Bacterial infection         

See microbial growth 



This is anything that is in the fuel which should not be there. This can include dirt (see particulates) bacteria (see microbial infection) and water (see free water and emulsified water).


Direct inject engines         

This are the modern form of engines. These work at much higher pressures than normal engines



The higher the emissions, the more it will cost the company. Contaminated fuel causes higher emissions, whereas filtered fuel significantly reduces emissions.

Emulsified water         

Emulsified water is the water which is not separated. It is mixed in with the fuel and sludge (see sludge)


Free Water   

Free water is the water that has been separated from the diesel before the fuel polishing process has begun

Fuel Polishing         

Fuel polishing is an industry buzz word that simply means fuel cleaning. It really is as simple as that with no 'magical' element to it. You may also hear it described less so as fuel conditioning, but regardless of how its described, the service is the same. Fuel that is cleaned with one of our fuel cleaning systems will ultimately last longer, meaning less waste and will hopefully keep your equipment free of damage that is normally attributed to dirty fuel.  

Fuel Additive         

Fuel additives are substances or products that are added to fuel to improve its quality, or to prevent something like bacterial or fungal infection from happening. As an example, our WASP Biokem SP15 is excellent at killing bacteria and fungi in fuel, which can lead to clogged filters. 

Fuel Filters         

Fuel filters are products that are added to a fuel system in an attempt to filter out contaminants such as water and dirt so as to ensure proper functioning. Our industry leading fuel filters provide great protection for virtually any type of fuel system. 

Fuel related breakdowns         

Fuel related breakdowns happen when the fuel in a back-up generator has not been cleaned. The unclean/contaminated fuel causes higher emissions and breakdowns’, which reduces the back-up generator’s ability to work efficiently or at all.



These turn liquid diesel into spray, which increases the surface area so that it can be burnt, and thus removed.

ISO standards         

ISO International Standards ensure that products and services are safe, reliable and of good quality. For business, they are strategic tools that reduce costs by minimizing waste and errors, and increasing productivity.



Lit/min stands for the flow rate, which is the number of litres per minute


Microbial growth         

Bacteria that grows in the diesel, particularly when there is water.


Microns are the ratings which denote what particles are filtered through the systems. For example, 30 microns will not allow anything that is 30 microns or bigger through the filter. Conversely, 2 microns will not allow anything bigger than 2 microns through the filter. This is why we are always innovating to reduce the microns down to 1 and 0.5 microns. 



Solid matter that should not be in the fuel. For example, dust, rust or sand.

PLC control         

Programmable logic controller


Quality Fuel         

Fuel is typically measured by ISO specifications. If the fuel quality meets or exceeds the ISO standards, then this is classed as good quality fuel



This is dirt/particles in the diesel which have a heavier gravity than the diesel.


Separ are the largest fuel polishing and fuel filtration supplier in Europe, supplying fuel filtration and preservation equipment to the generator, marine, building services, truck, bus and heavy equipment markets since 1980’s.


The result of contaminated fuel (see contamination) and microbial growth

Standby/back-up generator         

A generator that is used for emergencies when there is a shortage of power or a power failure (see fuel related breakdowns)


W range         

W stands for our WASP range, which includes our standard and our premium product ranges

WB range         

WB stands for WASP basic range

How to Order

Call or email us to place your order. We accept ALL major credit and debit cards, bank transfer and also PayPal. 

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Expert advice

Unsure which spare parts you require? Or if a Separ filter will meet your requirements? 

Talk to our expert team. Call 01923 276 007



Delivery options

We have a wide range of shipping options available to suit your destination and budget.



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Contact Us

3 Kingley Park, Station Road, Kings Langley, Herts, WD4 8GW

Tel: +44 (0)1923 276007

Fax: +44 (0)1923 267463

Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

Here to Help

Product guides

Fuel Specs


Selecting a Filter