Chapter CXLVII: Section 81: Safety Appliances

(_See also p. 182._)

=2487. Guard for spur gearing.=

=2488. Guard for bevil gearing.=

=2489. Safety nut= for a running screw. The nut takes no strain until the thread in the main nut gives way from wear.

=Fire alarms= (automatic) depend for their action on increase of
temperature above a normal maximum.

=Diaphragms= are inserted in the pipe connections to hydraulic lift
cylinders to admit or discharge the water at moderate speeds only, so
that in case of a burst the lift should not descend too rapidly.

=Retaining valves,= or non-return valves, are employed to confine any
sudden shocks from hydraulic machines or from breakages, to local
pipes.

=Relief valves= are applied to all hydraulic pressure systems to
obviate the effects of shock.

=An extra wire rope= is frequently employed on suspended lifts to act
as a safety rope.

=2490. Safety centrifugal hooks= to arrest a revolving shaft when the speed becomes excessive. The hooks fly out and engage with pins on a fixed disc.

=Rope guards boards, screens, guard rails, &c.,= are necessary to
protect persons from running ropes in hoisting and rope-driving gears.

=2491. Collar and set screw,= to prevent a key from working out. A set screw only--tapped into the shaft--is sometimes employed for this service.