Today, successful machines or products must not only perform their intended functions, and perform to customers’ expectations, but they must do so without creating unnecessary hazards that could cause personal injury or property damage. Although no machine is perfectly safe (nothing is perfectly safe), machines are expected to be reasonably safe. They are expected to meet not only safety standards required by governmental codes and regulations, but also standards and criteria found in voluntary industry standards, as well as applicable international standards. In addition, they are expected to consider information and guidance found in textbooks, handbooks, and design manuals, and guidance found in various industry publications (technical journals, published seminar papers, magazine articles, etc.). Even industry customs and practices should be considered when addressing machine safety.

Machines (products in general) need to be designed to minimize, within reason, the possibility of personal injury or property damage. Machine designers must anticipate situations and events that are reasonably foreseeable relative to individuals operating the machine, individuals working on or around the machine, and individuals simply in the vicinity of the machine. They must consider the various ways the machine could cause or become involved in a mishap and the various ways a person could get hurt. Designers must consider the possibility / likelihood of a person getting caught, nipped, pinched, drawn-in, trapped, entangled, crushed, struck, run over, cut, sheared, abraded, punctured, injected, jolted, vibrated, dragged, flung, wrenched, radiated, burned, scalded, blinded, deafened, poisoned, sickened, asphyxiated, shocked, electrocuted, overexerted and overextended, as well as losing a grasp, losing footing, losing balance, slipping, tripping, misstepping, falling on, falling into and falling off. In addition, machine designers must consider the machine’s potential to cause harm to animals (unintentionally becoming caught, injured or killed), property (being struck, contaminated, chemically altered, weakened, flooded, overloaded or burned), or the environment (unacceptably polluting or unacceptably altering environmental or biological systems). The best and most effective time to assure a machine is reasonably safe is during the design process, not after.

Ergonomics is closely tied with machine safety. Ergonomics, sometimes referred to as ‘human factors,’ is a technical discipline concerned with (relative to design of machinery) interrelationships between humans and equipment. Ergonomics is applied for the purpose of integrating human capabilities and limitations with equipment characteristics, not only to reduce operational and safety issues and problems, but also to improve human-work effectiveness. The types of problems that can be mitigated by the application of human factors include: the failure to perform a required task, performing a task that should not have been performed, the failure to recognize a hazardous condition, a wrong decision in response to a problem, inadequate or inappropriate response to a contingency, or poor timing to a response, to name a few. For a machine to be reasonably safe for its operators or bystanders, ergonomics (human factors) must be part of the design process.

The subjects of machine safety and ergonomics have been written about in a number of well-researched books. In addition, industry safety standards have been created through collaborations of experts in their fields. It should be noted that the books and standards cited at the end of this chapter are not the only literature to which one should refer. They represent, however, a useful cross-section to which a machine designer can refer to understand today’s expectations. The reader must understand that the material in this chapter is necessarily brief and general in nature. Hopefully, this introduction will encourage every designer to read further and seek a better understanding of the subjects. Section 2.5 of this chapter provides a list of recommended resources.

Section 2.1

ERGONOMICS

Ergonomics is a discipline that studies humans, their characteristics, capabilities, and limitations, in relationship with their surroundings. Relative to machine design, it is the science of designing a workspace environment and machine interface to fit the user. Like safety, ergonomics is a broad topic that is the subject of many excellent texts. Poor ergonomics can result in either acute injury or long-term repetitive use injury. It is essential to consider not only the physical geometry and arrangement of workspaces, but also the forces involved and the frequency in which they are encountered during a given workday. Actions like bending, reaching, grasping, lifting, turning, positioning, applying force, and releasing all must be conducted with proper ergonomics to achieve efficiency and assure a safe workplace.

Ergonomics issues one must consider when designing equipment and work space are:

•Operator body and workspace dimensions

•Operator performance capabilities and limitations

This section is meant to be an introductory reference only. The reference books and industry standards cited at the end of this chapter provide detailed information for the reader on these subjects.

RECOMMENDED RESOURCES

•A list of books and industry standards are provided in Section 2.5 of this chapter.

BODY AND WORKSPACES DIMENSIONS

The figures and tables in this section represent only one set of data; many sets are available that generally represent information that has been accumulated by various groups and individuals over the years. Care must be taken to choose and refer to the appropriate information source for any given design task at hand.

BODY DIMENSIONS

Anthropometry is the study of body dimensions for the purpose of understanding human variations. Figures 2-1, 2-2, and related information are examples of anthropometric information available from various sources. The information in Tables 2-1 and 2-2 provide basic body dimensions representative of the adult civilian population in the United States. This type of information is particularly useful when designing workstations and controls and when determining various task assignments.

WORKSPACE, CLEARANCES, ENCLOSURES AND ACCESS OPENINGS

Machine workspaces for routine operation as well as maintenance and repair must be designed to accommodate operators as well as maintenance personnel. Interior access openings must be sized appropriately for the various purposes for accessing the area, whether for normal machine operation or for maintenance or repair. Openings must not only accommodate those parts of the individual needing access, but must also be large enough to accept whatever equipment the individual must insert or remove as well. Ideally, access openings should provide not only room for reaching and working, but also additional space for an individual to be able to see.

Figure 2-1: Body Dimension Illustrations

Additional anthropometric and workspace information can be found in industry standards ISO 14738, EN 547-1, EN 547-2, ISO 15534-1, ISO 15534-2 and ISO 15534-3 (see details in Section 2.5), ISO 14738 being particularly useful for designers of machinery.

Table 2-1: Body Dimensions, Inch

Adapted from: Pheasant, 2002¹

OPERATOR PHYSICAL CAPABILITIES AND LIMTATIONS: REACHING / GRASPING / MOVING / LIFTING

Ergonomics relative to individuals’ physical capabilities and limitations also plays an important role in the design of machinery, not only to make the machine functional and productive, but also to assure the workspace is reasonably safe. Issues of physical movement strength and limitations, and exposure to surrounding environmental conditions must be understood during the design process.

Table 2-2: Body Dimensions, Metric

Adapted from: Pheasant, 2002²

Equipment, tools, or work areas that require reaching, grasping, or moving things must be designed to accommodate the strength capabilities and limitations of ordinary operators — being mindful of gender differences. Gender differences must be considered and planned for.

The illustrations in Figure 2-3 are examples of ergonomic information that can be found in the available literature (see citations at the end of this chapter). These types of illustrations are often accompanied with specific force (weight) limits, often representing the 5th percentile adult male (the weakest fifth percent) for the cited population group. Industry standard EN 1005-3 recommends that force limits for professional users correspond to the 15th percentile of the whole adult population (males and females) between 20 years and 65 years of age. For machines intended for domestic users, forces should be limited to the 1st percentile (the weakest one percent) of the same total population. This EN 1005-3 standard also provides de-rating factors for movement velocities, movement frequencies, and application durations. For an understanding of capabilities/limits one might expect in a given situation, refer to and compare data from several sources, understanding what the information and chart numbers represent.

Figure 2-2: Clearances for Work Spaces

Source: Sanders and McCormick, 1993³

Note: These clearances may qualify as confined spaces and require a safety assessment.

Among the types of movement and force limits to be considered include (but are not limited to):

•Pedal force limits

•Handwheel rotational force limits

•Hand-cranking force limits

•Finger-grip/squeeze and hand-grip/squeeze strength limits

•Hand-grasped item twisting force limits

•Weight carrying limits in various carrying modes

•Arm — up, down, in, out, pull, push — force limits

•Whole body pushing, pulling force limits

•Lifts above shoulder height weight limits

Table 2-3: Access Openings

Source: MIL-HDBK-759

Figure 2-3: Reaching — Grasping — Moving Illustrations

Lifting is often required of machine operators while operating equipment or moving material into or out from a machine. An operator may be required to perform many lifts during a normal shift. There are limits to how much total lifting a person can do in a given workday, and it is dependent on the geometry of the lift, the weight involved, and the frequency of performance. When determining if a lifting task is reasonable, the Applications Manual for the Revised NIOSH Lifting Equation should be consulted (available online at www.cdc.gov under “lifting,” which, at the time of this book’s printing, was http://www.cdc.gov/niosh/docs/94-110/). It is recommended that a qualified professional review any ergonomic lifting scenarios.

Additional human physical performance information can be found in industry standards EN 1005-2, EN 1005-3, EN 1005-4 and EN 1005-5, MIL-STD-1472, and the book Human Factors Design Handbook, EN 1005.3 is particularly helpful for machine designers.

CRITICAL CONSIDERATIONS: Ergonomics

•Obey all applicable codes and standards when designing any machine for human interaction. See the recommended resources in Section 2.5 for more information.

•Safety and ergonomics are broad and specialized topics. Have a qualified professional evaluate all applications.

Section 2.2

MACHINE SAFETY: DESIGN PROCESS

A properly designed machine must be reasonably safe for its intended or foreseeable use. This means that it is not just safe for operators and individuals working around the machine while it is operating and performing its primary function, but it is also safe for individuals involved with all aspects of the machine. This includes:

1.Initial assembly and set-up

2.Production job set-up

3.Machine start-up

4.Normal production operation

5.Unusual production circumstances

6.In-production adjustments, clearing and troubleshooting

7.Cleaning and routine maintenance

8.Non-routine maintenance

9.Relocation

10.Decommissioning and scrapping⁴

In addition, a machine should be reasonably safe for reasonably foreseeable misuse as well. The following foreseeable behavior of operators, maintenance personnel, and by-standers must be considered:

•Normal carelessness, inattention, or zeal (but not including deliberate and calculated misuse of the machine)

•Reflex behavior in cases of malfunction, disrupting incidents, failures, jams, etc., during use of the machine

•For some machines, particularly those foreseeably used by non-professionals, the foreseeable behavior of certain innocent, untrained, or unknowledgeable persons, such as children or disabled individuals.

To design a reasonably safe machine, the designer must understand the hazards and risks associated with the machine, and how to effectively reduce them to an acceptable level. Industry standards ISO 12100 and EN 1050 approach this task by working through two basic activities: Risk Assessment and Risk Reduction.

RECOMMENDED RESOURCES

•A list of books and industry standards is provided in Section 2.5 of this chapter.

RISK ASSESSMENT

Risk Assessment is a series of systematic steps to enable the examination of the various hazards associated with the machine. Risk Assessment is followed, when necessary, by Risk Reduction. It must be assumed that a hazard will sooner or later lead to an injury or damage to health (or property) if no Risk Reduction safety measure is taken. This process is a repeating iterative one to eliminate or reduce hazards as far as possible. Risk Assessment steps include:

1.Risk Analysis

(a)Understand the machine, its function, requirements, and limits:

-Understand the machine’s space requirements, power requirements, operator requirements, maintenance requirements, intended use, and foreseeable misuse throughout all phases of the machine’s life cycles.

(b)Identify hazards and perform analysis:

-Identify and describe all reasonably foreseeable hazards associated with the machine.

-Identify all individuals who will be operating or maintaining or in the general area of the machine. Consider their skill levels and likely training.

-Understand the frequency and duration of each hazard’s exposure, as well as the relationship between exposure and likely consequences.

-Consider all reasonably foreseeable situations and conditions.

(c)Estimate risks:

-Perform a systematic analysis of risk based on:

• the severity of the possible harm, and

• the probability of occurrence

-Consider the individuals or property exposed, the type, frequency and duration of exposure, and the relationship between exposure and the effects.

-Refer to recognized industry standards for risk estimation procedures, including specifically MIL-STD-882 and ANSI B11. TR3. Other standards to consider include ANIS B11-2008, ISO 12100:2010, EN 1050, ISO/TR 14121-2, ISO 14121-1, EN 1005-5, and ISO 13849-1.

2.Risk Evaluation

(a)Based on the results from Risk Analysis, determine if Risk Reduction (or additional Risk Reduction) is required.

(b)If Risk Reduction is needed, then take appropriate safety-improvement steps. These could include eliminating a hazard, providing additional safeguarding, restricting or improving access, interlocks, etc.

(c)Repeat the Risk Assessment process until an acceptable level of risk is achieved.

There are several methods customarily used for analyzing hazards and estimating risks. Each has its own unique approach, strengths, and limitations. Although it is not imperative that any one of these methods listed should necessarily be used, some organized methodical approach should be, and the process should take place while the machine is being designed — not after. Some methods for analyzing hazards and estimating risks include:

Failure Modes, Effects, and Criticality Analysis (FMECA—sometimes known as FMEA) is a method of assessing designs or processes with respect to the various ways they can fail. Failure modes can affect safety as well as machine function. FMECA uses a worksheet (or software) to identify failure modes, their effects, risks, probabilities, and control (mitigation) methods. FMECA is covered in more detail in Chapter 12.

‘What If’ Analysis is a simple system of questions and answers. For machines or systems that are not too complex, “what if” questions are asked and answered in a systematic way about the machine and its operation for the purpose of evaluating the consequences of component failures, operator mistakes, or certain operational situations. The suitability of the machine, its controls, and its safeguarding and safety-related equipment are evaluated.

Fault Tree Analysis (FTA) uses deductive logic. This method starts with an unwanted event (the unwanted consequence) and works backwards to reveal the individual failures that can lead to that event. It enables individuals to find the various critical paths that can lead to the eventual unwanted event. The end event is first identified, then the various events and failures (and combinations of failures) that can lead to the final event are identified and listed, followed by estimates of probabilities of failure. A fault tree analysis can be used to determine the impact of alternative designs.

Preliminary Hazard Analysis (PHA) is an inductive analysis tool that helps identify and address machine hazards at the earliest stages of design. It is a means of creating an initial list of all hazards that may exist in every machine area and system and operation. It helps overcome the tendency to focus only on immediately obvious hazards, forcing an evaluation of potentially more serious or hidden dangers within a machine. Proposals for safety measures are the end result.

The DELPHI Technique involves providing questionnaires to a group of experts, individually, in successive steps. The results of the previous round of questions and answers, together with additional information from the others in the group, are communicated back to the participants. During the third or fourth round, the questions concentrate on those issues for which there is little or no general agreement. Because of its use of experts, this technique is notably efficient.

It should be understood that there are many methods of hazard identification and analysis. These listed are only a few. Each method has advantages for certain applications; therefore, it may be necessary to adjust or combine methods to match the situation at hand. It is important, whatever method is or methods are chosen, that hazard identification and analyses be performed early and often during the design process.

RISK REDUCTION

Risk Reduction is the process of taking sequential steps to either eliminate hazards or reduce hazards to an acceptable level. Although there are variations of lists of such steps, the following steps are commonly cited (listed in sequential order of most effective to least effective):

1.Eliminate or reduce the severity of the hazard (design the hazard out).

2.Safeguard the hazard (barrier guards or protective devices).

3.Instruct and warn the user (in manuals, and when appropriate, on the machine).

4.Describe requirements for training the user (safe work procedures training).

5.Recommend personal protective equipment (ear protection, eye protection, etc.).

The Risk Reduction process, unlike the Risk Assessment process, requires actual design creations and decisions — some take the form of designs that eliminate or provide safeguarding for hazards; others are in the form of warnings, instructions, or information (literature and manuals that provide information, instructions, and warnings are a part of the total machine). When risks have been properly assessed, and when the machine’s design has satisfactorily reduced the risks, the resulting machine can be judged to have reached its safety goals. The Risk Assessment / Risk Reduction iterative cycle would then be complete. (For a detailed understanding of this process, refer to industry standards ISO 12100:2010, ANSI B11-2008, and others listed in Section 2.5.)

CRITICAL CONSIDERATIONS: Machine Safety: Design Process

•Be sure to comply with all safety and ergonomics laws, codes, and standards. Consult the recommended resources (Section 2.5) for more information.

•Conduct Risk Assessments on all designs and processes. Conduct risk analysis early and often during the design process.

•Designing a hazard out should be the goal of any risk reduction activity. If this is not possible, other methods may be employed.

•Risk of long-term repetitive use injury should never be underestimated. This is an important factor in the design of workstations, tools, and industrial equipment.

Section 2.3

MACHINE SAFEGUARDING

Most machines have moving parts, both rotating and linear-moving, that can cause injury. Moving machine parts may be found in numerous locations on or around a machine, including:

(a)At the point of operation where work is performed on the work piece or material,

(b)In the power transmission components that transmit power throughout the machine (shafts, pulleys, belts, sprockets, chains, flywheels, couplings, spindles, gears, cams, cranks, rods, and other moving parts), or

(c)In other moving parts of the machine (machine components that move during operation, such as rotating parts, reciprocating parts, or traverse-moving parts).

All parts that move have the potential to contribute to accidents that can result in personal injury. Both rotating motion and linear movement can be dangerous.

Rotating components, even smooth rotating shafts, can grip an item of clothing or hair — even skin — and draw it into the machine. The danger of rotating components increases if they contain irregular or uneven surfaces or projecting parts, such as adjusting screws, bolts, slits, notches, or sharp edges. Rotating machine parts can also create dangerous in-running nip points with adjacent rotating or wedging components.

Vertical, horizontal, and reciprocating motion can cause injury in several ways, including causing a person to become caught between a moving machine part and some other object, shoving or knocking into a person, catching a person in a nip point, or causing injury with an unexpected movement of a sharp edge.

In addition, many machines have hydraulic or pneumatic systems that transmit power, or components that store energy. Springs, components under pressure, and elevated masses are examples of stored energy that can be released suddenly and hazardously. These power-transmitting and energy-storing components, should they fail or be released unexpectedly, pose hazards that must be considered during the machine design process. For example, a burst hydraulic line can spray oil that can be scalding hot, or can produce pin-point spray capable of penetrating skin. A whipping hose can become violent. A failed pneumatic fitting can release a potentially dangerous blast of compressed air, or release the pressure on an air cylinder causing unexpected movement and potentially dropping a load. The sudden release of a deflected spring or sudden drop of an elevated component can be very dangerous.

If a given hazard cannot be designed out of a machine (or neutralized by the nature of its remote location), then safeguarding, in some form, must be provided. Safeguarding can be categorized as either Designed-into-the-machine safeguarding, or Procedural safeguarding. (Procedural safeguarding is sometimes known as Information for use, or information and warnings).

Designed-into-the-machine Safeguarding can be either a guard, which is a physical barrier that prevents access to a hazardous area, or a protective device, which is a safeguarding means other than a barrier guard that controls access to a hazardous area. Examples of protective devices are photoelectric curtains, cable pull-backs, pressure sensitive mats, trip bars, and two-hand controls. Protective devices are often used to control access specifically to a machine’s point of operation. Guards and protective devices can be (and often are) integrated together (an interlocking guard, for instance) when appropriate to enhance productivity or further enhance overall safety. Safeguarding will be detailed later in this section.

Procedural Safeguarding (Information for use) is information, instructions, procedures, and/or warnings posted on the machine, in manuals, or in training sessions instructing individuals how to operate the machine, how to avoid certain actions, or how to take certain steps to avoid a particular hazard. Procedural safeguarding is inherently less effective than barrier guards or protective devices designed into the machine because it relies on factors that are unpredictable. Procedural safeguarding relies on every individual doing everything in accordance with all instructions — 100% of the time — with no exceptions.

Safeguarding that is designed into a machine is far more effective than procedural safeguarding (information and warnings). Only when the hazard cannot be designed out of the machine and cannot be effectively safeguarded (the 1st and 2nd steps in the sequential Risk Reduction steps — see earlier) should the designer turn to those steps that fall into the ‘Procedural Safeguarding’ category (the 3rd, 4th, and 5th steps).

RECOMMENDED RESOURCES

•A list of books and industry standards are provided in Section 2.5 of this chapter.

GUARDS

When a hazard cannot be designed out of a machine, safeguarding the hazards (guards or protective devices) are next in priority. Physical barrier guards (and shields) have significant advantages over other means of safeguarding. They can provide operator protection from:

•Contact with moving parts of the machine

•Contact with splashing or misting chemicals or liquids

•Contact with thrown objects, hot chips, or other discharged objects or particles

•Contact with failed machine components (mechanical, hydraulic, pneumatic, electrical, etc.)

•Harmful contact due to human frailties and human traits, such as: curiosity, distraction, zeal, fatigue, worry, anger, illness, corner-cutting, or deliberate risk taking

Guards and shields should also be considered as protection for certain components of the machine itself. They can protect components susceptible to damage, such as electrical wires, electrical components, hydraulic lines, or small functional mechanical components that could otherwise be exposed to damage. (This damage could be due to such things as human error during machine handling, set-up, operation or maintenance and repair; machine malfunction and workpiece variations; or the machine’s exposure to workplace traffic, to name a few). Guards and shields can be used to protect machine components from damage from:

•Contact with hard objects (workers’ tools, workpiece material, etc.)

•Contact with a failed machine component

•Exposure to harmful liquids, mists, fumes, or chemicals

•Exposure to radiation or harmful light

Guards and shields are intended to provide protection. For the design and construction of a barrier guard to be fully effective, it should:

•Provide adequate protection from the danger zone during operation.

•Conform to applicable federal and state laws and regulations.

•Be considered as a permanent part of the machine. (If capable of being opened or removed, it should be simple and quick to close or re-install, and it should become obvious or required that it be closed or re-installed before machine operation continues.)

•Be durable and robust (able to withstand the stresses of the process and environmental conditions, able to hold up under normal wear and impact and corrosion damage, and able to withstand extensive use with minimum maintenance).

•Be easily reparable.

•Not weaken the structure of the machine.

•Be convenient — not interfering with the efficient operation of the machine, and not causing aggravation or discomfort to the operator.

•Be designed for the specific machine and for the specific danger zone.

•Have provisions for inspecting, adjusting, maintaining, and repairing the machine.

•Itself not create a hazard (having sharp edges, creating a pinch point, etc.).

Regarding guards themselves, the allowable opening in or under a machine guard changes with the distance from the point of danger. Guards close to a point of danger must restrict sizes of openings, while guards further away can allow larger openings. One standard identifying these distances and openings are cited in OSHA regulations (1910.217(c), Table O-10 — see Figure 2-4). Other industry standards provide more thorough information on this subject, including those cited in Section 2.5 of this chapter (specifically: EN 294, ISO 13852, EN 811, ISO 13853, ISO 13857, and EN 999).

There are four basic types of guards commonly used today: fixed, adjustable, self-adjusting, and interlocked. Fixed guards and interlocked guards are the most common type for guarding mechanical power transmission components and other machine moving parts. For these applications, there are few reasons to employ adjustable or self-adjusting guards. For guarding a machine’s point-of-operation, depending on the situation, any one of the four types of guards may be appropriate. Examples of guards can be found in the National Safety Council book Safeguarding Concepts Illustrated and the industry standard BSI PD 5304 Safe Use of Machinery (Section 7), as cited near the end of this chapter. For point-of-operation guarding, Table 2-4 provides a list of advantages and disadvantages for these four types of point of operation guards.

Figure 2-4: Guard Openings vs. Distances from Point of Danger

•Fixed guards, if they are designed appropriately, are the safest type of guarding. When they are in place on the machine, by their fixed design and fixed location, they provide the protection they were designed for — every time.⁵ (The guarding over the top of the blade of a powered circular saw is an example of a fixed guard.)

•Adjustable guards are a type of guards that have adjustable parts to permit various machine settings and various operations. An example of an adjustable guard is a guard at the entrance to a machine’s point-of-operation that can be adjusted to admit variations in work piece shapes. (Adjustable guards are often found at the point of operation of band-saws.)

•Self-adjusting guards are designed such that the whole guard or a portion of the guard is free to move and can automatically adjust (move) to accommodate movement of the machine or movement of material being processed. (Self-adjusting guards are commonly found on the underside — under the support shoe — of hand-held circular saws.)

•Interlocking guards are guards that interact with a device that is interconnected with some operational function of the machine to automatically stop (or alter) a prescribed function should the guard be out of place.⁶ Interlocking guards are common on light industrial machinery where frequent, safe access to hazardous areas is required. Interlocking guards can include doors, lids, and gate guards. Gate guards are physical barrier guards that automatically close off access during the hazardous operation of the machine and open for access when the machine has finished the unsafe activity. (The top lid to a top-loading clothes washing machine is an example of an interlocking guard, interconnected with the machine to prevent spin-cycle operation when the lid is open.)

Table 2-4: Point-of-Operation Protection: Barrier Guards

Based on U.S. Department of Labor, OSHA publication OSHA 3170-02R 2007

PROTECTIVE DEVICES

For a machine’s point-of-operation, a less desirable alternative to physical barrier guarding is a protective device. Point-of-operation protective devices work to prevent an operator’s hands and other body parts from entering the point-of-operation danger zone during machine operation. Generally, they do not prevent discharge of hot chips, thrown particles, or liquid splash as barrier guards do. They also do not protect others in the vicinity other than the operator.

Protective devices can be categorized into four basic types: restraints, proximity detection devices, two-hand controls, and gates.

Restraints include fixed restraints that limit the operator’s movement, or pull-back devices that physically pull the operator’s hands out of the danger zone prior to machine cycling. Restraints protect only the operator, not others who may be in the area.

Proximity detection devices include interlocking devices, light curtains, weight-sensitive floor mats, pressure-sensitive bars or edges, contact probes, and other devices. These devices protect everyone in the area.

Two-hand controls are primarily devices placed some safe distance away from the danger zone that require both of the operator’s hands to contact cycle start switches simultaneously. The distance from the danger zone is calculated such that operators cannot push the buttons and then quickly move their hands into the danger zone. These devices are also often called “two-hand no-tie-down devices”. These devices protect only the operator, not others who may be in the area.

Gates are physical barriers that move to block access to the danger zone when the machine cycles. These devices protect everyone in the area.

Examples of protective devices can be found in industry standards BSI PD 5304 (including in Section 8), and in other literature cited in Section 2.5 of this chapter. Table 2-5 provides a list of advantages and disadvantages of various point-of-operation protective devices.

Table 2-5: Point-of-Operation Protection: Operator Protective Devices

Based on U.S. Department of Labor, OSHA publication OSHA 3170-02R 2007

PROCEDURAL SAFEGUARDING: INFORMATION, INSTRUCTIONS AND WARNINGS

Information and instructions, customarily in the form of machine manuals⁷, are an integral part of a machine. Manuals provide information and instructions about the machine and its use. Information and instructions should be complete enough to ensure proper and safe installation, set-up, use, and maintenance. Instructions are important, but on their own, they are not enough to ensure operators will work safely.

Regarding specifically safety, manuals must also include information and warnings about hazards and risks that may not be known to users, not just when the machine is used as intended, but in reasonably foreseeable misuse situations as well. Although there is not a duty to warn of hazards that are open and obvious (the sharpness of a kitchen knife, for instance), it is important to understand that what may be obvious to a machine’s designer may not be obvious to an ordinary user. Procedural safeguarding, the 3rd, 4th and 5th priorities⁸ in the machine hazard risk reduction hierarchy list, starts with the information, instructions and warnings found in the manual. This section is intended to be only a brief introduction to the subject. The reader is encouraged to become familiar with books and industry standards on the subject, some of which are cited in Section 2.5.

Regarding warnings, when a hazard that can cause serious injury cannot be designed out of a machine (or protected by its remote location) and cannot be effectively safeguarded by a barrier guard or protective device, if the hazard is not obvious or readily known to an ordinary user, there is an obligation to provide a warning likely to be seen and understood. Although warnings provide information and instructions about hidden or unknown hazards, it must be understood that they have a limited impact on making mishaps less probable. The ultimate aim of a warning is to alter behavior, by encouraging an individual either to do something, or to avoid doing something.

Once it is determined that a warning is needed, the resulting warning must be crafted to be, at minimum, “adequate.” An “adequate” warning is one that would lead an ordinarily reasonable person to understand the hazard and take steps to avoid harm. In general, a warning can be viewed as “adequate” if:

-the warning is in a form that could reasonably be expected to catch the attention of a reasonably prudent person,

-with a message understandable to the ordinary user,

-conveying a fair indication of the nature and gravity of the harm that could result from the hazard,

-conveyed with a degree of intensity that would cause a reasonable person to exercise appropriate caution.

The development of a warning can be a simple process of providing understandable information and instructions in an effective way or, in some situations, a complex process involving product research, message development, and focus group responses. In all cases, warnings—both those included in manuals and those posted on machines—for them to be “adequate” must be clear, readable, and understandable to the ordinary user.

WARNINGS INCLUDED IN THE MANUAL

Warnings included in a machine’s manual must be capable of conveying the same information as those posted on the machine itself. When writing warnings for the manual, the following should be considered:

•All warnings a user may need to know about should be included in the manual.

•From a style perspective, warnings in a manual must be reasonably consistent with each other, and they must be consistent with the warning labels posted on the machine.

•Warnings that warrant the “DANGER” level (DANGER being the most serious level) must be not only included in the manual but also posted on the machine itself.

•Warnings must stand out from the rest of the information in the manual.

•Never mix warnings with ordinary instructions.

•Never bury warnings in the text in such a way that it might be missed.

•If there is a section in the manual dedicated to listing all warnings and safety instructions (at the beginning of the manual, for instance), also include the warnings elsewhere in the manual text where appropriate.

•It is good practice to illustrate in the manual every warning label posted on the machine, indicating its location on the machine. Along with these illustrations, it is good practice to provide the label’s part number to simplify replacement if necessary.

It must be remembered that not all individuals who will be operating the machine will have had access to or have read the manual. And many who have read the manual will not remember certain pieces of information contained within. It is important to remember that for a warning to be effective, it must be seen, read, understood, remembered, and heeded. As a result, warnings placed only in the manual will not likely meet at least one of the requirements for it to be deemed “adequate.”

WARNING LABELS POSTED ON THE MACHINE

Warnings located in the manual are simply not going to catch the attention of a machine user who has not read it or doesn’t recall its contents.

Some hazards that cannot be eliminated or guarded are serious enough to warrant the posting of warning labels on the machine itself. The design of machine-posted warnings has developed over the years, based on industry experience and controlled studies. One definition of an effective warning is one that changes behavior in a way that results in a net reduction in negative consequences. It has been found that the effectiveness of machine-posted warnings improves when warnings:

•are located near the zone of danger itself,

•are conspicuous (eye-catching) and in a location likely to be seen,

•have a ‘signal word’ of appropriate strength (such as “CAUTION” or “WARNING” or “DANGER”), indicating the seriousness of hazard,

•have a hazard statement informing the reader in a clearly stated manner what the danger is,

•have a consequence statement telling in a clearly understandable way of the consequence of the hazard,

•have an instruction statement providing clearly stated instructions on what to do to avoid the hazard.

The machine designer should have a basic understanding of warnings and what factors influence their effectiveness. Effectiveness is influenced by choice of colors, placement, ‘signal words,’ pictogram illustrations, wording of statements, size of letters, and durability, to name a few. The subject of warnings and what makes them effective has been studied and written about extensively. Our discussion presents only very basic information about the subject. For more information, consult industry standards such as ANSI Z535 (series), ISO 3864 (series), ISO 17398, EN 842, EN 457, EN 981 and ISO 7000, along with various books on the subject.

CRITICAL CONSIDERATIONS: Machine Safeguarding

•Be sure to comply with all safety and ergonomics laws, codes, and standards. Consult the recommended resources for more information.

•Physical barrier guarding should be the first choice if a hazard cannot be designed out of the machine.

•Procedural safeguards must be written, and training of personnel should be formalized and recorded.

•Have a qualified safety professional evaluate all equipment, tools, and workspaces.

Section 2.4

OTHER SAFETY ISSUES

There are other machine design safety features and issues that cannot necessarily be classified as safeguarding. It is important that all aspects of machine safety be analyzed during the design process and appropriate steps and design features be considered. The following are only some of the safety-related aspects of a machine that were not included earlier in this chapter; designers must be mindful of them during the machine development process.

An excellent source for understanding a machine’s safety goals and the associated design process is industry standard ISO 12100:2010. It is recommended that machine designers not only become familiar with much of the literature cited in Section 2.5, but also become familiar with specifically this standard.

RECOMMENDED RESOURCES

•A list of books and industry standards are provided in Section 2.5 of this chapter.

EMISSION OF AIRBORNE SUBSTANCES OR MODIFICATION OF SURROUNDING ATMOSPHERE

The machine designer must be aware of the potential for the machine to emit undesirable or potentially harmful airborne substances such as mists, vapors, fumes, particles, dust, or other contaminants, or to cause a modification of its surrounding atmosphere, such as enriched oxygen, carbon-dioxide, or nitrogen. Such airborne substance or modified atmosphere, when certain levels are exceeded, could affect not only the performance, safety, or health of individuals, but also potentially the value of surrounding property.

It is important that a machine that emits such substances or gases be designed such that such emissions can be appropriately controlled. Controlling such substance or gases can be accomplished either within the confines of the machine itself (designed into the machine), or through information and instructions provided with the machine, providing information about the emissions (nature of the substance, likely volumes of emission, and potential effects), and instructions or guidelines for their control (the type and basic capacity of emission control equipment needed).

EMISSION OF RADIATION, INTENSE LIGHT, VIBRATION, HEAT

The machine designer must consider the potential for the machine to emit radiation (X-rays, gamma rays, ultraviolet, infrared, microwave, etc.), intense light (welding beam, laser beam, etc.), substantial vibration, or substantial heat. Such emissions, if beyond an acceptable level, can affect the health and safety of individuals in the area as well as surrounding property, and must be controlled. Control can be achieved through the use of radiation filters, screens or shielding, limiting radiation power, providing remote operation, providing vibration isolators or dampers, providing cooling ventilation, etc.

EMISSION OF NOISE

All machines that have moving parts emit noise. According to U.S. OSHA requirements, employers must take steps to control noise employees are exposed to, and achieve, at minimum, levels not exceeding those cited in the regulation (Table G-16 of 29 CFR 1910.95(b)(1); see Table 2-6). Machine noise can be controlled, and designers should understand excessive noise is generally not desirable. Ways of reducing machine noise include increasing the mass of panel material, using sound insulation, damping or cushioning sources of impact or vibration, and reducing or muffling compressed air emissions. When noise at the operator’s ears exceeds limits set in OSHA regulations, hearing protection is required, and such information and instructions must be included with the machine. Machine noise levels should be measured in accordance with ANSI B11.TR5.

Table 2-6: OSHA Noise Exposure Limits

Duration of Exposure hours	Sound Level DBA (slow response)
8	90
6	92
4	90
3	97
2	100
1.5	102
1	105
0.5	110
0.25 or less	115
Impulse Noise	140 peak

HAND/ARM VIBRATION

Hand/arm vibration (HAV) is defined as the transfer of vibration from a tool to a worker’s hand and arm. The amount of hand/arm vibration is characterized by the acceleration level of the tool when grasped by the worker and in use. The vibration frequencies that most affect hands and arms lie in the 5 to 1,500 Hz range. The types of machines typically associated with significant vibration include chain saws, chipping hammers, grinders, hammer drills, and powered compactors. NIOSH publication No. 89-106 “Criteria for a Recommended Standard: Occupational Exposure to Hand-Arm Vibration,” 1989 (found at www.cdc.gov/niosh/89-106.html) provides helpful information.

WHOLE BODY VIBRATION

Whole body vibration (WBV) is the transfer of relatively low frequency (0.5 to 80 Hz) motion to the whole body through a broad contact area. It is most commonly transmitted through the feet when standing, or through the buttocks when sitting. Off-road unsprung vehicles are the type of machines most typically associated with the vibration, jarring, and jolting associated with WBV. Whole body vibration can jostle organs, contribute to back pain, cause fatigue, and cause a reduction in a person’s work performance. NIOSH, as well as Health and Safety Executive (found at www.hse.gov.uk/), provides additional information on this subject.

MACHINE USE IN EXPLOSIVE ATMOSPHERES

If it is intended or if it is foreseeable that a machine will be used in the presence of an explosive atmosphere (gases, vapors, mists, or combustible dusts), components capable of operating in such atmospheres safely (spark-free, for instance) must be selected. The industry standards EN 1127-1, EN 50020, EN60204, as well as UL standards titled “Hazardous (Classified) Location ...” and the European Union directive ATEX95 94/9/EC provide guidance in such situations.

MOVING THE MACHINE

When it is determined moving a machine is hazardous, then provisions for jacking, lifting, and hoisting should be provided to help the moving process and enhance safety. When it is foreseeable that a machine’s weight, center-of-gravity, or lift point material strength could be misunderstood by movers, moving instructions should be made available and made obvious to movers. These instructions should provide such information as the machine’s weight, center-of-gravity location, lift points, loose component tie-down points, and other information necessary for a safe move. Professional riggers should be used to move extremely heavy, large, awkward, or sensitive machinery.

MACHINE STABILITY

A machine must be sufficiently stable for it to be used as intended safely. Its weight distribution and base footprint must be such that it remains stable, taking into account machine vibration, dynamic movement of components, movement of work pieces, foreseeable mishandling, accidental bumping, forces of nature, etc. If necessary, provisions should be provided for anchoring (bolting) the machine into position (to the floor, for instance).

LUBRICATION

To avoid exposing individuals to unacceptable risks when lubricating a machine, lubrication points should be located in accessible and safe-to-reach locations, when possible.

DANGER WARNING ALARM SIGNALING: AUDIBLE SIGNALS AND VISUAL SIGNALS

When the health or safety of an individual is put at risk by an unstaffed machine in a defective or dangerous state, according to accepted industry standards the machine must be equipped to transmit an appropriate audible or visual warning alarm signal indicating the danger. The warning alarm signal must be immediately and easily recognized and understood; it must have priority over all other signals (except not over emergency signals, which have absolute priority). The characteristics of warning signals are outlined in industry standards, including EN 981, EN 842 and EN 457.

Audible danger signals must be such that anybody who hears them recognizes them and can react immediately. The characteristics which make a danger signal effective are its sound (audibility), its ability to be recognized immediately (discriminability), and that there is absolutely no doubt as to what it refers to (unequivocability). For further details, industry standard EN 457 is recommended as a reference.

Visual danger signals must be designed such that that anybody who sees them will recognize them and respond immediately. A visual danger signal must be clearly visible, even in strong light (visibility), distinguishable from other lights and light signals (distinguishability), and understood immediately (unequivocability). The visual signals must be positioned where it reaches all of the area affected, and its message must be clearly understood — whether it refers to a machine, a group of machines, a production line, or a complete department. For further details, industry standard EN 842 is recommended as a reference.

LOCKOUT/TAGOUT REQUIREMENTS

Federal OSHA regulations (29CFR1910.147) require employers to ensure that all new machines provided to employees are capable of being locked out during service and maintenance for the purpose of preventing unexpected start-ups, the energizing of machinery, or the release of stored energy that could cause injury to employees. The lockout standard applies if (1) the employee is required to remove or bypass a guard or other safety device during service, (2) an associated danger zone exists during a machine operating cycle, or (3) the employee is required to place any body part into the machine’s point-of-operation area.⁹

All new machinery and equipment needs to be designed to accept lockout devices.¹⁰

EMERGENCY STOP DEVICES

An emergency stop device is a manually actuated control device that requires deliberate action to bring the machine to a stop when a dangerous situation is recognized. The E-stop (emergency stop) device must be continuously operable and within easy reach. Each operator panel must contain at least one E-stop device. Additional E-stop devices must be available and readily accessible, at minimum, wherever a machine operator is intended to be or would foreseeably be during normal operation. E-stop devices should stop the machine as quickly as possible without generating additional hazards. Emergency stops must safely neutralize energy to and within that portion of the machine affected, including electrical power as well as pressurized air. E-stops are not safeguards, and are not alternatives to safeguarding.

Because emergency stop switches and circuits can remain inactive for long periods of time, it is important that they be designed with reliability in mind. In addition, instructions for maintenance requirements and periodic testing are important to assure confidence that the system will function as intended.¹¹

Emergency stop components and circuitry must be failsafe, and the appropriate components for E-stop use are normally clearly identified by component manufacturers. Emergency stop devices come in various forms, the most common of which are cable pulls and mushroom-type button switches. When an E-stop device is actuated, it must latch in, and it must not be possible to generate the stop command without latching in. The resetting of an E-stop device must not cause a hazardous situation. To restart the machine, a separate and deliberate action must be required.

Emergency stop device details can be found in industry standards BSI PD 5304 (section 5), EN 418, EN-13850, ISO 13852 and ISO 13850. Design and selection of components for E-stops should be performed by a qualified controls professional.

CRITICAL CONSIDERATIONS: Other Safety Issues

•Comply with all laws, codes, and standards governing environmental hazards. Consult the recommended resources for more information.

•Design of an E-stop circuit and selection of related components should be conducted by a qualified controls professional.

•Lockout/Tagout procedures are required by law to isolate all sources of energy (electrical, pneumatic, hydraulic, mechanical, etc.) when maintenance activities are performed. Consult the recommended resources for Lockout/Tagout procedures and requirements.

•Have a qualified safety professional evaluate all equipment, tools, and workspaces for environmental and machine hazards.

Section 2.5

RECOMMENDED RESOURCES

Machinery safety and ergonomics information is found in governmental statutes, codes and regulations, industry standards, handbooks, textbooks and manuals, and scientific and technical literature found in magazines, journals and periodical articles. Safety requirements are found in governmental statutes. Safety expectations — just as important for machine safety — are found in various books, standards and periodical literature.

Society’s expectations of what is acceptable relative to product safety evolves with time, and usually it is the industry standards, and the books, that most accurately reflect what society views as the ‘best practices’ to achieve what is viewed as reasonably safe. For this reason, although governmental statues are certainly important and necessary to be included in this literature list, the designer should understand that well-organized books and up-to-date industry standards are of paramount importance in designing safe machines and products. Because of the fluidity and time-limited exposure of periodical literature, this chapter does not attempt to cite notable magazine articles, journal papers, technical studies, government ‘fact sheets’ and bulletins, or other such literature, despite their importance.

GOVERNMENTAL REGULATIONS, STATUTES, CODES AND PUBLICATIONS

•Code of Federal Regulations 29 CFR 1910: Occupational Safety and Health Standards, parts 1910.1 through 1910.399 (authorized through the Occupational Safety and Health Act—OSHA)

This is the U.S. Department of Labor’s regulation that covers general worker safety, including 1910’s Subpart ‘O’ - Machinery and Machine Guarding (1910.211 through 1910.219), and Subpart ‘P’ - Hand and Portable Tools and Other Hand-Held Equipment (1910.241 through 1910.244). Parts 1910.1 through 1910.399 do not detail many of the engineering requirements for compliance. Instead, they reference other industry standards, including standards issued by or through such organizations as ANSI, ASME, ASSE, IEEE, ISO, NFPA, and UL, to name a few. OSHA standards represent the minimum level of regulatory compliance requirements within the United States.

•Code of Federal Regulations 29 CFR 1926: Safety and Health Regulations for Construction, parts 1926.300, and 1926.302 through 1926.307 (authorized through the Contract Work Hours and Safety Standards Act, and the Occupational Safety and Health Act—OSHA)

This is the U.S. Department of Labor’s regulation covering certain hand tools and power tools, including those typically used in the construction industry, as found in 1926’s Subpart ‘I’ -Tools - Hand and Power (1926.300 through 1926.307).

•Code of Federal Regulations 29 CFR 1928: Occupational Safety and Health Standards for Agriculture, part 1928.57 (authorized through the Occupational Safety and Health Act—OSHA)

This is the U.S. Department of Labor’s regulation covering certain agricultural equipment, as included in Subpart ‘D’ - Safety for Agricultural Equipment, in section 1928.57 - Guarding of farm field equipment, farmstead equipment, and cotton gins.

•Military Standards and Handbooks

These are often used or referred to in private industry for guidance for design, manufacturing, quality control and maintenance, relating to services, machines and equipment.

MIL-STD-882 System Safety Program Requirements

This is a standard that addresses hazard identification and risk analysis / reduction, employing an integration of hazard identification and hazard severity applicable to machines and systems (military and non-military).

MIL-STD-1472 Human Engineering Design Criteria for Military Systems, Equipment and Facilities

This standard is acknowledged worldwide as an authoritative source for human factors requirements and design criteria. It provides most aspects of human factors information and performance criteria / limitations helpful for the physical design and layout of machines, equipment, and facilities, including operational controls (for both military and non-military applications). This standard focuses more on task and operational performance than worker health and safety.

MIL-HDBK-759 Human Engineering Design Guidelines

This handbook guideline provides a broad range of human factors information and performance considerations as a supplement to MIL-STD-1472.

DOD-HDBK-743 Anthropometry of U.S. Military Personnel

This document provides body size information on military personnel of the United States, as a supplement to MIL-STD-1472.

•NASA Reference Publication 1024 Anthropometric Source Book Volume I: Anthropometry for Designers (N79-11734) National Aeronautics and Space Administration, Scientific and Technical Information Office, Lyndon B. Johnson Space Center, Houston, TX 77058 (edited by the Staff of Anthropology Research Project, Webb Associates, Yellow Springs, Ohio, 1978)

This publication contains 550 pages of extensive and easy-to-use anthropometric information on adult men and women, including data on certain non-U.S. population groups.

BOOKS

•Product Safety Management and Engineering, by W. Hammer; American Society of Safety Engineers, Des Plaines, IL, 1993

This is a thorough, well-organized, well-written text with numerous charts, checklists, and tables addressing designing safe products and machines.

•Accident Prevention Manual for Business & Industry: Engineering & Technology, 13th Ed., National Safety Council, 2010

This manual is periodically published and updated by the NSC, and includes chapters on industrial safety, including machine safety.

•Human Factors Design Handbook, 2nd Ed., by Woodson, Tillman and Tillman; McGraw-Hill Inc., New York, NY, 1992

This is a notably useful compilation of human factors data, including numerous guidelines, illustrations, checklists, tables, charts, diagrams, and practical examples.

•Ergonomics A Practical Guide, National Safety Council, 1993

This book contains practical ergonomics information.

•Safeguarding Concepts Illustrated, 7th Ed., National Safety Council, 2002

This book contains 140 pages of 300 to 400 illustrations and pictures of actual machine and equipment guards, with explanations, in well-organized chapters and groupings.

•Human Factors in Engineering and Design, 7th Ed., by Sanders and McCormick; McGraw-Hill Inc., New York, NY, 1993

This book provides human factors information, emphasizing workplace locations and situations.

•Warnings and Risk Communication, by Wogalter, DeJoy and Laughery; Taylor & Francis Inc., Philadelphia, PA, 1999

This book provides insight into the effectiveness and ineffectiveness of warnings, based on extensive research.

•Handbook of Warnings, by Wogalter; Lawrence Erlbaum Associates, Mahwah, NJ, 2006

This handbook contains extensive information on warnings as they are applied to a broad range of situations.

•Writing and Designing Manuals, 2nd Ed., by Schoff and Robinson; Lewis Publishers, Inc., Chelsea, MI, 1991

This book is a guide for writing, illustrating, and organizing manuals for machine and product owners, operators, and service personnel.

•The Measure of Man & Woman, Dreyfuss & Associates; John Wiley & Sons, Inc., New York, NY, 2002

This book contains extensive and useful anthropometric charts and data for U.S. civilians in the 1st, 50th, and 99th population percentiles (information beyond the more typical 5%-50%-95% numbers), as well as charts and data for children and youths.

•Anthropometry of Infants, Children and Youths to Age 18 for Product Safety Design — SAE SP-450, Society of Automotive Engineers, Warrenburg, PA, 1977

This book has 627 pages of useful anthropometric information compiled in the 1970s based on 4,127 young subjects.

•Safety and Health for Engineers, 2nd Ed., by R. Brauer; John Wiley & Sons, Inc., Hoboken, NJ, 2006

This book contains 740+ pages of text outlining information applicable to occupational safety and health. This is the type of reference book certified safety engineers would find helpful.

•Bodyspace, Anthropometry, Ergonomics and the Design of Work, 2nd Ed., by S. Pheasant; Taylor & Francis Inc., Philadelphia, PA, 2002

This is a British publication providing some workplace ergonomics guidance.

•Encyclopedia of Occupational Health and Safety, Fourth Edition (4 Volumes), (also available in CD Rom format), Jeanne Mager Stellman, editor; International Labour Office, 1998

This is a set of four books containing 4,000 pages of health and safety-related information, some of which applicable to the machine designer.

INDUSTRY SAFETY STANDARDS

An industry safety standard, most of which are voluntary standards, is a document relating to a product, process, service, system, or personnel that is developed through a collaborative, balanced, and consensus-based approval process. Industry safety standards are developed for the purpose of identifying design or performance requirements that are viewed as necessary to achieve a basic, usually a minimum, level of safety, below which an individual’s safety cannot be assured. A voluntary safety standard is the result of a periodic and iterative process of assessing hazards, risks, and accident data, reviewing technical developments, and balancing this information with product utility, marketplace economics, and public sentiment. Requirements contained in an industry safety standard are for the purpose of avoiding the recurrence of accidents, or avoiding the existence of hazards which are understood to be causes of accidents. Accident data, technical developments, and the threshold of the public’s acceptance of a basic level of safety evolve over time. As these criteria evolve, standards can be expected to change. Any given issuance of a standard is merely a reflection of these criteria at the time of publication.

Relative to machine safety standards, there are a number of organizations (ANSI, CEN, ISO, BSI¹², CSA¹³, ASABE¹⁴, ASME¹⁴, SAE¹⁴ and UL¹⁵, to name the most prominent ones) involved in standards development. Some are independent standards development organizations; others are engineering and technical societies. The three more prominent standards development and distribution organizations are ANSI, CEN, and ISO.

•ANSI (American National Standards Institute) is the prominent standards administrating organization for voluntary standards in the United States, the ANSI standards. Mandatory provisions of those standards (those containing the word “shall” or other mandatory language) — as well as all other (non-ANSI) standards that are cited in U.S. Federal Regulation 29 CFR 1910.6 — are adopted and incorporated as a part of the Occupational Safety and Health Act (OSHA), and thus are required by U.S. law.

•CEN (European Community for Standardization) is the organization that develops and manages EN (European) standards for the 31 participating European community countries. All 31 countries reference by law many of these EN standards, elevating them from voluntary standards to the level of legislated legal requirements.

•ISO (International Organization for Standardization) is the organization that develops ISO standards. ISO was formed to facilitate and manage international industrial standards for the broader international community (approximately 140 countries). In many countries, ISO standards, too, are referenced in laws.

In 1991, an agreement was signed by ISO and CEN to establish cooperation and coordination of European and international standards to harmonize text to create similar language in the two organizations’ issued ISO and EN standards. By 2011, this process has resulted in ISO and EN standards having many of the same requirements. At the time of this book’s printing, more than 30% of these standards have identical language.

Machine safety standards should be viewed as being grouped into one of three basic types: those addressing basic concepts and principles applicable to all machines, those dealing with human factors and certain types of safety devices applicable to a wide range of machines, and those offering specific requirements for specific types or classes of machines or specific industries. The following hierarchy of standards groupings has been adopted or recognized by CEN, ISO, and ANSI¹⁶:

•Type ‘A’ standards (fundamental safety standards): These standards give basic concepts, principles for design, and general considerations that can be applied to all machinery. Type ‘A’ standards provide designers and manufacturers an overall framework and guide for the design and production of machines that are safe for their intended use, including when no type ‘C’ standards exist.

•Type ‘B’ standards (group safety standards): These standards deal with one safety aspect, or one type of safety-related device that can be used across a wide range of machinery.

-Type ‘B1’ standards, which address particular safety issues (e.g., safe distances, surface temperatures, noise)

-Type ‘B2’ standards, which address safety-related devices (e.g., two-hand controls, barrier guards, interlocking devices, presence-sensing devices)

•Type ‘C’ standards (machine-specific safety standards): These standards provide detailed safety requirements for a particular type or group of machines. (Historically, the overwhelming majority of ANSI safety standards have been machine-type-specific; thus, it would be logical to classify most of them as Type ‘C’ standards.)

The standards cited in this chapter are focused primarily on safety requirements applicable to the broad range of machinery in general. Because of the many different types of machines and specific industries they are used in, this chapter does not attempt to cover Type ‘C’ standards. (When designing a machine for which there are specific industry safety standards, it is incumbent upon the designer to become familiar with that industry’s and that machine’s requirements.) In addition, electrical components, although important to the machine designer, are not generally addressed (with some exceptions) in this chapter.

The following are standards with which the machine designer should be or become familiar:

•Type ‘A’ Standards

ISO 12100: 2010	Safety of Machinery — General Principles for Design — Risk Assessment and Risk Reduction
BSI PD 5304	Safe Use of Machinery
	(This Published Document from BSI, although not strictly a standard, covers practical measures and techniques to safeguard operators, maintenance personnel, and others, along with covering the safe use of machinery.)
ISO 12100-1:2009	Safety of Machinery — Basic Concepts, General Principles for Design. Part 1: Basic Terminology, Methodology
	(This is in process of being replaced by ISO 12100:2010)
EN 292-1	Safety of Machinery — Basic Concepts, General Principles for Design. Part 1: Basic Terminology, Methodology
ISO 12100-2:2009	Safety of Machinery — Basic Concepts, General Principles for Design. Part 2: Technical Principles
	(This is in process of being replaced by ISO 12100:2010)
EN 292-2	Safety of Machinery — Basic Concepts, General Principles for Design. Part 2: Technical Principles and Specifications
ANSI B 155.1	Packaging Machinery and Packaging-Related Converting Machinery — Safety Requirements for Construction, Care, and Use
EN 1050	Principles for Risk Assessment
ISO 14121-1	Safety of Machinery — Risk Assessment — Part 1: Principles
ISO 14121-2	Safety of Machinery — Risk Assessment — Part 2: Practical Guidance and Examples of Methods
EN 1070	Safety of Machinery — Terminology

•Type ‘B’ Standards

EN 614-1	Ergonomic Design Principles — Terminology and General Principles
EN 547-3	Human Body Measurements — Anthropometric Data
EN 1005-1	Human Physical Performance — Terms and Definitions
EN 1005-2	Human Physical Performance — Manual Handling of Machinery and Component Parts of Machinery
EN 1005-3	Human Physical Performance — Recommended Force Limits for Machinery Operation
EN 1005-4	Human Physical Performance — Evaluation of Working Postures and Movements in Relation to Machinery
EN 1005-5	Human Physical Performance — Risk Assessment for Repetitive Handling at High Frequency
ISO 14738	Safety of Machinery — Anthropometric Requirements for the Design of Workstations at Machinery
EN 349	Minimum Gaps to Avoid Crushing of Parts of the Human Body
ISO 13854	Minimum Gaps to Avoid Crushing of Parts of the Human Body
EN 294	Safety Distances to Prevent Danger Zones being Reached by the Upper Limbs
ISO 13852	Safety Distances to Prevent Hazard Zones being Reached by the Upper Limbs
EN 811	Safety Distances to Prevent Danger Zones being Reached by the Lower Limbs
ISO 13853	Safety Distances to Prevent Hazard Zones being Reached by the Lower Limbs
ISO 13857	Safety Distances to Prevent Hazard Zones being Reached by Upper and Lower Limbs
ISO 13855	Safety of Machinery — Positioning of Safeguards with Respect to the Approach Speeds of Parts of the Human Body
EN 999	The Positioning of Protective Equipment in Respect of Approach Speeds of Parts of the Human Body
EN 547-1	Human Body Measurements — Principles for Determining the Dimensions Required for Openings for Whole-Body Access into Machinery
EN 547-2	Human Body Measurements — Principles for Determining the Dimensions Required for Access Openings
ISO 15534 (series)	(parts 1 thru 3) Ergonomic Design for the Safety of Machinery (relative to access openings)
EN 563	Temperatures of Touchable Surfaces — Ergonomics Data to Establish Temperature Limit Values for Hot Surfaces
ISO 13732-1	Ergonomics of the Thermal Environment — Methods for the Assessment of Human Responses to Contact with Surfaces — Part 1: Hot Surfaces
ISO 13732-3	Ergonomics of the Thermal Environment — Methods for the Assessment of Human Responses to Contact with Surfaces — Part 3: Cold Surfaces
ANSI B11.19	Performance Criteria for Safeguarding
ISO 14120	Safety of Machinery — Guards — General Requirements for the Design and Construction of Fixed and Movable Guards
EN 953	Guards — General Requirements for the Design and Construction of Fixed and Movable Guards
CSA-Z432-04	Safeguarding of Machines
ANSI B15.1	Safety Standard for Mechanical Power Transmission Apparatus (including ANSI B15.1 Interpretation)
ISO 14119	Safety of Machinery — Interlocking Devices Associated with Guards — Principles for Design and Selection (also Amendment 1:2007 — Design to Minimize Defeat Possibilities)
EN 1088	Interlocking Devices Associated with Guards — Principles for Design and Selection
IEC 61496-1¹⁷	Safety of Machinery — Electro-Sensitive Protective Equipment — General Requirements and Tests
IEC 61496-2¹⁷	Safety of Machinery — Electro-Sensitive Protective Equipment — Particular Requirements for Equipment Using Active Opto-Electronic Protective Devices
EN 982	Safety Requirements for Fluid Power Systems and their Components — Hydraulics
ISO 4413	Hydraulic Fluid Power— General Rules and Safety Requirements for Systems and their Components
EN 983	Safety Requirements for Fluid Power Systems and their Components — Pneumatics
ISO 4414	Pneumatic Fluid Power— General Rules and Safety Requirements for Systems and their Components
EN 842	Visual Danger Signals, General Requirements, Design and Testing
EN 457	Audible Danger Signals, General Requirements, Design and Testing
EN 981	System of Auditory and Visual Danger and Information Signals
ISO 13850	Safety of Machinery — Emergency Stop — Principles for Design
EN 13850	Emergency Stop — Principles for Design
EN 418	Emergency Stop Equipment, Functional Aspects — Principles for Design
ISO 13851	Safety of Machinery — Two-Hand Control Devices — Functional Aspects and Design Principles
EN 574	Two-Hand Control Devices — Functional Aspects — Principles for Design
EN 954-1	Safety-Related Parts of Control Systems — General Principles of Design
ISO 13849-1	Safety-Related Parts of Control Systems (ISO 13849-1 replaces EN 954-1)
EN 1037	Prevention of Unexpected Start-Up
ISO 14118	Safety of Machinery — Prevention of Unexpected Start-Up
ANSI/ASSE Z244.1	Control of Hazardous Energy, Lockout/Tagout and Alternative Methods
CSA-Z460	Control of Hazardous Energy — Lockout and Other Methods
ISO 14123 (series)	(parts 1 and 2) Safety of Machinery — Reduction of Risks to Health from Hazardous Substances Emitted by Machinery
EN 626-1	Reduction of Risks to Health from Hazardous Substance Emitted by Machinery — Principles and Specifications for Machinery Manufacturers
EN 1127-1	Explosive Atmospheres — Explosion Prevention and Protection
ANSI B11.20	Safety Requirements for Integrated Manufacturing Systems
ANSI/RIAR 15.06	Safety Standard for Industrial Robots and Robot Systems
ISO 10218-1	Robots and Robotic Devices — Safety Requirements — Industrial Robots
ISO 10218-2	Robots and Robotic Devices — Safety Requirements — Industrial Robot Systems and Integration
UL 1740	Standard for Robots and Robotic Equipment
ISO 11161	Safety of Machinery — Integrated Manufacturing Systems — Basic Requirements
CSA-Z434	Industrial Robots and Robot Systems — General Safety Requirements
ANSI A12.1	Safety Requirements for Floor and Wall Openings, Railings, and Toe Boards
ANSI/ASSE A1264.1	Safety Requirements for Workplace Walking/Working Surfaces and their Access; Workplace, Floor, Wall and Roof Openings; Stairs and Guardrails Systems
ISO 14122 (series)	(parts 1 thru 4) Safety of Machinery — Permanent Means of Access to Machinery
	(relative to working platforms, walkways, access between levels, stairs, ladders and guard-rails, etc.)
ANSI Z535.1	Safety Color Code
ANSI Z535.3	Criteria for Safety Symbols
ANSI Z535.4	Product Safety Signs and Labels
ANSI Z535.6	Product Safety Information in Product Manuals, Instructions, and Other Collateral Materials
ISO 7000	Graphical Symbols for Use on Equipment — Index and Synopsis
ISO 3864-2	Graphical Symbols — Safety Colours and Safety Signs — Part 2: Design Principles for Product Safety Labels
ISO 3864-3	Graphical Symbols — Safety Colours and Safety Signs — Part 3: Design Principles for Graphical Symbols for Use in Safety Signs
ISO 17398	Safety Colours and Safety Signs — Classification, Performance and Durability of Safety Signs
EN 894-1	Ergonomics Requirements for the Design of Displays and Control Actuators — General
EN 894-2	Ergonomics Requirements for the Design of Displays and Control Actuators — Displays
EN 894-3	Ergonomics Requirements for the Design of Displays and Control Actuators — Control Actuators
CSA -Z431	Basic and Safety Principles for Man-Machine Interface, Marking and Identification — Coding Principles for Indication Devices and Actuators
EN 60204	Safety of Machinery — Electrical Equipment of Machines
ANSI/NFPA 70	U.S. National Electrical Code
ANSI/NFPA 70E	Standard for Electrical Safety in the Workplace
ANSI/NFPA 79	Electrical Standard for Industrial Machinery
ANSI C1	National Electrical Code
UL 987	Standard for Stationary and Fixed Electric Tools
UL 745(series)	Standard for Portable Electric Tools
UL 1439	Test for Sharpness of Edges on Equipment
ANSI B11.TR1	(technical report) Ergonomic Guidelines for the Design, Installation and Use of Machine Tools
ANSI B11.TR3	(technical report) Risk Assessment and Risk Reduction — A Guide to Estimate, Evaluate and Reduce Risks Associated with Machine Tools
ANSI B11.TR5	(technical report) Sound Level Measurement Guidelines — A Guide for Measuring, Evaluating, Documenting and Reporting Sound Levels Emitted by Machinery
ISO/TR 14121-2	(technical report) Safety of Machinery — Risk Assessment — Part 2: Practical Guidance and Examples of Methods
ISO/TR 18569	(technical report) Safety of machinery — Guidelines for the understanding and Use of safety of machinery standards

•Type ‘C’ Standards

ANSI, BSI, CEN, ISO, CSA, ASABE, ASME, SAE, and UL (and others) have developed many hundreds of industry-specific and machine-type-specific machinery safety standards to achieve a basic level of safety. The design of a machine should be in conformance with not only Type ‘A’ and Type ‘B’ standards, but also those standards (if they exist) that apply to that specific machine type. A list of Type ‘C’ standards covering all machine types and all industries is too lengthy to be included in this chapter. It is, therefore, left to the designer to learn the targeted industry and the machine’s intended use so the appropriate Type ‘C’ standards can be obtained and used during the design process.

INTERNET WEB SITES

In addition to this list of statutes, books, and industry standards, today’s machine designer should also be aware of and take advantage of information available through the Internet. Notable sites include, but are not limited to:

•OSHA: www.osha.gov helpful link: www.osha.gov/SLTC/machineguarding/index.html helpful link: www.osha.gov/Publications/Mach_SafeGuard/toc.html

•ANSI (American National Standards Institute):www.ansi.org helpful link: www.osha.gov/SLTC/machineguarding/scope98.html

•CEN (European Committee for Standardization): www.cen.eu/cen/pages/default.aspx

•ISO (International Organization for Standardization): www.iso.org/iso/home.html

•BSI (The British Standards Institution): www.bsigroup.com

•CSA (Canadian Standards Association): www.csa-international.org/about

•SAE (Society of Automotive Engineers): www.sae.org helpful link: http://standards.sae.org/commercial-vehicle/safety/standards/current/

•ASABE (American Society of Agricultural and Biological Engineers): www.asabe.org helpful link: http://asae.frymulti.com

•ASME (American Society of Mechanical Engineers): www.asme.org

•UL (Underwriters Laboratories): www.ul.com/global/eng/pages

•National Safety Council: www.nsc.org/Pages/Home.aspx helpful link: www.nsc.org/products_training/Products/Pages/OnlineProductCatalog.aspx

•CDC - Workplace Safety: http://www.cdc.gov/Workplace helpful link: www.cdc.gov/niosh/docs/94-110/ helpful link: www.cdc.gov/niosh/89-106.html

•Other Helpful Websites www.schmersalusa.com/catalog_pdfs/<http://www. schmersalusa.com/catalog_pdfs GK1_2008.pdf (specifically, the last 65 pages) and www.sti.com/ltr2/access.php?file=pdf/807.pdf

APPLICATION OF LITERATURE TO DESIGN TOPICS

The list of codes and standards cited in Table 2-7 is not intended to be complete or exhaustive. It is intended to provide the reader with reference literature from which to learn more about safety and ergonomics in machine design.

Table 2-7: Selected Codes and Standards for Machinery Safety

¹ S. Pheasant, Bodyspace, Anthropometry, Ergonomics and the Design of Work, 2nd Ed., Taylor & Francis Inc., Philadelphia, PA, 2002

² S. Pheasant, Bodyspace, Anthropometry, Ergonomics and the Design of Work, 2^nd Ed., Taylor & Francis Inc., Philadelphia, PA, 2002

³ Reproduced with permission of the McGraw-Hill Companies: Sanders, M. and McCormick, E. Human Factors in Engineering and Design Seventh Edition. McGraw-Hill: New York: 1993

⁴ Typically (ideally), the overwhelming majority of a machine’s active life will be spent in process of performing its primary function, as identified as categories 2, 3, 4, 5, and 6 above. Because of this, a separate section in this chapter, Section 2.3, is devoted specifically to machine safety issues which are most important during this machine-active time, issues known as “safeguarding”.

⁵ See industry standards BSI PD 5304 (Section 7), ANSI B11.19, ANSI B15.1, EN 953, WN 1088, ISO 14120, ISO/TR 5046, and the book Safeguarding Concepts Illustrated.

⁶ Interlocking guards are discussed in greater detail in industry standards BSI PD 5304 (Section 9), EN 1088, ISO 14119, and in the book Product Safety Management and Engineering (Chapter 11). Be aware, also, that the interlocking part of interlocking guards are a part of the machine’s “safety-related control system,” discussed in some detail in a footnote later in this chapter.

⁷ Although customarily this information and instructions has been in manual form, increasingly, it is becoming more and more common to find electronic media used as well. The book Writing and Designing Manuals provides further information on writing machine manuals (cited in Section 2.5).

⁸ These being: “3. Instruct and warn the user,” “4. Describe requirements for training the user,” and “5. Recommend personal protective equipment.”

⁹ In manufacturing settings, tags are normally attached to lockout devices identifying the person who placed the lockout on the machine. In cases where multiple persons are working on a machine simultaneously, it is not uncommon for there to be multiple identifying tags placed on a lockout device. This prevents communication errors between work crews from jeopardizing the lockout.

¹⁰ Plug-connected electric machinery for which exposure to hazards is controlled by unplugging the machine and by the plug and cord being under the exclusive control of the employee performing the maintenance work is exempted from OSHA’s lockout/tagout standards.

¹¹ Emergency Stops and their associated parts are components of a part of a machine’s control system identified as the machine’s “safety-related control system”, or SRCS. A machine’s safety-related control system is that part of the machine’s control system that prevents a hazardous condition from occurring, either (1) by preventing the initiation of a hazardous situation (e.g., two-hand controls), or (2) by detecting the onset of a hazard (e.g., emergency stop switches). Safety-related control systems are designed to perform safety functions. A machine’s SRCS must continue to operate correctly under all foreseeable conditions, and because they perform a safety function, the components in the system must be verifiably reliable. Industry standards ISO 138491-1 “Safety Related Parts of Control Systems” (ISO 13849-1 replaces EN 849-1), EN 62061 “Safety of Machinery — Functional Safety of Safety-Related Electrical, Electronic and Programmable Electronic Control Systems,” and, related to control reliability of pneumatic and hydraulic systems, ANSI B 155.1 “Safety Requirements for Packaging Machinery and Packaging-Related Converting Machinery” address requirements of machine safety-related control systems and their components.

¹² BSI, The British Standards Institution, another significant standards development and distribution organization, is the National Standards Body (NSB) of the U.K. (BSI organized the first Commonwealth Standards Conference in 1946, which led to the establishment of the International Organization for Standardization (ISO).) CEN includes BSI transpositions of EN standards.

¹³ CSA is not a part of the Canadian government. CSA is a not-for-profit organization that represents Canada on various ISO committees.

¹⁴ ASABE, ASME, and SAE are engineering societies that, among other things, develop safety standards applicable to the design and construction of machines associated with their industry.

¹⁵ UL is an independent organization, not a part of any government, that, among other things, develops (and provides testing services for) safety standards applicable to products and machines.

¹⁶ (as observed in ANSI B11-2008)

¹⁷ The IEC (International Electrotechnical Commission) is a non-governmental internationally recognized standards organization that develops and issues standards for electrical and electronic technologies and related equipment, including componentry often used in machinery.

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