Air Brake Pressure
 

It was my understanding that the required air pressure for the safe operation of semis was at 120 psi, that anything less and I mean under 100 psi was not safe to drive. I had a recent job where quite a few of the trucks had this problem. I would hear over the company radios from other drivers how they would lose air pressure and to send out the mechanic. My last truck had this problem. We rarely drove the same trucks day after day so when we got into a truck that the problems weren't reported by the previous driver we, and I mean the responsible drivers, took care of these existing situations before we picked up our loads for the day. Long story short, this truck showed 100 psi on the primary guage and 75 psi on the secondary guage. The engine had to be revved up to over 2000 rpm in order to build up enough pressure for up to 5 minutes in order for the secondary air pressure guage to even get anywhere near 100 psi, and that is where the guage would not show anymore buildup.

All the air pressure built up in this proceedure was nor nought due to the fact the air pressure would go down once we applied the brakes. The head mechanic would then try to build up more pressure until the governor kicked in once again at 90 to 100 psi. The mechanic then told me if I was hearing the governor kick in it was safe to drive even though the primary would be between 100 - 110 psi and the secondary showed anywhere from 75 - 100 psi. At this point he would not do anything more saying it was now ready and safe to drive.

What is the required psi for air brakes in order for safe driving and not having to worry about losing air pressure all at once due to a faulty system? [ATTACH=CONFIG]1186[/ATTACH]

Min press is 90 PSI the governor should kick in at 90 PSI and build to 120 PSI . It should 30 PSI difference between kick in and kick out depending on governor settings. Your mechanic is an idiot some of the accessories air actuated is prioritized at 80 PSI such as cab air bags or air seat or steering column lock (Freightliner) You have an air leak somewhere in the system both circuits should have the same pressure ( even one is prioritized over the other one ) when your check valve on the air dryer burst both circuits should have same pressure. Your mechanic should adjust the pressure on the governor to built in specs.( supposing that he know how to do it and where to wrench it )