Safety Fieldbus Design Requirements for Process Industry Sector Applications

摘要

The advantages of field bus for process control applications are well known in the process, manufacturing, auto, and machinery industries, Consequently, there are several standards for implementing field bus e.g., IEC-IEC/SC 65C/MT 9, ANSI/ISA 50.02, and IEC-61158. The current field bus standards do not however, address issues and requirements of field bus, for safety applications. Specifically, the requirements noted in IEC-61508, "Functional Safety of electrical/electronic/programmable electronic safety related systems", and the sector specific standards e.g. IEC-61511," Functional Safety: Safety Instrumented Systems for the process industry sector", IEC- 61513, "Nuclear power plants - Instrumentation and control for systems important to safety", or other sector safety standards. That is, risk reduction factors or safety integrity levels (SIL) and reliability requirements, are not addressed in the current field bus standards for process control applications. As of this date, there are no national or international standards for safety bus but there are some protocols recognized for safety applications e.g. (PROFIBUS) in the machinery industry. Safety busses have not yet been accepted in the process industries. Moreover, the ISA 84 committee is concerned that some will implement buses with a detrimental impact on safety. In order to address these concerns, the ISA Committee formed a working group (WG-1) to address high level or global bus issues. This paper will discuss those global safety bus requirements that users as well as vendors, have recognized. In addition, the requirements listed in the draft ISA Techical Report ISA TR84.00.06 will be discussed in detail.