The Basics Of PLC Technology

The world of the industrial gas distributor involves a significant investment in capital equipment and manpower to successfully fill both high-pressure and portable liquid cylinders. The typical filling facility utilizes manually operated gas control panels, manifolds and scale systems. This equipment requires trained cryogenic and gas personnel to ensure that the correct liquids and gases are transfilled into the appropriate containers. Since this transfill process is labor intensive, equipment automation is the answer to reduce costs, provide consistent quality product, increase production and allow for documentation of the processes.

Programmable Logic Controllers (PLCs) were invented in 1968 for the automotive industry. Since then, PLCs have been used for automating electromechanical devices in thousands of applications. These units replace mechanical timers and manual components while providing temperature sensing, data acquisition and Ethernet communication. PLCs fit into industrial gas production in several ways, starting with the cryogenic pump.

Automated Pump Processes
Traditional pump installations include the electric motor, cryogenic drive “warm end,” cryogenic “cold end” and the motor start/stop. The fill plant operator manually opens the cryogenic bulk tank liquid valve and re-circulation valve to start the pump cool-down process. Once the operator determines that the pump has been cooled, he starts the pump and watches for any leaks or if the pump is not primed and cavitating. These conditions can damage or shorten the life of the pump and can result in significant repair and replacement costs. By automating the pump with a PLC system, the controller automatically senses the correct cool-down temperature, senses any leaks, starts the pump and ensures proper function of the pump, allowing fill plant personnel to perform other functions in the plant. The PLC can determine if a problem has been discovered and shut down the system until proper maintenance has been done. This can reduce overall pump life-cycle cost.

Automated fill plant

PLC automation frees up operators to spend time on other tasks.

With a video touch screen, the operator simply follows the commands on the touch screen and touches the appropriate command. The PLC processes these commands to the mechanical components, which function to automatically fill the cylinders with the appropriate gas or mixes until the cylinder is full. This capability frees personnel for other functions, ensures product quality and completes cylinder fills every time. If the PLC malfunctions, the plant can continue to run manually.

Data collection and transmission become faster and more accurate with the PLC. PLCs record and transmit data via an Ethernet connection, which provides valuable distribution and tracking information that is currently performed manually.

Portable liquid cylinder filling systems also benefit from PLC technology. Manual liquid cylinder filling systems require plant personnel to monitor the filling process until the l scale registers the correct DOT weight. The operator then shuts off the cylinder filling process. With automation, the operator can program a digital scale system to stop filling at the pre-determined weight and continue on to other duties. The cylinder will automatically fill and shut off at the desired setting.

PLC technology now fits into the palm of your hand and offers a tremendous opportunity to reduce plant costs while enhancing product quality and safety.

Gases and Welding Distributors Association
Bill Jones Meet the Author
Bill Jones is national sales manager at CTR Inc., headquartered in Rock Hill, South Carolina, and on the Web at