System Parts第 8 / 60 题
What happens to the spring brakes when air pressure drops to a very low level (for example, 20 to 45 psi)?
a.They release and the vehicle can roll freely
b.The springs apply the brakes automatically
c.The compressor speeds up to rebuild pressure
d.The service brakes are disabled entirely
解析
When air pressure falls into the range of about 20 to 45 psi, the spring brakes come on automatically because there is no longer enough air to hold the springs back. This can bring the vehicle to a sudden stop, so a driver must safely control the vehicle if this begins to happen. It is a fail-safe designed to stop a vehicle that loses air.
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