This group includes valves that can be operated by personnel (1–2 people) without auxiliary power. They are typically valves operated infrequently, or installed where no auxiliary power is available. Depending on the task, they can be used for on/off or control duty.

Types:

• Hand lever: simple lever or lockable lever design. Typically for quarter-turn valves: operating ball valves and butterfly valves up to DN 150, depending on torque requirements.
• Handwheel: hand-operated wheel without gearing. Typically on multi-turn valves, e.g. globe valves, gate valves, knife gate valves, diaphragm valves. The handwheel size is matched to the torque requirement.
• Gearboxes, e.g. worm gears: gearboxes multiply the torque applied via the handwheel through various gear ratios (e.g. gear wheels), so that valves with higher torque requirements can also be operated manually. The handwheel size matters just as much as the gear ratio(s).
• Other: designs not covered above, for example for emergency operation and disengagement in the event of a power failure of pneumatic or electric drives.

This group includes actuators driven by liquid or gas. Compressed air systems are the most widespread because of their favourable price, versatility and reliability.

By direction of motion:

• Linear cylinders (e.g. for globe valves, knife gate and gate valves), and
• Rotary cylinders (typically for quarter-, half- or three-quarter-turn valves, e.g. ball valves, butterfly valves).

By mode of operation:

• Double-acting: both strokes (opening and closing) are performed by air; typically the valve stays in the same position in an emergency, or the position does not matter;
• Single-acting or spring-return: one stroke is performed by air and the other by a spring. In an emergency, the spring moves the valve to a predefined position. When sizing, it must be determined whether this is the open or closed position.
  It is tempting to think that if a valve must move to the open or closed position in an emergency, only a spring-return solution will do. This is not true. If supply air is still available (i.e. the air line is undamaged and air reservoirs are provided for the plant or directly for the valve)
  and only the control signal (to the solenoid valve) is lost, the solenoid valve can also be air- and/or spring-return, so that it moves the valve to the desired fail-safe position in the event of a fault.

By mechanism:

• Rack and pinion: a pinion on the shaft and a rack on the piston(s). Characterised by linear torque. We keep the Rotork GT type in stock for 0…90°, but 0…120°/180°/240° ranges are also available on request.
• Scotch yoke: a compact yet robust design in which a pin attached to the piston moves along a track guided by the yoke over a quarter circle. Its advantages are higher torque at both end positions (beneficial for quarter-turn valves), a shorter piston stroke, lower air consumption and weight. A further advantage of this design is a longer service life and greater reliability than rack and pinion. It is therefore particularly suitable for higher demands such as control duty and frequently operated valves. We keep Rotork RC 200
  products in stock, designed for a minimum of 1,000,000 cycles.

Coming soon!

Coming soon!

• With air reservoir: for multiple operations in an emergency
• With handwheel: for manual operation in an emergency
• Fast-acting: with larger ports
• For extreme temperatures: for ambient temperatures of +150 °C or as low as -47 °C