The fan manufacturer is normally responsible for machine guards. In the case of standard fans, a distributor may package the fan with its driver and other equipment and it would become the distributor’s responsibility to supply and fit guards.
Standard guards are generally made of painted steel. Sometimes aluminium is used because it is easier to bend and may not need painting. When fans are to be installed in a potentially hazardous environment special motors are used to reduce the chances of the motor igniting any gas present. A steel coupling rubbing on a steel guard could cause a spark and is not appropriate. Onshore, in these situations, an aluminium or bronze guard would be fitted. Offshore fans in potentially hazardous atmospheres have brass guards; the salt laden atmosphere offshore is not compatible with most aluminium alloys. Aluminium and brass guards would be described as “non-sparking” guards.
With high speed couplings the distinction between high and low speed is subjective. There is a remote chance that the coupling may fail physically and explode due to the centrifugal force acting on the pieces. It is generally thought that bolting is the weakness link and may be sheared due to an unforeseen overload. If the coupling is not “burst-proof, see Figure 12.19,then the guard must be capable of retaining any scattered material.
Figure 12.19 Burst-proof diaphragm coupling with spigotted spacer
Within Europe, the safety of machinery in general is covered by the Machinery Directive which is implemented by EN 292, Safety of Machinery. The safety of fans is covered by prEN 14461. Guards are specifically regulated by EN 953, Safety of machinery; general requirements for the design and construction of guards (fixed, movable).
Other interesting safety Standards worth reviewing include BS 5304, DIN 31001, ANSI B15.1 and OSHA coupling guard requirements.
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