Test Your Air Brakes

runaway truckOn February 26, 2016 a loaded dump truck was caught on camera as it slammed into a car and careened out of control through a busy intersection at 2222 and Jester Blvd in Austin, TX, resulting in a crash that involved four vehicles.

On February 29, 2016 an 18-wheeler loaded with gravel slammed into a home at 260 Windsor Drive in San Carlos (between Redwood and San Francisco, CA). It was the second time in two years, according to the daughter of the homeowner. The driver was taken to the hospital.

In both of these recent crashes, the trucks were not able to stop.

Brakes are the No. 1. Out-of-Service (OOS) Violation

Every year the Commercial Motor Vehicle Safety Alliance (CVSA) holds its annual International Roadcheck. Every year the number one Out-of-Service violation is a faulty brake system.

While the numbers are trending down, last year 27.5% of vehicle violations were for bad brakes (and 15.5% of OOS was for brakes that were out of adjustment).

Out-of-adjustment brakes and brake system violations combine to represent half of all out-of-service violations issued for commercial vehicles on the road. Brake systems that are improperly installed or poorly maintained can reduce the braking capacity and stopping distance of trucks or buses, a serious safety risk. CVSA

Some Simple Brake Tests

Always chock the wheels when preforming brake checks!

Smaller commercial vehicles may have hydraulic brakes

• Hydraulic Brake Check

With the engine running, pump the brake pedal three times, then hold the pedal down for five seconds. The brake pedal should not move (depress) during the five seconds.

•Air Brakes

Air Gauge(s) Check ►

For vehicles built after April 1, 1977, check for presence of two (2) air pressure gauges (or a single gauge with dual needles).

Gauge(s) must be accurate to within ± 7% (at 100 PSA 7% = 7 PSI).

Governor Check ►
Check air brake system governor operation. While building up system air pressure, note pressure at which governor cuts-out (compressor quits compressing). With engine still running, pump brakes to lower air pressure until compressor cuts-in (starts compressing again). Note pressure.
(a) Cut-out pressure is too low (below 100 PSI) or too high
(above 130 PSI).
(b) Difference between governor cut-out and cut-in pressure
exceeds 25 PSI
(c) Cut-out pressure is below 120 p.s.i. (for buses equipped with air dryer system; repair).

Parking Brake Check or “Stall” Test ►

With parking brake applied, place in gear and gently tug against the brake to see if it will hold the vehicle.

Air Loss or Leak-Down Test ►

With the engine running, air pressure should be at the governed cut-out (120-125 psi).
1) Shut off the engine (in 2nd or 3rd gear).
2) Release (push in) the YELLOW tractor protection valve/parking brake valve. RED valve should be IN also.
3) Roll down window and listen for any audible air leaks which may be a blown diaphragm in the chamber or leak in line. (Any audible air-leak is a NO-GO condition)
4) Make a note of the air pressure.
5) Apply the foot brake, and hold for one minute.
6) Note air pressure drop resulting from brake application. Check the air gauge to see if the air pressure drops more than three pounds in one minute (single vehicle) or four pounds in one minute (combination vehicle) or five pounds in a minute for combination vehicle with doubles.

NO-GO: If pressure drop is greater than 15 p.s.i. do not move the vehicle until brakes have been adjusted or repaired.

Low air warning devices §393.51(c)
Turn the key to the “on” position without starting the
engine and begin fanning off the air pressure by rapidly applying and releasing the foot brake.

Low air warning device(s) (buzzer, light, or flag) should activate before air pressure drops below 60 p.s.i. on gauge.

Protection valves Pop-off Test §393.43
• Continue to fan off the air pressure starting with at least 60 p.s.i. in air system and noting air pressure at which valve “pops out.”

Between approximately 20-40 PSI on a tractor-trailer combination vehicle, the tractor protection valve and parking brake valve should close (pop out). On other combination vehicle types and single vehicle types, the parking brake valve should close (pop out).

NO-GO: If valve pops over 50 psi or does not work between 15 – 40 PSI.

Check Your Air Brakes Daily

Drivers can inspect their brake systems every day. Even if you can’t go under the vehicle, you can listen for air leaks, check low air signals and look for component damage. If you can go under your vehicle, you can measure pushrod stroke the same way a CVSA-certified inspector does, and compare the results to the pushrod stroke limits set by regulation.  CVSA

Thank you for reading this.

More . . . Operation Airbrake Inspection Procedures

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