Last edit: 03/03/2023
Risks shall be reduced by using Table 3 – The Hazard Control Hierarchy (ANSI B11.0).
Inherently Safe by Design
Safe Design is the first and most important step in the risk reduction process. It is recognized that a safe design is the most effective approach if applied from the outset for the design of a new machine.
In this first phase, risk reduction requires:
- to consider the geometric factors and the physical aspects (e.g. avoiding crushing points, shearing points, and entanglement points);
- to select the most appropriate technology;
- to limit exposure to hazards (e.g. automation of loading / unloading operations);
- to respect the ergonomic principles.
For example, the standard provides indications on minimum spaces to avoid crushing by including requirements of the ISO 13854 standard.
A safe Design is often difficult to implement. Engineering Controls can be provided to prevent access to hazards that cannot be eliminated.
Engineering Controls- Guards
The standard defines a ‘guard’ as “a barrier that provides protection from a hazard.”
The protections include fixed, mobile, interlocked, adjustable guards, partial guards, perimeter guards, etc.
If the hazard concerns a part of the machine that is not to be accessed, it should be protected by means of a fixed guard. Annex E of ANSI B11.19, provides indication on the safety distance of the guards based on where the danger is located.
The new version of the standard makes a clear distinction between the moving part of an interlocked protection and the interlocking device. This distinction highlights that mobile protections without interlocking devices can also be used to reduce the risk, provided they are securely fixed and to prevent unauthorized adjustments.
There are many devices available that allow you to detect the presence of a person who enters or is inside a dangerous area. Choosing the best means depends on a number of factors, including:
- Access frequency,
- Stop time of the dangerous part,
- Importance of completing the machine cycle, etc.
The mobile guards can be interlocked. The interlocked protections can also be with guard locking to prevent access to the machine during the cycle and when the machine takes a long time to stop.
Access detection devices such as light curtains, sensitive carpets and laser scanners are often selected when operators have frequent access to the area.
Engineering Controls- Control functions
The protections, as described above, are generally associated with the safety functions. A safety function must prevent dangerous machine movements from starting until the error is corrected and the control system is reset.
The safety functions must intervene in time to prevent the operator from reaching the danger area.
Engineering Controls- Devices
An essential aspect for choosing a protective device is the space available. It is necessary to ensure that the dangerous state can be eliminated in time before reaching the danger.
The minimum distance required depends on the size and type of the protective device.
Standard B11.19 provides tables and formulas that help in choosing the most suitable device.
The standard also indicates for the first time the requirements for trapped keys in alignment with the technical standard ISO / TS 19837.
Finally, risk reduction measures can be applied to further reduce the risk to a level considered acceptable. These measures represent the third and final step and they are essentially dependent on human actions or behavior. However, when used in conjunction with other measures of the hierarchy and applied iteratively according to the risk assessment process, administrative controls assist further reduction of risk to a level considered As Low As Reasonably Practical.
- Awareaness Means: they allow people to be informed of any residual risks that have not been eliminated through design or protective devices. Such devices include warnings, alarms, visual signals and acoustic signals that can be used to warn of an impending dangerous event. The new version of the standard has introduced an informative annex to establish parameters to be used for ‘awareness (safety) markings (e.g: colors, patterns) when used for risk reduction.
- Training and Procedures
- Supervision: Without supervision, measures applied previously from the control hierarchy can be bypassed or circumvented, rendering the investment wasted.
- Personal Protective Equipment (PPE): a common measure used in almost every workplace to reduce residual risks that cannot fully be addressed with other risk reduction measures.
- The standard also includes control of hazardous energy among the Administrative Controls since lockout and tagout (LO/TO) rely on human action and behavior to reduce risk. The approach used is that of ASSE Z244.1-2016