Inflatable valve-seats are becoming more and more popular especially in controlling the flow of solid goods through pipelines where abrasive effects occur at the seat in the process valve. However, the seat has to be inflated after turning the disc and it is to be deflated before starting to turn the disc into open position.
Hafner Pneumatik offers a pure pneumatic solution for that. The Hafner CBN 700 control block is an important element of Hafner’s range of accessories for Smart Valve Automation. The control block for double acting actuators with inter-face according to 1/4“ Namur standard, is to be used on process-valves with inflatable valve seat. The control-block receives signals to open and close from a standard 5/2-way Namur valve. The block is to be put between the actuator and the Namur-valve. When the closing-signal is fed through to the actuator, the seal is inflated with time-delay.
When the process-valve is to be closed, first the seal is deflated. After a set time-delay the actuator opens the process-valve. Opening- and closing time-delay can be adjusted independently but they are related to the operating pressure. The 6-bar time-delay can be adjusted between 0 and 2 seconds.