Abstract
The safety system stipulated in EN764-7 (Safety Systems for Unfired Pressure Equipment) effectuated recently as a European Standard is equipped with pressure releasing means (e.g., safety valve, relief valve, rapture disk). However, this safety system is not adequately functional as a safety system because the pressure releasing means cannot ensure the security for safe-side failures or degradation characteristics. In view of this, this paper proposes an interlock system applicable to pneumatic control systems based on the safety (confirmation) principle. This interlock system is constituted in such a way as to stop the load to dismiss the possibility of hazard-side failures by cutting off the power supply, and also nearly conformable to the International Standards ISO 12100 and ISO 13849. Therefore, the interlock system can be said as an ideal safety system that does not exert the influence of hazard-side failures (safety hazards). This paper also discusses the consistency of the interlock system with the safety system stipulated in EN764-7.
