APL-510N Explosion-Proof Limit Switch Box (Ex)

The APL-510N is the top-tier, 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 the most 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 in critical applications.

Superior Explosion-Proof Certification
Unlike standard enclosures, the APL-510N is built with a certified flameproof enclosure (Ex d IIC 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. The IIC gas group certification makes it suitable for environments containing the most volatile gases, including hydrogen, acetylene, and carbon disulfide. It meets strict international standards (EN50014 & EN50018) for use in hazardous locations (Zone 1 & 2) where the highest level of 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-510N 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-510N 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. 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 with a unique spring-loaded design prevent loss during maintenance and ensure proper closure.

Rugged Construction for Harsh Environments
Built to withstand the most demanding industrial and marine environments, the APL-510N 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 offshore or chemical plant 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 mounting bracket are constructed from stainless steel for maximum corrosion resistance.

Versatile Options
The APL-510N series offers extensive flexibility to meet various application needs:

• Switch Options: Up to 4 mechanical switches or 4 proximity sensors (inductive or magnetic).

• Analog Feedback: Potentiometer (1k, 5k, 10k ohm) or 4-20mA current position transmitter.

• Enhancements: IP68 enclosure, three-position indicator (Green/Red), and extended temperature ranges

APL-5N Series

1. Degree of protection: IP67 / NEMA4, 4X, 7,9 (standard) IP68 (option)
2. Explosion-proof grade: EEx d IIB T6, EEx d IIC T6, EEx ia IIC T6
3. Sturdy and beautiful housing, the housing is equipped with a spindle (biaxial)
4. Easy installation of visual position indicator
5. Unique design fixes the cap by bolting the cap
6. Dual cable entry: 2 / 4PF (standard) / M20, M25, NPT3 / 4 “, PT3 / 4”
7. Terminals: 8 points (0.08-2.5mm2)
8. Anti-off bolts, spring reinforcement
9. The unique design holds the bolt in the housing, and the bolt does not fall off when the housing is opened
10. Easy to install bracket
11. Stainless steel spindles and stainless steel or steel brackets are NAMUR compliant