20 kg Bins and Bulk Totes: Pads for Loads That Outgrow a Tray

A further-processing site switched from 20 kg trays to 200 litre wheeled totes to cut handling, and kept the same pads. Within a week, every tote was holding 3 to 4 litres at the base, product at the bottom was discoloured, and the pads were floating free somewhere in the middle of the load. The pads had not failed. They were being used at a scale where a flat sheet cannot work, because a tote loads from above and drains from below, and nothing in between routes the liquid.

Bulk containers are where pad design assumptions break down. This article covers the geometry problem, the three arrangements that work in a tote, and the capacity arithmetic that decides between them.

Why a Flat Pad Fails Inside a Tote

In a tray, product sits on the pad across its full area and liquid has a short vertical path, typically 100 to 150 mm of product depth. In a 200 litre tote, product depth reaches 500 to 600 mm and the load is 60 to 90 kg. The pad at the base is under the full weight of that column, which compresses the core and reduces its effective capacity by 30 to 50 percent.

Worse, product settles. Fines, trim and small pieces migrate to the bottom and form a mat over the pad, which seals it. Liquid then sits above the mat and the pad stays dry while the tote holds three litres.

The Three Arrangements That Work

A perforated false bottom 40 to 60 mm above the tote base, with the pad laid on the false bottom, is the most effective. Liquid drains through the perforations, the pad stays uncompressed because it carries only the fraction that passes, and the product never touches the pad directly. A 200 litre tote needs a false bottom of about 550 by 750 mm and two 400 gsm pads to cover it.

A hanging absorbent sock, suspended from the tote rim and reaching to just above the base, suits operations that cannot modify the tote. It intercepts liquid at the wall where runoff concentrates, and it can be pulled and replaced without unloading. Capacity is lower, around 800 millilitres per sock, so it suits drip rates under 2 percent.

A layered arrangement, with a pad every 150 mm of product depth, works but is labour-heavy and creates disposal volume. It is the right answer only where product cannot be unloaded mid-cycle.

Capacity Arithmetic for a 60 kg Tote

Sixty kilos of pork shoulder at 3.5 percent releases 2.1 litres. Against a working capacity of 450 millilitres per 400 gsm 550 by 750 mm pad under load, that is five pads, or three pads plus a mid-cycle change at twelve hours. Most sites specify two and discover the arithmetic at the first wet floor.

For poultry at 5 percent, 60 kg releases 3 litres and the count rises to seven. At that point a false bottom with a drain to a sump is cheaper than pads, and the honest answer is to change container rather than absorb the load.

Unloading, Cleaning and the Cross-Contamination Trap

A tote that has held drip for 24 hours has liquid on the walls above the product line, which transfers to the next load. Totes need a wash between uses, and the wash water is a high-COD stream that should go to drain with the rest, not to a floor gully that feeds a fat trap.

Pads in a tote also tend to be forgotten at unloading. A pad left in a tote that is then refilled becomes a contamination source with no visible sign, which is why tote pads should be a distinct colour from tray pads.

Bulk thaw is a routing problem more than an absorbency problem, and the pad is one component in it. Our SAP pad and sock formats for bulk bin thaw are cut to standard tote footprints.