DOE 2000. - Waste Isolation Pilot Plant - U.S. Department of Energy

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 4
The waste hoist is an electrically driven friction hoist. The 600 HP DC voltage waste hoist motor is
designed for a maximum operating speed of 13.5 RPM. The motor’s field is formed by wound poles,
and is supplied with a constant DC current obtained from rectifying a 480 volt three-phase supply. The
DC voltage magnitude and direction controls the speed and direction of the hoist. The maximum rope
speed of the waste hoist is approximately 500 ft (152.4 m) per minute. There is one silicon controlled
rectifier (SCR) power supply to power the hoist. The brake system can safely stop and hold the
conveyance without the drive motor. Automatic control circuitry will sense electrical problems with the
drive motor and stop the hoist.
There are two brakes, mounted approximately 180 degrees apart, on each braking flange of the hoist
wheel. These disc brakes (four total) are spring set, and are released by hydraulic pressure. Brake
switches indicate brake set, release, and wear. A redundant hydraulic power supply exists to supply
hydraulic pressure to release the brakes. Each hydraulic unit has its own motor, pump, and oil
reservoir. There is an automatic switch over from the primary system to the standby system if the
hydraulic pressure decreases below the set point. There is no automatic switch over from the standby
system to the primary system. A timed back up pressure relief path exists to set the brakes if for any
reason the brake pressure is not released within a few seconds after the application of the brake set signal.
Hoisting, tail, and guide ropes are provided for the safe operation of the conveyance and the
counterweight. The hoisting ropes are 1-3/8" (3.5 cm) diameter, fully locked coil bright steel ropes
suitable for use with a friction hoist. The tail ropes are 2-1/4" (5.7 cm) diameter, non-rotating bright
steel, with a synthetic fiber core. The three tail ropes approximately balance the weight of the six
hoisting ropes. The guide ropes are 1-3/4" (4.45 cm) diameter, half-lock bright steel with internal and
external lubrication and are designed to operate with minimal field lubrication only. There are four guide
ropes for the conveyance and two guide ropes for the counter weight. Tension in these ropes is
maintained by weights on the bottom of the ropes. The size of the weights are different to prevent
harmonic vibrations during hoist operation.
A conveyance and counterweight over-travel arrester system exists to stop movement if the normal
control system has failed. Four timbers are provided at the tower and the sump regions for both the
conveyance and the counterweight to assist in absorbing energy to stop an over traveling conveyance or
counterweight. Retarding frames rest in notches either at the top of the wood arresters (sump area), or at
the bottom of the wood arresters (tower area). The retarding frames have knives that cut into the timbers
if driven by the conveyance or the counterweight.
If the conveyance over-travels against the upper crash beams and the hoist ropes fail, safety lugs on the
conveyance mate with pivoting dogs on the catchgear mounted in the head frame to prevent the
conveyance from falling if the ropes break. The counterweight catchgear system functions in a similar
fashion to stop the counterweight from falling. Each catchgear frame is mounted on a hydraulic shock
absorber which absorbs energy from a descending conveyance or counterweight. Lever arms are used to
raise the pivoting dogs if they are not supporting any weight.
Emergency stop buttons are provided at the Master Control Station (MCS) and at all control stations to
effect an emergency stop of the hoist. These buttons are operable in all modes of hoist operation, and
when pressed, will open the control power loop and set the hoist brakes. These buttons provide the most
rapid means of bringing the hoist to a stop. A controlled stop button that will decelerate the conveyance
before setting the brakes is located on the control panel, to the left of the MCS. The controlled stop is a
slower and softer stopping action than the emergency stop.
4.2-23 January 28, 2003