ANSI B11.0: Safety of Machines

Last edit: 03/03/2023

This Type-A standard applies to new, existing, modified or rebuilt power driven machines, not portable by hand while working, that are used to process materials by cutting; forming; pressure; electrical, thermal or optical techniques; lamination; or a combination of these processes.  This includes associated equipment used to transfer material or tooling, including fixtures, to assemble/disassemble, to inspect or test, or to package.  The associated equipment, including logic controller(s) and associated software or logic together with the machine actuators and sensors, are considered a part of the industrial machinery.  

This can be a single machine or a machinery system(s).
Informative Note 1:  To improve readability, the terms “machine,” “machinery,” “machine tool” or “machinery system(s)” are used interchangeably throughout the document, either in singular or plural form.
Informative Note 2:  A machine system is a systematic array of one or more industrial machines that is not portable by hand while working and includes any associated material handling, manipulating, gauging, measuring, or inspecting equipment. 
Informative Note 3:  See ANSI B11.20 for additional information on integrated manufacturing systems.

This standard specifies basic terminology, principles and a methodology for achieving safety in the design and the use of machinery.  It specifies principles of risk assessment and risk reduction to help designers, integrators and users of machinery in achieving this objective.  These principles are based on knowledge and experience of the design, use, incidents, accidents and risks associated with machinery.  Procedures are described for identifying hazards and estimating and evaluating risks during relevant phases of the machine life cycle, and for the elimination of hazards or the provision of sufficient risk reduction.  Guidance is given regarding the documentation and verification of the risk assessment and risk reduction process.

Other industry sectors may benefit from applying this standard.  A risk assessment may be required to determine if a machine specific (Type-C) standard covers the hazards associated with the application of the machine covered by the Type-C standard.  

Where a machine-specific (Type-C) standard exists, the requirements of the machine-specific (Type-C) standard shall generally apply.  Deviations from the requirements of this standard or from any machine-specific (Type-C) standard shall be based on a documented risk assessment.
Informative Note 1:  See clause 6 for additional information on risk assessment.
Informative Note 2:  See 7.16 for a list of example machines covered by other specific standards.

A new edition of the standard was publised in 2020

Risk Assessment and Risk Reduction

In Annex A the standard details the typical approach to risk reduction in machinery, used in USA and Canada.

The selection of risk reduction measures can be illustrated in two ways. 

First of all there is the traditional hierarchy of controls shown here.

However, there are many variations of this hierarchy available in the safety literature.  A more recent application of this hierarchy is referred to as the two stage approach and is shown in the Figure below.

In order to effectively implement a safety application using the hierarchy of controls, it is necessary to implement the hierarchy in two stages. 

  • “Stage 1” has two elements with a goal of eliminating the hazard(s) under analysis. 
  • The second stage “Stage 2” has five elements that need to be implemented in a balanced approach to reach the desired goal of reducing all remaining hazards or risks under evaluation to an acceptable level. 

The same method can be represented with the more familiar 3 step method of ISO 12100, present also in B11.0 and represented in the figure hereafter.

There is one important aspect to be noticed: on the right hand side of the graph it is represented both the probability of hard and the severity of it. As you can see, by applying the different risk reduction methods, at each method is associated a reduction in the probability of the harm, but not of the severity! Only the implementation of “Inherently safe design methods” reduces the severity of the harm, however no engineering controls nor Information for use risk reduction methods reduce the severity of the harm.

That is the reason why in the new edition of ISO 12100, that is still under development in 2023, the term Protective measures, that by definition reduce the severity of an harm, will be replaced by Risk Reduction Measures, used already in the B11 standards.

Risk Reduction Measures are means to eliminate hazards or reduce risks. Therefore, glycolic water in Forging Presses is a type of Risk Reduction by Inherently Safe Design, while a safeguarded space with an interlocked door is a type of Risk Reduction by Engineering Controls (B11 language) or Safeguarding (ISO 12100 language).

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