The operation of a fuel polisher system is typically connected directly to the diesel tank using two separate lines. The inlet line draws fuel into the polisher with a pump, positioned at the lowest point possible inside the tank. This is because foam and contaminants tend to settle at the bottom, where the hose can easily extract them.
The fuel is pumped into the polisher and then returned to the tank from the highest point on the opposite side. This prevents the polished fuel from being drawn back into the polisher.
Stages of a Fuel Polisher System
The most basic operation of a fuel polisher system consists of a minimum of two cleaning devices. The first stage of fuel polisher usually involves filtration and free water separation. The second stage uses a coalescer, which removes emulsified water, essentially dissolved water vapor.
1. Free Water Separation
Free water is water that has settled inside the fuel tank. This water does not dissolve into the fuel and can be easily removed using a centrifugal water separator. Many vessels already have water separators installed, so this process is not unfamiliar to some people.
Centrifugal separators work by spinning the mixture and separating the fuel and water based on their densities. Centrifugal separators are also useful for filtering out large particles and sludge, such as some accumulations caused by diesel bugs.
2. Filtration
Fuel polisher systems typically filter the fuel at least once, usually before it enters the coalescer. These fuel filters use very fine membranes to separate all the dirt particles, debris, and other contaminants with sizes around 25 microns.
However, fuel filters and centrifugal water separators cannot remove emulsified water or dissolved contaminants from diesel fuel, which is why the coalescer is needed after the filtration.
3. Coalescer
The coalescer in a fuel polisher system is essentially an advanced filter. This device is capable of separating different chemicals based on molecular weight and can remove dissolved and emulsified water as well as other contaminants from the diesel fuel.
Some coalescers use charged plates, while others rely on purely mechanical processes. Many fuel polisher coalescers also contain fine filters to remove any remaining particles that may have passed through the first two stages.
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What is the Cost of a Fuel Polisher System?
Fuel polisher systems are relatively expensive, with the most affordable ones ranging from $1,500 to $3,500. Prices usually increase with the polisher capacity.
The basic fuel polisher systems at the entry-level price range use very basic control systems and may require manual input to start and stop them.
The more expensive fuel polisher systems typically operate autonomously and can keep your fuel tank clean for an extended period. High-tech sensors monitor the filter’s lifespan, the fuel quality in your tank, and the duration required to polish the remaining fuel.
