 Bob Kolatac Metalfab Technology Manager Visit Website |
Bob Kolatac has been Metalfab’s Technology Manager since 2001, and first started in the materials’ handling business in May 1968 as a Laboratory and Field Service Technician testing and developing discharging and metering equipment for a wide range of customer applications. Today, he is involved in research and development and is responsible for pre-sales equipment selection and sizing, lab testing, and field service projects worldwide.
Bob received a Certificate of Industrial Chemical Technology from Newark College of Engineering (1970); a BS in Industrial Engineering (1977); and a MS in Management Science from New Jersey Institute of Technology (1981). He has written and published numerous articles on feeding and conveying of dry bulk materials, is a contributing chapter author in the “Bulk Materials Handling Handbook”, and has led numerous engineering seminars on metering of bulk solids materials in the US and abroad.
Metalfab, Inc. has more that 35 years of experience as a manufacturer of dry bulk material handling systems and equipment inclusive of their proprietary MetaTech™ Volumetric Feeders and Better-Weigh® Gravimetric Feeders, Posibin™ Storage Bins, Bin Activators, Bulk Bag Loaders and Unloaders, Convey-All™ Flexible Screw and Vibrating Tube Conveyors, and other specialized equipment including PAC Storage and Handling Systems for the Power Generation industry.
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Feeders Q&A
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I have a Vortec slide gate on the discharge of a ribbon blender. It is continually jamming because powder gets into the slide mechanism. What can be done to minimize or eliminate this problem?Answered May 19th, 2010 by Expert:I am are pleased to offer some comments in answering your topic question regarding problems associated with a knife gate valve installed on the discharge of a process ribbon blender. [Assume most materials are very fine particulates?]
Knife gate valves [KGV’s] are not ‘new’. If you research the early recorded use of such cut off gates, you will find a link to the sale and fabrication of KGV’s to a Swedish company dating back to 1650! Since then, different valve types, products and designs were made available, starting in the 1800’s through present day.
Unfortunately, not a lot of technical improvements were made, particularly for KGV’s during these early years, simply due to the fact that these valves [and other types as well] were made for use in liquid and gas control, whose properties are known and fairly constant [I.E. consistent and uniform]. When faced with a solids control problem, engineers were forced to select and make fit, KGV’s designed for liquids or gases.
A quick review of US Patents issued or pending from 1960 through the present, indicate most deal with valve operation improvements rather than design improvements. Valve operating improvements to seals, packing, seats, and valve liners are most often cited. The design remains the same with improvements being directed to the internal components.
There are a few valve companies who have come along over the last twenty years or so, who have specialized in dry bulk solid valves due to the very problems referenced. One of these is Salina-Vortex, which you are familiar with.
Your problem looks like it is due to a seal problem associated with the knife gate sealing against the body. Powder material can build up in the open chest area and remain ‘trapped’ eventually causing the problem you describe. Several solutions include: installing an inlet shield or shear protector, which is designed to minimize direct powder contact with expose seals, and other moving parts. This generally works best when the KGV is slightly ‘oversized’; providing purged air to the enclosure for seal / seat protection; or the most obvious is to replace the valve with an “Orifice Gate” design which has slide gate blade/seal modifications referenced above and consider air purging as well.
I hope this has been helpful?