Safety-related control systems functional tests

Specified techniques and measures, namely project management, documentation, separation of safety-related systems from control systems, functional testing, maintenance instructions, user friendliness and protection against operator errors... 

Functional tests of safety-related control systems, such as emergency stops... 

Title Safety of Machinery - Safety Related Parts of Control Systems Description Parts of machinery control systems are fi equently assigned to perform safety functions. Part 1 of this standard provides safety requirements and guidance on the general principles of safety related parts of control systems. Part 2 specifies the validation process including both analysis and testing for the safety functions and categories for the safety-related control systems. 

The level of site acceptance testing should be such as to demonstrate satisfactory operation of the system functions in conjunction with the manufacturing process equipment and may involve control loop tuning. Site acceptance testing in its basic form should include installation checks, power-up, diagnostic checks, and commissioning of process and safety-related operational I/O, controls, sequencing, interlocks, alarms, and reports. 

Operational checks are normally presenting process control computer systems. These systems may contain code that is part of the master production record. At the system level, the purpose of operational checks is to execute algorithms, sequencing of operations, and safety-related functions as required in the applicable customer specification. Inspections and testing are fundamental processes to be performed during the validation of critical system sequences. In addition, an ongoing program must be established to frequently verify that critical operations occur in the proper sequence. 

However, lEC 61508 was written from the point of view of process control installations, and functional safely practitioners often have difftculty interpreting how it should be applied to equipment, systems and installations that are not safety-related systems as defined rather narrowly in lEC 61508. For example, the lEC medical standards community eschews lEC 61508, despite its official pilot function , and instead applies ISO 14971 (ISO 2007), which has the same basic approach as lEC 61508 but uses different terminology and is nowhere near as detailed. The automotive industry also has difficulty with applying lEC 61508, and so is writing its own functional safely standard ISO 26262 (ISO 2009). And what about household appliances Their basic standard lEC 60335-1 (lEC 2006a) covers functional safety, but has a simple test standards-based approach to EMI that is quite unsuitable for this task, as discussed in Section 4 of this paper. 

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