butterfly valves with chainwheel for valve in a high location installation

1. Working Principle

Mechanical Transmission:  A pair or multiple pairs of bevel gears are used to convert the horizontal manual chain pull into vertical rotational force, driving the valve stem to rotate.

Torque Amplification: The torque is amplified through the gear ratio (e.g., 3:1, 10:1, 36:1, etc.). This means that with very little force applied to the chain, the valve can generate significant closing/opening force, making it particularly suitable for large-diameter or high-pressure valves.

Remote Operation: By extending the length of the chain, the operating position is extended from a high location (at the valve) to the ground.

2. Key Accessories (Very Important)

Simply buying a gearbox and mounting it at a high location is not enough. For safe operation from the ground, the following accessories are usually required:

Chain Box/Collector:

Function: Installed below the gearbox, it is used to store excess chain.

Necessity: Without it, the chain will swing freely in the wind, easily getting stuck or damaged, and posing a safety hazard. It allows the chain to hang neatly.

Limit Switch Box:

Function: Although it's a manual chain operation, many high-altitude valves require feedback signals of "open/closed position" to the control room.

Function: When the chain is pulled to its limit, and the valve is fully open or closed, it triggers a microswitch, cutting off the circuit or sending a signal.

Chain Lock:

Function: Used to secure the chain in a specific position, preventing accidental operation or the chain being moved by wind, thus preventing unintended valve movement.

3. Core Advantages

Safety: Eliminates the need for scaffolding or lifting equipment, avoiding the risks of working at heights.

Labor-saving: For large valves with a diameter of DN300 or more, it's impossible to turn them manually with just the handwheel; a gearbox with a reduction ratio is necessary.

Durability: Typically uses a ductile iron casing, and the internal gears are heat-treated, making it suitable for harsh outdoor environments.

4. Selection Guide (How to Purchase)

If you need to purchase this type of product, you must provide the following parameters to the supplier:

Valve Torque:

You need to know the maximum opening/closing torque of the valve (N·m).

Formula: Output Torque = Hand Pull Force × Chain Radius × Reduction Ratio × Efficiency.  It is generally recommended that the selected torque be 1.2 to 1.5 times greater than the maximum valve torque. (The 1.2/1.5 is the safety factor to choose the gearbox )

Connection Dimensions:

Input Square Hole: The size of the chain wheel shaft (usually standard, such as 1/2", 3/4" square).

Output Connection: The flange standard connected to the valve (e.g., ISO 5211) or the valve stem square head size.

Valve Type:

Specify whether it is a rising stem (requires a through-hole) or a non-rising stem (does not require a through-hole).