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BRAKE
PRO, LTD. TECH BULLETIN
For your information
| VOLUME 3, #3 |
BRAKE DIAGNOSIS RECOMMENDATIONS
Heavy-duty air brake systems are very important to proper operation of
transportation vehicles worldwide. Closer inspection and adherence to
guidelines are necessary to prevent failures in the field. Reducing the
failures in the field starts with inspection and determination of needed
services. Here are some recommendations for insuring that good methods
are used for that inspection.
BASIC DIAGNOSIS OF TOTAL SYSTEM
Before inspection, during a PM, the brakes should be diagnosed using a
temperature-sensing device that will allow the technician to determine
if the proper timing and balance are present. By measuring the brake temperatures,
it can be determined which brakes are working the most and least. This
specification is essential to any brake diagnosis. If this step is not
performed, then brake life and safety can be overlooked, and proper maintenance
cannot be performed. It is the basis for all other required parts replacement
determinations. It is imperative to know this information before hand.
AIR SYSTEM DIAGNOSIS
Air system diagnosis is essential to determine the safety and practical
information on brake system timing and response when the brakes are being
used in the field. Determining the amount of moisture in the air system
along with any oil contamination is essential. Oil in an air brake system
causes many problems, and improper braking is one of the most serious.
Oil present in the air system will cause slow valve operation and in turn
cause braking imbalance. Oil is also a common problem in most vehicles
in determining when air dryer service should be performed. Moisture is
often found before oil contamination is present. When there is more than
four ounces of moisture in the wet tank, it is an indication that oil
is on its way. Oil can be avoided if each vehicle system is watched carefully
for moisture content. When it is found to have too much moisture, 2 ounces
if drained each day, then it can be considered to be a candidate for dryer
service to prevent the oil from advancing.
WHEEL END INSPECTION
Wheel end inspection is usually a cursory inspection of the thickness
of the lining remaining at each brake shoe table. This is as far as it
goes during brake inspection. When the vehicle is brought in for friction
material service, all of the other components must be checked and certified
to be within specifications.
BRAKE LININGS
The new brake linings must be of the type and specification designed for
use on the axle rating or better. Rating systems such as EE, FF, or GG
are not definite rating systems. It is recommended to determine the ability
of a lining to provide safe and effective stopping that is the same on
each brake application with the least amount of swell and shrinkage over
the lifetime of its operation. When the technician looks at the old, removed
lining, it tells a story regarding contact, overheating and spider alignment.
Careful training of all technicians should be done so that each can read
the conditions found and determine a course of action to be taken during
re-line. After the brake reline, new linings must also be checked, to
determine if the maximum amount of lining is touching the brake drum during
brake application. Lining that has an inadequate amount of contact will
create more heat in a concentrated area and thus shorten the lining's
life.
