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Air filters: What is the purpose of a safety filter?

The Filter Guys

What is the purpose of a safety filter? Safety filter, secondary filter, inner filter; there are many names, we prefer to call it a safety filter.

A safety filter backs up the primary filter, and protects the clean air ducting while the primary is out of the housing during service. The engine should never be run with only a safety filter in place.

The safety filter is NOT a spare filter! Its purpose is to protect the engine if something goes wrong with the primary (main) filter. Until then, all it does is take up space and add a little bit of restriction.

What can go wrong with the primary filter?

It may have hidden damage from shipping that you missed when you inspected it before installation; damage from cleaning (if you carry out such an unrecommended procedure); maybe even a manufacturing glitch; mis-installation by the mechanic (but this never happens, right?); a ‘will-fit’ that doesn’t quite fit; or it’s the wrong part altogether and doesn’t fit at all into the housing (but mechanics would never try this, would they?)

All of these things happen more often than any of us like to think. We determined many years ago that a really good way to provide additional protection for large engines operating in heavy dust conditions was to always offer and for you to always use a safety filter.

There are some characteristics about the safety filter which you should be aware of, so you understand what it does and doesn’t do for your engine:

  • is smaller than the main filter, with less media.
  • is more open and less efficient for lower restriction.
  • has less contaminant-holding capacity so that it will plug rapidly if any engine-damaging dust particles get past a damaged primary filter.

A safety filter offers protection against mistakes when fitting and reduces the need to open the clean air side of the system by 66% (they usually only need changing once every three main filter changes) compared to systems without a safety filter. They are an excellent insurance against contaminants entering your engine and upon a critical failure of the main element can save your engine from serious damage.

How Filter Media Functions In a Filtration System

The Filter Guys

How Filter Media Functions. The job of the media is to capture particles and allow the fluid to flow through. For fluid to pass through, the media must have holes or channels to direct the fluid flow and allow it to pass. That’s why filter media is a porous mat of fibers that alters the fluid flow stream by causing fluid to twist, turn and accelerate during passage.

The fluid changes direction as it comes into contact with the media fibers, as illustrated above. As the fluid flows through the media, it changes direction continuously as it works its way through the maze of media fibers. As it works its way through the depths of the layers of fibers, the fluid becomes cleaner and cleaner. Generally, the thicker the media, the greater the dirt-holding capacity it has.

Looking at a cross-section view of the fibers:

we can see how the flow stream is accelerated as it flows into the spaces between the fibers.

This is applies to all liquid filters, be they oil, fuel, water of water glycol. For more information on filtration products and replacement elements please contact us for a chat. We’re here to help.

How Filter Media Collects Particles

The Filter Guys

How Filter Media Collects Particles. There are four basic ways media captures particles.

The first, called inertia, works on large, heavy particles suspended in the flow stream. These particles are heavier than the fluid surrounding them. As the fluid changes direction to enter the fiber space, the particle continues in a straight line and collides with the media fibers where it is trapped and held.

The second way media can capture particles is by diffusion. Diffusion works on the smallest particles. Small particles are not held in place by the viscous fluid and diffuse within the flow stream. As the particles traverse the flow stream, they collide with the fiber and are collected.

The third method of particle entrapment is call interception. Direct interception works on particles in the mid-range size that are not quite large enough to have inertia and not small enough to diffuse within the flow stream. These mid-sized particles follow the flow stream as it bends through the fiber spaces. Particles are intercepted or captured when they touch a fiber.

The fourth method of capture is called sieving and is the most common mechanism in hydraulic filtration. As shown at right, this is when the particle is too large to fit between the fiber spaces.

Changes to Gas Oil Used in Off-Road Equipment.

The Filter Guys

From the 1st of January 2011 all gas oil (red diesel) for use in off road machinery and boats will contain no more than 10mgs of sulphur per kilo of fuel (current level is 1000mgs/kg). The changes are to reduce burned sulphur from entering the atmosphere. The Department of Transport are advising all gas oil users of the following precautions when storing and using red diesel for off road and recreational boat use:

Increased care when storing: The oxidation stability of this fuel will be poorer than that of current gas oil. This can cause solids to form in the gas oil. This will cause increased contamination that will require filtering from the gas oil. Suitable and regular filtration of the fuel will help prevent wear and tear on transfer pumps or off road engines.

Water removal: Water in fuel encourages bacterial growth which can block fuel systems and damage engines. Increased use of bio fuel as an additive to modern gas oils means that there is an increased risk of bacterial growth where water is present. Ensuring that suitable water separators are fitted can help reduce bacterial growth and reduce down time from breakdowns.

Solvent characteristic of the low sulphur fuel: The new sulphur free gas oil has a more solvent characteristic than current gas oil and will potentially remove any deposits within the storage tank. It is advised that fuel tanks are cleaned and equipment filters be replaced after the initial 2-3 tank fills of sulphur free gas oil and then be maintained and serviced regularly. If ever in doubt, change your fuel tank filters.

The cost of regular filter servicing is much lower and cost effective than the cost of even one single pump or engine fuel system replacement.

Further information and advice can be found on the Department for Transport web site by following the following link:

http://www.dft.gov.uk/pgr/roads/environment/fuel-quality-directive/

British Antarctic Survey.

The Filter Guys

Sterling Filtration Ltd has supplied air filters to the British Antarctic Survey. The British Antarctic Survey (BAS) is the UK’s national Antarctic operation and has an active role in Antarctic Affairs. BAS is part of the Natural Environment Research Council (NERC) and has over 400 staff. It operates five research stations, two ships and five aircraft in and around Antarctic. It’s involved in joint research projects with over 40 UK universities.

National Oceanography Centre.

The Filter Guys

Sterling Filtration Ltd has been a supplier of various filters to The National Oceanography (NOCS) in Southampton. The National Oceanography Centre, (formerly Southampton Oceanography Centre), is a collaborative Centre owned by the Natural Environment Research Council (NERC) and the University of Southampton. NOCS is based at a purpose-built waterside campus in Southampton, and is home to some 520 research scientists, lecturing support and seagoing staff as well over 700 undergraduate and postgraduate students.

Damaged or Missing Vac Valve.

The Filter Guys

The Vacuator™ Valve, a standard item on most Donaldson air cleaners, is an important part of the functionality of the air cleaner during the pre-cleaning stage.

If your Vac Valve is cracked, torn, missing or remains open, dust particles that are normally expelled can deposit themselves onto the filter and will significantly shorten the filter service life. It will need replacing.

For proper operation, the valve should be located at the lowest point on the air cleaner or with the dust cup pointing down. Normal engine pulsing and operation causes the Vacuator™ Valve to open and close. This action automatically expels any collected dust and water. The valve also releases its load when the engine is stopped.

Call Sterling Filtration for more information about this product.

Ever considered…. T.R.A.P. Breathers?

The Filter Guys

T.R.A.P. BREATHERS

(Thermally Reactive Advanced Protection)

Part No. P56 4669

 

The T.R.A.P. breather begins absorbing moisture at 15% relative humidity compared to 40% humidity for silica gel. This is particularly advantageous for use on short cycles of hydraulic circuits.

Increased prevention of condensation at an earlier stage helps prevent corrosion, maintain fluid quality and extends fluid life.

Its lightweight robust structure makes it is suitable for stationary and mobile applications and it’s also effective to -40F.

The reversible flow through the media allows moisture to exit the tank or reservoir.

It stops particles down to 3 micron.

1” NPT

A visual indicator, activated by pressure differential, flashes red to indicate change is needed.

Replacement and installation is easy. Simply hand tightens.

Call Sterling Filtration for more details.

The Importance of Lube Oil Filtration

The Filter Guys

Lube Oil Filtration. While oil is primarily used to lubricate and cool moving parts of an engine it also carries out another very important function: that of transferring any harmful abrasive particles to the sump. These particles must be removed before the oil can circulate around the lubrication system again. An efficient way of removing these particles, preventing unnecessary wear or damage, is to pass the oil through a filter before it reaches any of the critical moving parts.

Sterling Filtration Ltd offers a range of stocked oil filter cartridges and cannisters from a number of leading suppliers including Donaldson, Fleetguard, Mann & Hummel, Hi Fi, Mahle, Coopers and Crosland, which cover a huge range of off and on highway applications.