can't detect actuator status in its plc mhj edition

CAN'T DETECT ACTUATOR STATUS IN ITS PLC MHJ EDITION SOFTWARE

If you place all four safety functions in a single logic solver, the logic solver must have a SIL 3 capability. Following a good design process, three of those risks are SIL 2 and one is SIL 3-an order of magnitude more stringent. For example, say you have identified four potential risks. There is one additional clarification worthy of mentioning if you choose to place all of the safety protection (more than one SIF) in one logic solver, then the entire logic solver must meet the highest SIL value assigned to a SIF in that logic solver. (note: SIL 4 rated safety instrumented functions require conformance to IEC 61508.) A safety instrumented function (SIF) is designed to reduce the risk of the identified hazard and it must meet the desired SIL level. Working through a very thorough design process, a SIL value (1, 2, 3 or 4) is established for each identified hazard. When considering equipment justification, all equipment must be considered.Ī key, but misunderstood SIS design element is the term Safety Integrity Level (SIL).

CAN'T DETECT ACTUATOR STATUS IN ITS PLC MHJ EDITION SOFTWARE

An SIS includes the transmitters and/or switches the logic solvers all programming, operating system, and communication software power supplies the final elements (i.e., block valves) and their actuators and all the interconnecting wiring. In other words, an SIS is much more than just the logic solver. It is important to understand that when these safety standards refer to the SIS they are including all of the hardware, software, mechanical parts and communication networks. The reality is that in order to design, specify, install, operate, and maintain an SIS application that conforms with the IEC 61511 standard, owner/operators must also conform to relevant sections of IEC 61508 and that brings us to the subject of this article, meeting the standards ‘Proven in Prior Use’ requirements. IEC 61511 refers directly to IEC 61508 for product certification requirements. IEC 61511 is an industry specific version of this standard with language, terminology and requirements that better fit project level work in the process industries. Despite its broad industry and technology coverage, it is very specific in its conformance requirements. IEC 61508 was developed to serve as a basic functional safety standard for a broad range of industries including chemical, refining, mining, and transportation. It is important to understand the origin of IEC 61511 because as users read and begin to apply the standard they will find frequent references to IEC 61508 and that quickly leads to the realisation that IEC 61511 is not a standalone standard. The IEC 61511 standard is an industry specific version of IEC 61508 Functional safety of electrical / electronic / programmable electronic safety-related systems (E/E/PES). Thus the ‘preferred list’ is all but non-existent when it comes to selecting components and subsystems that will produce a safety instrumented system (SIS) that conforms with International Electrotechnical Commission’s (IEC) 61511-1 Functional safety – Safety instrumented systems for the process industry sector standard. However, when asked to produce supporting documentation, most simply can not. When contributors to the list are asked about a specific component or subsystem they will expound, often in great detail, how a particular device achieved its preferred list status.

Within the minds of those who helped develop these lists, each device is on the list because it has proven its capability, reliability and suitability in prior use. Because of unique process conditions, these preferred lists often include ‘no substitute’ notations for specific plant areas. Such lists are usually the result of long-time relationships between the engineering and maintenance departments and the various devices themselves. It is fairly common for companies to have developed a ‘preferred list’ of transmitters, valves, actuators and other process control components and subsystems.

Can't detect actuator status in its plc mhj edition