Semi-Technical Watermaker Questions

[matauwhi]

G'day, VirtualVagabond. The boat came with a Sea Recovery unit when we purchased it. I replaced the membranes that came with the unit in 2002. Using the watermaker routinely, with good pre-filters, in petroleum free seawater adds to the life. Also helps to keep the recommended flowrate across the membranes. I also biocide the membranes when leaving unit unused for extended periods of time. That's what I can offer. Cheers.

[foggysail]

Originally Posted by matauwhi

If you are going to use a booster pump, along with your high pressure pump, you are going to need more than 20 amps. More like 30 to 40 amps. You will get by on 20 amps for your high pressure pump, but not with the 1/3hp booster pump. Cheers.

Matauwhi--

I thought there was PEE in my water when I read your earlier thread about 900 psi requirements!!! But a quick trip down ROSA Lane provided me with a quick kick in the tank. No way will I reliably get the product rates I expected (38g/hr). It all depends on the water temperature.

I took several passes through ROSA and it looks like at 55 degrees F which is not uncommon during spring here in Massachusetts, the best I can expect and still stay within the limits of my 2HP motor is around .54 g/min or just over 32 g/hr. This is based on my assumption of our water having a TDS of 35,000. The calculated pump pressure for this output is just over 841 psi.

When our water temperature improves to 60 or higher which I expect after June, things get better with a product of 35 g/hr and at 70, product soars to about 38. It appears that the thing to do is just set the pressure and what ever I get--- I get.

HEY--- ALL IN ALL, NOT TO SHABBY. Of course, the more you do simulation, the more one can believe its the real thing.

Another clarification I need to make deals with the so called "booster pump." I mistook that to be my pre-pump, the little guy that will help overcome the pressure drop across the prefilters that supply water to the high pressure pump. Some systems do use a booster but I have no clue how they use it. With this clarification, my line current should remain at or below 15 amperes. By the way--- ROSA is much in agreement with my earlier pump power requirement of 1.46KW for pressure in the 840psi range.

I plan to use the pressure stepping start up and shut down as I explained in earlier posts. DOW does make that recommendation for their membranes plus I will need a lower pressure during my auto flush cycle. Also it will help avoid nuisance circuit breaker tripping.

Foggy

[foggysail]

I was doing timing diagrams, logic truth tables and block diagrams today for the electrical circuit design and I ran into another dilemma!!!

I got stumped with how I should design the flush circuit. Mechanically, my plan is to fill a bucket with product at every start up. the bucket will provide the needed water to flush out the brine from the pump and lines. I believe I can handle that design without too many problems but the flush itself is an issue.

The easiest way for me to do the flush is to monitor the water flow entering the high pressure pump. When the bucket empties, the flow will rapidly diminish, and because the flow rate will be measured, an electrical circuit can shut the system down at that point. This is a much easier approach than dealing with float switches.

PROBLEM!!!

The plunger pump will force a small amount of air into the high pressure components such as the membranes when the flush bucket runs out of water. Not much air but never the less, small quantities of air will get into the high pressure components. Because air is compressible, the air pressure will be much less than that of raw water.

How will the membranes react with air in them??? I really don't want to get into float switches, they create too many problems.

Suggestions? Comments??

Thanks--

Foggy

[Tellie]

Foggy, ya know I love ya man, but you are making this more complicated than it needs to be. "timing diagrams, logic truth tables and block diagrams"? I'm a very big proponent of the KISS rule. Simply Tee off your house water line and route it to your watermaker. Install a one/way valve just before a charcoal filter where it's easy to get at and when you are ready to fresh water flush just open the valve and let your boats fresh water pump supply you with the flow you need. No buckets no electronics and no fuss. If you want to get a bit fancier, install a three/way valve instead and route the second line to back flush the system to the thru hull with fresh water. I do this and it protects and back flushes the raw water strainer which keeps down the cleaning and rusting out the SS screen. Remember that there will be many times when your watermaker will sit for several weeks without use. You will want to give a fresh water flush at least once a week, or more in the summer tropics. If you set up a system that you have to run it to make product water to use to flush with it becomes another pain. This way you just head down to your watermaker and open the valve and you have the fresh water you need at the flip of a valve.

[CharlesFCook]

My system should provide between 36-40 product gallons/hour

Why do you need so much water? How many people are on this boat?

Sorry if you have gone over this somewhere.
Charlie

[toodleoo]

I normally just lurk on this forum but thought that I might be able to add in here. 12 years ago I designed a watremake capable of max outputing (3) 2.5" 40" membranes. It was one of the best functioning self-designed systems on the boat. I started out with this pump http://www.oberdorfer-pumps.com/Spec_sheets/104M.pdf straight off of a seachest which then fed through 2 gravel/sand filters to parallel 5 micron filters to the HP pump. I started out with using the single phase 3 HP motor but ended up belting it off of a 2 cylinder Kubota that drives a 225 amp alternator. I turn the alternator off when I'm making water to keep from overloading the engine. My inverter supplies the AC for the LP feedpump. The only inlet pressure that I measure is the drop across the 5 micron filters. As I see the drop decrease on the inlet side to these filters from the normal 23 psi I know when to backflush the sand filters. I have run this system in very silty harbors with no problems. The 5 micron filters last for a long time because of those sand filters. The system is completely manual and i wouldn't have it any other way. It uses a high pressure needle valve (Whitney) on the downstream side of the membranes to regulate pressure/product output. Always start/stop the system with vavle wide open! I divert all output to a spigot on a sink next to the control panel until the TDM or taste) is acceptable then manually move a the 3 way divert valve so that it flows into the freshwater tanks. MY HP pump is a Giant SS that is rated at 7.3 GPM. For that person looking for that 3 HP single phase motor, my brand new unused one has been sitting down at Sailorman for the last 10 years on consignment.
I still own the boat but it has been in storage for the last 8 years. When I recommission the watermaker, besides new membranes the only change will be to go DC on the low pressure feedpump. Hope some of this helps.

[foggysail]

Originally Posted by Tellie

Foggy, ya know I love ya man, but you are making this more complicated than it needs to be. "timing diagrams, logic truth tables and block diagrams"? I'm a very big proponent of the KISS rule. Simply Tee off your house water line and route it to your watermaker. Install a one/way valve just before a charcoal filter where it's easy to get at and when you are ready to fresh water flush just open the valve and let your boats fresh water pump supply you with the flow you need. No buckets no electronics and no fuss. If you want to get a bit fancier, install a three/way valve instead and route the second line to back flush the system to the thru hull with fresh water. I do this and it protects and back flushes the raw water strainer which keeps down the cleaning and rusting out the SS screen. Remember that there will be many times when your watermaker will sit for several weeks without use. You will want to give a fresh water flush at least once a week, or more in the summer tropics. If you set up a system that you have to run it to make product water to use to flush with it becomes another pain. This way you just head down to your watermaker and open the valve and you have the fresh water you need at the flip of a valve.

Tellie-- HEY! I like your idea for flushing but because I already have flow solenoids I can incorporate them into an automatic flush. I need to flush after every use, brass pump restrictions.

My goal was/(is?) to be able to start the watermaker and let it do everything without me bother with it. The electronics is simple, a piece of cake with teh most complex components being a couple of frequency to voltage converters. The electronics, for me at least is the easiest part of the system. Remember my earlier worry AC current surge about tripping the input power circuit breaker when the pump motor starts under full load? I guess I can overcome that but it will require de-loading the system using the CAT7370 each time the system is started.

Got to think about the plumbing complexity of metering the high pressure output from the pump, the flow tubes for measuring the input water along with measuring either the brine or the product. I have eliminated all this needed plumbing but will still enjoy metering the important stuff, digital in my case to read out the high pressure, the input flow along with the brine flow. All this without worrying about pipes, tubes, fittings, water leaks with high pressure, plus a real pain risk of raw salt water spraying all over the place if a high pressure leak should occur.

I will need only one high pressure tube/hose in the control panel for the CAT7370 post regulator. That is simple plumbing. Look at Glen Ashmore's control panel. He did a GREAT JOB but look at his plumbing complexity!

OK, I guess I can get by without much of the metering but then a lot of guess work is needed. I could measure the pump's input current with a clamp on ampere meter, use that to calculate the high pressure knowing that the flow rate is a function of the pump's fixed RPM. But the product will be a real guess unless I measure its flow into a bucket and remember, that is a function of the membrane condition and water temperature.

Your suggestions share real life solutions to watermaker problems. I appreciate them dearly!!! But I cringe at doing the plumbing. Many posts ago, I made a comment about somebody's system. MY statement was something like "what a great design job" or similar words. Gordie followed my post with his "YES---- AND WHAT GREAT PLUMBING SKILLS!" He was right on the mark. I can plumb, but I am a hacker.

Please keep your thoughts, good or bad coming! I look forward to reading ALL your posts where you share your valuable experience!!

Foggy

[foggysail]

Originally Posted by toodleoo

I normally just lurk on this forum but thought that I might be able to add in here. 12 years ago I designed a watremake capable of max outputing (3) 2.5" 40" membranes. It was one of the best functioning self-designed systems on the boat. I started out with this pump http://www.oberdorfer-pumps.com/Spec_sheets/104M.pdf straight off of a seachest which then fed through 2 gravel/sand filters to parallel 5 micron filters to the HP pump. I started out with using the single phase 3 HP motor but ended up belting it off of a 2 cylinder Kubota that drives a 225 amp alternator. I turn the alternator off when I'm making water to keep from overloading the engine. My inverter supplies the AC for the LP feedpump. The only inlet pressure that I measure is the drop across the 5 micron filters. As I see the drop decrease on the inlet side to these filters from the normal 23 psi I know when to backflush the sand filters. I have run this system in very silty harbors with no problems. The 5 micron filters last for a long time because of those sand filters. The system is completely manual and i wouldn't have it any other way. It uses a high pressure needle valve (Whitney) on the downstream side of the membranes to regulate pressure/product output. Always start/stop the system with vavle wide open! I divert all output to a spigot on a sink next to the control panel until the TDM or taste) is acceptable then manually move a the 3 way divert valve so that it flows into the freshwater tanks. MY HP pump is a Giant SS that is rated at 7.3 GPM. For that person looking for that 3 HP single phase motor, my brand new unused one has been sitting down at Sailorman for the last 10 years on consignment.
I still own the boat but it has been in storage for the last 8 years. When I recommission the watermaker, besides new membranes the only change will be to go DC on the low pressure feedpump. Hope some of this helps.

WOW WHAT A SYSTEM!!!! But that is complex. HEY--- HOW ABOUT SAILORMAN!!! Isn't that a GREAT place??? I have purchased all kind of stuff from them and they stand behind what they sell. Six years ago I purchased a used davit crane that is currently mounted on the bow of my boat to lift my dinghy into and out of the water.

But back to your watermaker. I thought about a 3HP motor when I started my design. But the best ways to use them include a 3 phase, 6 pole beast so the RPM is low or by belts and pulleys. The only single phase motors I found were 2 pole. WOW-- over 7 gal/minute!!! Heck, you could make enough product to sell.

Pressure delta over the filters--- I thought about doing that, but....

Sand filters! I doubt I have the space for such luxury but good for you!!! Nice reading about reading what others have accomplished!!!

Thank you for sharing your experience!!!

Foggy

[foggysail]

Originally Posted by CharlesFCook

Why do you need so much water? How many people are on this boat?

Sorry if you have gone over this somewhere.
Charlie

Charlie--- My plan is to only run the machine for about an hour daily or as needed of course. Way back in yesteryears, Wifey and I lived almost for a week on the 30 gallons stored in my Hunter 30 sailboat. My how things have changed.

We now go through over 30 gallons a day with hot showers, 1 freshwater head and plans to convert the other to freshwater. I want to be able to freshwater wash my boat on anchor, be able to wash down the anchor chain plus live more water extravagantly than we even do now.

But I don't want to run a watermaker for hours at a time when away from the dock because that means running the generator for hours. Everyone seems to use what is available. When we only had 30 gallons. that was what we used. Now the tank holds 100 and every drop gets used.

Foggy

[goboatingnow]

Foogy , why the issue re flushing. Firslty use your tank water ( and maybe a charcoal filter to be safe), youll need a lot more then a bucket full anyway. Plumb in behind the feed pump and as Tellie says you can use a three way valve to back flush the filters ( or two logic linked solonoid valves). Then open the back pressure reg and use the two pumps to flush the system, There will no air issues to deal with.

I would avoid any tranducers or valves on the high pressure run to the membranes. Maybe at the very most a pressure transducer., flow rates meters on the low pressure input and product output are the main indiciators of performance. A safety bypass set at 950psi should be fitted to the pump ( these often come with built in unloaders anyway). ( keep a manual pressure guage in the high pressure line in case all else fails)

Dont bring the system immediately up to running pressure, ie with the back regulator set on. There too much shock for the membranes.

I designed a control system using a PIC. ps , dont mind teh KISS people, even with a few valves and to us electronic bods, the electronics KISS anyway.

I like your idea of a completely digital control panel, Im actually thinking of going the same way and using one of these Industrial Computer,Automation & Embedded Computers Solutions - Advantech eStore - buy.advantech.eu I have some of them in front of me now. Bit of embededed C and i'm away ( litle mimic diagram maybe!). for 300 euros i could hardly buy the parts.

Id actually like to motorise my needle valve, I can actually fit a little geared motor and still be cheaper then a 7370, if it was fast acting enoigh I could even simulate a low speed response back regulator , it would certainly be enough to control a watermaker. Utimately id like to have a automatic controlled slow start system, with the control system slowly closely the needle valve until the setpoint product flow is reached ( or the system operating pressure max is achieved)

Next step is to investigate a energy recovery solution, Danfoss are making great strides here for small RO watermakers, still a little pricy. Ultimately energy recovery will trickle down from big RO systems, will give Spectra a run for its money then.. ( see http://www.isave.danfoss.com/index.asp?inc=isave for interest)

By the way its easy to rig a TDS detector and subsequent divertor/dump valve on the product output, TDS is only a conductance probe, bit of signal electronics, some logic in a processor chip and hey presto.

Dave

[foggysail]

GEEZ Dave, you have me salivating!!! Problem is its been over 15 years since I did anything in C but just the remembrance of creating solid electrical designs gets my attention. I will comment though, a micro is too heavy for this project. Simple components using an old timer such as the 555 along with maybe a down counter and maybe a few gates can go a long way toward automatic control unless your getting into a step motor to control a valve. And no software is required.

I will have a high pressure solenoid to shunt the pump's output for the initial start into a lower pressure regulator. After the motor comes up to speed, the plan is to switch to the higher pressure regulator. Sort of minimizes the pressure transient applied to the membrane but certainly is not a slow start.

Back to flushing-- Tellie's suggestions are similar to yours. I am backing away from the flush bucket after reading his suggestion. Will instead use the stored product water in my main tank. Yes, a charcoal filter is needed but they are inexpensive.

Energy recovery! Yes, that sort of baffles me as to why more has not been done. There are other ways beside the Clark approach to achieve energy efficiency improvements. No need for me to even go down that avenue while I have a 7.5KW generator on board.

Strange that you should mention a TDS sensor. I have intentions to at least get a better grip on the relationship between ohms and dissolved solids. Enough! Got to get back to Green Bay as they whip Chicago!

Foggy

[goboatingnow]

Simple components using an old timer such as the 555 along with maybe a down counter and maybe a few gates can go a long way toward automatic control unless your getting into a step motor to control a valve. And no software is required.

for us micro age boys ( born in 60) micros are easier. !.

PS in realtion to TDS metering , really all you need is a simple conductance probe, it doesnt even need to be calibrated. Find the conductance valve that corresponds to your taste buds and then scale from there, theres no real need to actually discover the salt content.

Dave

[goboatingnow]

Btw fellas , I have an issue how to introduce the pickling solution into the circuit. I had intended to feed it rather like the flushing water into the low pressure feed pump. But I read elsewhere that deposits build up in the HP pump. Some recommend introducing into the high pressure circuit hence only pickling the membrane. But I'd prefer not to have a diverter valve in the high pressure line. I also have to ruin up a return circuit to allow the pickling fluid to circulate. ( or should I just let it flow put the dump line). Comments ? Tellie your wisdom?

Ps I reckon the steelers have the SB !

Dave

[Bergovoy]

the KISS is basically for 'safety' and to avoid problems/complications when you are somehwere when the 'control' system is on the fritz...

having an electronic control system to have complete control of the watermaker mean an all encompassing type of system. and for each solenoid you will need a flow sensor to confirm that the solenoid is in fact operating as commanded. (I knowthere must be some type of term for this, maybe two way solenoid, or feedback solenoid?)

so in essence you will need to components for each function, at least... and then maybe a back up...

When i was trying to think of an 'aquarium controller', I was thinking about getting flow sensors for the plumbing, and found those parts to be really expensive for saltwater.. in the $300 range.

I think part of it or maybe most of it was for non corrosive parts that would leech metals into the aquarium water and adversly affect the fish and coral.. not sure if that would be an issue for the flow sensors for a drinking water system...

anyways, i am all for turning one valve after use... i.e. turn the system on for an hour, or for you, push a button, then when done push a button, for me it would be turn a valve, then turn the power off...

just giving you my unexperienced/laymen perspective, for whatever it's worth...

btw, they make aquarium controllers,

check out

www.neptunesys.com

[Tellie]

Originally Posted by goboatingnow

Btw fellas , I have an issue how to introduce the pickling solution into the circuit. I had intended to feed it rather like the flushing water into the low pressure feed pump. But I read elsewhere that deposits build up in the HP pump. Some recommend introducing into the high pressure circuit hence only pickling the membrane. But I'd prefer not to have a diverter valve in the high pressure line. I also have to ruin up a return circuit to allow the pickling fluid to circulate. ( or should I just let it flow put the dump line). Comments ? Tellie your wisdom?

Ps I reckon the steelers have the SB !

Dave

I don't particularly care for any of the powdered pickling solutions. They all work but are a bit acidic. If deposits on the HP pump where a problem I would assume the same deposits would be even more of a clogging issue on the membrane. Of course remember with any solution the system has to be run without pressure both when pickling and when flushing the storage solutions. I prefer Propylene Glycol -100 for storing a watermaker system. PG -100 protects the membrane twice as long as the powdered solutions, is much more gentle on the membrane and has lubricating properties that help protect the insides of the system. Also for those whose boats spend the winter in the freezing zones, which looking at the weather up north right now is very important, it does a perfect job of protecting the system from freezing which will damage watermakers.