Valves, Actuators & Pump Control


Pro-Cap capping valve for pulping

October 2014 Valves, Actuators & Pump Control

Since 1899 NAF valves have been developing and manufacturing for the process industry integrating traditional mechanical construction with intelligent systems. The company’s new capping valve ensures safe, time saving processing of wood chips in pulp digesters. The Pro-Cap is a high tech valve for chips filling one of the most critical applications at a pulp batch digester plant as it is crucial that cooking is done in a safe and time saving way and to control the time of the cooking sequence.

The capping valve is mounted on top of the batch digester for automated filling of wood chips and to provide tight shut-off to atmosphere during the cooking sequence. The unique design of the NAF Pro-Cap is based on a segmented ball valve to prevent wood chips from getting stuck between the housing and the ball.

Design and function

The segment is mounted on an upper and lower stem. The uniqueness of the design is that each of the stems is mounted in an eccentric hub. The stems can be moved along the valve by rotation of the eccentric hubs.

The upper eccentric hub is used for a once off manual adjustment of the assembly. This provides the correct load and scraper function between segment and seat. The lower hub is automated with a Turnex actuator to lift and load the segment against the seat. This is done during each cooking sequence, thus providing a tight seal on the upstream side of the valve. After the cooking sequence is completed, the process is reversed. Other features include:

* Batch digester capping valve.

* PN 16-25 and ANSI 150.

* Body in EN 1.4408/ASTM A351 CF8M.

* Valve inspection and testing acc to API 598.

* Unique design uses the eccentric hubs to load the seat and provide tight shutoff.

* Jammer device for locking the valve in open or closed (filling or cooking) positions.

* NAF Turnex high performance actuators used for operation and eccentric hub.

For more information contact Fred Venter, Valve & Automation, +27 (0)11 397 2833, fred.venter@valve.co.za, www.valve.co.za



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