Processing Magazine

Safety Relay Module

September 4, 2012

The SRM Safety Relay Module from Moore Industries has been certified for single use in Safety Instrumented Systems up to SIL 2. The SRM is part of the Moore Industries’ FS FUNCTIONAL SAFETY SERIES and accepts single contact closure inputs from logic solver trip outputs including Moore Industries’ STA Safety Trip Alarm and the SPA2 Programmable Limit Alarm Trip. With three contacts per alarm input, the SRM allows for the addition of alarm contacts to safety processes without special installation or configuration. Unlike many other interposing relays, the SRM is a Force Guided Relay, avoiding the possibility of having contacts become stuck in both Normally Open (NO) and Normally Closed (NC) positions at the same time and avoids potential problems caused by issues such as welded contacts. The SRM is built using a safety-related relay with forcibly guided contacts, which are monitored and mechanically linked to the same armature as the output contacts. The SRM has been developed following the IEC 61508 standard and offers a high level of availability for safety-critical applications and for use as a component part of Safety Instrumented Systems (SIS). While most safety relays are in a plastic case, the SRM in housed in a durable and rugged “universal” aluminum DIN case that can be mounted on either a 32mm G-type or 35mm Top-Hat DIN-rail. A major design consideration of the SRM is its ease of use. It features a front-panel visual diagnostics, with three LED indicator lights reflecting the current Input, Output and power status. It can also be installed in an SIS with minimal wiring.