At the time of writing the article scheduled annulment 29.12.2009 of the standard EN 954-1, on the design of the parts of the system of command responsible for the security features of the machines, synchronizing the entry into force of the new machinery directive with the end of the period of co-existence during whichfor the presumption of conformity of the parts of the system of command with the directive, could opt to use the standard EN 954-1 or EN ISO 13849 (and, through it, the EN IEC 62061).

However, at the last minute was decided to extend the validity of the standard EN 954-1 for two years, until 31 December 2011. Everything that was said in the article is still valid except the effective cancellation of the entry into force of the standard EN 954-1. In this situation the question arises by the manufacturer of machinery: what standard is preferable to use? Is it preferable to follow with the EN 954-1, easier to implement, or already definitively pass to the EN ISO 13849?

If we have a simple machine, with few safety functions resolved with very basic components (for example, a switch of position whose drive produces the opening of a contactor), is indifferent to use one or another standard; in any case, the design is very easy. On the other hand, if we are dealing with complex machinery, with many security features to deal with sophisticated security components (e.g., programmable safety PLCs), for this author, the answer is very clear: without a doubt, the best is change as soon as possible (if not already done already) and use the standard EN ISO 13849 for designing the parties system command that make security features. Endorsing this statement occur to me a few solid reasons, what happened to comment on:

• It is a bad habit of Latin, which must not persevere, the leave things to the last minute. Two years (to this day, less than two years) happen very quickly and it is preferable to avoid the inherent burdens to step them because time is running out. Certainly, this time we have not been latinos 'guilty' of the change made at the last minute. Often barrage of criticism would be receiving from the 'North' if we were! But best not left the change by the end of 2011, the effort will be greater and with increasingly limited ahead.
• The standard EN ISO 13849 is more demanding and rigorous than the EN 954-1. Be the first to design the control system leads to build safer machines.
• Not only the machine is going to be really more secure but, moreover, is an image of modernity while using, can be used as a marketing argument. You could say that, with the safety of machinery, passes with the honesty of the wife of Caesar, which not only has to be it, but also appear to be so.
• The CEN has already changed a number of rules of type C, which refer to the PL to security features, they are no longer refer to the category of the EN 954-1. Therefore, if you still using the category of the standard EN 954-1, the presumption of conformity which gives the type C standard by applying the PL proposed for each security role if it does not apply in its entirety, i.e., may not be invoked. Although the standard EN 954-1 remains in force as a rule of type B, criteria of a type C standard take precedence, when they are applicable, on the of a rule of type B. If you decide not to follow them, you lose the presumption of conformity. And, gradually, all type C standards end up having withdrawn its references to EN 954-1.
• Recalling that we are referring primarily to machine sophisticated with many security features, the standard EN ISO 13849, possibly aided by the EN IEC 62061, allows the use of the software for the security functions. The use of robots for security means in a great simplification of cabling, of the diagnosis of abnormalities and, ultimately, a considerable real savings over the considerable hassle inherent in multiple modules of security for the role of self-control cabling.
• The EN ISO 13849 and EN IEC 62061 are global, EN 954-1 is only at European level. Manufacturers seeking to export its machinery outside Europe suits them much more not allow field.
• It is very common that, eventually, installed machinery is on-site subjected to changes, processes of integration of machinery, etc. These changes often makes the same user or a specialized company, and if they are of sufficient substance, require a new CE marking and a new EC declaration of conformity. When the standard EN 954-1 is definitely cancelled at the end of 2011, changes in the components that make security features will complicate enormously if you mix both standards, EN 954-1 and EN ISO 13849.

We are sure that there must be even more reasons to support the immediate incorporation of the standard EN ISO 13849 plans of manufacturers of machinery. Perhaps can argue against the greater complexity of its calculations to the simplicity of the standard EN 954-1. The author of this article has developed a course of a day, which can be done in company, using as case studies itself the company's machinery, which is based on an Excel very easy to use for calculations. That book excel is also provided free of charge upon request to the address of electronic mail of the final.