APL-310N Limit Switch Box

The APL-310N is a rugged and reliable limit switch box (also known as a valve position indicator or feedback device) designed to provide both local visual indication and remote electrical feedback of valve position. It is specifically engineered for mounting on quarter-turn pneumatic or electric actuators, such as those used for ball valves and butterfly valves, in applications where weatherproof protection (IP67) is sufficient.

Clear Visual and Electrical Feedback
The unit features a durable, transparent polycarbonate dome with a highly visible mechanical indicator. The indicator shows a clear Yellow flag for the “Open” position and Red for “Closed” , allowing operators to instantly verify valve status from a distance. Internally, the APL-310N is equipped with 2 x SPDT (Single Pole Double Throw) mechanical switches as standard, which provide separate electrical signals for the open and closed positions to a PLC, DCS, or remote monitoring system. Each switch includes a common (COM), normally open (NO), and normally closed (NC) contact, offering maximum wiring flexibility.

Tool-Free Adjustment and Easy Installation
One of the key features of the APL-310N is its “Quick-Set” cam mechanism. The cams are spring-loaded and mounted on splined shafts, allowing for fast and precise adjustment without any tools. Once set, they maintain their position, ensuring reliable long-term operation even under vibration. The box includes a mounting bracket that complies with the NAMUR VDI/VDE 3845 standard, guaranteeing a perfect fit on most commercially available pneumatic actuators. Captive cover bolts prevent loss during maintenance .

Rugged Construction for Harsh Environments
Built to withstand demanding industrial and marine environments, the APL-310N features a die-cast aluminum alloy enclosure with a corrosion-resistant polyester powder coating . It boasts an IP67 protection rating, making it dust-tight and protected against temporary immersion in water, suitable for outdoor or below-deck installations. Dual cable entries (standard 1/2″ NPT) provide flexibility for wiring, and an internal 8-point terminal strip simplifies electrical connections .

Versatile Options
The APL-310N series offers flexibility to meet various application needs. Options include up to 4 switches (mechanical or proximity sensors), potentiometers for analog feedback, 4-20mA current output units, and extended temperature ranges (-40°C to +80°C or -20°C to +150°C).

APL-3N Series

1. Degree of protection: IP67 / NEMA4 & 4X (standard) IP68 (option)
2. Sturby beautiful shell design addiniotal limit
3. Switch: 3~4 mechanical switch addiniotal wiring
4. Terminal: 8~16 points
5. The switch position can be cleared by the indicator
6. Two-wire interface: Dual 1 / 2NPT pipe interface (standard) /M20,PG13.5,PF1/2 “, PT1 / 2” (option)
7. Terminal: 8 points (0.08-2.5mm2)
8. Anti-off bolts
9. Easy installation, stainless steel spindle connection part and mounting bracket are in line with NAMUR standard