Feedwater Level indicators

[Mfoxchicago]

Hey guys, working on the TULE PRINCESS here. My feedwater tanks are having level indicator problems. I have determined there is a Marcra Liquid Level Probe installed in the tank that is connected to a level gauge via a small flexible pneumatic tube that is apparently pressurized by a small brass hand pump that makes the gauge indicate a level. The hand pump works, the pneumatic tubing needs replacing, AND, the probe is very old and probably needs replacing.

Does anyone have experience with these pneumatic liquid level probes? Does anyone still manufacture them? The previous Captain's log entries indicate the original company is out of business.

Second, how do you other captains monitor their feedwater tanks; other than the standard "dip stick". I had hoped to have a bit more modern method than a stick.

Anxious to hear how you other guys do it.

As always, I appreciate your advice and help!

[fredrosse]

No problem! More info later..........

"Second, how do you other captains monitor their feedwater tanks; other than the standard "dip stick". I had hoped to have a bit more modern method than a stick."

Well, to start with, most of us don't have a boat that is even close to 10% of your displacement! So we can easily check everything without having to take a long walk to the bowels of the ship to do tank soundings.

[dhic001]

Can the tanks be fitted with sight glasses? If not, and in the bowels of the ship, there are plenty of modern electric alternatives that would do the job, although the cost may be greater. Modern boat tank indicators, when set up properly, can be great, you can monitor multiple tanks with one remote indicator.
Daniel

[Mfoxchicago]

Sight glasses would be impractical, too low. These two tanks are saddle tanks integrated into the hull. Yeh, I had taught a more modern electronic/RV style sensor would be good for this job so I could monitor either tank at a glance.

Do you have any recommendations of a specific model?

[DetroiTug]

This would work, just a standard fuel gauge and sending unit.

http://www.westmarine.com/buy/teleflex- ... P000385684

-Ron

[Oilking]

It appears that what you have is the same as a well level air line system, just that the distand from the gage to the top of the water is much shorter.
http://pubs.usgs.gov/tm/1a1/pdf/GWPD13.pdf This page tells it clearly. In your area I would think it wouldn't be hard to find some well people that coud help you out.

King-Gagehttp://www.king-gage.com/ is an icon in air tank gauging, "King Gage" gets used Like "Skill Saw" when it comes to air tank gages.

Good luck

Dave

[gondolier88]

Modify 3 12v bilge pump float switches mount it at full level, half full and 3/4 empty level in your tank. However, instead of actuating a pump they switch an LED on in the engine room, three LED's, when they all light up it's full, as they go out as the gloat switches stop floating you can follow the level.

Either that or a broom handle through the filler cap....

Greg

[Lopez Mike]

If your feedwater isn't too pure you could use the holding tank gauges from an RV supply place. Is this makeup water or the hot well? They are not continuous reading, i.e. they usually have several LED's for empty, 1/4, 1/2, etc. and the fluid must be reasonably electrically conductive. No problem with sewage or gray water.

The air pressure ones you have now are advertised in the yacht supply magazines but the price is steep and the ones I've seen require you to push on a little pushbutton pump each time you want a reading. Kinda bogus.

In industrial settings they run off of compressed air. We call them bubbler systems. Completely maintenance free which in a many thousand gallon sewage tank is a GOOD thing!

[fredrosse]

This level indication requires no electricity, and has been used for well over 100 years for remote tank level indication. The attached diagram is applicable to an atmospheric vented tank, and a similar arrangement can also be used for a pressurized tank, more on that later.

The pump is a small air pump, a bicycle pump is OK, or the very low volume discharge from any air pressure source at a few PSI. When to pump puts air into the system, a pressure buildup is needed to overcome the static water pressure at the discharge of the tubing inside the tank. This pressure is proportional to the level in the tank, and can be indicated by a manometer or pressure gauge at the instrument panel.

For example, say the tank level is 27 inches of water above the open end of the sensing tube inside the tank. A stroke of the air pump forces air thru the open end inside the tank, and creates an air pressure throughout all of the tubing corresponding to 27 inches water column. If the manometer is filled with water, then the differential shown on the manometer will be the same, 27 inches, and this is the indicated tank water level. If the manometer is filled with Mercury (specific gravity 13.6), then the manometer will register 27/13.6 = 2 inches of Mercury. A scale on the manometer can be made appropriate to the fluid used in the manometer. A dedicated pressure gauge might also be used as long as its pressure range is appropriate to the pressures involved, with a dedicated face scale as required.

[Mfoxchicago]

As always, you guys are amazing! Such wealth of knowledge shared here. I have spent two full days running around town asking anyone in town that I thought had experience with water tanks or water well systems and would have heard of this device - non of them did. It was suggested that I wait till one of the more experienced RV guys gets back from vacation to see if something in the RV industry would work. After these postings, I will probably rehab the existing system, at least with new tubing. The old tubing cracked, plus it seems really small. All the old brochures said to use 1/8" tubing, plus the gauge & air pump both have 1/8" nipples. There seems to have been 1/16" tubing used. The probe has a VERY small nipple, but the air pump and the gauge both had the 1/16" tubing "jammed" on the 1/8" nipples. I'd like to see if I can find a fitting with the 1/8" nipple to install on the probe - get it all standardized.

As regards the standard "universal" Sending Unit from Westmarine. I already installed a similar universal unit purchased at NAPA Auto Parts on my fuel oil tank, which wasn't working either - once connected, worked correctly straight away (love it when that happens). The Auto Parts dealer made some calls and I was advised a fuel system sending unit would NOT work in a water oriented tank application.

Thanks again guys for all the input, data, links and drawings to help me work things out. I am very grateful!!!

Hope to welcome all of you aboard sometime and have you look her over.

Thanks again!