Air Brake REFRESHER and TEST procedures incl. Leak test

[dentmac]

Safety FIRST.
-The operating range for an Air Brake system must be between 80 and 135 psi.

-With the engine between 600 and 900 rpm , the cut in pressure for the compressor must be above 80 and the cut out must be below 135.
---------------- With the engine running and the emerg. brake set , fan the brake peddle (on and off) and note the cut in pressure, then wait to note the cut out pressure.

-The low pressure warning alarm must come on above 55 psi (usually 60)
-----------------With the engine not running and the spring/emerg on , fan the brake peddle until the light/alarm comes on. The warning light/sound must occur before the gauge reads 55 psi.

Note that the Spring/emerg brakes will automatically activate near or below 55 PSI

-Pressure build up timing will check the compressor. The build up from 85 to 100 psi must be under 2 minutes at 600 to 900 rpm
----------------- After the previous test (or with the pressure below 80 psi) and the emerg brake on. Start the engine and with the idle RPM (between 600-900) , record the time required to go from 85 to 100 PSI. This must be under 2 minutes.

-Check for leaks. a maximum of 3 psi per minute is allowed.
----------------With the pressure above 100, the spring brakes OFF and the engine not running, apply and hold significant pressure on the peddle. Note the pressure loss per minute. (easiest to hold for 2 or 3 minutes and average since 3 pounds is difficult to read on the gauge.)

Check Spring brakes,
---------------With the emerg. brakes set, put the transmission in gear and slowly add a little engine power. The vehicle will not move if the Spring brakes are functional.

[Deb N Randy]

(10-15-2014 17:56)dentmac Wrote:  Safety FIRST.

-The low pressure warning alarm must come on above 55 psi (usually 60)
-----------------With the engine not running and the emerg on , fan the brake peddle until the light/alarm comes on. Must come on before the gauge reads 55 psi.

Note that the Spring/emerg brakes will automatically activate near or below 55 PSI

Always good to check brakes. But when checking the automatic spring brake do not have your emergency brakes on, as that is what you're testing. Chock the wheels if necessary.. Usual range is 20-40 psi.

[GregOConnor]

I always pump the air out of the tanks ( pump the service brake peddle) when I plan to leave the rig unattended. This way no one can release the park brake without starting the engine.

My one fear is depending on the park brake springs and losing bag pressure on the park brake drive axle while the tag is still inflated.

One other test that is mind opening is to roll at about 3 mph then set the park brake. it is far from an emergency brake. Not sure but I dont even think it is called or labeled "emergency brake".

[dentmac]

Perhaps I wrote it a bit confusing---

But the test you quoted is to check when the low pressure warning signal activates--- It must activate before the pressure falls to 55 PSI

The test (in the post) that the Spring brake is working-- It has to be set--- then try to drive.(adding a little power in gear)

Ross

sa

(10-16-2014 10:57)Deb N Randy Wrote:  

(10-15-2014 17:56)dentmac Wrote:  Safety FIRST.

-The low pressure warning alarm must come on above 55 psi (usually 60)
-----------------With the engine not running and the emerg on , fan the brake peddle until the light/alarm comes on. Must come on before the gauge reads 55 psi.

Note that the Spring/emerg brakes will automatically activate near or below 55 PSI

Always good to check brakes. But when checking the automatic spring brake do not have your emergency brakes on, as that is what you're testing. Chock the wheels if necessary.. Usual range is 20-40 psi.

[Deb N Randy]

I just took the Non CDL driving exam a couple of months ago and the test for the air brakes was to check for air leaks as you described. Then turn off the ignition, without the parking brake engaged (no chocking as we were level), pump the brakes and point at the air gauge when the low air warning came on (~60 psi). Then pump some more and point at the air gauge when the spring brake engaged (~30 psi). After that I turn back on the ignition and I had to point out I was aired up, supposed to be above 90 psi in 3 minutes.

Other than that they wanted me to go 3-5 MPH and hit the brake hard to make sure it had no sway, left or right. Then set the parking brake and put it in gear and make sure it didn't move.

/.Randy

[davidbrady]

(10-16-2014 12:33)GregOConnor Wrote:  My one fear is depending on the park brake springs and losing bag pressure on the park brake drive axle while the tag is still inflated.

One other test that is mind opening is to roll at about 3 mph then set the park brake. it is far from an emergency brake. Not sure but I dont even think it is called or labeled "emergency brake".

Greg,

My H3 Prevost has spring brakes both on the drive and the tag axles. This would be a nice addition to our Wanderlodges.

When I owned my LXi I replaced the piston style drive axle brake canisters with 3036 diaphragm style, MGM part number: 3532051. The folks at MGM told me the 3036 piston offered the same service braking and parking brake forces as my old MGM30 piston style. I think any tag equipped Wide Body bird should have 3036's on the drive, anything less and you may not have the parking brake performance (and service brake performance) that you need. A while back a poster on wog talked about driving up the grapevine (I may be wrong about the location), setting his brakes, leaving the bus only to turn around and with amazement spotting his SP at the bottom of the ravine. I don't know if anyone ever reported on the actual cause of his parking brake failure, but I often wondered if someone replaced a canister with an incorrectly sized diaphragm.