Pneumatic

Pneumatic describes a method of brake actuation that utilizes compressed air as the power source to generate the clamping force. This technology is valued for its cleanliness, responsiveness, and excellent controllability, making it a preferred solution for a specific range of industrial applications.

There are two distinct and opposing principles of operation for pneumatic brakes:

1. Pneumatically-Applied / “Normally Open”: This is the more common configuration for process control. In this design, the brake is disengaged in its default state. To engage the brake, compressed air is fed into an actuator (like a diaphragm or piston), which then applies force to the brake pads or calipers.
   • Key Feature: The braking torque is directly proportional to the air pressure supplied. This allows for extremely fine and dynamic adjustment of the braking force, which is why this design is the industry standard for tension control applications on unwind stands for paper, film, and foil. By precisely regulating the air pressure, a constant tension can be maintained on a moving web of material. This is an “energize-to-engage” system and is not fail-safe.
2. Pneumatically-Released / “Normally Closed”: This is a fail-safe design. The brake is held powerfully engaged by a set of mechanical springs in its default, de-energized state. Compressed air is used to overcome the spring force and release the brake, allowing the shaft to rotate.
   • Key Feature: If there is a loss of plant air pressure, the brake automatically engages and safely stops or holds the load. This design is used for safety-critical holding and emergency stopping applications where compressed air is the most convenient power source available.

In summary, choosing a pneumatic brake is driven by specific operational needs. When precise and variable torque is required for process control, the “Normally Open” design is ideal. When a clean, reliable, and fail-safe holding brake is needed and plant air is readily available, the “Normally Closed” spring-applied, pneumatically-released design is the appropriate choice.