Plan "B"

Our original plan, Plan "A", was to assemble the parts we needed to build an RO water maker of our own design.  Last year Providence guided us to a complete RO system that had been removed from a boat being prepped for an Atlantic crossing.  Rebuilding this used system and modifying it for our situation is Plan "B".

Now, a year later, we're living ashore part time and I finally have some real time to invest in this project.  Good thing too because we'll definitely need it when we go to the Bahamas this winter.  Time to get back to work.  The system is 11 years old so parts of it need to be replaced but everything was supposedly in working condition three years ago.  The Sea Recovery (click here) dealer in Annapolis came through with an owners/installation manual and a rebuild kit for the high pressure pump.  I'm not planning to use the original feed pump because it draws too much power and will require periodic service.  Instead I'll use the Iwaki fish tank pump I had purchased for my home grown system.  The original membranes and housings were in bad shape so I tossed them after stripping off all the fittings and hardware.  Replacing these is now the biggest expense for this system.  I decided to increase the fresh water output from 24 to 40 gph by using two 2.5" x 40" membranes (FilmTec SW30-2540, $170 each) and housings (HCTI PV-2540-SW, $395 each).  Most of the fittings on the old membranes were brass and I wanted to use stainless steel so I had to replace those too along with a new high pressure hose to join the two membranes in series.  I got all these parts from Discount Hydraulic Hose (click here) and McMaster Carr (click here).  The stainless fittings are pricey but I got everything I needed for about $200.  The 1/2" high pressure hoses I got with the original system are all in very good condition and have stainless swivel connecters.  All the low pressure tubing and plastic fittings for the product water are also in very good condition.  The braided 3/4" hose for the feedwater is looking kinda sad so I'll replace that but reuse the fittings and clamps.  There are several relays that I'll reuse if they still work but I'll probably back them up with replacements just in case.  The system also included several nice two and three-way valves that I'll clean up and reuse.

I've had the new membranes and housings since last February.  These don't come with any assembly instructions so I spent some time on the net hunting for info.  Found this paper from FilmTec (click here) which was a help.  The end pieces for the membranes are anodized aluminum with three "O" rings at each end, two on the outside surface and one where the membrane nipple gets inserted.  The end that goes toward the high pressure pump also has a brine seal on the membrane.  The "O" rings need to be lubricated with silicone or glycerine or you'll never get them into the housings.  The membranes come packed in a sealed bag with hydrogenated water or some such thing to keep them moist and well preserved.  Rinse out the housings (not the membranes) to clear any dust and particulate matter.  Mount one end piece on the intake side of the membrane and slide it into the housing from either end.  The end piece has to be tapped into place with a rubber mallet so only the flange extends past the end of the housing.  Two anodized aluminum half shells clamp over the end of the housing and hold the membrane firmly in place.  The other end piece is installed from the other end, tapping it in place and securing with the half shell clamps.

With the membrane housings put together I next assembled the fittings and connector hose.  The fittings I got are reusable and fairly easy to assemble.  They come in two pieces.  Installation requires a vise and wrench.  Separate the two pieces of the fitting and secure the socket end into the vise.  Lubricate the hose and screw it into the socket conterclockwise until it bottoms out, then back out a 1/2 turn.  Next lubricate the nipple part of the fitting and screw it into the other end of the socket using a wrench until the hex shoulder is against the socket.

I'm mounting everything to a short length of 1/2" plywood to hold it all in place as a sub-assembly.  The housings are held in place with some vibration damping clamps modified to work in this setting.  I got these from McMaster Carr (click here) but they're meant to be welded in place so the base needs to be modified so they can be screwed down to the plywood.  I'm cutting recesses into the back of the board for nuts and washers and running all-thread up through the clamps from underneath.  The bottom of the clamp is held firmly to the board and the top section slips over the all-thread and gets snugged down with nuts and lock washers.  To fit the 2 1/2" high pressure housings I had to get the clamps sized for 2 7/8" pipe.

I next took on the valves and fittings.  For the most part they were in good condition and only needed cleaning and resealing the connections.  I used teflon threading tape on all the NPT fittings, wrapped three times and kept below the first thread to prevent pieces getting into the RO system.  I disassembled the valves and cleaned and re-lubed them where necessary with silicone.

After I got the valves and fittings cleaned up I took on the control panel.  The owners manual has good block diagrams and schematics showing all the wiring connections and using these I was able to identify all the external wiring.  I labeled everything with blue painters tape and a sharpy marker for easy identification later on.  I also traced out all the wiring inside the control box just to familiarize myself with how this thing was put together.  By spending the time and going through it all I became familiar with all the system components and how they should be connected.  Even pulled the fuse and verified it was good using my multi-meter.  Once I had it all figured out and everything cleaned up I made a temporary power cable to connect the control panel  to a wall outlet.  Pressing the start button gave me a lit up panel display and I was able to use my meter and check various voltages in the system.  Looks like everything is in good working order.

As I went through the wiring I discovered I had an even better system than I originally thought.  It has a TDS (total dissolved solids) probe that displays the level using a bank of LED's on the control panel.  This level is monitored automatically and if it goes above a set point will open a solenoid operated diversion valve that will redirect the product water over the side instead of contaminating the fresh water in our tank.  This is nice but the TDS display is kinda old school.  Last year I had bought a nice TDS controller for my home made system that has a digital display, audible alarm and can control two valves or pumps or whatever using an adjustable set point.  I'll be running both units here to give me multiple controls and readouts.  Sweet!

The control panel has a section that contains low and high pressure gauges, flow meters and the pressure regulator.  I completely disassembled this and cleaned it up.  Many of the fittings used in the original system were brass and showed serious corrosion so I replaced these with stainless steel parts.  The two flow meters and both gauges were damaged so these were also replaced.  The aluminum mounting panel for all this stuff is anodized black but salt water had collected in some areas and caused some serious corrosion and pitting.  With the panel stripped of all hardware I took it outside and scrubbed it down with soap and water.

For now, it feels good to be back into this project.  I plan to break it down into sub-assemblies mounted to plywood so when the time comes for installation on the boat it should go fairly smoothly.  Originally I was going to mount everything in the chain locker and under the sole in the forward cabin.  Plan B now has the membranes, filters and control panel mounted in the aft head and the pumps mounted behind the cabinets in the Main Salon.

More info to follow as progress is made.