How to Choose Normally Open or Normally Closed Motorized Ball Valves

The power failure reset function of the motorized ball valve keeps people safe during power outages. It also helps avoid economic losses. We choose a normally open or normally closed motorized ball valve based on the situation and safety needs.

Normally Open Type: During emergency power failure or malfunction, the valve automatically returns to the open position.

Normally Closed Type: During emergency power failure or malfunction, the valve automatically returns to the closed position.

 

Core Selection: Safety

This is the most critical selection factor. You need to understand: during an emergency power outage or system failure, what valve state will ensure greater safety for the project and personnel?

1. Applications Suitable for Normally Open Valves

Applications requiring continuous supply: such as fire protection pipelines, production lines requiring continuous material conveyance, or situations where emergency pipeline shutdown would cause production interruption or equipment overheating, resulting in economic loss or danger.

Prevent excessive pressure buildup: In the pressure relief pipeline, valves must remain open during malfunctions to prevent dangerous situations caused by excessive pipeline pressure.

2. Applications Suitable for Normally Close Valves

Conditions requiring emergency shutdown: This is the most common scenario, such as for natural gas, fuel, and other media. In the event of an emergency power outage, the system automatically cuts off the supply of combustible gases to prevent fires and explosions.

Preventing damage to critical equipment: In certain operating conditions, continuous water flow during a malfunction may cause equipment damage, necessitating the use of normally closed ball valves for automatic shut-off.

 

Other selection factors

Factors to consider beyond safety

1. Energy Consumption

Normally Open Motorized Ball Valve: The electric actuator uses no power when fully open. It only uses power when closing the valve. If the valve stays open most of the time, choose a normally open valve.

Normally Closed Motorized Ball Valve: The electric actuator consumes no power when the valve is fully closed. Power is supplied only during the opening process. If the valve remains closed most of the time, a normally closed valve should be selected.

Hold-type electric actuator: This actuator uses power only when opening and closing. It turns off by itself after the action is done. This helps save energy and improves safety.

2. Switching Frequency

For valves that switch frequently, hold-open actuators offer longer service life.

3. Cost

Hold-open and hold-closed actuators are similarly priced.

Hold-open actuators feature more complex internal structures, resulting in higher costs.

 

Real-world application scenarios

Irrigation System: Normally closed valves automatically shut off when not irrigating and open when needed, ensuring efficient water conservation.

Gas Supply Piping: Normally closed valves automatically cut off gas flow during power outages to prevent explosions.

Chemical Media: Normally closed valves automatically close during malfunctions to prevent leaks of corrosive substances.

Fire Water Supply Piping: Normally open valves ensure uninterrupted flow of firefighting water under all conditions.

Compressed Air Piping: Normally open valves remain open during malfunctions, preventing disruption to compressed air supply in other equipment.

 

Summary

1. Safety is paramount.

2. Efficiency is the second priority.

3. Select maintenance-free electric actuators for special circumstances.

When making specific selections, thorough communication with technical personnel and motorized valve suppliers is essential to clarify operating conditions and safety standards, ensuring the most appropriate choice.