Inspection System for Beer Keg Quality Assurance

Creating a safe-and-reliable, beer-barrel, cleaning, and pressurization line

By David Thode and Josh Hemstreet -- Control Engineering, 12/15/2005

Green Bay, Wis.-based Tosca Ltd. cleans and reconditions many different food-industry containers. Examples include: bulk cheese containers; bulk plastic bins, for pizza crust production and transportation; returnable plastic containers, for transporting produce and meat; and beer kegs.

Several different brewers employ Tosca to repair and clean their kegs. After repair of a beer kegs, valve inserts are placed back in the barrels and a retaining ring is positioned in the stem so the valve cannot pop out of the stem. Next, the keg is pressurized and checked for leaks prior to shipment.

Ifa retaining ring is not placed or properly seated, this could pose a quality issue for the customer. Tosca quality assurance personnel perform visual secondary inspections on 100% of their finished product to ensure that each barrel's retaining ring is properly inserted.

Curt Dhein, Tosca's Green Bay plant manager said, "This was very time-consuming, and we were sure there had to be a better way to ensure the retaining ring had been properly installed during our process. We had used vision systems in some of our other operations with good success, so we wondered if that technology would work in this application." Consequently, HiTech Control Systems Inc., also of Green Bay, was contracted to design a vision system to verify the presence of the retaining ring on kegs with slotted valves and notify the operator if a retaining ring is missing.

HiTech's system-integration approach encompassed:

• Project characterization and management;
• Vision design, programming, configuration;
• Configuring inspection tools for:
• Ring/no ring/partial ring,
• Screw-in valve types;
• Camera setup and lighting;
• System startup, users' manuals and training;
• Mounting equipment in panel;
• Mounting a cloudy day illuminator in camera; and
• Field service support;

There are two keg sizes and two valve-insert types—threaded and slotted—that go through inspection. Retaining rings are necessary in kegs using slotted valves, but are not used in kegs fitted with threaded valves. Keg color is either black or silver. "The highly reflective, stainless-steel keg-neck and valve posed a challenge for generating images," stated Josh Hemstreet, electrical engineer, HiTech.

The system must notify the operator if the retaining ring is not fully inserted. An exception is a second keg type that has a screw-in valve; it must be identified and automatically passed.

The retaining ring is properly placed at the first station. There the operator places a keg on the stem holder where a threaded valve is turned in and torqued to specification. A slotted valve is inserted and a retaining ring is placed on the plunger mechanism. After the operator pushes two buttons—one with each hand—the plunger is activated, pushing down on the valve. This allows the operator to insert the retaining ring between the valve and the end of the valve stem. Next, the operator presses the third button to retract the plunger mechanism.

The operator then moves the keg to the inspection station. Here the part is repeatedly positioned to within ¼ in. of the fixture. A DVT-530 Smart-Image-Sensor camera and a continuous diffuse illuminator are positioned over the barrel stem holder.

A continuous diffuse illuminator was selected to light the keg stem to avoid creation of image saturation areas. Inspection is initiated by a pushbutton. The keg remains at the inspection station until the vision equipment passes the keg.

If there is a threaded valve, or a slotted valve with a fully inserted retaining ring, a green light illuminates, and the keg is automatically moved to the pressurization station. If the retaining ring is not present, or partially inserted, a red light is activated, an audible alarm sounds, and the keg stays in the inspection station.

Tosca also uses DVT vision systems for spinach crate inspection. DVT was used due to scalability and availability of no-cost programming-software and training. DVT programming software allows camera system connectivity from any company location via Ethernet link. HiTech is a certified systems integrator for DVT and Cognex vision systems.