Questions and Answers about Storage Silos for Plastic Resin

Material Storage

Questions and Answers about Storage Silos for Plastic Resin

What are the benefits of a storage silo for resin?

Some of the benefits of using a silo for storage include the ability to buy resin in bulk.  This will allow you to pay a lower cost.  Silos also reduce the time and labor associated with handling and moving material in gaylords and bags.  By storing your resin outside in a silo, you eliminate or reduce plant floor storage space requirements for bulk materials.  You will also eliminate the waste and disposal costs of packaging.

What are storage silos made of, and how are they constructed?

Silos are built using either coated carbon steel, aluminum, or stainless steel and may be constructed in several different ways.  Bolted silos are multi-piece, bolted units which are shipped in pieces then assembled by on-site personnel. Welded silos are factory welded units are are shipped in one piece, then erected onto a prepared foundation, usually in a single day (Stainless steel silos are usually of this type).  Spiral formed silos are roll formed at the factory, shipped in one piece, then erected onto a prepared foundation, also in a single day.  Typically these are produced only in aluminum.

Of the materials, coated carbon steel is the lowest cost and therefore is more widely used in silo construction. However, the carbon steel panels used in silos must be protected from surface rust and corrosion, since these could potentially contaminate resin. So, all carbon steel used in resin silos has a durable epoxy coating on the internal surface and a primed and enamel-coated surface on the exterior.

Aluminum costs significantly more than carbon steel, but requires no surface coating or treatment and is virtually maintenance-free for its lifetime. Aluminum may be chosen by processors because it virtually eliminates any risk of resin contamination due to rust, corrosion, or flaking.

Stainless steel is a premium priced material, typically the material of choice for silos handling resins that will be used to make high-purity medical or food-contact products. Of course, stainless steel is also corrosion free, contamination free, and virtually maintenance free.

What are the ‘must have’ features for a resin storage silo?

One of the must haves is weather tight construction to keep resin dry and contamination free.  Another feature is the ability to select the degree of the bottom cones (45°, 60°, or 45°/70° compound cones) to ensure proper downward flow of various resins or powder.  Weather tight roof structures which includes access hatches and air vents.  Safety features such as personnel ladders with safety cages, rest platforms, fall arrest systems, and perimeter guardrails are a must.  Lastly, mounts/flanges for resin loading and conveying equipment: vacuum receivers, railcar or truck fill points, level indicators, slide gates, and distribution controls.

How do the different types of resin storage silos compare?

Bolted silos Welded silos Spiral silos

Materials of construction

Coated Carbon Steel, Aluminum Coated Carbon Steel, Aluminum, Stainless Steel Aluminum only

Initial cost

Lowest Higher

Higher

Cost to ship

Lowest Higher

Higher

Time to erect

Multiple days One day

One day

Dimensions:

·      Heights

·      Diameters

 

24-64 ft. (7.3-20m)

12.25 to 18.5 ft. (3.7-5.6m)

 

18 to 72 ft. (5.5-22m)

10 to 14 ft. (3.0-4.3m)

 

24-60 ft. (7.3-18.3m)

11.5 to 14.7 ft. (3.5 to 4.5m)

Capacities 1,901 to 10,412 cu. ft. 838 to 9,826 cu. ft.

1,292 to 8,001 cu. ft.

* Silo types, materials and dimensions based on products offered by Conair.

 

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