Storage Volumes:
What is Water Full?

Water full refers to the capacity of a silo or storage tank assuming it is filled with a liquid (or water). Liquids will settle and have a flat (horizontal) surface and utilize the full volume of the storage container. Dry bulk materials such as: grain, coal, or aggregate form a cone shape pile. Due to the geometry of the cone shape, there are voids at the top of the pile inside the silo that cannot be completely filled. These are important to consider when estimating how much storage you will need. This article will cover the volume difference and how to know how much storage is right for you.

FIGURE 1: Conical Pile (top), Water full Pile (bottom)

FIGURE 2: Example Material Properties Table

ROOF JOISTS

Flat roof concrete silos much also account for roof joists and beams when considering the best practive to avoid contact between these structures and the stored material. Overfilling the silo and “burying” the joists could result in structural damage as well as accelarted corrosion of the joists / beams. With proper joist and fill placement, the silo can be filled the roof height without interferring with the joists.

VOLUME LOSS

CAUTION: Manual manipulation of the stored material is NOT advised. Personnel should NEVER walk of the top of a storage pile witout need and without proper safety procedures and equipment. Engulfment is a real danger anytime someone is walking on stored material.

CONICAL ROOFS

Conical roofs are a way to eliminate the open air space shown in Figure 1, but do not provide the benefits they may appear to offer. Conical roofs are expensive to construct, provide less area for mechanical equipment, and maintenance access. They also provide no extra storage volume at the same overall silo height compared to a flat roof. Conical roofs are common on steel silos, but are not recommended for concrete silos. inversely, flat roofs are common for concrete silos but not recommended for steel silos. You can learn more about the difference between Concrete and Steel storage in this article.

FIGURE 3: Conical Roof

MULTIPLE FILL OPENINGS

The best way to reduce the lost storage volume is to use multiple filling inlets. Multiple inlets create multiple conical piles inside the silo, filling up more space. See Figure 4. Multiple inlets are the most common configuration, but note that the volume benefit is only parallel with the inlets. The volume loss perpendicular to the fill openings remains unchanged. Multiple fill inlets, spread evenly around the silo, will best optimize the storage capacity, but may be inefficient and expensive for conveyance and handling equipment to be arranged in that configuration. Many times, opting for additional height on the silo walls can be the most cost-effective way to increase storage volume.

FIGURE 4: Multiple Fill Opening

VOLUME CALCULATION

As multiple fill openings are added, the top cone shape can become complex and calculating the volume can be difficult. It becomes more difficult when adding in different types of hoppers or sloped floors. In order to easily configure the silo and find the correct size and volume of storage you need, try our Volume Calculator Tool. It allows you to utilize multiple silo designs and configurations, with up-to-date data for different bulk materials. You can check different sizes and options to find what will work best for you.