Safely clearing silo, hopper, and chute blockages

The signs of a clogged silo, hopper or chute are obvious. Nothing is discharging from the spout. Material is compacted, or there is spillage caused by overflow or conveyor backup. When production stops, workers can get creative, hitting the side of the vessel with tools or strapping on a harness to enter it. Both approaches create serious safety hazards.

In response, air cannons have become a viable alternative across bulk handling sectors, offering greater safety, reducing labour requirements, and significantly minimising downtime.

Martin^® Air Cannons clear and prevent clogs to promote material flow. The first step is to understand how, where, when, and why clogs occur. The second is to remove workers from the process of clearing blockages. The third is to monitor the flow aid system to maximise efficiency.

Why do silos, hoppers, and chutes clog?

• Weather – Humidity and temperature can affect how material flows and builds up.
• Material weight, size and shape – Gravity can be both friend and foe to bulk material flow. Materials with variable shapes and sizes, as well as different flow rates and characteristics, can result in obstructions.
• Structural design – Choosing a square or round vessel for optimal flow depends on the characteristics of the material. Material Flow Analysis software can be used to model flow.
• Load speed, volum,e and distribution – Speed and volume should not exceed the vessel’s specifications, or clogs may occur. To avoid buildup and eccentric loading stress, discharge distribution should match the geometry of the vessel.

Unsafe practices for silo, hopper, and chute clearing

Once a clog has been detected, there are several unsafe practices that may seem harmless at the time but can result in serious worker injuries or fatalities.

• Beating the vessel walls with objects to loosen adhered material can create bumps and ridges on the wall, forming ledges that promote further accumulation. This approach also puts workers near the spout, exposing them to sudden surges of material.
• Poking or lancing underneath the clog at the discharge point can cause a sudden surge of material, potentially burying or crushing workers below.
• Confined space entry is a major cause of worker injuries and fatalities when clearing obstructions. Bridging material could pull a worker into the cavity, while material buildup on the sides of the vessel could release from above, resulting in serious injury or burial.

How do air cannons work?

Martin Air Cannons use the site's compressed air to deliver a powerful blast that aerates material and dislodges buildup. The basic components include an air reservoir, a fast-acting valve with a trigger mechanism and a nozzle that distributes the air in the desired pattern to clear the accumulation effectively.

Often installed in a series and precisely sequenced for maximum effect, the network can be timed to suit individual process conditions or material characteristics.

With outward-facing valves for easy maintenance, the cannons can be connected to a solenoid box up to 61 m (200 ft) away, providing safer and easier access. This allows them to be linked to and activated from a centralised control system or fired manually from the solenoid.

Bulk material flow technology

The N2^® Air Cannon Intelligence (ACI) System gives bulk handlers greater insight into air cannon performance, enabling entire installations to optimise throughput. It provides operators with continuous monitoring and detailed analytics through a secure web-based dashboard and mobile interface.

Fitted to each air cannon in a plant, the N2^® ACI sensor measures firing characteristics, helping operators monitor, identify, and diagnose problems. Early identification allows maintenance staff to focus on prevention rather than reaction, helping to reduce unscheduled downtime. Remote monitoring also reduces the labour required for inspection, lowering operating costs.

Improving safety and production

Martin Air Cannons and the N2 ACI System have helped cement plants, ports and terminals, mines, quarries, agricultural operations and recyclers mitigate blockages and improve production at silos, hoppers, and chutes.

By installing a modern air cannon network, bulk handlers can improve safety, reduce downtime and lower operating costs.

Read the article online at: https://www.drybulkmagazine.com/material-handling/20082026/safely-clearing-silo-hopper-and-chute-blockages/