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Understanding how a crusher or sizer deals with tramp can have a huge impact on your operation's productivity. Everyone agrees that you want to stop tramp from going downstream from the crusher where it can damage other equipment. The real question is: what is the best way to stop the tramp and remove it from the process line?
Over time, two schools of thought have developed as to the best approach in dealing with tramp. There is the stop and dig option, which is the only option you have with a sizer. Then there is the pass and remove system, which is made possible with roll crushers that are fitted with either a spring or oil/nitrogen tramp relief system
On the surface, the simplest system is no system at all: you just let the crusher stall.
When tramp (or any uncrushable) enters a sizer, the rolls will stall, reverse direction for a short time, and then run forward again.
The unit will attempt this action two or three times, depending on the circuit, and then shut down. The tramp is right where you can find it, in the crotch of the rolls, directly under tons of material.
Since sizer rolls are fixed, they have no adjustment method, or easy means of disassembly. Your only choice is to go in and dig out the tramp to get the unit running again. Digging through tons of material can take considerable time and manpower, and of course your line is offline until the job is done.
The secret to getting the tramp out of the line before it damages your equipment isn’t stalling the crusher but installing a simple removal system just below the crusher.
Gundlach roll crushers fitted with spring or oil/nitrogen tramp relief can be coupled with a tramp removal system that gives you a complete pass and remove system.
If you get something uncrushable in your unit, one roll will automatically relieve to pass the tramp and immediately reset. The tramp passes the crusher with minimal or no damage. The tramp, along with a small amount of wanted material, is then easily removed from the line without shutting down.
Gundlach roll crushers with tramp protection are easily fitted with a detector that monitors movement of the adjustable roll. A simple detection device such as an LVDT (Linear Variable Differential Transformer) monitors the movement of the adjustable roll, while a downstream device such as a gate, sweep arm, or sample system, can be activated to remove the tramp with a minimal amount of good material and no shutdown of the equipment.
The movable roll may be fit at the factory or in the field with the movement detection device. The detector can be set to activate on very small movements, although more commonly it is set for roll movement of 1 inch or more. A time delay is easily calculated to determine when the piece of tramp will be in position for removal. By using this signal with the time delay, the removal device is activated to remove a small amount of material along with the unwanted tramp. In testing at Gundlach with a simple movable gate, the system consistently removed the unwanted tramp from an 18 inch transfer belt. Including the tramp, just 1 cubic foot of total material was removed from the line.
Gundlach supplies the tramp relief system (spring or Nitroil) with an LVDT or similar device. The downstream removal device of your choice is readily available from a number of vendors. If you wish, Gundlach can assist in the selection and review of an appropriate removal device.
