November 11, 2010

7 Min Read
Low-Headroom Bulk  Bag Dischargers Offer Expansion Solution for Shower Pan Manufacturer

General view of the Spiroflow Model T5 low-headroom calcium carbonate bulk bag discharger at Just Trays

Just Trays Ltd of Leeds, West Yorkshire, UK, is the country’s leading manufacturer of acrylic resin based shower pans. Founded in 1988, Just Trays combines more than two decades of experience and craftsmanship with innovative technology. Currently, the company offers a selection of 800 different shower pans in six ranges from engineered installation solutions to hand-made contemporary designs.

Quality and innovation are two key principles that drive the company’s business, with heavy investment and development in both areas. In the past two years, more than $1.6 million has been invested at the Leeds facility to improve equipment and processes to ensure production of the highest quality acrylic based shower pans.

New Casting System Installed

Just Tray’s most recent capital equipment purchase is a new pan caster whose annual output will enable the company to literally double annual capacity on its low-profile shower pan production line from more than 200,000 pans a year to more than 400,000 pans a year.

The previous pan caster had an integral bulk bag unloading hopper. Bulk bags were loaded into place and supported during discharge by an overhead hoist. When difficulty was experienced in discharging calcium carbonate from compacted or otherwise problematic bags, the hoist was used to raise and lower the bag to promote flow.

Just Tray’s new pan caster differs from the previous system since it requires delivery of the calcium carbonate and recycled glass beads, to two separate buffer hoppers located on top of the machine. These additives are metered at differing rates into the mixing chamber where they are mixed with resins according to the specifications of the shower pans to be cast.

The Spiroflow-supplied main control panel at Just Trays

The problem faced by Just Trays was identifying the best way to feed the calcium carbonate beads and recycled glass beads into the new pan caster.

Bulk Bag Dischargers and Flexible Screw Conveyors Installed

Without any suggestion on how to solve the feeding problem from the pan caster manufacturer, Darren Rhodes, operations director for Just Trays, found a possible solution at a trade show he attended.

“We were looking for a competitive price, a supplier with a reputation for quality products, and a track record for quick delivery and service,” Rhodes noted. “In the final evaluation, Spiroflow met all of the criteria”.

Equipment supplied by Spiroflow to Just Trays includes two Model T5 low-headroom bulk bag dischargers with integral flexible screw conveyors. Spiroflow’s partner company for North and South America, Spiroflow Systems Inc. is located in Monroe, NC.

With the Model T5 discharger, the top frame is removed by a forklift truck and moved down to floor level. A full bulk bag is then installed and the frame, complete with bag, is re-positioned back onto the base of the discharger. Installing bags into the discharger this way considerably reduces the amount of headroom required meaning that these dischargers can often be used in places where competitive units cannot.

Just Trays’ production manager, Ricky Dumbleton, visited Spiroflow to witness the discharging and conveying tests on their calcium carbonate and recycled glass bead material. As a result of the tests, the bulk bag discharger for the calcium carbonate beads was also furnished with optional bag massagers to promote the flow of compacted bags.


Two Spiroflow flexible screw conveyors at Just Trays feeding the hoppers above the pan caster.

According to Rhodes, “This is much more efficient, clean, and safe than having to bump the bag up and down on a hoist as we did previously.”

Two Spiroflow flexible screw conveyors were installed, both integral to the two bulk bag dischargers. The first conveyor was integral with the calcium carbonate beads discharger and supplied with the more usual round spiral. The second conveyor, that is integral for the recycled glass beads discharger, was fitted with a flat spiral screw due to the fragile nature of the glass beads.


So as not to disrupt production and the supply of shower pans to the market, the new pan caster was delivered to Just Trays and installed while the previous one was still in operation.

To facilitate this, Spiroflow loaned Just Trays two Model T5 low-headroom bulk bag dischargers with appropriate flexible screw conveyors from its comprehensive stock at its test center. Once the new equipment was manufactured a few weeks later, it was jointly installed over a weekend by Just Trays and Spiroflow to avoid losing any production time during the week. Start-up was in early March 2010.

“The Spiroflow equipment has been in operation for several months now and is operating absolutely to our satisfaction,” confirms Rhodes.

How the Bulk Bag  Discharger Works

The Type 5 low-headroom bulk bag discharger is specifically designed for applications with restricted headroom and consists of two sections. The upper section, which holds the bulk bags, is lifted off the lower section by the forklift truck’s two tines and lowered to ground level. Bags are brought up to the upper section by forklift using a special lifting frame on to which the bag’s loops are attached for lifting. Full bags can be loaded to the upper section with the forklift tines only having to be raised a little higher than the height of the bag and its extended lifting loops. Once the bag is safely in place, the upper section is again lifted by the forklift tines at its base onto the lower section of the discharger. Because the upper section is lifted from its base, the mast of the forklift does not rise above the top of the upper section as it is repositioned. This enables the discharger to operate in lower headroom areas compared to single section dischargers. The upper section is then locked into place on the lower section using a dust-tight docking seal located between the upper and lower sections.

General view of the casting process from the Spiroflow Model T5 low-headroom recycled glass bead bulk bag discharger at Just Trays

An access door in the dust containment cabinet (mounted above the discharged material collection hopper of the lower section) allows the bag to be untied. If the product is of a dusty nature, then it is preferable that the discharger be fitted with an optional pneumatically operated outlet spout clamp. This enables the neck of the bag to be ‘strangled’ so that the outlet spout can be untied without emissions or spillage. With a spout clamp, flow from the bag can only begin once the dust cabinet door is closed and the interlocked spout clamp is opened. Spout clamps are not necessary for non-dusty granular materials.

Pneumatically operated bag massagers are a further option. They can be positioned to act upon the sides, corners, and/or base of the bag as required. They deal with bags that contain products that are poor flowing or which have become compacted during storage or transportation. It is these bag massagers that make it essential that the two sections of the discharger are locked together.

The Model T5 discharger provides the same spring-loaded side tension arms as all other Spiroflow models. These raise the bulk bag as it empties helping to ensure complete discharge while preventing the neck of the bag from sagging into the conveyor or other equipment below. The versatility of the discharger means that multiple bag frames can be purchased for batching different materials. Multiple options are available including loss-in-weight load cells to dispense accurate batches of product or to meter materials at a required rate. The discharger is available in carbon steel or stainless steel.

Spiroflow is a worldwide supplier of a wide range of both standard and custom powder handling equipment, specializing in bulk bag dischargers and fillers, flexible screw conveyors, aero mechanical conveyors, tubular drag conveyors, pneumatic conveyors, a range of 50-lb bag packing and unloading equipment, and flexible storage silos.For more information, call 704-291-9595 or visit

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