Pass or Fail?

They probably figure whats 5psi amongst friends.

 

Nope, the trailer supply button has to close (Pop out) before either primary or secondary falls below 20 psi. For this test pumping down is “not” a valid test. The test in the CDL manual is “not” a valid test of the TP system. Disconnecting both air lines is the only valid test.

 

Negative, the only valid test is disconnecting both air lines and following the procedures recommended. I’ll list them if you need them otherwise since I type slow I won’t.

 

I have a single track mind.

Generally when the buttons come out that means the springs are coming on like it or not, it has to happen prior to the 20 PSI. The physical decision by the truck to pop the buttons will be somewhere in a range above 20 but below 40 roughly.

I focus on the alarm situation at 60 and less. If you don't have it at 60 that's a fail. It does not matter if the failure of the buttons to come out on their own after. (They should)

If you DID pull the emergency line that will activate the protection valve so fast. Even with full primary and secondary as designed. MR pop should get to work quickly.

 

Oh do tell considering that pump down is the recommended way for CVSA inspections

They have a 7 step brake test method. Look it up, or don't. But you are incorrect.

 

unhookING the blue line doesn't do anything the red line will leak air until the red valve pops out around 40 psi then nothing ... tractor brakes will not pop out. so that isn't really a test ... the only way is to pump the brakes or drain the tanks .... it's called the static brake test and they have been doing for 40 years that I know about .... only reason a dot should unhook your air line is to check your rubber gaskets

 

The pump down is not the recommended method of CVSA inspectors. It’s the method in the CDL manual, which is not the same thing.

Standard CVSA Roadside Inspection/Test Procedure
When conducting a roadside inspection, the officer will confirm that the towing vehicle protection system (tractor protection system) is functioning properly in the event of trailer separation.
Testing of the towing vehicle protection system is done under pressure with the engine off and shall be conducted as follows:
1. The system must be within its normal operating pressure range (i.e., between compressor cut-out and cut-in).
2. Wheels must be chocked and all brakes must be released (all dash valves pushed in).
3. Explain to the driver that the supply/emergency and the service/control gladhand couplings must be removed to simulate a trailer breakaway event and to determine compliance of the towing vehicle protection system under this condition. Always have the driver perform this step and make sure to advise the driver to be careful and to take protective action to avoid injury from the high-pressure air, water, oil or dirt that could escape from the supply/emergency gladhand coupling upon separation.
4. Air will immediately escape from the supply/emergency gladhand line. Listen for and ensure that the air stops escaping from the supply/emergency gladhand line. In most cases, the air will stop almost immediately. In some systems, the air will escape for a period of time and then stop; but in no case, should the valve fail to close once the gauge pressure drops to 20 psi (138 kPa) in either the primary or secondary system. When the valve fails to close before the pressure drops below 20 psi (138 kPa), the power unit’s trailer supply valve (TSV) is defective. This vehicle has a violation* that is an OOS condition.
5. When the gladhand couplings are disconnected, the trailer emergency (spring) brakes must also apply automatically. Failure to do so indicates that the breakaway system on the trailer is defective. The trailer has a violation* that is an OOS condition.
6.When the gladhand couplings are disconnected,the trailer system must close automatically.Check the supply/emergency gladhand coupler on the trailer for air bleeding back. Air leaking from the gladhand coupling on the trailer indicates that the trailer’s spring-brake control valve is defective. The trailer has a violation* but this is not an OOS condition.
7. Once the air has stopped and you have checked the pressure, have the driver return to the cab of the power unit and instruct the driver to apply the service brakes and hold it.
8. Check for any air escaping from either the supply/emergency or the service/control gladhand line. When air escapes from either gladhand line, the towing protection valve (TPV) is defective. This vehicle has a violation* that is an OOS condition.
9. Once the test has been completed, instruct the driver to reconnect the gladhands. *U.S. – 49 CFR §393.43, Canada – NSC Standard 11b

 

I notice that, correctly, the driver is to perform the disconnect. I would not want anybody removing the trailer lines for me.

 

In believing that you are misunderstanding the whole purpose of the test. The reason for unhooking the blue line (In addition to unhooking the red line) is that after noting the pressure that the red button pops at (It can never be lower than 20psi and usually between 20-45psi) you apply service brakes. If air comes out of the blue line, the tractor protection valve did not close and is considered defective. In other words it failed the test. I posted the CVSA inspection method above, its bulletin 2010-01, look it up. Also there is no federal requirement for the yellow button to pop, CVSA bulletin 97-01.

 

That is correct, and neither would I.