Section § 393.51: Warning signals, air pressure and vacuum gauges.

Guidance Q&A

Question 1: Is the low pressure warning device required to activate before the tractor protection valve?

Guidance: No. Section 393.51 does not explicitly require the warning device to operate before the protection valve. It is implied that if the operating pressure of the warning device is at least 1/2 of the governor cut-out pressure, and that pressure is not less than the pressure at which the protection valve (or similar device) activates, the requirements of § 393.51 are satisfied.