coal and then telling you it has the same chemical elements.

Folks...please do not take this guess data and use it...or you could damage your system. Because what other piece of info is our good friend missing?


Not even a "Thanks Rich, you were right...."

Of course if I wouldn't have pushed the issue just how many other completely Bogus "facts" and internet cruise rumors would have been started by this thread sending how many folks astray? Yet the lessons seem not to be learned...that's the saddest part in all this. You have people telling you they are right then sha-zam they admit they were wrong and just as adamantly publish more incorrect information.

It's not the fact that people want to learn and figure things out that is the problem, it's the publishing of Rumors and Guesses, Stated as Facts that is the problem. Those bogus facts then cause EVERYONE in the water maker industry heartache and we spend hours on the phone and email troubleshooting with cruisers who screwed up their system because someone on the internet told them to do something. The best ever was a bloke that pickled his water maker with Urine...yes PEE. Why? Because he told me he read on the internet that Urine is sterile and good for pickling water makers. This is for real folks and people posting technical advice on the internet need to take more responsibility for what they are posting because it can be damaging to others that hear what they want to believe.

Quick...someone ban me from the internet because I can't take it anymore...Tellie...you were right....I should have ran and ran fast....

Rich, I thought you were the one who recently complained about blanket statements. There appear to be only those in your reply. You claim that my numbers are incorrect, but you do not correct them, nor post links that can be used to help support your claims. An entire post dedicated to just ramblings seems a bit over the top.

On the other hand, here is the link to the design guidelines from DOW, regarding FILMTEC membranes. It is only a three-page PDF, so it's easy to find the table (on top of page two), which specifies a maximum element recovery rate of 13% for seawater applications with open intake: http://msdssearch.dow.com/PublishedL...romPage=GetDoc.

Perhaps I read this incorrectly. Perhaps it doesn't really mean what DOW says it means. Again, I'm eager to be enlightened.

Now, when you have recovered from whatever it was that temporarily took you out of commission, please post your data, or links to technical documents, allowing us all to learn something from you. That last post did neither you nor us any favors.

[Pizzazz]

@ Everyone tired of this:
We are trying to reverse engineer the Spectra line of watermakers and this is not easy. We are investing a couple of hours of mental effort vs. thousands of hours of paid engineering time by Spectra. Our understanding will evolve and I think this is part of what the forum is all about. Clearly, we are making mistakes but I believe eventually we will get it right. We are close.

@ Frode:
I do not think we fully understand pressure intensifiers yet. My understanding is that the numbers 7%, 10%, 15%, 20% refer to the ratio of the output area to the plunger area, so the inverse of these numbers is equal to the intensification effort as you say. I may be wrong but most intensifiers have a fixed intensification ratio, so it seems logical. Spectra says not to exceed 125 psi inlet pressure, which x10 is 1,250 psi. This will damage the membrane but there will be frictional losses and I am sure they employ some sort of a bypass valve set at 800 or 1,000 psi. The pressure will also depend on the temperature, etc.

Next, their literature says that a single pump generates 20-25 psi static pressure which rises to 60-80 psi feed pressure. If you look at the specs for the standard Shurflo 2.8 gpm pump, it says it maxes out at 45 psi. Please, check to confirm they are using a standard pump. Thus, the existing pumps will not be able to produce enough pressure to start R.O. in static mode. I believe that when you switch on the watermaker (e.g. in single pump mode) the pump produces only 20-25 psi pressure which is intensified 10x but as the energy recovery starts happening, it becomes easier on the pump to push and the pressure and flow increase to the nominal values.

Now, when you install a second membrane in series, nothing bad will happen to the pump, it will still intensify 10x but since you will be withdrawing 2x product (say at nominal 10% recovery for each membrane), the return to the pump will be 80% instead of 90% and the energy recovery will be lower. I am not sure if you will have enough energy recovery to increase the pressure to 800 psi. Installing more pumps with max static pressure of 45 psi will not help because without energy recovery, the pressure will max out at 450 psi which is not enough. It may be the case that you get partial energy recovery and it works OK but then the amperage on the pumps will increase. Basically, you are killing the best part of Spectra, the energy recovery device and making it more like a conventional watermaker. Little point in doing that.

Another way to go at it is to add a membrane in parallel and increase the flow as much as the pump can take. There must be a max flow rating of the Spectra pump and it is likely well above the nominal value. Actually, since the nominal flow is 2.8 gpm which is well below the max 6.0 gpm of the membrane you do not need a second membrane as you correctly say. Just add a third pump (with a variable switch, you can get a pwm device from Amazon very inexpensively), start increasing the flow and see what happens. Ideally, you would want to put a pressure gauge and a flow meter in line and see what it is actually doing. Do not go above 125 psi as Spectra says. This is more likely to work than the series membrane that will mess up the recovery system.

Now, if Tellie can tell us what is the max rated flow of the Spectra pump, things would be much easier, you know what the limits of the pump are and you can safely go up to the limits. Plus, you can adjust the output based on available power and needs. Best of all, you only need another pump and low pressure fittings, nothing else.

A separate point. While researching pressure intensifiers, I came across a the device linked below. It is a pressure intensifier, fits in the palm of your hand, intensifies pressure up to 13x, stainless steel, works with seawater, etc. Cost from the distributor was quoted as over $1,000 - let's see if it can be had for less. The idea would be to take a 200 psi seawater pump ($134), this device operating at 4x intensification, possibly an oscillation damper and a safety valve and the membrane. It will produce 0.6 gpm at 800 psi, nearly silent, with minimal losses (no energy recovery here, just a smaller size and quiet relative to a high pressure pump). If this works (they specify a minimum inlet pressure of 280 psi for oil, less for water, so not sure if 200 psi will be enough) this device would allow a new kind of a watermaker design. Food for thought.

HC2W miniBOOSTER | Hydraulic pressure intensifiers | miniBOOSTER Hydraulics A/S

SV Pizzazz

[SV THIRD DAY]

Interesting how it went from stating things as facts to now trying to reverse engineer.

Good luck gentlemen, the Clark pump patent has expired so there you go.

The decreasing entertainment valve combined with the 3rd glass of Brunello wine has causes me to tag out...enjoy the science project.

[newhaul]

Originally Posted by SV THIRD DAY

Interesting how it went from stating things as facts to now trying to reverse engineer.

Good luck gentlemen, the Clark pump patent has expired so there you go.

The decreasing entertainment valve combined with the 3rd glass of Brunello wine has causes me to tag out...enjoy the science project.

Rich I actually did get something out of this besides entertainment. Was wondering about running my survivor 35 with a windshield wiper motor and that was in one of the posts so now I will go ahead and make the brackets for that. Found one that is 50 rpm and 8.5 ftlbs torque.

[SV THIRD DAY]

Originally Posted by Frode

On the other hand, here is the link to the design guidelines from DOW, regarding FILMTEC membranes. It is only a three-page PDF, so it's easy to find the table (on top of page two), which specifies a maximum element recovery rate of 13% for seawater applications with open intake: http://msdssearch.dow.com/PublishedL...romPage=GetDoc.

Perhaps I read this incorrectly. Perhaps it doesn't really mean what DOW says it means. Again, I'm eager to be enlightened..

What you are not understanding about the 13% recovery rate is the context. Dow is NOT talking about batch process water maker like marine units in the date sheet you site, but rather plants like the 10,000 GPM I once built that are running 24hrs per day, 365 days per year and want a 7yr membrane life to minimize ongoing O&M costs. You have to know what data you are looking at and apply it properly to the situation for it to make sense and then to draw the proper conclusions from it. Consider yourself enlightened...

Again...no one, including myself, has any problem with folks bouncing around ideas and being open to learning and asking questions. But that is NOT how a few posters in this thread were conducting themselves. Go back and read your posts where you stated guesses and opinions as FACT. I don't do BS well not because I care people are wrong but again, as I said before, because it does a disservice to the cruising community. Change your tone from blowing BS up people's aS@ to asking questions and you will get a different response from me and others.

[Pizzazz]

Originally Posted by newhaul

Was wondering about running my survivor 35 with a windshield wiper motor and that was in one of the posts so now I will go ahead and make the brackets for that. Found one that is 50 rpm and 8.5 ftlbs torque.

Newhaul, I went through that last year. Here are the options I explored:

1. Windshield wiper motor + linear drive from a reciprocating saw. The piston travel required by the Survivor 35 is exactly 1" 1/8, so make sure you get a similarly sized saw. Worked OK, there were issues with alignment, attachment of the motor and eventually corrosion of the aluminium casing from the circular saw. It works though.

2. I also looked at linear actuators but could not find one rated at 100% duty cycle that was inexpensive. If you find one, it would be much easier to interface.

3. A third option that I now think is best is the pump+motor below. It produces 8-12 gph @ 800 psi for $269. It could possibly drive the Survivor 35 to 2 gpm but I am not sure. It is a good quality pump, Buna-N seals and so on. They also have a stainless steel version but it costs more $540. My suggestion will be to unscrew the pressure valve from the Survivor 35 and feed the output of this pump in that opening. This way, you retain the manual option for emergencies and it is plug and play.

https://www.dultmeier.com/products/0.851.861/6793

At the end you will find that the Survivor 35 produces very little water. It could be made very quiet (you can hardly hear it when you are sailing) so it could run for long periods of time but it is a hassle. One option I did not experiment with was to feed the Survivor 35 at higher gpm, may be it will produce more output. For example, feeding it with a 0.5 gpm pump. That way you can probably go up to 3 gph product but the efficiency will suck. I have no idea.

However, I do think that it is a cost efficient solution. You get a used Survivor 35 from ebay.com for $200, the pump for $270 and you are in business. Some units may need a new membrane but you are still ahead.

[newhaul]

Originally Posted by Pizzazz

Newhaul, I went through that last year. Here are the options I explored:

1. Windshield wiper motor + linear drive from a reciprocating saw. The piston travel required by the Survivor 35 is exactly 1" 1/8, so make sure you get a similarly sized saw. Worked OK, there were issues with alignment, attachment of the motor and eventually corrosion of the aluminium casing from the circular saw. It works though.

2. I also looked at linear actuators but could not find one rated at 100% duty cycle that was inexpensive. If you find one, it would be much easier to interface.

3. A third option that I now think is best is the pump+motor below. It produces 8-12 gph @ 800 psi for $269. It could possibly drive the Survivor 35 to 2 gpm but I am not sure. It is a good quality pump, Buna-N seals and so on. They also have a stainless steel version but it costs more $540. My suggestion will be to unscrew the pressure valve from the Survivor 35 and feed the output of this pump in that opening. This way, you retain the manual option for emergencies and it is plug and play.

https://www.dultmeier.com/products/0.851.861/6793

At the end you will find that the Survivor 35 produces very little water. It could be made very quiet (you can hardly hear it when you are sailing) so it could run for long periods of time but it is a hassle. One option I did not experiment with was to feed the Survivor 35 at higher gpm, may be it will produce more output. For example, feeding it with a 0.5 gpm pump. That way you can probably go up to 3 gph product but the efficiency will suck. I have no idea.

However, I do think that it is a cost efficient solution. You get a used Survivor 35 from ebay.com for $200, the pump for $270 and you are in business. Some units may need a new membrane but you are still ahead.

I already have 2 of the manual units (ex mil units) im happy with the 1.5 gph just get tired of pumping after a while.