Tank gauges

Hi everyone!

what is the best way to measure tank levels? fuel, waste and fresh water tanks on yachts of size 15 - 50 meters. sailing or motor
I have tried ultrasonic sensors, float gauges, pressure sensors on 30 different projects and not satisfied yet.
I will like to know anykind of idea about a reliable gauge system.

thanks,

kk

 

What do you need the reading for, real time manual/automatic control or once a watch logging? For absolute simplicity and relaibility not much will beat a sounding tape/dipstick or sight glass.

 

The only gauges I have ever trusted are sight gauges on the tank. Once properly calibrated they are pretty close to perfect. Other than these however I haven't found one that works reliably.

 

Any gauge system in conjunction with sight glass so you keep an eye on gauge accuracy.

 

All road vehicles on this planet, from cheap city cars to Ferrari's, use float sensors in their fuel tanks. For water tanks in RV's some builders use optical level detectors at 1/4. 1/2 and 3/4 levels because the automotive float sensors are open and corrode quickly in a water tank.

It seems nobody saw there is a market for a float sensor with a sealed shaft and a plastic or stainless housing. Such a device can easily be constructed using an industrial "cermet" or wire-wound potentiometer having a stainless shaft, neoprene seal and potted gold plated terminals.

 

I have perfectly reliable float sensors for fuel and water and perfectly reliable pressure sensors for waste. If I have the time today Ill look thru my literature and forward the manufactures name. These sensors are now 17 years old....never a problem.

 

The really cheap one arm bandits are rusting crap, but there are some that the float goes up SS shaft that work good.

 

a simple float gage could be made using a piece of ss wire with a float on one end and a small knob on the other moving up and down in front of a scale

or a redone home heating tank gauge could be used

or it could be used to activate a standard float gage on the outside for remote reading

 

As mydauphin said the resistor type with a float on an arm are very unrelaible, but they are cheap so builders install them. There are much better ones that have a float that has a tube down the center and use induction or capacitance to sense the position of the liquid. These are less prone to bouncing and the electronics are solid state so there is nothing to wear out. http://www.wemausa.com/

There are also sensors that are attached to the outside of a tank that sense the level of the fluid.

Sight glasses are fine but cannot be used for any volatile liquid like gasoline. Large vessels still use sounding tubes. This is a long tube that goes to the bottom of the tank. You drop a tape with a weight on the end down the tube. Before doing that you put chalk on the tape and it shows where the fluid level is. You then compare this to a pre made table that shows the amount of gallons in the tank. This is by far the most accurate. In fact my first job in the marine industry was measuring sounding tubes and preparing the tables for sounding the tanks on ships.

 

Ike,

I'll second the Wema brand as being exceptionally reliable. The coil resistor types (like VDO) RUST and are simply hopeless (but cheap, as was said earlier).

Stick with the Wema if you want reliability, and they are not expensive either.

 

Yes indeed...I have those sensors...fuel and water...100 percent reliable. Black and grey tank sensors are pressure. A simple PCV tube is vertically inserted into the tank, calibrated and the pressure in the tube equals volume in tank. Very reliable..prone to clogging but very simple to extract, clean, recalibrate.

 

thanks to everyone,

what I am after is to have reliable readouts; realtime during a cruise and before departing for a cruise. ups and downs due to rolling and/or pitching of the yacht are not big issues.
pressure sensors: on waste water tanks residue and grease (coming from galley) is my biggest problem. however I also agree that they are relaible for diesel or fresh water tanks once they are well calibrated and not positioned close to suction or filling ports.
sigth gauges; 100% the best but does anyone know a class (RINA, BV, LR, etc.) approved sight gauge manufacturer for diesel tanks?
wema; if it is reliable it can be a good choice for fuel or fresh water, as there will not be any residue but I hesitate if they will work properly if they will not be taken out of the tank and cleaned properly. 3 months are very easy to pass by during a busy charter season on a 30-40 m yacht.
and last Dear Michael Pierzga,
could you please explain a bit more using a pressure sensors together with a PVC tube? I am not sure if I understand it right.

thanks again

 

The PVC tube is perhaps 50mm,, open at the bottom..air pressure sensor at the top and outside of the tank. . The pressure builds up INSIDE the PVC tube as the fluid rises. You are not sensing the pressure of the whole tank...only the pressure inside the tube, then you calibrate your gauge. The advantage of the PVC tube is that you dont get so much grease on the inside of the tube. Perhaps somewhere I have an actually picture , description of the PVC tube assembly and sensor . The whole assembly inserts into the top of the Black and Grey tanks. The installation is about 15 years old and Its so reliable that its been years since I had to consult the manual for repair instructions. ...I look around my ships manuals and post if I do.

 

Merhaba,

Wema does black water sensors too. You will find them in Tuzla tersane area.

Dont´listen to michaels drivel.

Regards
Richard

 

Michaels' drivel isn't far off. I worked in a shipyard in the 70's on Destroyers and LPDs. part of my job was calibrating all the tank level indicators. They all worked on a similar principle to what michael is describing. The had an upside down chamber or "bell" at the bottom of the tank, usually about 6 - 8 inches in diameter and about 4 to 6 inches deep. Inside was a diapraghm. Connected were two tubes One inside the other, called capillary tubes,filled with a fluid. The tubes went to a guage topside that looked a lot like a barometer. The bell sensed the pressure at the bottom of the tank and the guages were calibrated (by me) by measuring their position (depth) in the tank. All you need to know was the head of fluid. They were extremely accurate.

But these were tanks holding from 1000 gals to 10s of thousands of gallons. One was 150,000 gallons.

Anyway they have much more accurate sensors now for ship use that use elctronics, radar, and other systems to measure tank level.

Do a search on ship tank level gauges, or tank level indicators.