Water contamination in diesel.

Water contamination is natural in biodiesel. It contains water when it’s manufactured and it attracts more water while it’s stored. Biodiesel is hygroscopic; meaning it attracts water. This makes it more prone to water contamination than the petrochemical diesel we used before 2011. Diesel fuel now contains up to 7% biodiesel; while this is great for the environment it’s not always good for organisations that store fuel.

Water contamination can occur through a delivery of contaminated fuel (left), condensation collecting in tanks (centre) or leaks through tank breathers and vents (right).

Water is bad news for diesel because it encourages the growth of diesel bug, rusts steel and leads to the formation of gums and resins which can stick to the side of fuel tanks, injectors and even causing layers of sediment to build up inside the tank.

It puts your critical power at risk.

The triple effect of water contamination in diesel

Water contamination causes three types of problem:

• Microbial contamination (a.k.a. the ‘diesel bug’) thrives in an environment where it finds both diesel fuel and water. The more water your diesel contains, the more likely you are to suffer from diesel bug contamination.
• Water has a detrimental effect on your engine. It can corrode components, encourage acid build-up, reduce lubrication and cause explosive damage to injectors if it becomes super-heated during combustion.
• Once past a certain point, water contamination reduces the CETANE rating of your fuel and causes performance problems for the engines in your generators, pumps and plant.

Water contamination in diesel takes many forms

Of all the contaminants found in diesel, water can be the most damaging. It is found in three states:

• Free water is water that has separated completely from the diesel. If usually sinks to the bottom of the tank where it is invisible to a casual inspection. If free water rises above the level of the fuel take-off pipe, generators will fail. At the very least, free water encourages the growth of the diesel bug.
• Emulsified water is water that has formed small droplets suspended in the diesel. It looks like droplets of oil in a salad dressing.
• Dissolved water is water that has completely dissolved in the diesel and is distributed molecule by molecule like sugar in tea.

Free and emulsified water present the greatest threat to reliable power. They deliver varying quantities of incombustible water to your engine.

How can you prevent water contamination in diesel?

Prevention is always best. The key to maintaining fuel quality is good housekeeping.

WASP recommends following a comprehensive fuel conditioning programme to ensure that your diesel-powered equipment runs reliably and economically. The ultimate prevention is to fit a fuel polishing system that includes a water filtration stage.

What can be done for tanks already infected with diesel bug?

WASP offers a comprehensive tank cleaning service that removes contamination that has grown beyond the level which polishing can clear. Our on site services will addresses water, microbial and solid particulate contamination.

How can I prevent fuel contamination?

Again, prevention is always best – the key to maintaining fuel quality is simply good housekeeping.

We recommend the following for best practice:

• Where possible, purchase your diesel from reliable sources to know specifications
• Ensure the condition of your fuel tanks; keeping them leak free and in good condition (ideally have an OFTEC tank inspection carried out)
• Always use fuel testing and sampling to monitor contamination levels
• Avoid fuel contact with zinc and copper containing metals as they promote oxidation
• If storing fuel in multiple tanks, employ rotation system so oldest fuel is used first
• Where possible keep fuel cool to minimise water absorption.
• Most importantly, impose a full Fuel Conditioning Programme covering testing, cleaning, polishing and stabilisation.

Water represents the most problematic form of diesel contamination. Water can damage engine components, impede combustion and encourage the growth of diesel bug.

Despite its threat, water is an inevitable part of life with biodiesel. Following a comprehensive fuel conditioning programme stops water contamination becoming a problem.