Gary Slaydon

New Actuator Offers Safe, Automatic Control of Cylinder Valves

Continued efforts to eliminate the use of chlorine gas for disinfection of water and wastewater make all participants aware of the hazards of using and not using chlorine. The Peruvian Government's decision to eliminate chlorine in its water supply resulted in a major cholera epidemic in 1991. Increasing demands by environmentalists (combined with concerns by chlorine manufacturers, distributors, and end users) have been responsible for the creation of many information and regulatory agencies.

The Chlorine Institute has provided guidance for the safe use of chlorine since 1924. Other organizations such as The Chemical Industries Association in the UK, US EPA, US OSHA, Canadian Centre for Occupational Health & Safety, Chlorine Chemistry Council, and the Chlorine Gas Disinfection Association offer guidance regarding the proper and safe use of chlorine.

The EPA began enforcement of the Risk Management Program (RMP) Rule in June of 1999. The primary purpose of the RMP was to make each end-user aware of the potential hazards by implementing a program to prevent accidental releases into the atmosphere. This program makes the user aware of potential exposures and impacts of hazardous substances in the environment.

Increased regulations on hazardous chemicals by various agencies have given rise to cylinder emergency repair kits, gas leak detectors, scrubbers, and other devices that can prevent catastrophes from occurring as the result of chlorine and sulfur dioxide releases to the atmosphere. Many end users have switched to less efficient disinfection systems to circumvent necessary safety devices when using hazardous compressed gases such as chlorine and sulfur dioxide.

In 1996, Bob Carsten received a patent for his "auxiliary automatic valve shut off system." This system closes the cylinder valve electrically after receiving a signal from another device, such as a leak detector. The intent was to close the chlorine or sulfur dioxide cylinder in the event of a leak. Other manufacturers followed with pneumatic devices to obtain the same result.

Valves with automatic control for almost any application are commonly used throughout the industrial world. But cylinder valves for chlorine and sulfur dioxide have never before been controlled automatically for both open and closed applications.

In 1999, at the WEFTEC exhibition in New Orleans, Louisiana, Robo-Control Inc. of Bridge City, Texas, introduced the Model 2000 for the automatic control of hazardous gas cylinder valves. With today's advanced computer and electronics capabilities, users can safely control the open and close operation of cylinder valves. Robo-Control offers the Model 150 for 150-pound cylinder valves and the Model 2000 for ton cylinders. Both have the same drive train and electronics.

Most industrial users and many municipalities have computer control of field devices. In the industrial plant control room, there are large sophisticated computers to control and monitor any important valve within the system. Until now, no actuator was available that could open and close cylinder valves from the control room Many municipalities now have SCADA systems to monitor and control remote water wells, lift stations, and booster stations. Some cities are monitoring the status of each pump, leak detector, flowmeter, and cylinder scale. The introduction of the Robo-Control units now allow the end user the same control capabilities that he has enjoyed on his other critical processes.

The Robo-Control actuator allows selection of individual cylinders for operation. Each unit includes a DC electric motor that rotates the valve stem toward the open or closed position, without interfering with or requiring additional adapters for dispensers or discharging hardware. Many end users have gas dispensers that mount directly to the cylinder valve. This design allows the end users continued use of their existing equipment, regardless of manufacturer.

The motor, gears, and microprocessor-based controls are assembled as one unit in a fiberglass NEMA 4X enclosure to eliminate the necessity for a separate control panel or interconnecting control wires. The Model 2000 can be mounted on a ton cylinder easily without any tools. As a portable unit with integral leak detector, it can be moved to other sites without any installation problems. The integral leak detector, available on both models, provides for local detection of a leak that results in an immediate closure of the cylinder valve. This could allow continued operation of the feed system when multiple cylinders are in use. Conventional leak detector systems allow the entire area to be exposed to the chemical before reacting. Outputs from the unit can be directed to alarms, lights, horns, or other remote devices. Those outputs include valve opened, valve closed, battery low/failure, or leak.

Both models have a potentiometer for a feedback signal of valve position that is displayed on a large LED indicator. The LED display enables the operator to easily read the actuator condition and valve position when mounted outdoors with bright sunlight. Programming is accomplished through an integral keypad. And both models are battery operated with trickle charge to provide four-hour operation without power. The unit is failsafe-close and will automatically close the valve when voltage decreases to a preset value.

Control signals to and from the actuator can be transmitted through conventional shielded cables or with the unique remote control system incorporated in the package. Radio control requires an interface unit to convert the customer's hardwired components to radio signals. The interface is called the Model RT/RR and is packaged in a NEMA 4X fiberglass enclosure with panic button.

Typical applications where the unit has advantages include emergency shutdown of gas cylinders, remote control without the need for conduits or hoses, automatic cylinder switchover, industrial plants, and municipal SCADA systems.

With the inclusion of the Robo-Control units into today's high tech world of SCADA and telemetry, chlorine cylinder control can be as close as the keyboard. Small leaks can be stopped immediately and large accidental releases to the atmosphere can be prevented as the EPA ordered and as we all prefer.