C6.3 Protective measures Flashcards
Guarding requirements
suitable good construction in good repair efficient working order no additional risk not easily disabled / bypassed at a distance from danger zone not unduly restrictive permit maintenance prevent contact secured to machine protect so that objects cannot fall onto moving parts introduce no new hazards do not interfere with the work allow safe lubrication
PUWER Reg 11 hierarchy of guarding
Fixed or enclosed guards
Interlocking guards or auto devices
Appliances, eg push sticks
Training, info, instruction, supervision
Types of guards
Fixed
Interlock
Automatic
Trip
Fixed enclosed guards
denies access to danger at all times
fixed to machine
need tool to remove
openings must not lead to danger
Adjustable guard
adjustable bars to allow workpiece only to enter
adjusts to allow variety of workpieces
self adjusting guard
barrier moves dependent on size of workpiece
eg circular saw
Two hand control
both hands needed on controls to operate
constant correct pressure
hands in a safe location
Interlocked guard
machine cannot operate when access available to danger zone guard closed = machine can operate operates by limit switches fail to safe electrical mechanical hydraulic pneumatic
automatic guard
sweeps danger zone clear
photoelectric devices
light curtain beam
machine stops if broken
capacitance field
machine stops if electric field broken
pullback devices
cables connected to operators hands
used with machine with stroke action
access allowed when device is up
hands pulled back as device descends
restraint device
hands attached to cables that restrain where hands can go
trip wire
pull wire to stop machine
gates
machine only operates if gate closed
robots
repetitive processes
prevent injury from repetition
use where unsafe / hazardous / unpleasant tasks
protective shields
protection from flying particles / substances
holding tools
used to place / remove items in danger zone
use as an additional control, not in place of
guard considerations
prevent any part of body reaching danger zone
any opening at distance to prevent reaching danger zone
ability to withstand force of ejection
protect against hazards identified
weight / size of guard
compatible with material being processed
resistant to possible contaminants
fixed distance guards
does not completely cover danger zone but places it out of reach
barrier considerations
height and distance to prevent reaching danger zone
1.8 metres for perimeter fencing
interlocks - sensing devices
rotating sensing
light beam
proximity device
position switch
interlocks - timing devices
mechanical, electric, electronic clock
delay relay
sequence valve
threaded bolt
interlock failure mechanisms
failure / interruption of power supply wiring malfunction earthing fault cross connection electrical interference disconnection of hose / pipe mechanical failure brake failure