Limit Switches

Limit switches are used on valves with pneumatic or electric actuators to confirm open/closed position, detect intermediate travel, and transmit status signals to PLC, DCS, interlock panels, or supervisory systems. Selection should be based on actuator type, rotary angle or linear travel, mounting standard, sensor type, installation environment, and the requirement for mechanical, inductive, or analog position feedback.

This category includes Eurotec limit switch boxes such as Big-Box, EuroBox, Flex Box, I-Box, Neptun Box, Wave Box, and D-Box, together with explosion-protected versions for classified areas. Big-Box is used where a larger enclosure is required for M30 cylindrical sensors or mechanical position switches to DIN EN 50041. Flex Box uses copper-free aluminium with copper content below 0.05%, which is relevant in salt-laden atmospheres, sulfur-bearing gases, and environments where ammonium nitrate is present.

For hazardous areas, versions are available with Ex de t, Ex t, Ex ec, and Ex tc protection concepts. Flex Box configurations are specified for Zone 1, Zone 2, Zone 21, and Zone 22, with markings such as II 2G Ex db eb IIC T4-T6 Gb and II 2D Ex tb IIIC T80°C-T135°C Db, depending on the protection method. Ex selection must match the area classification, gas or dust group, temperature class, and field wiring method.

Eurotec limit switch boxes are supported by documentation for ISO 9001, ATEX-QM in accordance with ISO/IEC 80079-34, declarations of conformity for the Machinery Directive, Low Voltage Directive, and EMC Directive, and FMEDA classification up to SIL 3 for use in safety-related loops. The same category also includes the OMC PTL7R for rotary actuators, with options for discrete limit switches, 4-20 mA feedback, or combined local position indication and analog output.

During installation, the shaft alignment, cam setting, cable entry sealing, grounding, moisture protection, and periodic verification of open/close signals under actual valve operating conditions should be checked.