Gear Boxes

Valve gearboxes are used for mechanical transmission of torque between a handwheel, actuator, or stem extension and the valve. They are applied where the required operating torque does not allow direct manual operation, or where controlled movement is required for butterfly valves, ball valves, plug valves, dampers, and multi-turn valves such as gate and globe valves. Selection is based on opening and closing torque under differential pressure, operating angle or number of turns, mounting standard, installation position, and environmental exposure.

This category includes Alfa Gear gearboxes in types E, M, MO, S, VA, and XK. The E, M, and S series are quarter-turn worm gearboxes for 0-90° rotation with ±5° travel adjustment, with interfaces according to EN ISO 5211 or DIN 3210 and a reference temperature range of -50 to +150 °C. Series E uses a GG25 cast iron housing, IP67 enclosure protection, and torque capacity up to 4,500 Nm. Series M and S use ductile cast iron GGG40, IP68 protection, and torque capacity up to 32,000 Nm.

The MO series is used as a manual override between a double-acting or spring-return pneumatic actuator and the valve, with optional 3/2 relief valve for automatic venting of air from the actuator circuit. The VA series is a quarter-turn design with body, cover, input shaft, and handwheel in stainless steel 316, with aluminium bronze quadrant and torque capacity up to 11,000 Nm, intended for corrosive industrial service where material compatibility is critical. The XK series is for multi-turn applications, with ductile cast iron housing, bronze alloy or ductile iron drive sleeve, axial bearings, and torque capacity up to 4,000 Nm.

During installation, the ISO mounting flange, square drive or insert system, operating direction, mechanical stops, housing sealing, lubrication condition, IP rating, and access for periodic inspection should be checked. In buried service or in humid, dusty, or chemically aggressive environments, coating selection and material specification directly affect service life, corrosion resistance, ingress protection, and maintenance requirements.