Semi-automated big bag filling for the construction materials industry

Loading of big bags of fly ash

Material: Fly Ash

Objective: To fill big bags by weight via gravity discharge from a silo.

The client, based out of California, is a producer of construction materials and offers contracting services for repaving roads, general construction for small private projects to public works, and R&D for building materials. The client was spending too much time and effort on cleaning up spilled fly ash from their manual big bag loading operation. They wanted to improve operator safety and ergonomics while wasting less material from spillage. The request was to design a dust-tight big bag filler that could work with minimal operator intervention and fully contain any dust or material spills. Further challenges to the project also included periodically handling hot fly ash which can be very abrasive.

Scope of supply:

1. Flowmatic 03 – Semi-automatic FIBC Filling Station
2. Dust Containment Enclosure

Palamatic Process has designed a big bag filling unit to handle most of the charging operation with minimal operator intervention required. Since the client needed to prevent exposure and fully contain the dust, most of the filling cycle was carried out via PLC automation. This includes:

• Inflation of the spout seal
• Tensioning of the big bag via pneumatic cylinder adjustments
• Inflation of the big bag via integrated fill head fan
• By-pass valve to switch over to dust collection system
• Opening of the material flow control valve
• Load cells read fill weight level and pneumatic cylinder lowers big bag onto densification table
• As weight limit hits 95% fill capacity, flow control valve switches to 4-20ma signal for low-speed flow control to improve fill weight accuracy
• 1st vibration activated on densification table
• Feed cycle finishes and valves are closed
• 2nd vibration activated to deaerate material and stabilize big bag
• Seal is deflated and automatic hooks release the big bag. Forklift operator can remove the filled big bag via forklift operation.

*All cycles are configured and controlled by the Pal’Touch PLC.

The powder filling unit is composed of two main elements:

• The main structure: installed on load cells for automatic gain-in-weight operation, this structure consists of forks for big bag hanging (automatic hooks available by option), pneumatic tension cylinder to accommodate various big bag sizes, and possibility of mobile skid via lockable casters or forklift.
• Filling head with double-jacket tube: fitted with a flexible sleeve to isolate the weight for load cell operation, the double jacket allows for material to fill through the inner channel and the air volume and fine dust particles to escape and balance through the outer tube.

The hanging forks can be either “round – style” for manual loading and unloading via pallet, or “u-shaped” to remove by handles via forklift.

The installation was placed under an outdoor silo with a discharge height of 8 feet from the ground. Fly ash is considered a toxic and abrasive material which were taken into consideration for the design of this equipment. Thanks to the smart design by Palamatic Process, the client was able to achieve a fill rate of 10 big bags per hour.

Due to the hazardous nature of fly ash, the client wished to install an extra safety precaution by surrounding the bulk material filling station with an enclosure. During the fill cycle the swing doors are secured and ensured via PLC controls and safety interlock switches. The filling sequence cannot begin until the dust containment enclosure is fully secured. The enclosure and filling station can also accommodate steel IBC units for when the fly ash is still hot. The enclosure is made of clear plexiglass, and can also be connected to a central baghouse dust collection system for further protection against operator exposure and a safe work environment.

By designing the station to maintain dust tight seals at all critical connection points: silo outlet flange, BFM flexible sleeve connection, inflatable seal for big bag spout and cabinet enclosure, the client’s design and production requirements were fully realized.

The main objective of preventing material spills and exposure to dust was realized.

The FlowMatic® 02 AshFlow big bag filler dedicated to fly ash could also have been used for this customer problem.