Machine Safety: Can end user companies comply with ISO 13849-1: 2006 without design engineering resources?
ISO 13849-1: 2006 is an updated international machine safety standard intentionally written for individuals who perform design responsibilities for control systems. These responsibilities are specifically for the design of control systems for machinery and the safety-related parts of control systems. Okay, so what industry standard do end user companies reference to maintain and/or modify their installed safety-related parts of control systems?
Am I the only fly in the ointment?
By definition, in the Scope statement of ISO 13849-1 you’ll find:
This part of ISO 13849 provides safety requirements and guidance on the principles for the design and integration of safety-related parts of control systems (SRP/CS), including the design of software. For these parts of SRP/CS, it specifies characteristics that include the performance level required for carrying out safety functions. It applies to SRP/CS, regardless of the type of technology and energy used (electrical, hydraulic, pneumatic, mechanical, etc.), for all kinds of machinery.
As stated above, this international standard has targeted “designers and integrators” of the safety-related parts of control systems (SRP/CS). Obviously the writers of this standard transitioned the required approach for achieving functional safety from a qualitative methodology (Categories B, 1, 2, 3 &4 from EN 954-1: 1996) to a quantitative methodology (PL a, b, c, d & e). It is well documented that by achieving this goal the risk levels of ISO 13849-1 and IEC 62061 are exactly quantitatively comparable. Conversely, the qualitative risk levels of Categories could not mathematically compare with the quantitative SIL (safety integrity level) risk levels of IEC 62061. The lack of this ability had been a criticism of the Category methodology originated by EN 954-1 versus the SIL methodology of IEC 62061. Hurray for this international achievement!
In the U.S. we didn’t adopt EN 954-1 because the U.S. doesn’t adopt EN (European Norm) standards. However, we did adopt the qualitative methodologies of EN 954-1 and the Category methodology for risk levels. Additionally, U.S. industries have focused training efforts at small and medium sized companies to learn and adopt this qualitative approach to manage and implement their machine safety strategies. In many of these small and medium sized companies, oversight and implementation resources are not graduate design engineers. Yet, these companies can readily handle their responsibilities for maintenance and modification of safety-related parts of control systems using the qualitative methodologies of Categories. However, transitioning their requirements to the new quantitative methodologies of ISO 13849-1 may not be possible via in-house resources. So, how will these companies provide a safe working environment for their employees around machines when the supply channel converts to Performance Level (PL) versus Category (Cat) for certifying safety products?
We must remember that our OSHA laws enforce machine safety compliance to end user companies and not to designers and integrators. In Europe under the Machinery Directive legal compliance is enforced on the designers and integrators.
Are end user companies in the U.S. abandoned by a zeal to mathematically compare risk levels of hazards between two standards?
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