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Technical
Service Bulletin 97-8R1
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The Impact of Dents on Canister Filters
Filter
manufacturers often receive used filters involved in warranty investigations
due to a crack in a filter canister. In many cases the crack is located
within or near a dent in the canister. This evidence predominantly indicates
that the dent caused the crack and that the failure was not within the
control of the filter manufacturer. Once the steel canister is dented,
a concentration of stress in the canister material is created, making
the canister more susceptible to fatigue.
The
fatigue to the material results from the pressure pulses within the system.
The pressure is regulated by a pressure regulating valve. This valve is
spring operated and intermittently opens and closes to regulate the pressure.
Once the pressure exceeds the setting of the spring in the regulating
valve, the valve will open and relieve pressure until the spring can expand
and close the valve. This function is repeated continuously during the
operation of the system, creating a pulsing effect. The canister of the
filters is subjected to the same pulsation. However, unlike the spring
in the pressure regulating valve, the canister material is susceptible
to failure after such fatigue.
Filters
are designed with a low carbon steel to resist fatigue and are formed
so the stress created by the pulses in the system are equalized over the
surface area of the canister. A dent provides an area of stress concentration
from pressure pulses and can greatly shorten the fatigue life of the canister.
Filters
that are dented prior to or during installation should not be used. Filters
dented after installation should be replaced immediately. The cost of
replacing a dented filter is much less than the cost of the damages that
could result from a dented filter that fails during service. If you receive
filters that were dented prior to your receipt, you should contact your
filter supplier for corrective action.
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 October 1998
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