The customer used tilt switches and admittance switches to adjust the boom luffing position. The tilt switches suffered mechanical damage, sometimes were buried and were a problem in high wind conditions. The admittance probes suffered when the conductivity of the stockpile changed and also suffered mechanical damage. Both technologies mechanically came in contact with the stockpile.
The customer had used Lanyard switches to protect the boom. The Lanyard switches are a high maintenance problem.
Solution
We used our low frequency (5kHz) acoustic wave transmitter mounted on either side of the conveyor. Because height control of the boom above the stockpile is important and that the boom angle changes. We mounted the 2x 5kHz transducers on pendulum brackets so the aim of the transducers were always the same, no matter what the boom angle. The 5kHz transmitter can operate in winds up to 70 knots. Dust, particles in suspension, fog, rain, repose angle changes on the stockpile, fast response are all within the capability of the 5kHz acoustic wave transmitters.
We used our range of microwave switches to replacing the Lanyard switches. The major advantages was ease of setup and obviously the microwave switch operated without mechanically touching the stockpile. The standard microwave has a maximum range of 50m on stacker boom protection. A high powered microwave version win operates up to 100m on shiploaders, stackers, stacker/reclaimers.
