Interfacing Pneumatics & Hydraulics With Electrical Safety Control Circuits

Pneumatic and hydraulic loads can be just as dangerous as electrical loads.  So how do you ensure they do not have any less safety integrity? 

Engineers often design safety systems to only de-energise the solenoid coil of a standard valve controlling a fluid power load.  By doing this they have no way of detecting if the valve has stopped the load, or if a fault exists within the valve.  This can provide a false sense of safety, potentially exposing operators to hazards arising from stored energy or jammed valve spools caused by contamination, silting, and worn or broken components. Accidents have occurred as a result.

As an example, consider a typical light curtain application.  If a valve that was performing well suddenly closes too slowly due to oil contamination etc, then an operator reaching through the light curtain may be exposed to a moving hazard.  With correct integration of dual spool monitored safety valve system, slow closure of either safety valve can be immediately detected & further machine operation prevented.

Monitored fluid power systems have fast become standard safety practice of industry and form the interface between electrical & fluid power safety control.  As this is a meeting of two technologies, both electrical and fluid power specialists need to be competent in providing a combined standards compliant solution.