Malt-handling isn’t such a back-breaker when you have a silo and a good delivery system
by George Manset
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Brewing may seem to be synonymous with heavy lifting unless a practical malt storage (read that silo) and efficient conveying system is part of the brewhouse. Without bulk storage and automatic handling, brewers may be destined to lift more than 100,000 pounds of bagged grain a year. But a properly designed silo (besides saving your back) can provide many economic benefits. Bulk storage shortens the overall brewing process, simplifies malt handling automation, and reduces the cost of malt. If you’re planning a microbrewery or considering an expansion, the following checklist will aid you in designing a silo for your needs.
Most silos chosen by brewers are either round, welded, smooth-walled silos or corrugated galvanized bolted silos. Both types are constructed of mild steel. Square silos are occasionally used by breweries, but are rare.
• Welded silos are sealed well for moisture; fully constructed, except for peripheral items as ladder/cage, indicators, etc.; and can be easily constructed to meet special design requirements. They are limited in size, however, to shipping constraints by trucking companies. The exterior finish is painted on a welded silo.
• Corrugated bolted silos require assembly; are most often less expensive to purchase and ship then a welded silo; and can be manufactured much larger than a welded silo. Corrugated silos can be installed in difficult to access rooms, without removing a wall. Bolted silos require more effort for moisture and dust sealing.
A silo’s volume is usually sized in cubic feet or bushels. In order to size a future silo, you must make a few calculations.
• First, figure the maximum barrels per month you will brew to estimate monthly malt requirements. Try to store about three months of malt if possible, without the possibility of malt sitting over five months.
• Call your malt supplier and have him or her quote you a minimum delivery without cost penalties. Silo size is often determined by the minimum volume delivered.
• Add about a week’s worth of malt volume to your silo size to ensure room for the new malt for an early delivery. This will give the malt supplier some flexibility in delivery without risking an empty silo. If your brewery is in a more isolated area, you may require more backup storage.
• Diameter is determined by space available and any limitations caused by truck hauling requirements. A 12-foot diameter silo is usually the widest most breweries would purchase of the welded type. Special pace cars are required for wider silo transportation/delivery, which is dependent upon individual state laws.
• Height is usually limited by local code or ease of access specifications. Longer welded silos may cost more to ship because a freight carrier may not be able to piggyback a second silo with a longer silo in order to share the expense of transport. Taller silos are more expensive to design for seismic or wind structural requirements, also.
• It is important to account for a 30 degree angle of repose (resting angle) for the malt. This will reduce the overall volume with certain silo designs.
Locating the Silo
By locating the silo properly, you can save costs final structural calculations should also be available if requested.
• The brewery should hire an engineer to design the pad, where the silo rests, to ensure the pad can withstand the fully loaded silo weight, seismic loads, wind loads, frost, heat, etc. Most silo footplates are bolted by the brewery to the pad.
• An engineer should review all designs for safety concerns around the silo.
Accessing a Silo
The silo may have to be accessed for inspection, clean out (very rare), replacing a worn fill tube elbow, servicing level indicators, or reaching other equipment on top of the silo (as a filter). The following options assist in accessing your silo:
• OSHA ladder and cage
• OSHA railing and toeboard (a ten degree roof will make walking easier on the roof)
• Access hatch on roof with an interior ladder
• Access manway on the cone.
Other Miscellaneous Options
A flow cone near the discharge of the silo helps ensure the grain near the sidewalls, flows out of the silo first.
• Various level indicators are available; such as electrical, mechanical, or a view glass.
• A pail fill spout on cone allows you to fill a container on the side without affecting your conveying equipment.
• Food grade epoxy coating is sprayed inside welded silos to prevent rust.
• Extra vents to tie into a central dust system.
• Special paint colors or emblems will usually cost more on welded silos, but can be appealing. Galvanized corrugated silos do not require painting.
• To secure your outside ladder and cage from young climbers, you may want to purchase a locking hinged door for the base of the cage.
Final Check Items
• All silos and equipment should be well sealed against rain. Wet malt will rot. Bolted silos should be carefully checked around seals for leaks.
• Before ordering a silo, lay out an architectural plan and elevation views with the building design to study conveying options and potential location problems. It should then be easy to determine the location of ladders, indicators, tubes, and filters in these views.
• It is most important that you always ask questions of the silo manufacturer. If something feels wrong to you, if is probably a very accurate warning sign.
George Manset is a silo specialist with Bratney Equipment Co., located in Bellevue, Wash. His phone is (206) 747-6352.
Article courtesy of the New Brewer and the Institute for Brewing Studies.