Failures to discharge from silos or hoppers mainly occur as a result of two different types of blockage: stable arching or rat-holing. In both cases the strength of the bulk solid is higher than the gravitational stresses, meaning that the structures are stable. The stresses in these structures increase as the size of the arch or rat-hole increases, hence it follows that if the outlet size of the hopper is continually increased, there will eventually arise a situation where the gravitational stresses overcome the strength of the material and the structure collapses, allowing flow to occur.
Consequently, for a silo to discharge successfully by gravity, without flow aids, the outlet size should be very large.
The most cost effective solution to resolve discharge problems in silos is actually to fluidise powders in order to promote flow by insufflating low pressure air. We dispose of a wide range of valves capable of discharging silos in a simple and clean way with an easy access for maintenance purposes.
Air Pads provide efficient means for applying fluidization air to hoppers and silos to promote flowability. We offer air pads in two types: low top (mounted on steel steep hoppers) and high top (mounted on flat concrete silo bottoms). Air pads can be used individually or in a multiple combination with air supplied from a common blower.
Both types of air pads utilize a 100% polyester screen, 5 mm thick, manufactured from abrasion resistant material and heatproof up to temperatures of 120ºC.
Slide Gate Valve
Slide gate valves are designed to provide positive cut-off or unrestricted flow of powder bulk materials from outlets of storage silos and other discharge points. Slide Gate Valves are mainly used to prevent material penetrating the rest of the extraction system when maintenance activities are carried out on drum-gate valves or other units. The sealing efficiency is high but not complete. Solid construction and precise machining assure proper alignment and free movement of the slide from full-open to full-closed positions.
Actuators available: manual, pneumatic, motorized and hydraulic. We also supplies custom configurations to meet a variety of application needs. These range from high temperature, high abrasion and excellent sealing, to very large slide gates for high capacity and severe duty.
Lump Crushers have been specifically designed to eliminate lumps generally created in silos by moisture.
- Lump Crusher in Aerated Box
- Lateral Lump Crusher
- Vertical Lump Crusher
Lump Crusher in Aerated Box and Lateral Lump Crusher are provided with aerated bottoms separated from the upper chamber by an abrasion resistant, 5 mm thick, polyester membrane (heatproof up to 120ºC).
Never use these units for grinding solids.
Flow Control Gate
Flow Control Gates have been specifically designed to control fluidised material flow when discharging silos. These units use a rotor with a V-shaped section to control the flow of material and are provided with an aerated bottom to avoid dead zones during material conveying. Flow Control Gates are known for having full tightness.
Actuators available: manual, pneumatic and motorized.
Shell Valves have been specifically designed to be located at non-aerated hopper outlets to provide positive cut-off or unrestricted flow. These valves are generally placed before a loading spout. Their working principle is based on a locking rotor operated by two pneumatic cylinders. This system provides 100% tightness with non-aerated solids.
Pressure-Vacuum Security Valve
Pressure-Vacuum Security Valves have been specifically designed to avoid hydrostatic overpressures during pneumatic loading and bottom aeration of silos and hoppers. These units are also used to avoid vacuum environments at the top of silos in case of stable-arching and the following structure collapse.
These valves are of great simplicity and do not require maintenance.
Outlet Air Distributor
Outlet Air Distributors can be employed to sequentially distribute fluidizing air in storage silos and in blending systems. These units are provided with two air inlets, one for ACTIVE air, which directs the air flow to an outlet, and the other one for INACTIVE air, which distributes the air flow to the three remaining outlets. When storage silo discharge is needed, the full volume of air is introduced through the ACTIVE air supply source. In this case the air flow is directed in sequence into each quadrant while the other three remain non-aerated.
When the distributor is used to homogenize materials the ACTIVE air is directed into the blending quadrant, while the INACTIVE air travels through the three aeration quadrants. The volume of blending air is considerably higher (75% of the total) than the volume of aeration air (25%). Each quadrant acts in sequence as the blending quadrant, while the other three serve as aeration quadrants.
Our Outlet Air Distributors are very reliable and of great simplicity, recommended when more complex solutions are not needed. Actuator available: motorized.