River City Enterprises’ Piston System in Combination with Assmann Plastic Storage Tanks Protect Viscous Product Integrity, Eliminate Product Waste, and Reduce Maintenance

In 1986 River City Enterprises, Division of Staffco, Inc., Peoria IL, developed a unique piston system to store and dispense viscous materials up to 500,000 centipoise. The non-pressure 400 gallon piston bins gave customers a system for the storage, handling and delivery of low, medium and high viscosity products. Rugged, lightweight, and durable, the piston bin provided a simple solution for handling viscous products and quickly became popular in many industries.

The piston system developed by River City is unique. It consists of a sealed, closed loop patented piston system and a plastic tank for storage. As the piston moves down, the inflatable piston seal wipes the inside tank wall, making the bin virtually 100% efficient. The piston also acts as a barrier to protect high quality, expensive materials from air, moisture, dirt, and other contamination. A positive displacement pump is used to fill and discharge the material through the 3” bottom valve and quick coupler.

Eight years ago, River City needed to find another bin supplier. After checking with several companies, they found that Assmann Corporation, Garrett, IN, was the best choice to design the bin they needed to use with the piston system. Since 1996, Assmann has been supplying River City with reusable 400 gallon polyethylene storage tanks. Assmann engineered the bins specifically for River City.

Commenting on the Assmann plastic storage tanks, Stewart Boal, President of River City, “said, “We chose Assmann tanks because they are high quality. The tanks stand up well and do the job. We also wanted an ISO certified manufacturer. Assmann is a 9001 ISO certified company.”

The Assmann bins used by River City are reusable vertical storage tanks that are rotational-molded from high density crosslink or medium density linear polyethylene. To manufacture the tanks, Assmann starts with the best resin for the application.

During the molding process, large efficient ovens which rotate end-over-end create optimum airflow and uniform heat and set the first stage of manufacturing the tanks. Air cooling sets the second stage. In the cooling cycle, Assmann never uses water to cool its tanks. Instead, the mold and the part inside are cooled gradually with very high volumes of air. This gradual cooling allows the cross linking process to complete all the way through to the inside of the tank wall. Although it takes longer than water cooling, air cooling delivers a more uniform resin cure, reduces wall stress, and improves shrinkage parameters for more consistent quality, greater structural integrity and longer life.

In addition, during the tooling stage, Assmann does not “shield” the outside of the tank mold. Shielding can trigger a loss of control in the process and result in uneven cooking and variation in gel percentages over the tank structure which leads to stressed and compromised parts. Dedicated to producing the highest quality tank, Assmann exceeds the ASTM design hoop stress minimums for the lower sidewall and carry this wall thickness as uniformly throughout the entire tank for structural integrity.

The polytanks have narrow diameter for space saving in-plant use and are more corrosion and chemical resistant than fiberglass, stainless or mild steel. They also possess excellent low temperature impact resistance and are U.V. stabilized. Plus, they are lightweight to same on freight.

The Assmann bins are also translucent so the product level can be easily seen. River City liked the fact that the product was visible and customers could see the amount of product remaining.

The River City piston system used with the Assmann tanks is pump operated. The system fills and discharges the product from a bottom 3" valve and quick connect fitting. Assmann designed the tanks with molded in openings the size that River City required.

For the pump to load properly, the material must be flowable. As the material is pumped out, the vacuum below the airtight piston pulls the piston along with the product while wiping the tank sidewalls clean. Because the material level can be easily viewed, customers use more product when compared to other containers. When completely discharged, only 5 or 6 gallons of material remains in the 400 gallon piston bin.

The River City bins are cost-effective. One bin replaces up to eight drums and the air-tight seal assists in the discharge of viscous materials while maintaining product integrity. The piston bins are reusable and returnable containers. They eliminate the high cost of drum waste, handling and disposal. The rugged, durable poly piston bins will last over ten years with minimum maintenance.

Boal summed up his long-time association with Assmann by saying, “We like working with Assmann. Assmann is a reliable company. The people are easy to work with and they deliver what they say they will. I give them the highest rating. Our association has been a good one.”

River City’ 400 gallon poly piston bins are widely used in many parts of the world to store lubricating greases, automotive undercoatings, silicones adhesives, plastisol sealers, fiber optic gels, and other viscous products.