Fuel Transfer System

Thought I would throw in another post on Iron Lady’s systems for all you boat geeky types.

Iron Lady has four main fuel tanks – one large tank forward and one large tank aft. There are also two smaller wing tanks – one port and one starboard which are primarily used to trim the boat and eliminate any port or starboard list. A tank tender in the office gives us the number of inches of fuel in each tank.

We have a laminated graph that converts inches of fuel to gallons/liters in each tank.

Iron Lady also has a day tank in the engine room which feeds all of the diesel consumers (main engine, genset and Kabola). As the name implies, the day tank holds roughly enough fuel to power the boat for 24 hours.

The day tank has a sight gauge to physically see the amount of fuel in the tank. The tank and sight gauge are visible to the right of the gray PVC pipe in the prior photo.

Each of the four tanks is plumbed to manifolds under the galley hatch – one is a supply manifold and the other is a return manifold. Unfortunately, I don’t have any pictures but each manifold has a four valves to open or close the supply and return lines to each tank and each manifold has a line which runs back to the engine room.

In the engine room, these lines connect to a second manifold which leads to two geared fuel transfer pumps and various filters to polish the fuel.

Sounds complicated when stated in words but the operation of the system is really very straight forward. The pumps move fuel around the boat. By altering the valving on the engine room and galley manifolds, fuel can be moved from any tank to any other tank. As part of the pump circuit, fuel is passed thru filters to remove any water and contamination from the fuel.

The following photo shows the manifold in the engine room, the two fuel transfer pumps (for redundancy) under the manifold and the two primary fuel filters below the right hand pump.

This is a closer shot of the pumps and the manifold.

Polishing is the term for moving the fuel thru the filters to clean it. All fuel that is being moved by the pumps passes thru the primary filters and a debug unit to remove water, contaminants and microbial life that likes to live in the fuel.

Typical polishing scenarios (usually done when the boat is at rest) are to take fuel from one of the five tanks, pump it thru the filters and debug unit and then return it to the tank it came from. We usually do this to all the fuel in all the tanks at the beginning of a cruising season and at any other time that we suspect contamination might be an issue (which it hasn’t been).

The system is also used to transfer fuel between tanks – again by setting the valving in the galley and engine room manifolds. The most usual fuel transfer is to replenish the day tank, but more about that in a minute. Another reason to transfer fuel between tanks is to balance the boat (fore and aft and list). To offset list, fuel can be transferred in to one of the wing tanks to add weight to one side of the boat or the other to counter list. Moving fuel between the aft and forward fuel tank alters fore/aft trim and improves performance in various sea states.

At the end of a cruising season, we also like to transfer all of our remaining fuel to one tank and that is the tank we burn first in the next season so we are using our oldest fuel first. This also permits us to isolate a new fuel load to one empty tank so if there is a problem with it, it is isolated from the other tanks and prevents cross contamination.

Getting back to the most common set up, valving is normally set to draw from one of the main fuel tanks and deliver the fuel to the day tank. To keep the boat balanced, we will normally shift which tank is being drawn from (fore or aft main fuel tanks) every few days. We also occasionally change which pump is the working pump just so they both get exercised.

There are several modes in which the pumps operate – an automatic mode to replenish the day tank and a manual mode when polishing and transferring fuel. The control box that determines which mode the pumps operate in as well as emergency overrides is located in the engine room near the day tank.

In the automatic mode, there are sensors in the day tank which control operation – a low level warning, 25% full which triggers the pump to refill the day tank, 50% full which shuts off the pump, 90% full which also shuts down the pump and a high level warning.

There are several ways in which we keep track of things at the helm station. The first are LED’s on the bilge pump panel which indicate the current level in the day tank (excuse the dust).

This panel also has a button to initiate fuel transfer at any time. When this button is pushed, the tank is automatically brought up to 90% full. This is a particularly nice feature when we take the dink off the boat as the boat lists to starboard. Running the tank up to 90% full offsets some of this as the day tank is on the same side of the boat as the dink.

Day tank levels and alerts for low or high day tank level as well as notification that a fuel pump is running are also displayed on the Maretron system at the helm and flybridge. We will be expanding the capability of the Maretron system but more about that in another post. We will be able to monitor Iron Lady’s systems from anywhere in the world over the internet – very cool.

Once in the day tank, fuel flows via gravity thru more sets of filters to the diesel consumers insuring that they are always getting ultra clean fuel. The left hand filter is for the genset and Kabola and the next two filter are for the main engine. There are additional filters on the engine, genset and Kabola. If you think we are anal about clean fuel, you’re right.

Finally, as part of the boat’s fire suppression safety systems, there is a remote fuel shut off outside the engine room that shuts off fuel flow to all the diesel consumers.

That about covers the fuel system – I will try to remember to put a picture of the galley manifold in a future post.