Piston pumps and inflatable seals create a system that protects employees and products.
Graco, Inc.

Imagine scooping and scraping a 55-gallon drum of tomato paste by hand. Imagine doing this five, 10 or even 20 times per day. Surprisingly, this is how many food producers unload ingredients from containers. Not only does this seem inefficient and labor-intensive, but with arms scooping into drums about three feet deep, this method is taxing to the human body and not ideal from a sanitation perspective. Even more surprising is that hand scooping is used for many high viscosity ingredients that are thick, sticky, and will not pour or fill back in when scooped. Some examples are peanut butter, tomato paste, icing, caramel and fruit filling.

Peanut butter transfer via piston pump container unloading system technologyImage 1. Peanut butter transfer via piston pump container unloading system technology (Courtesy of Graco, Inc.)

There are four general methods typically used for unloading high viscosity ingredients: scooping, dumping, pumping with a stand-alone pump and unloading with a container unloading system. There are pros and cons to each option.

Manual Scooping

Manual scooping was once the only option available to food manufacturers. It is becoming less common for four main reasons: labor costs, ergonomics, sanitation and waste. Scooping is the most labor intensive of the four options and is not usually feasible from an economic standpoint in areas where labor is more costly, such as the United States, Canada and Europe. It is more prevalent in areas where labor is less expensive, such as South America, Asia and Mexico. In the latter areas, manual scooping can be the least costly option when compared to purchasing equipment.

One drawback for manual unloading is the effect it has on employees. Ergonomics can be an issue, and it is not uncommon for employees to become injured from performing this task repeatedly. Compensation claims can quickly negate any cost savings realized by not investing in other equipment.

In addition, manual unloading exposes the ingredients to the atmosphere and allows employees to introduce contaminants into the food product. A person who has been scooping tomato paste all day would understandably be dirty and sweaty and can easily introduce bacteria and contaminants into the food products.

Lastly, manual scooping can leave material waste in the drum.

315 gallon tote of peanut butter being unloaded by a bin evacuation systemImage 2. 315 gallon tote of peanut butter being unloaded by a bin evacuation system

Dumping Systems

One solution to replace manual unloading is dumping ingredients into a mixing kettle or hopper for further processing. There are several options for products that lift an entire drum or tote of material and dump it into the kettle. Another option for dumping is to grab the aseptic liner or plastic bag liner inside the drum or tote and cut it open over the kettle or hopper. This allows all products from the bag to fall into the kettle for the mixing process. Some facilities also use squeegees or rollers to remove any residual material left in the liner, which reduces waste. Overall, the dumping process is a quick and efficient method to remove the product from the container.

However, there are several concerns with dumping product out of containers or liners. First, when material is dumped it is exposed to airborne contaminants and can introduce bacteria. The weight of the material can damage the mixer blades or other equipment.

From a safety standpoint, a bag or drum being suspended in the air means a lot of weight off the ground, potentially over workers in the area. Workers often need to cut the bag open and allow the material to dump out, which can create safety concerns. For systems to raise and lower hundreds to thousands of pounds, hydraulics are often involved. The industrial components can get dirty and drop debris into the mixing kettle while holding the bags for dumping. Even though the dumping process happens quickly, it introduces other issues into the food manufacturing facility.

Stand-Alone Pumps

The third option is to use a stand-alone pump, such as a progressive cavity pump or rotary lobe pump. A stand-alone pump may have issues dealing with higher viscosity materials because it is difficult to load the pump without watering down the product to allow flow. Adding water is acceptable, but it is typically done with an open top drum and a pump on a winch and chain hung over the open drum (which can drop debris into the product). This method can also leave a large amount of residual waste in the container and still be labor-intensive for users. Pumps and equipment can also be damaged when not loading properly and dry-run conditions can create additional costs and time in maintenance repairs.

Container Unloading Systems

The fourth option is to use a container unloading system with a pump mounted to it. The main difference between this method and the stand-alone pump is that the container system uses a ram system to feed the product into the pump. The ram plate covers and seals the container and material, blocking airborne contaminants from entering the product during evacuation. This helps prevent contamination and bacteria growth.

Ram units consist of a ram plate and an inflatable seal to seal the plate with the outside of the drum. This inflatable seal does not require any fasteners to affix it to the ram plate, which makes cleaning easy. The inflatable seal also allows for evacuation of 99 percent or more of the material from the container to minimize potential product waste for end users. It allows for easy removal of the ram plate from the drum since users have the ability to deflate the seal at the bottom of the container before moving the ram plate.

Container unloading systems include a pneumatic piston pump mounted on the ram plate, which can generate up to 1,200 psi of outlet pressure. This pressure is often required to move higher viscosity materials such as peanut butter. Piston pumps are self-priming and can be run dry without damage. Container systems to unload totes can be outfitted with multiple piston pumps (up to four) to unload the large volume in seven to eight minutes if required.


There are several methods for unloading high viscosity ingredients within the food manufacturing process. Arguably the most flexible, cleanest and most ergonomically safe option would be the container unloading systems that address many concerns with other methods employed within facilities.