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The process of silo selection starts
with a series of questions that require answers before proceeding.
This is one of the main problems witnessed in today’s dry bulk
storage market. Tank and silo selection many times is based on
a preferred “construction type” in lieu of “stored material”
performance requirements. Silo manufacturers tend to process
customer information relative to their standard storage products and
design parameters, which leaves the client responsible for the
outcome. This is an archaic approach which is safe for the
vendor, but many times misses the mark in
achieving a functional and efficient storage system that performs
per your requirements.
The “top 10” list below includes
basic considerations that should be addressed on every storage
application. If the application under review is routine and no
problem areas exist with the stored material or the discharge
stream, a standard tank quote can be generated. If any of items
listed are a concern, a specialist in integrated storage
applications can advise you on the correct approach. Considerations 1. How much material will be stored….tons / cubic feet? 2. Are there any unique characteristics of the stored material to consider? 3. What materials of construction should be used? 4. What product density should be used for volume and design calculation? 5. Is material degradation a concern? 6. Is material segregation a concern? 7. What type of material discharge pattern is preferred or required for the application? (i.e., funnel flow, mass flow, expanded flow, etc.) 8. Is a hopper flow aid device required for reliable discharge? 9. Should my material be tested by a “flow specialist”? 10. Do I need a reliable performance guarantee from the silo supplier?
You don’t need to have all the
answers, but you do need to know a reliable storage specialist in
dry bulk applications that can advise you in these areas. With the
basics covered, the selection process can be now be narrowed for
customer review and preference.
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We need to store 5000 cubic feet of hydrated lime. Based on the capacity requirements as detailed below, a bolted or shop-welded tank is correct for the application. Based on experience with the material and an extensive number of applications in the field, a flow aid device is required. A bin activator sized at half the tank diameter will provide reliable material discharge. A bin activator provides a “funnel flow” material discharge pattern. The material does not need to be tested. Material degradation should not be a concern. |
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Exam Storage application requires 25,000 cubic feet of a granular product. It is desired to minimize material segregation during discharge. First we will note that size selection exceeds a shop-welded tank. This eliminates the shop-weld tank, unless we break the capacity requirements into a two tank package. The correct storage selection is a bolted smoothwall tank. The correct flow discharge selected is mass flow. This does not mean we specify a silo designed for “mass flow” design loads. The correct request is to specify a silo designed for “functional mass flow” discharge. In order to provide reliable “functional mass flow” (FIFO) discharge, the material will need to be tested.
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T ■ Shop-Weld Construction Applications: Plastic resins, food products, dry chemicals, minerals, wood waste & misc. dry other - Hopper capacities under 10,000 cubic feet - Shop-controlled quality - One piece tank construction - Factory applied coating systems - Increased freight cost to the jobsite
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Less field installation
requirements |
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Applications: Cement, fly ash, coal, limestone, lime, aggregates, minerals, chemicals, plastics, select foods, wood waste & misc. dry other - Hopper capacities from 1000 – 100,000 cubic feet - Shop-controlled quality - Modular construction requires bolted field assembly - Decreased field installation timeframe - Factory applied powder coating systems |
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Applications: Minerals, aggregates, dry chemicals & misc. dry other - Hopper capacities from 20,000 – 250,000 cubic feet - Shop-controlled quality – minimize large piece count - Modular construction requires field welded assembly - Increased field installation timeframe - Field applied coating systems
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Applications: Minerals, grains, wood waste & misc. dry other - Hopper capacities from 20,000 – 300,000 cubic feet - Slip-form quality – high - continuous pour, monolith design - Jump-form construction - cold joint construction - Increased field installation timeframe - Increased foundation requirements
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field-weld & concrete construction) Applications: Cement, fly ash, coal, limestone, lime, aggregates, minerals, chemicals & misc. dry other - Hopper capacities from 20,000 – 150,000 cubic feet - Shop-controlled quality - Modular construction requires field assembly - Decreased field installation timeframe - Factory applied powder coating systems
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Bolted FP (flat panel), field-weld, concrete and hybrid silos are typically utilized in large volume storage applications. All four designs are routinely specified in the power industry. In the industrial market, bolted FP and hybrid construction are the most cost efficient silo designs. Field-weld and concrete construction require extended field installation timeframes, which equates to higher installed cost. Relative to steel and alloy “materials of construction” selection, bolted, shop-weld and field-weld silos are available in coated carbon steel, stainless steel and aluminum construction. All tanks/silos are customized for the application and are available with full skirt support, leg supports, structure supports or lug supports. Typical silo accessories include a filter flange connection for dust control, level control nozzles, manway access into silo deck and hopper areas, maintenance access platforms, caged ladders, spiral stairways, perimeter guardrails, pressure vacuum relief devices and custom requirements for system integration. In summary, if the basics are covered in storage silo selection, years of trouble free containment and reliable discharge can be expected. In today’s industrial market, a storage specialist should advise or confirm your selection. In all cases, a reliable integrated storage system starts with a properly designed and configured silo. Guesswork has been removed from the equation. |
