6.4 Specified machinery

Question 1

(a) Describe the following hazards associated with an abrasive wheel: (i) mechanical (ii) non-mechanical 5 5 marks

Answer 1

(a) (i) mechanical hazards associated with an abrasive wheel include:  Contact with rotating wheel  Trap between wheel and tool rest  Entanglement around axle  Ejection of parts of work piece or from burst wheel (ii) non-mechanical hazards associated with an abrasive wheel include:  Dust  Sparks / fire  Electricity  Noise  Vibration  Stability of machine  Positioning / working posture

Question 2

(b) Describe the protective devices and guards that would be found on an abrasive wheel to minimise the risk of injury from mechanical hazards. 4 marks

Answer 2

(b) Protective devices and guards against mechanical hazards would include:  wheel enclosed as much as possible by a fixed guard  adjustable guard over exposed part of wheel (if fixed guard not appropriate)  interlocked guard to ensure the machine can’t operate until the guard is in place, that opening the guard will stop the machine and that closing the machine doesn’t itself restart the machine.  transparent screens fitted to fixed machines to intercept sparks and particles (as an alternative to eye protection).

Question 3

(c) Explain the risks associated with an abrasive wheel arising from its deterioration. 3 marks

Answer 3

(c) Risks associated with abrasive wheels include:  injury from flying abrasive and metallic particles  inhalation of dust from dry grinding operations  noise and vibration related injury  physical injury from flying fragments if the wheel burst (centrifugal force/speed increase)  wheel breakage

Question 4

(d) Explain why employees require training for activities involving an abrasive wheel. 3 marks

Answer 4

(d) Employee training in all aspects of mounting and using abrasive wheels is essential to ensure that employees are aware of the hazards, risks and precautions, including how to store, handle and transport them, inspect for damage, to assemble and balance correctly before use, to adjust and use suitable PPE while using. Note: More in the HSE guide Safety in the use of abrasive wheels (HSG17)

Question 5

A manually operated lathe is to be fitted with a Computer Numeric Control (CNC) system. Outline: (a) additional hazards this may introduce 4 marks (b) measures required to minimise the risks associated with these hazards 6 marks

Answer 5

(a) The fitting of a computer numeric control to a manually operated lathe would introduce additional risks such as:  an increase in the speed of the machine and the potential rise in noise levels that could accompany this increase  the possibility of unexpected movements or aberrant behaviour  errors in programming and software  risks arising during setting and teaching operations together with those arising from the operators’ unfamiliarity with the system. (b) Measures that would be required to minimise the risks include:  the completion of a risk assessment for the new system  the provision of fixed or interlocked guards to prevent access during the automatic cycle  the provision of manual operation for setting and cleaning such as a hold to run system  the relocation of the controls outside the danger zone  the provision of additional training for operators and maintenance staff  updating the instruction manual for using, setting, cleaning and maintaining the machine  carrying out regular testing of the software and screening for RF interference.