Pneumatic actuation for dirty environments

Integra Coal’s coal preparation plant, serving Camberwell and Glennies Creek coal mines in the Hunter Valley, uses an array of pneumatically actuated knife-gate valves to control coal flow to the preparation area. The company found that the two traditional methods of pneumatic actuation previously used in the plant were ineffective and inefficient.

While direct-mounted pilot valves offered fast switching times, the high-conductivity water environment aggressively degraded pilot valve electronics. However, when pilot valves were encased within protective remote cabinets, air drop-off (loss of air flow rate over distance) caused a significant reduction in switching speeds and process effectiveness.

In response to this problem, Burkert Fluid Control Systems has developed an ingenious solution for faster and more effective pneumatic actuation in dirty and wet mining and mineral processing environments.

Keith Dumbrill, from Burkert Newcastle and Hunter Valley, worked with Integra to develop a new solution for pneumatic switching that addressed the dual concerns of protecting the pilot valves from the extreme environment and also ensuring a high flow rate of pneumatic air delivered at the point of use. Burkert’s innovative solution is simple, highly effective and suitable for all dirty-area pneumatic actuation applications (including hazardous areas), and comprised a cost-effective method for protecting pilot valve electronics without suffering air flow drop-off.

To achieve this, the pilot valves were divided into two components - pilot and slave modules - with a separate air supply to each. The pilot valves comprised electronics and pneumatic valve components and were located behind closed doors in a cabinet; slave valves were pneumatic only and mounted directly to the knife-gate valve actuator.

The pilot valves operate with low air flow and at low current, and are used only to switch the slave valve - not to actuate the knife-gate valve. Positioned within a cabinet, the pilot valves are well protected from dirty and wet conditions as found in mining and mineral processing operations. By relocating the electrical valve component to the pilot valve cabinet, the primary reason for valve failure is removed.

Although Burkert’s standard 8640 valve bank is suitable to pilot this solution, it was recommended by Burkert that the IP67 FreeLine pneumatic valve bank be used within a cabinet for double-redundant pilot-valve protection.

To maintain the high switching speeds required for efficient operation, it is necessary that a strong air flow be delivered to the slave valve on the knife-gate valve. To achieve this result, Integra Coal applied a separate air supply directly to the slave valve to actuate the knife-gate valve. By applying air directly at the site of actuation, high switching speeds and efficient operation are maintained with no air drop-off over the tubing length.

The slave valve used by Integra was a Burkert 0475 pneumatic valve without electronics. This valve is unaffected by dirty, wet and grimy conditions, making it suitable for the application.

“The Integra Coal knife-gate valve pneumatic actuation solution has operated for many months without a single failure, and the system has since been utilised at other mining facilities,” said Dumbrill.

“Equipment for mining needs to be hard working and able to continue working no matter the conditions. Our solution for pneumatic actuation in dirty and wet aggressive environments is perfect for the job,” he said. “We have adapted this pneumatic actuation solution to a variety of coal processing applications, and other metallic mineral processing sites.”

Using the Burkert pneumatic actuation innovation, Integra has improved valve switching speeds and operation, as well as saved time and money in maintenance operations.

“This type of innovative solution takes the best from tested and new technologies to deliver a better solution to a broad section of the industry,” he said.