Part I: What Is Safety? The Social Background
In the manufacturing industry, production consists of processing,
assembling, and transporting materials. In modern times, machines use
large amounts of energy to absorb the burden from workers to assist in
production. This result in the wide range of development in machines that
we see today. And trained workers based on experience in operating the
machines create more stable quality, causing the relationship between
machines and production to continue and evolve into many forms today.
1. The Social Background to Machine Safety
(1) Changes in People
In some countries, changes in social structure have brought changes in the
people that work at production sites. For example, many experienced
workers are retiring while the working population shrinks due to lower
birth rates. At the same time, forms of employment continue to diversify,
such as the increasing number of temporary employees and there is a
continued increase in employees working overseas. Diversification also
continues to increase in other ways, such as age, sex, experience,
language, and social habits.
(2) Changes in Machines and Production Facilities
Today's society is facing more
diversification in consumer needs driving demands for more variation in
products. Production sites are required to change between many different
products at relatively short intervals, resulting in frequent changes to
production facilities. Machines required for production must support more
functionality. This and many other changes require that workers must
master new techniques and working procedures.
(3) Changes in Production Locations
Market globalization has taken production sites from fixed sites across
national borders. Domestic production is faced with the need for more
competitive products and new markets combined with demand for production
sites in newly industrialized countries, such as BRICs. Offshore
production means dealing with different laws, infrastructures, cultures,
and values. The machines and production facilities resulting from the
accumulated know-how of industry domestically must now be used in
different human environments.
(4) Changes in Social Consciousness
In mature civil societies, companies must take social responsibility for
their activities. For example, they must assume product liability for the
products that they produce. Although conditions vary by country, all
countries now have laws requiring product safety to protect the consumer.
(For example, Japan and the USA have product liability laws and the EU has
the EC directives.) It is not necessary to provide examples of product
accidents to realize the very strict monitoring of manufacturing liability
for safety and ease of mind in societies that share a common ideal of
respect for human beings. And based on these ideals, the responsibility of
companies for the safety of workers on production sites is also strictly
monitored. (For example, OSHA in the USA, the Revised Industrial Safety
and Health Law in Japan, and EC directives in the EU.) Companies face not
only criminal, civil, and damage liability for any accidents that might
occur, but their corporate image is greatly hurt as a result. The social
liability of companies for the safety of their workers has skyrocketed in
The relationship between workers and machines and the environment in which
they operate has thus changed on a global scale. And yet, manufacturing is
not possible until a worker operates a machine. Across changes in the
operating environment, society demands that machines and production
facilities can be used safely regardless of where they are used or who
uses them. This is required not only in the workers, but also in the
machines and hardware technology. As a result, global standards for safety
are required for today's production sites. This is the concept of Machine
The European Standards (EN Standards) in force since 1993 are
representative standards on machinery safety. They are technical standards
enacted to ensure compliance with basic safety requirements stipulated by
the Machinery Directive across Europe, and compliance with these standards
is a condition for obtaining the CE marking, required since 1995 for
distribution in Europe. The following sections describe the basic concepts
of machinery safety. These safety concepts are currently incorporated into
the safety standards of each country as standard international safety
1. Hazards Generated by Machinery
Hazards occur in areas where machine work areas (machine operating output)
and human work areas overlap.
Classifications and Examples:
The general hazard classifications according to EN ISO 12100-1, where the
basic concepts of machinery safety are defined, are shown below.
(1) Mechanical Hazards
Crushing, entanglement, stabbing or puncturing, shearing, drawing-in or
trapping, friction or abrasion, cutting or severing, high-pressure fluid
(2) Electrical Hazards
Contact by a person with live parts, i.e., parts that normally carry a
voltage, or parts that have become live under faulty conditions,
especially as a result of an insulation failure, etc.
(3) Thermal Hazards
Burns and scalds from flames, explosions, radiation from heat sources,
(4) Hazards Generated by Noise
Hearing loss, tinnitus, etc.
(5) Hazards Generated by Vibration
Serious damage to the entire body, particularly to the hands, arms, and
(6) Hazards Generated by Radiation
Low frequencies, radio frequencies, ultraviolet, infrared, X-rays, etc.
(7) Hazards Generated by Materials and Substances
Toxins, irritants, dust, explosions, etc.
(8) Hazards Generated by Neglecting Ergonomic Principles in Machine Design
Unhealthy postures, human error, etc.
(9) Hazards associated
with the environment in which the machine is used
(10) Hazards combinations
2. Strategies for Selecting Safety Measures
(1) Safety Measure Strategy
All machines fail and everyone makes mistakes. Therefore, basic designs
that take every precaution to ensure the safety of workers is required in
the event of a fault.
(2) Machinery Hazard Prevention
Machinery hazards occur in hazard areas, where the human workspace
overlaps the machine workspace. Preventing machinery hazards begins by
eliminating mechanisms that facilitate hazardous conditions. The following
strategies are generally used to achieve this goal.
I Spatial separation between human
and machine workspaces (Isolation principle: Safety protection like
II Temporal separation (Stoppage
principle: Safety protection like interlocking devices *)
* An interlocking device refers
to a mechanical or electrical device that was designed to prevent
machines from operating unless certain conditions are met, such as
closing a guard for example. (ISO14119)