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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

One of the great benefits the Internet has brought to busy process engineers is the easy access it provides to information that can help improve their processes. At the heart of this information revolution you'll find an increasing number of companies publishing their own white papers that are full of useful process information.

This wealth of practical knowledge and know-how is freely shared in white papers that can be found on corporate websites and cited in blogs and help forums. Following are a few of the white papers that have come across my web browser most recently.

Application Example: Feeding & Conveying in Polyolefin Production
This 12 page document by the K-Tron Process Group may be the most comprehensive white paper they've yet published, which is saying a lot considering the 28 other white papers available for download, covering food, pharmaceutical, chemical and the plastics industries. The carefully illustrated paper proves a complete review of the many processes available today in producing the most important polymer resins used in the world today. You can download Feeding & Conveying in Polyolefin Production here. Registration is free and gives you access to all the other white papers, spec sheets and brochures on the site. While you're there on the Polyolefin Production page, you'll also see a cool fly-through animation of feeding and conveying in the dry-end of the polyolefin process.

BlueLevel Technologies: Level Measurement and Monitoring White Papers
BlueLevel Technologies currently offers 11 white papers on their website covering a variety of topics and issues related to level measurement and monitoring.  Topics include overviews of products and technologies available for powder and bulk solids applications, industry-specific applications, and safety issues. BlueLevel Technologies' Managing Director Joe Lewis was an early advocate of publishing white papers that document a company's expertise on a particular subject and serve as educational tools. See his White Papers Are Great Tools For Assessing Vendor Expertise article that he wrote for this blog in 2005.

Hosokawa Micron Powder Systems: Powder Processing Educational Center
The Hosokawa Micron Powder Systems website provides an Educational Center where you'll find 12 technical articles on a variety of powder processing topics: 

• Advances in Powder Micronization Technology for the Pharmaceutical Industry
• Advances in Powder Processing Technologies for Chemical, Food and Mineral Applications
• Combustion Research Center Quits Milling Around, Starts Milling On-Site
• Dry Agglomeration Technology Using Bepex Roller Co
• Fluidized Bed Jet Milling for Economical Powder Processing
• Stirred Freeze Drying – 3 pages
• Homing in On the Best Size Reduction Method
• Innovative Milling & Micronization Techniques For the Pharmaceutical Industry
• Sizing Up Grinding Mills
• The Future of Freeze Drying
• Toner Tests Mill, Mix, and Classify Ingredients
• Increasing SOx removal efficiencies in Dry Sorbent Injection Systems

The white papers are PDFs and free to download. In The Future of Freeze Drying you'll find a brief history of the process, which is said to go back to the ancient Incas, who preserved food by freezing it in the winter mountains. At those high altitudes the frozen water is removed through the low vapor pressure of the water in the surrounding air. Although the process was slow,
the quality of the food remained remarkably good over time.

Malvern Instruments: Online Knowledge Base
Malvern Instruments makes you register before you can even see what they offer in their Applications Library, but if you take the time you'll be rewarded with 769 white papers. The Malvern website also offers on-demand multimedia presentations, podcasts, e-learning opportunities, user training and web seminars. In addition to English, some content is available in other languages such as German, Italian and Portuguese. You can preview one of Malvern's white papers before you take the trouble to register on their website. Go to 10 ways to Control Rheology by changing Particle Properties right here on the News Center.

A Standard by which Companies Are Judged
In a recent news release, Joe Lewis cites a 1922 white paper by Winston Churchill as the first instance of a white paper. Another source points to lengthy 19th century Blue Papers published by the British government and presented to Parliament wrapped in a blue cover. Shorter position papers were published with white rather than blue covers. Soon the name white paper became associated with any brief, well-focused background report. Americans adopted the term during World War II to apply to government and business reports.

But it wasn't until the 1990s and the growth of the Internet that white papers came to play an increasingly important role in business. For today's engineers white papers have become one of the most fruitful places to find practical process knowledge. And for those selling to process engineers, well written white papers are now a standard by which companies are judged to be serious players in the industry.

Don Dunnington
Blog Moderator