By Katherine Vanover
To understand phase separation, it is necessary to consider the nature of blended fuels. Blended fuels contain varying levels of ethanol, a simple alcohol often made from the distillation of corn. Alcohol is a molecule that contains carbon atoms at one end with oxygen and hydrogen at the other end. The oxygen and hydrogen atoms in alcohol are arranged in the same way that they are arranged in water. This similarity in the molecules allows the water to absorb into the fuel, a liquid they would otherwise not mix with.
The ethanol in the fuel will allow it to absorb water to an extent. This limit of water absorption is called a saturation point. Each blended fuel will have a different saturation point. E-85, which is 85% ethanol, will hold more water than E-10, being only 10% ethanol. More ethanol means a higher saturation point. Likewise, higher fuel temperature means a higher saturation point. Cold fuel holds less water than warm fuel.
When the saturation point, or water absorption threshold is breached, phase separation occurs. The fuel can no longer hold the water so it falls out of solution. To make matters worse, the ethanol is more highly attracted to the water than the fuel so the water takes the ethanol with it when it separates. The result is phase separation. Two layers form: fuel on top and water on bottom.
What are the Consequences of Phase Separation?
First and foremost, the most straightforward result is reduced-octane fuel. Part of a blended fuel’s octane rating is due to the ethanol content. The loss of the ethanol is a loss of octane. However, your tank doesn’t just contain below-spec fuel. It also contains a mixture of water and ethanol that act as a powerful solvent. The result is the degradation of lubricants and the deterioration of hoses, gaskets and seals. This layer is damaging to both ancillary tank equipment and vehicle engines. This results in a downed tank, lost productivity and lost revenue.
How Can Phase Separation Be Prevented?
The ultimate cause of phase separation is water infiltration, and the short answer is to keep water out of the tank. The long answer is that a rigorous housekeeping schedule and a vigilant monitoring of your tank and its access points are required. The following is the checklist that we give our customers.
Daily
- Check fill access for water
- Visually inspect fill cap and gasket, especially after fill access is opened or disturbed
- Visually inspect vapor recovery
Monthly
- Check monitor access for standing water
- Ensure cable and cap are correctly seated and secured
- Inspect STP lid
- Check STP sump for water
- Visually inspect STP sump interior and motor head conditions
- Check for missing or damaged vent caps
- Stick or sample tank to check for water
- Sample at point of sale—cloudy fuel is a sign of water absorption that is close to the saturation point
Biannually
- Visually inspect shear valve
- Check filters for type
- Perform flow rate test
These are the recommendations we give to our customers, and we feel these housekeeping practices are the best first line of defense against phase separation. Keeping a tank dry is paramount. Of course, the easiest route is to prevent phase separation before it happens. Unfortunately, we don’t live in a perfect world and sometimes water finds a way in, especially during times of heavy rainfall and flooding. Once phase separation occurs, prompt professional intervention is needed to return the fuel to usable condition.
Katherine Vanover is the Director of Marketing for Clean Fuels National, an industry leader in fuel quality maintenance, providing fuel filtration and tank cleaning to major fuel retailers and fleets nationwide. Clean Fuels National is family owned and operated, working coast to coast every day, offering emergency cleaning as well as preventative maintenance programs. Contact 260-273-7032 or [email protected] or visit www.cleanfuelsnational.com for more information.
