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If you've ever been around a crusher you've probably heard the arguments about the best way to handle tramp. Do you stop the crusher and accept the consequences of a line shutdown, or do you let the tramp pass downstream where it may do further damage?

There is strong sentiment in some camps that it's best to stop the tramp in the crusher so it's not passed along to downstream equipment that can't handle it. This "leave it right where you can find it" option is popular among sizer users because, frankly, that's all a sizer can do with tramp.

When tramp (any uncrushable) enters the sizer, the rolls will stall, reverse direction for a short time, and then run forward again. The unit will attempt this 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 the rolls are fixed and have no adjustment method, or easy means of disassembly, you're faced with going in and digging out the tramp from under all that material. But as you expend your sweat and downtime digging, perhaps you're comforted in the knowledge that you know right where the tramp is.

Roll crushers that are fit with tramp relief, on the other hand, give you an easier and far less costly option. It's true that if you simply let the tramp pass downstream to equipment that is not equipped to handle this tramp, you've protected the crusher at the expense of the downstream equipment. One option is to stop the line and get to the tramp (if you can) before it does downstream damage. A better option is to install a simple tramp removal system that is triggered whenever your roll crusher lets an uncrushable pass.

Gundlach roll crushers for example can be fit with either a spring or oil/nitrogen tramp relief system. Either of these systems gives you two features that sizers do not. One is that if you need to change your product size, it can be done in a matter of minutes without shutting the crusher down. The size range varies by machine, but it can be configured at the time of order to give you the product range you may need in the future without major refit or the cost of a new unit.

Additionally, either of these relief systems gives you protection from tramp. This means that if you do get something uncrushable in your unit, one roll will automatically relieve to pass the tramp and immediately reset, allowing a small amount of wanted material to pass with the tramp. This feature has protected equipment for over 50 years with good results. By using it in conjunction with a detection and removal system as described below, you have a system that can:

• Be adjustable for different product sizes without shutting down
• Pass tramp material without shutting down
• Remove the tramp from the system, without shutting down

Gundlach roll crushers fit with tramp protection can easily be fit with a detector that monitors movement of the adjustable roll. When the roll moves to allow tramp to pass the crusher (with minimal or no damage), a simple detection device such as an LVDT (Linear Variable Differential Transformer) triggers a signal to remove the tramp downstream. This downstream device may be as simple as a gate, sweep arm, or sample system. When activated it removes the tramp with minimal amount of good material and no shutdown of the equipment. In testing done at Gundlach with a simple movable gate, unwanted tramp was removed every time with just 1 cubic foot of total material. It never missed getting the tramp.

Where would you rather retrieve the tramp? Catch it in the sizer or let it pass to a simple removal system? Passing sounds a lot more profitable to me.

You can learn more here about tramp detection and removal systems in crushing applications. There are a number of manufacturers who make downstream removal devices, such as the Ramsey Primary Sweep Type Sampler, the PEBCO Single Blade Diverter Gate and James A. Redding sampling systems.  

Mike Hamby
Vice President Sales & Service - NAFTA
Gundlach Equipment Corporation
www.gundlachcrushers.com

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