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