Proposal of Interlocking System for Solving Hazardous Side of Error in Pneumatic Driving System

Abstract

The pneumatic driving system, since it resorts the regulation of pressure limited for ensuring safety to the reliability of the regulator, has two problems: one is that it is not virtually interlocked with a stop (power shutoff) function against dangerous errors, and the other is that it is not relieved of risks due to dangerous errors if the pressure monitoring is omitted. This paper shows a configuration example of the pneumatic driving system. The paper implemented FMEA on each component, and, as a result of FMEA, identifies a component that may cause a pressure rise error (dangerous error). Based on this, the paper proposes “monitoring through a window” to be provided at the point where the power regulating unit is decoupled from the driving unit so that pressure rise/fall errors of the power regulating pressure can be monitored. Thereby, the paper deduces that an interlock to avoid dangerous errors can be realized by shutting off the power supply. Furthermore, the paper logically reviews four different interlock systems as to the output shutoff characteristics (unite logical relationship) against dangerous errors, and describes the characteristics and effects of the pneumatically-driven system having an interlock by means of “monitoring through a window.” Lastly, the paper proposes the procedure detailed herein as one of the design guidelines related to the interlock of the pneumatic driving system.