Fuel Polishing Explained: Do You Really Know What It Means?

It is these problems that highlight the importance of fuel filtration and polishing. But do you know exactly what fuel polishing is? And perhaps even more importantly, is it even a fuel polisher you’re looking for?

Fuel polishing refers to cleaning the sediment, water and microbial contamination from diesel fuel down to an ISO standard. It is essentially getting your stored diesel fuel back to the cleanliness level it was when you first had it delivered, but often even to a higher standard. It usually involves emptying a tank entirely of fuel, polishing it and then returning the clean fuel back into the tank.

But when is fuel tank polishing required over just installing fuel filters on your tank?

Unlike other fuel tanks that get used daily like vehicle refuelling tanks, the fuel in generator back up tanks can sit for months or even years, allowing the water to settle and the diesel bugs to grow and create nasty sludge. Stagnant fuel presents a greater risk of generator failure and results in expensive repairs and downtime. For that reason, it is common to use a diesel fuel polishing system, or recirculating system for generators – whether installed on the tank or during annual servicing.

This is a fuel conditioning unit that targets the ISO 14/13/11 diesel cleanliness standard via multipass, and aims to keep the water content well below the industry norms, but doesn’t guarantee it like a fuel polishing system would. It is fitted to the tank and circulates the fuel from one side of the tank to the other, filtering out particles and water in the process, and uses a magnetic conditioner to break up the microbial growth to prevent diesel bug sludge from forming.

Use of terminology incorrectly means that we often see people ask for a diesel fuel polishing system when they are not actually looking for fuel polisher, but a less expensive diesel fuel conditioning unit. It is worth finding out what is you/your client needs as this may be it.

For tanks used regularly where the diesel has not had time to degrade or get stagnant, the use of fuel filters and water absorbers is typically sufficient. For generator installations where the fuel is not regularly used but is critical in its use when required, a higher level of fuel maintenance is required.

However, whether a fuel polisher is actually required here can vary and is often determined in the design specification of the fuel system. For example, some emergency power specifications state that they need a system to circulate and filter the fuel over set intervals but does not specifically mention reaching ISO fuel standards. In this instance, it may be that it is just a fuel conditioner or recirculation unit required as fuel polishing is planned to be carried out as an annual service or part of a full fuel maintenance program with regular fuel testing.

No - the CTS fuel conditioning system is to be used as part of a fuel maintenance programme, installed on the tank to help maintain the cleanliness/quality of the fuel in between annual / or periodic fuel tank polishing or testing services.

For critical applications such as emergency power for hospitals and data centres, the design team will specify the exact type of system, however many customers use a fuel conditioner installed on the bulk tank, with a documented fuel testing regime, and on an annual basis have the fuel polished if required. The fuel recirculation unit actually speeds up any annual polishing process as the fuel is kept in good condition prior.

So, if you’ve been looking for a fuel polishing system for a generator critical power applications this article should have helped clear up a few questions you have and common misconceptions! For more information contact our sales team on enquiries@centretank.com.