Advice on multiple fuel tanks sensors

[sndog]

I am looking for the fuel tank sensors for my three fuel tanks (diesel).

1st fuel tank, day tank, is easy. It is a normal rectangle and holds around 250~300 gallons

2nd fuel tank, center tank, is shaped liked the L Tetris block. This tank holds 1000~1500 gallons.

3rd fuel tank, bilge tank, is an odd fuel tank as the hull is the bottom layer of the fuel tank. It is ~14' wide at the top and ~18' long. Due to the hull being, well, a hull, it is an odd shape tank. It is ~2000 gallons.

I have been looking at the maretron tlm100, but was wondering if there are any other solutions for this out there.

 

[fgarriso]

Do you carry 3800 gals of fuel?

 

[Comodave]

I assume the in hull tank is fiberglass, but what are the other tanks made out of?

 

[sndog]

I assume the in hull tank is fiberglass, but what are the other tanks made out of?

All fuel tanks are steel. Hull is 3/8" thick, so that would be the thickness of the bottom of the L shaped and the bilge tank.

Sides and top are 3/16"

 

[sndog]

Do you carry 3800 gals of fuel?

I have a very long trip ahead when it is launched after refit, so yes, I will have that fuel onboard. After the trip, the bilge tank will be emptied, and more than likely the center tank will only be filled occasionally.

 

[ranger58sb]

I am looking for the fuel tank sensors for my three fuel tanks (diesel).

1st fuel tank, day tank, is easy. It is a normal rectangle and holds around 250~300 gallons

2nd fuel tank, center tank, is shaped liked the L Tetris block. This tank holds 1000~1500 gallons.

3rd fuel tank, bilge tank, is an odd fuel tank as the hull is the bottom layer of the fuel tank. It is ~14' wide at the top and ~18' long. Due to the hull being, well, a hull, it is an odd shape tank. It is ~2000 gallons.

I have been looking at the maretron tlm100, but was wondering if there are any other solutions for this out there.

CruzPro makes a tank level gauge that will "learn" fill levels of odd-shaped tanks. Compatible with several senders; you just select resistance range on the gauge set-up menu.

The "learning" process is a bit tedious, but easy enough.

They also have a less complicated gauge for rectangular (cubic) tanks.

-Chris

 

[Pete Meisinger]

Thats a lot of fuel.

Since gauges are so difficult and unreliable I think I would just keep a milage log and calculate from that.

pete

 

[Portage_Bay]

Comodave asks the material of the tanks. Choose a system that makes it easy to install the sensors given the tank material. Also consider the access to where the sensors will go.

Another consideration is what instrumentation do you already have? If you have Maretron systems installed already that makes your choice very simple. You're just adding 3 pressure sensors assuming you have reasonable access to install the sensors.

At the other end of the technical spectrum is the Tank Tender by Hart Systems A very accurate pneumatic system requiring no electrics or electronics. Installation is easy if you have good access to the top of the tanks over the deepest part of the tank. One disadvantage is it is not a real time reading. As much fuel as you carry I don't think that is a major consideration. If you go with Tank Tender buy direct from Hart Systems. The support is outstanding during purchase and setup.

Either Maretron or Tank Tender are measuring pressure which needs to be converted to volume. Tank #1 is a cube you will be able to get very close just by measuring the exterior and estimating the wall thickness. Tank #2 not much harder if the sides are vertical and top and bottom are flat, If the L is horizontal it's a simple gallons per unit pressure calibration. If the L is vertical treat it as two cubes. For those two your initial estimates will be very close and can be fine tuned on subsequent fill ups. Tank #3 will be the challenge, it will be the one that requires incremental fill and read the gauges to get beyond a rough estimate.

The rough estimate for #3 could be pretty darned good. Here's how I'd go about it if the Tank Tender system is used which measures inches of fuel. I don't know the unit Maretron reads out in but the process will be similar.

1. Calculate the area of the aft end of the tank.
2. Calculate the area of the aft end at 1" increments.
3. Calculate the percentage of the area in step #1
4. Multiply each 1" percentage by 2000 gallons
5. Verify by incremental filling, adjust as needed.

 

[sunchaser]

Questions:
- Do you have believable calibrated sight tubes on any of the tanks?
- Are you able to dip the tanks to assess fuel level?
- Can you transfer via a positive displacement pump from tank to tank?

I'd not trust any electronic sender unless it has been calibrated to actual fuel fill by shore fill pump numbers. Even then a known gallonage visual tank level is best. If you could calibrate your non integral tanks by actual pump numbers and marked sight tubes, it should be easy to fill and calibrate the integral tank from the calibrated side tanks as they are drawn down.

Once you know the gallonage of your calibrated tanks via sight tubes and marked levels, there are many options for monitoring fuel transfer and GPH consumed. A stopwatch and knowing the run time of the positive displacement pump should allow you to quite accurately establish the pumped volume/gallonage to and from the integral tank.

 

[DennisB1]

I have the hart system on my boat. The hart system measures the depth of the fuel. To use it effectively you need to create a volume (gallons) to depth curve. The rectangular tank is easy. The second tank could be calculated easily if you have the dimensions. The third tank requires calibration by measuring the depth with hart gauge and the measured volume of fuel added. You need a number of stopping points to obtain a good curve as the tank is not linear. With the cal curves the system works quite well. I have it on two fuel tanks 500 gal; 3 water tanks and 2 holding tanks. There is a small manual air pump that you use to obtain the fuel/water depth. The gauge has two scales one for water and one for fuel. With the depth in inches you look at your cal curve to obtain the fuel or water quanity.

 

[sunchaser]

Visit the ER of a Nordhavn to see how large fuel tanks are monitored. Given all the TF threads about instrument electrical problems A-Z, for long passages a fool proof fuel tank visual system like a Nordhavn is hard to beat. That doesn't mean a Maretron system for tank level measurement can't be done. Redundancy is good.

 

[sndog]

Great advice so far.

The only tank that has a sight gauge is the day tank, and the calibration is a fancy yard stick....

I think adding sight gauges to the two is not a bad idea at all.

Electronics are being installed next month. It is going to a timezero professional sw/computer setup, with 2 19" displays in the helm, and 2 19" displays in the flybridge.

There is also another system that will run maretron software, along with a video wall scaler, so I can get 2 19" monitors in each location out of that, while not violating the software license of a single monitor out. There is also 9" Raymarine Chartplotter as a backup, as well as to monitor the Flir engine cameras.

 

[ranger58sb]

I'd not trust any electronic sender unless it has been calibrated to actual fuel fill by shore fill pump numbers.

FWIW, that's what's involved with the CruzPro setup routine, for that "smart" (my word) gauge the offer.

-Chris

 

[sndog]

Also, the tanks are all connected via a fuel pump system that is used to pump fuel into the day tank.

 

[bkcorwin]

I carry 2600 gallons of fuel, in four tanks plus a day tank. I had a system with KUS float sensors and a simarine system. It worked poorly so I am transitioning to maretron.

I asked this question on the nordhavn owners group and the general consensus was to not use the TLM100s and to instead either use pressure transducers mounted in tank fittings or their submersible pressure sensors that drop in through a standard 5 hole fuel tank fitting.

I also added a flow meter to the transfer pump so I can calibrate my tank level senders using the fuel transfer system and not have to sit at the fuel dock filling up the boat slowly and getting in other people's way.

 

[SteveK]

would a fuel flow system be a fit for this. something that could be set to all full tanks gallons and as used report gallons left. Of course return fuel measured, and perhaps one for each tank.
The other one mentioned that learns sounds interesting.

 

[Martin J]

Here are a few pics etc from a previous thread https://www.trawlerforum.com/forums/s31/stainless-water-tanks-sensors-44189.html

Showing my digital gauges which are coupled to wema / kus senders. I also measured the tanks every inch of depth and calc'd the fuel and matched it to the % gauges. I still have my tank dipping rods etc . Found the gauges to be amazingly accurate. I just look up the % fuel and check against the tank fuel graph i have drawn up. Any errors would show on passage when we record our fuel consumption log, and match it against the time/ distance/ consumption etc.

 

[sndog]

would a fuel flow system be a fit for this. something that could be set to all full tanks gallons and as used report gallons left. Of course return fuel measured, and perhaps one for each tank.
The other one mentioned that learns sounds interesting.

I purchased Chetco's engineering system for converting engines to N2K, plus fuel flow to the main engines. Generators will not have it though.

 

[sndog]

Here are a few pics etc from a previous thread https://www.trawlerforum.com/forums/s31/stainless-water-tanks-sensors-44189.html

Showing my digital gauges which are coupled to wema / kus senders. I also measured the tanks every inch of depth and calc'd the fuel and matched it to the % gauges. I still have my tank dipping rods etc . Found the gauges to be amazingly accurate. I just look up the % fuel and check against the tank fuel graph i have drawn up. Any errors would show on passage when we record our fuel consumption log, and match it against the time/ distance/ consumption etc.

Very interesting. Thank you

 

[RickyD]

Comodave asks the material of the tanks. Choose a system that makes it easy to install the sensors given the tank material. Also consider the access to where the sensors will go.

Another consideration is what instrumentation do you already have? If you have Maretron systems installed already that makes your choice very simple. You're just adding 3 pressure sensors assuming you have reasonable access to install the sensors.

At the other end of the technical spectrum is the Tank Tender by Hart Systems A very accurate pneumatic system requiring no electrics or electronics. Installation is easy if you have good access to the top of the tanks over the deepest part of the tank. One disadvantage is it is not a real time reading. As much fuel as you carry I don't think that is a major consideration. If you go with Tank Tender buy direct from Hart Systems. The support is outstanding during purchase and setup.

Either Maretron or Tank Tender are measuring pressure which needs to be converted to volume. Tank #1 is a cube you will be able to get very close just by measuring the exterior and estimating the wall thickness. Tank #2 not much harder if the sides are vertical and top and bottom are flat, If the L is horizontal it's a simple gallons per unit pressure calibration. If the L is vertical treat it as two cubes. For those two your initial estimates will be very close and can be fine tuned on subsequent fill ups. Tank #3 will be the challenge, it will be the one that requires incremental fill and read the gauges to get beyond a rough estimate.

The rough estimate for #3 could be pretty darned good. Here's how I'd go about it if the Tank Tender system is used which measures inches of fuel. I don't know the unit Maretron reads out in but the process will be similar.

1. Calculate the area of the aft end of the tank.
2. Calculate the area of the aft end at 1" increments.
3. Calculate the percentage of the area in step #1
4. Multiply each 1" percentage by 2000 gallons
5. Verify by incremental filling, adjust as needed.

I had Tank Tender on my last boat. Loved it. Accurately monitored four fuel tanks, one water tank and a black water tank. I did need to clean the air line in the black water tank once.