Precision Fuel Solutions
Many tanks have Access Plates to clean and inspect the interior. Sometimes there is good enough access to clean, inspect, and maybe even repair a tank. Most of the time there isn't.
There is no set layout for valves in a fuel system. For various reasons a valve might be almost anywhere in the system.
A couple things most would not include in the fuel system are the Bilge Pumps and the Bilge. Hopefully they will never become active components!
On-shore tanks almost always have a shell around them known as the Secondary Containment. If the inner shell leaks the outer shell will keep the fuel contained. On a boat the hull is actually the Secondary Containment. If fuel leaks from the tank or plumbing the Bilge becomes an active part of the fuel system.
What nobody ever wants to see happen is for a Bilge Pump and Overboard Discharge to become an active part of the fuel system!
Sometimes it does happen though...........
This is an example of a very basicmarine diesel fuel system. Most systems will have more components in the mix and a few might have less. These are most of the important ones for a basic understanding.
(Yes, I know the bilge would probably be under the engine. However, it is so important to be aware of that it needed to be shown.)
Let's start at the beginning.
The Fuel Pickup is where the suction side starts. It may be as pictured, a fitting near the lowest point of the tank, or it may be a "pickup tube" extending down through the top of the tank. A "pickup tube" will usually come within an inch or two of the bottom of the tank near the lowest point of the tank.
The Primary Filter/Separator is usually the first line of defense against water and other contaminants in the fuel. It usually has a canister type filter element. It may be not bein the same place in each system, or there may be multiple units, but it will always be on the suction/supply side of the system.
The Fuel Supply Manifold basically determines which tank the engine(s) draw fuel from.
The Secondary Filter is a much finer filter and is usually a "spin-on."
The Fuel Pump, for our purposes, just moves the fuel to and from the engine. It pulls from the suction side and sends excess fuel back to the tank. We are mainly just concerned about the pump getting a adequate supply of clean, dry, air-free, fuel. Other than the return plumbing, what it does with the fuel then is a job for a pump/injector specialist or a very good mechanic.
The Return Manifold controls which tank the fuel not burned by the engine returns to.
One bit of plumbing not pictured is a Crossover. That is a hose or pipe connecting two or more tanks that will allow fuel to transfer between them.
There are many more components that may be in a fuel system besides those shown. There will probably be more fuel lines, filters, and pumps going to generators and heaters. There may be all kinds of filters, sensors, valves, and other plumbing not shown here.
Every fuel system is different.
A Word About Biocide
Biocide is something that should be added to every diesel tank nowadays. Once in a long while, when I was a commercial fisherman, I would hear something about someone or another that got "algae" in their fuel tank and it clogged up their fuel system. I never heard of biocide; nobody seemed to need it! Considering that most of the people I was around all had fishing boats, heavy equipment, or farm equipment that ran on diesel , it was very uncommon. Today, with fuel that is ultra-low sulfur (sulfur kills bacteria) and more unstable (easier to digest), and the probability of genetically enhanced bacteria not stopping at cleaning up oil spills, it is almost a certainty.
Today there are three types of diesel tanks: tanks that have always used biocide consistently, tanks that have just started using biocide recently, and tanks that have never used biocide.
The last two types will probably be a mess inside. Whether there is active biological growth or not anymore, the mess created before biocide will still be there.Biocide just kills it, it doesn't help clean up the sludge already in the tank. If the growth in the tank is the variety that actually grows up the side of tank biocide will make it lose its grip, adding to the sludge!
The first step to a fuel supply you can count on is to find out what’s in your tank. The best time to do this is before you notice a problem.
If biocide is a new word to you, or if you’re just not sure about the tanks history, it might be time to find out. Examining fuel samples from the lowest points in the tank will usually tell the story.