 |
Technical
Service Bulletin 89-3R3
|
Servicing Heavy Duty Air Filter Elements
When
to Service?
The element
in any air cleaner should be serviced when the maximum allowable restriction,
established by the engine manufacturer, has been reached. The element
should not be serviced on the basis of visual observation because this
will generally lead to over-servicing.
Over-servicing will cause increased service cost, both time and material, and may cause dust contamination of the engine due to:
1. Element damage from excessive handling,
2. Increased chance of improper installation of element,
3. Increased initial inefficiencies.
Achieving
Maximum Air Filter Efficiency
The efficiency of an air filter increases as it is used. As soon as the
air filter is put into operation, it begins to remove harmful dust particles.
As these particles accumulate throughout the filter medium, the microscopic
openings in the medium become obstructed. This on-going reduction in the
size of the openings helps the filter stop increasingly finer dust particles,
thus resulting in a more efficient filter. As the filter continues to
plug with contamination, the restriction to air flow will increase. Most
engine manufacturers establish a maximum degree of vacuum in the air induction
system that the engine can tolerate and still operate efficiently.
What
is Restriction?
Restriction is the resistance to airflow through the air cleaner system
into the engine.
What
Instruments Do We Use to Measure Restriction?
Restriction is best recorded by a water manometer, an air cleaner service
indicator or a dial gauge calibrated in inches of water or Kpa (other
units may also be used). Since some users will not have a water manometer
or dial gauge available, the use of permanently mounted service indicators
should be considered. The indicator can be mounted in an area where the
operator can monitor the condition of the element constantly.
How
is Restriction Measured?
Accurate restrictions can only be measured at maximum airflow. On naturally
aspirated or supercharged (not turbocharged) diesels, the maximum airflow
occurs at maximum RPM (high idle) without regard for engine power. On
gasoline, LP, or turbocharged diesel engines, the maximum airflow occurs
only at maximum engine horsepower at governed RPM. Most engine manufacturers
suggest a maximum allowable restriction between 15 inches and 20 inches
of water (3.75 - 5.00 Kpa) for gas and LP engines, and from 20 inches
to 30 inches of water (5.00 - 7.50 Kpa) for diesels. Exceeding these maximums
will affect engine performance.
The operator should not be alarmed when the signal on the restriction indicator begins to appear. The air filter manufacturer furnished your service element to withstand several times these recommended maximums without collapsing or leaking dirt into the engine.
Where
Is Restriction Measured?
Restriction is measured in the air cleaner outlet tap (if provided), at
a tap in the air transfer tube, or within the engine intake manifold.
Measuring
Restriction in Dry Air Cleaners
As a dry air cleaner element becomes loaded with dust, the vacuum on the
"engine side" of the air cleaner (at the air cleaner outlet)
increases. This vacuum is generally measured as restriction in inches
of water or Kpa.
The engine manufacturer often places a maximum allowable limit on the amount of restriction the engine can withstand without loss of performance before the element must be serviced.
Mechanical gauges, warning devices, indicators, and water manometers are available to inform the operator when the air cleaner restriction reaches this recommendation limit. These gauges and devices are generally reliable, but the water manometer is the most accurate and dependable.
To use the manometer, hold vertically and fill both legs approximately half full with water. One of the upper ends is connected to the restriction tap on the outlet side of the air cleaner by means of a flexible hose. The other end is left open to atmosphere. With the manometer held vertically and the engine drawing maximum air, the difference in the height of the water columns in the two legs, measured in inches, is the air cleaner restriction.
A restriction indicator´s "lock-up" restriction level is generally marked on the indicator itself. A quick method to check a visual indicator is to remove it, wipe the base clean, then suck on the indicator with your mouth. If the indicator locks up, it is optional, if not, replace indicator. A more accurate method is to check the calibration against a water manometer.
Why
Service?
Proper air cleaner servicing will result in maximum engine protection
against the ravages of dust. Proper servicing can also save you time and
money by increasing filter life and efficiency. Two of the most common
servicing problems are: 1) Over-servicing - new filter elements increase
in efficiency as dust builds up on the media. DON'T BE FOOLED by filter
appearance, it should look dirty. By using proper filter restriction measurement
tools you will use the full life of the filter at maximum efficiency.
2) Improper servicing - your engine is highly vulnerable to abrasive dust
contaminants during the servicing process. The most common cause of engine
damage is due to careless servicing procedures. By following the steps
shown, you can
How
to Service: The Do´s
Remove the filter element as gently as possible - Be extremely
careful with the dirty element, until you get it completely out of the
housing. Accidentally bumping it while still inside means dropped dirt
and dust may contaminate the clean side of your filter housing, before
the new filter element has a chance to do its job.
Always clean the inside of the housing carefully - Dirt left in the air cleaner housing may be harmful to your engine. Use a clean, water-dampened cloth to wipe every surface clean. Check it visually to make sure it´s clean before putting in a new element.
Always clean the gasket sealing surfaces of the housing - An improper gasket seal is one of the most common causes of engine contamination. Make sure that all hardened dirt ridges are completely removed, wherever filter gaskets contact of the cleaner housing.
Check for uneven dirt patterns on your old element - Your old element is a valuable clue to potential dust leakage or gasket sealing problems. A pattern on the element clean side is a sign that the old element was not firmly sealed or that a dust leak exists. Make certain the cause of that leak is identified and rectified before replacing the element.
Press your fresh gasket to see if it springs back - Make sure your new element is made with a highly compressible gasket that springs right back when your finger pressure is released. A quality gasket is one of the most important parts of the element. On a radial seal element the gasket surface is the inside diameter of the open end cap.
Make sure the gasket is seating evenly - If you don´t feel the gasket is seating evenly for a perfect seal, you may not have protection. Re-check to see if the sealing surface in the housing is clean, or if the element is the correct model number. It may be too short for the housing.
Check connections and ducts for air tight fit - Check that all clamps and flange joints are tight, as well as air cleaner mounting bolts. Seal any leaks immediately - they mean dirt is directly entering your engine. All duct joints, from air cleaners to engine, must be tight.
Safety element service - The safety element should never be cleaned. For maximum engine protection and air cleaner service life, replace the safety element with a new safety element every third primary element change.
How
Not to Service: The Don´ts
Don´t remove element for inspection - Such a check will always
do more harm to your engine than the good your inspection can do. Ridges
of dirt on the gasket sealing surface can drop on the clean filter side
when the gasket is released. If you utilize scheduled maintenance, stick
with your maintenance schedule. If you´re on restriction maintenance,
follow your indicator reading; replace the indicator with a new one if
you don´t trust it.
Never rap an element to clean it - only to destroy - Rapping hard enough to knock off dust often damages the element and jeopardizes your engine protection. Deeply embedded dirt is never released by tapping. It is always safer to keep operating until you can change to a fresh filter.
Never judge your element´s life by looking at it - A dirty-looking element may still have plenty of life left, while a restricted element may appear clean. Your best bet for lowest filter maintenance costs and best engine performance is to follow a restriction indicator. It´s a smart, low cost investment.
Never leave an air cleaner open longer than necessary - Your open air cleaner is a direct entry to your engine. If the element is not going to be changed immediately, you are better off leaving the dirty element in place. At a minimum, cover the opening. Don't overlook a worn or damaged gasket in the housing - if your air cleaner has a cover gasket, inspect it and replace it with a new one if necessary. Always ensure that any traces of the old gasket are removed. If your filter model calls for a new gasket with each use, never reuse the old one.
Don´t overlook a worn or damaged gasket in the housing - If your cleaner has a cover gasket, replace it with a new one. Always check to be sure no piece of the old gasket is not worn. If your filter model calls for a new gasket with each use, never reused the old one.
Don´t use a dented filter element - Never install a dented or punctured element, because it cannot protect properly against contamination. A dent can make a firm seal impossible or can indicate damaged media.
Never use a warped cover on a housing - Replace with a new cover as soon as possible. A warped or damaged cover cannot make a proper seal. Also check to make sure there is no damage to the air cleaner housing that could cause a leak.
Never
substitute an incorrect element model number - Elements may look almost
identical but can differ by a fraction of an inch in length a difference
that may make a positive seal impossible. You´re always better off
using the dirty element until you can get the correct model.
For additional information, contact:
Filter Manufacturers
Council
P.O. Box 13966
Research Triangle Park, NC 27709-3966
Phone: 919/406-8817 Fax: 919/406-1306
www.filtercouncil.org
Administered by Motor & Equipment
Manufacturers Association
Revised
April 2006
Back to Top
Back to Technical Service Bulletins