Discharging Modes of Steel Silo You Must Know

Nowadays one of obvious trends of steel silo is that the larger capacity of single silo is built more and more. With increasing storage capacity, how to ensure storage material to be discharged safely and effectively has become the key problem for people to consider in design and use of silo.

The basic material of the steel silo can be divided into two types: single cone discharging type and multi cone discharging type.

Single Cone Discharging Type

Gravity Discharging of Full Cone

Gravity discharging of full cone is based on concrete foundation (including concrete cone) and full steel supporting structure. Its advantages refer to high effective discharging, no residue in the silo body and simple process to be used easily by the fluidization method. The silo capacity can be fully utilized with no loss, and full cone itself can effectively increase storage capacity. The disadvantages include: a. silo cone is higher, resulting in high construction cost of its concrete foundation. b. silo might be limited in diameter, the construction cost would be even higher if it is too large. So the way of gravity discharging of full cone is generally not suitable for large diameter silo.

Gravity Discharging of Steel Cone Combined with Secondary Backfill

The advantages include: a. after the storage material is output by fluidization and gravity discharging, there is no residue inside the silo; b. steel cone foundation in height is lower than full cone. Some disadvantages include: the backfill occupies a part of storage capacity, resulting in the actual capacity may be slightly reduced. This discharging way is only suitable for large and medium silo in diameter.

Multi-hole Discharging for Flat Bottom Silo

On the bottom board of silo some holes are cut out for material discharging (usually an odd number) according to the certain distance. For multi-hole discharging for flat bottom silo, the advantage is that all storage capacity can be fully used with less backfill. Meanwhile, construction cost is less due to its lower foundation, less. The disadvantage is that there need more equipments under the bottom when the silo is empty after multi-hole gravity discharging.

Multi-cone Discharging for Flat Bottom Silo

Table Backfill Volume of Common Silo

Silo Diameter (m)	Output Diameter (m)	Backfill Angle	Backfill Height (m)	Backfill Volume (m3)
6	2	15	0.54	7.92
8	3	15	0.67	16.66
10	3	15	0.94	39.62
12	4	15	1.07	62.75
14	4	15	1.34	112.26
15	5	15	1.34	131.20
16	6	15	1.47	156.63

On the bottom board of silo some holes are cut out as outlet points for material discharging (usually an odd number) according to the certain distance. The characteristic of multi-cone discharging for flat bottom silo is that the material cannot be discharged empty by gravity with more backfills and other ways to assist in clearing.

Multi-hole Discharging for Reversed Cone Bottom Silo

IBUA homogenizer in the building materials industry adopts continuous homogenization technique introduced from Hamburg Company of Germany. At the bottom of homogenizing silo a big cone is arranged in the center. The material weight in the bottom part can be transferred to silo wall through the cone, which bottom annular space is divided into 6-12 filling areas 10°slanted to the center. In each area there’s a discharging hole at lower part of cone from which the material is discharged. The characteristic is that each outlet can discharge material individually or commonly. The disadvantage is that the way might cause eccentric discharging probably, which might bring about extremely disadvantageous influence and damages on silo wall. Therefore the way is not suitable for steel silo.

Discharging of Spiral Steel Silo

The spiral steel silo is now generally used of the dual-combination way of gravity discharging and pneumatic discharging. With no pneumatic assistance, the material at high part of the silo can be conveyed by gravity discharging. Using the fluidization device, the material at the lower part of silo can become loose material and be discharged itself. Gravity discharge of the material can greatly reduce energy consumption. Except a low pressure and blowing rate Roots blower, there are no other operation equipments in the silo, reducing maintenance cost.

The discharging corridor is determined according to the diameter size of silo body. When the material is filled with steel silo, as the needs firstly, discharging valve of some part can begin to open and make the material flow smoothly in the common role of pneumatic force and gravity. The material pressure is evenly distributed in the bottom of steel silo, here is not provided with a fluidization device.

The discharging and conveying by Roots blower can provide enough air quantity, through the fluidization device inflated by gravity angle, the material effectively discharge to the conveying device in the corridor. The whole system can achieve centralized control and automatic control.

The specific selection of the steel silo should be comprehensively considered from specifications, discharging way, storage process, use frequency, economy, location and the other aspects. Generally speaking, if it is a smaller silo (Diameter below 10 m), a large cone with small backfill or gravity discharging of full cone is better choice for it. If it is a 10-16m silo in diameter, it can be used with gravity discharging of steel cone combined with backfill or multi-hole discharging with backfill. If it is a more than 16m silo in diameter, due to higher construction cost, multi-hole discharging way ( Ground foundation). How do you choose discharging way? Here according to the specific conditions, to make a reasonable choice is the key point.

Flyer can help every client’s specific requirements to design best drawing and construction plan with outstanding and suitable discharging way of the spiral steel silo. With dozens of years’ construction experience and practice, we promise to bring every client a satisfactory and best result of modern and advanced steel silo.