Regarding the Tractor protection valve, when the air flows in the supply line through TPV , it presses down the plunger , connecting the tractor and trailer service ports. When the air do not flow in the supplyline , the plunger moves upward thus disconnecting the service ports. When the vehicle is parked , air do not flow in the supplyline. and hence the tractor -trailer service ports are not connected. and air cannot flow through the service line. How the anti-compounding feature works in the above situation. How the air flows in the service line for applying the service brakes. Next how the anti -compounding works is not clear. Please elaborate the explanation.
You are correct that when talking about the trailer, when the TPV is closed and not connected, anti-compounding is not an issue. The only time the anti-compounding feature is needed on the SR-5 valve would be if the TPV is open and the supply line is charged, releasing the parking brakes. If the driver then applies the service brakes, charging the service line, and then pulls out the system park or trailer park valve, the anti-compounding feature will prevent the spring brakes from automatically applying until the pressure is released from the service brakes. Here is a nice schematic from Bendix that shows the layout of the system: hnctruckparts.com/images/airbrake.jpg This is the only scenario where anti-compounding would be relevant on a trailer, normally it is more of an issue on the truck/tractor.
Yes, on modern trucks the parking brake relies on mechanical spring force. That makes it more reliable and an air leak will not cause the parking brake to release. There was a time when older trucks did not work this way and air pressure was used to apply the parking brake. There a lot of stories of those trucks rolling down hills if the truck shut off and the system lost air pressure.
(Jim Mack) Am I to conclude, after all these years, that the "monster" spring in the spring brake chamber application is doing most of the torque in an application, carefully manipulated by air pressure regulation? Great vid, by the way!
That is not what typically happens, only in the case of a failure in a the primary circuit and only then if the truck/tractor is equipped with what is commonly referred to as an "inversion valve". 51:31
SR-1 Spring brake relay valve takes care of the rear axle spring bakes , when there is a loss of air in the primary reservior by diverting the air from the secondary reservior. How about the rear service brakes , in case if there is a loss of air from the primary reservoir. How can these brakes can be applied. Pl explain
The inversion valve would do what you are asking. Not all trucks are equipped with them but if they do have an inversion valve and the primary circuit has an air loss, it uses pressure from the secondary reservoir to bleed pressure off the mechanical spring brakes to achieve some braking on the rear axles. You can see more about the inversion valve here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-lBzP2D4pt4M.html
It can enter the compressor but in most cases it will not cause any lasting damage. It would probably cause a build up of some oil in the wet tank, similar to the oil buildup caused by worn rings in the air compressor.
@@SuperDoeboy77 An obstruction in the cylinder bore of an air compressor which would lead to vacuum above the piston drawing oil past the piston rings. Or, an obstruction in the compressor discharge line which could also create a carbon buildup or overheating.
