Chapter 3 -
Guard Construction
Chapter 3
Guard Construction
Today many builders of single-purpose machines provide point-of-operation
and power transmission safeguards as standard equipment. However, not all
machines in use have built-in safeguards provided by the manufacturer.
Guards designed and installed by the builder offer two main advantages:
- They usually conform to the design and function of the machine.
- They can be designed to strengthen the machine in some way or to
serve some additional functional purposes.
User-built guards are sometimes necessary for a variety of reasons. They
have these advantages:
- Often, with older machinery, they are the only practical safeguarding
solution.
- They may be the only choice for mechanical power transmission
apparatus in older plants, where machinery is not powered by
individual motor drives.
- They permit options for point-of-operation safeguards when skilled
personnel design and make them.
- They can be designed and built to fit unique and even changing
situations.
- They can be installed on individual dies and feeding mechanisms.
- Design and installation of machine safeguards by plant personnel can
help to promote safety consciousness in the workplace.
However, they also have disadvantages:
- User-built guards may not conform well to the configuration and
function of the machine.
- There is a risk that user-built guards may be poorly designed or
built.
Point-of-Operation Guards
Point-of-operation safeguarding is complicated by the number and
complexity of machines and also by the different uses for individual
machines. For these reasons, not all machine builders provide
point-of-operation guards on their products. In many cases a
point-of-operation guard can only be made and installed by the user after
a thorough hazard analysis of the work requirements. Poorly designed,
built or installed guards may create a hazard rather than eliminate one.
To be effective they must safeguard the employee while allowing the work
to continue with minimum disruption to the production process.
Mechanical Power Transmission Apparatus Guarding
A significant difference between power transmission guards and
point-of-operation guards is that the former type needs no opening for
feeding stock. The only openings necessary for power transmission guards
are those for lubrication, adjustment, repair, and inspection. These
openings should be provided with interlocked covers that cannot be removed
except by using tools for service or adjustment.
To be effective, power transmission guards should cover all moving parts
in such a manner that no part of the operator's body can come in contact
with them.
Guard Material
Under many circumstances, metal is the best material for guards. Guard
framework is usually made from structural shapes, pipe, bar, or rod stock.
Filler material generally is expanded or perforated or solid sheet metal
or wire mesh. It may be feasible to use plastic or safety glass where
visibility is required.
Guards made of wood generally are not recommended because of their
flammability and lack of durability and strength. However, in areas where
corrosive materials are present, wooden guards may be the better choice.
Chapter 4
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