“The automatic emergency-parking brakes on some Bucyrus 848 Un-A-Haulers may take four to five seconds to activate after the panic bar is hit,” the company explained.
“When this type of equipment is field tested, the brake must engage within one second after hitting the panic bar.”
As a precaution, Bucyrus asked all mines using the 848 Un-A-Haulers to field test units to determine proper braking – that is, that the brakes activate immediately when the panic bar is hit, a federal regulation under 30 CFR 75.523-3(b)(1).
The company also outlined a remedy for the delayed activation: a pilot-to-close check valve and the replacement of the original L-H788X5 solenoid with Bucyrus’s solenoid kit (#241103) is required.
The system connection for the kit must be made in compliance with the Bucyrus brake system diagram no. 623842 848 (241103 Solenoid Update).
Those mines needing assistance with solenoid replacement or with general questions should contact Bucyrus directly. The OEM is also distributing large copies of the drawings needed for MSHA-compliant amendments to the units.