APL-410N Explosion-Proof Limit Switch Box (Ex)

The APL-410N is a heavy-duty, explosion-proof limit switch box (also known as a valve position monitor or feedback device) designed to provide both local visual indication and remote electrical feedback of valve position in potentially explosive environments. It is specifically engineered for mounting on quarter-turn pneumatic or electric actuators used for ball valves, butterfly valves, and other automated valve packages.

Certified Explosion-Proof Safety
Unlike standard enclosures, the APL-410N is built with a certified flameproof enclosure (Ex d IIB T6). This heavy-duty, precision die-cast aluminum alloy housing is designed to contain any internal spark or explosion, preventing ignition of flammable gases or vapors in the surrounding atmosphere. It meets strict international standards for use in hazardous locations (Zone 1 & 2), making it ideal for Oil & Gas, petrochemical, and marine applications where safety is paramount.

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-410N is equipped with 2 x SPDT (Single Pole Double Throw) mechanical switches (standard configuration), 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-410N 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 stable signal settings even under high-vibration conditions typical of high-pressure pipelines. 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-410N 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 harsh outdoor or deck installations. Dual cable entries (standard 3/4″ NPT) provide flexibility for wiring, and an internal 8-point terminal strip simplifies electrical connections. The shaft, springs, and hardware are constructed from stainless steel for maximum corrosion resistance.

APL-4N Series

1. Degree of protection: IP67 / NEMA4, 4X 7, 9 (standard) IP68 (option)
2. Explosion-proof grade: EEx dIIB T6, certified by China NEPSI
3. Rugged and beautifil Additional limit switch: 3~4 mechanical switches
4. Additional terminals: 8 to 20 points
5. A variety of optional switches
6. Cable access: 2×3 / 4 NPT (standard) / M20, M25, PF3/4″, PT3/4″ 4 Cable entries
7. 0 Wire port: 8 points (0.08-2.5mm2)
8. Easy installation, stainless steel spindle connection part and mounting bracket are in line with NAMUR standard