As a storage silo manufacturer, we take in quite a number of inquiries from customers looking for silos to fit their storage needs. Many times the calls we take are from customers only looking for additional storage capacity. Quite often the request entails only basic information: capacity wanted and product being stored. If the customer is only adding storage, and is not soliciting the help of an outside OEM material-handling firm, he may find the options surrounding something as simple as product storage daunting.
This column will spotlight one type of storage silo—the shop-welded, one-piece type vessel—and will not concern itself with bolted or field-welded designs. There are many different aspects that need to be clearly thought through before a silo can be bid, designed, or built for an application. We will look at the basic considerations that need to be defined to maximize the benefit of utilizing a silo that can be designed, built, painted, and shipped in one piece. There are several phases of decision making that need to be performed.
Silo design considerations are the first phase of definition. This is a question and answer phase where all things are looked at. Is the silo a skirted, legged, or a lug supported design? What is the product’s bulk density? Where will the silo be located? Is the stored product powdered, granulated, or pelleted type product, or possibly a liquid? These types of questions are ones that help narrow down the construction of the silo, style of silo, flanges, and connections to be utilized, etc. This will also assist in determining hopper apex angles to promote material flowability, and available paint systems to consider. During this phase many ideas will be put down on paper, some of which will be discarded, or others added.
Fabrication of the silo is the second phase. The construction of the silo is typically straightforward in that, by the time the project reaches this phase, the customer has very few decisions left to make. If there are in process changes, this is the last point at which they should be performed. For the most part, each silo that is fabricated goes through the same process of manufacturing even though one silo may be substantially different from the next.
The third phase deals with painting of the storage silo. Paint seems to be a stumbling block at times to determine what type of coating would be best suited for a certain application. Paint systems can range from no coating at all, to sophisticated multicoat paint systems, or systems with high DFT profiles to withstand a harsh chemical environment. Some coatings require NACE (National Association of Corrosion Engineers) inspection in order to satisfy federal, state, and city regulations.
With such a wide variety of paints, the fabricator needs to be a specialist in this field. Being a custom applicator such as this has its drawbacks when it comes to meeting EPA guidelines, health issues with certain paints, and equipment suitability to product being applied. The customer may have several options and recommendations on what paint may be best for his application. This can make a decision on what to apply for the long term difficult, especially when one needs to consider that paint coatings are not only used to provide protection from corrosion, but should also have a good appearance to the public.
Transportation of the silo is the last phase of definition. This is a big consideration, literally. The sheer size of a silo fabricated in one piece understandably will require special shipping considerations. Large over-dimensional loads such as this can require the use of a specialized trailer, such as a perimeter trailer, or the newest type of trailer, called a Schnable trailer. These specialized trailers allow more maneuverability and can be lowered or raised in the air depending on site circumstances.
Once all the decisions are made, and all phases completed, the customer will be left with a storage silo that is quality built, pleasing to the eye, and will serve the company for many years.
Tom Nomady is Senior Industrial Project Manager at Imperial Industries Inc. (Wausau, WI). He has an extensive background in the design and function of bulk storage silos and tanks and has been with Imperial Industries since 1993.