Fuel and Water tank senders
Most modern tanks on boats will have some form of sender to transmit the amount of fluid left in the fuel or water tanks to a dial or digital display. If these are not reliable it can lead to many problems including being caught out without fuel miles from safety. Older vessels rely on visual displays or a simple dipstick to measure the amount of liquid left in the tanks, but these methods can prove unreliable if the boat is moving.
"Privateer" had a faulty marine fuel gauge which was not reliable
Faulty Marine Fuel Gauges
A 52ft Privateer Trawler based at Mylor had been experiencing problems with the senders in the 8 tanks on board with false, unreliable readings.
The 6 fuel tanks and 2 water tanks were factory fitted with ultrasonic senders to give readings of the amount of fuel/water in the tanks. These senders were erratic, giving false readings that could not be trusted. This was making the owner very uneasy about taking the boat on long passages.
After reprogramming and replacing some of the senders, the problems disappeared, but only temporarily, this was followed by many lengthy discussions with various ultrasonic sender manufacturers. It was concluded that their units were not suitable for the tanks on this particular vessel, the tanks being of irregular shapes and have a total capacity of up to 1800L of diesel.
Standard float type senders were not suitable as there was little clearance above the tanks, so research and discussions continued for some time with various manufacturers before finding the solution.
A small (15mm) attachment to the outside of the tank allows the tube to enter the tank and holds it in place
The gauge can fit discretely inside a cupboard for easy access. This one was fitted onto a piece of wood made by our shipwrights
"Hart" Tank Tender System
Used in medical and dental applications, the “Tank tender system” measures the pressure in a tank and converts this to cubic millimetres of liquid.
“Tank Tender operates on air pressure. Select the tank, then pump a small amount of air through tubing to the bottom of the tank. When the air pressure in the tube equals the liquid pressure at the bottom of the tank, the gauge displays this pressure in inches (mm³ in UK) of liquid.” (http://www.improducts.co.uk/products/tank_gauges/)
One unit can read up to ten tanks, so as an experiment, the customer decided to install the system into four of the fuel tanks in the engine room. The tubes entered the tank at the top but they can also be installed on the side so different tanks can be easily accessed. The tube was fed into the tank and given 25mm clearance of the bottom of the tank to allow for sediment.
The gauges have proved to be very accurate and maintenance free if installed and calibrated by a professional, ensuring the tubes are not kinked in any way and also the measurements and mathematics involved in the calibration is done precisely. If a tube does become damaged in any way the gauge will simply not read the pressure.
The gauge itself was set into a box made up by our shipwrights and hidden in a cupboard with easy access for viewing.
Tank Tender System in Practice
Marine Trak electricians fit and repair many types of tank senders for various vessels but have concluded that the Hart Tank Tender System is by far the most user friendly and accurate tank monitoring system available. It is simple to install and use.
We would advise having the system installed by a professional as there is a lot of precise measuring required to accurately calibrate the tank tender system, especially if the tanks are not completely empty or of a regular shape.
Now that the gauges are all reading accurately the customer is more confident in the range of the vessel and happy to take her on longer cruises knowing exactly how much fuel there is left in the tanks.
“The Tank Tender System works brilliantly. I would fully endorse this system to anybody having tank monitoring systems.” Mr A Jenkins, Owner of "Privateer"
