IOSH MANAGING SAFELY Preventing Accidents & Incidents in the Oil & Gas Sector

in partnership with

TOBY CLARK BSc FIOSH AIEMA MCot Cert Ed

IOSH MANAGING SAFELY

MODULE 4

Machinery Safety

Mechanical Hazards

BS EN 292• Crushing – caused when part of the body is caught between

either two moving parts of machinery or a moving part and a stationary object

• Shearing – When two or more machine parts move towards/past one another a “trap” is created. Can result in a crush injury or amputation e.g. power presses, guillotines, scissor lifts

• Cutting/severing – Saw blades, knives and even rough edges, especially when moving at high speed. Can result in serious cuts or amputation e.g. saws, slicing machines, abrasive cutting discs

Examples of in-running nips

Guarding arrangements for drilling machines

Working at a guillotine – risk of crushing & amputation of fingers

Clear plastic fixed guarding at a milling machine

Protection against Machinery Hazards

Photoelectrical Safety Systems• Operate on the principal of the detection of

an obstruction in the path taken by a beam or beams of light, a curtain or light or any combination of these necessary to provide the required safeguard

• The light may be visible or invisible, continuous or modulated

Proximity sensor

Light curtains at a weaving machine

Rotating light curtain

Rotating light curtain

Testing the integrity of a light curtain

Power press guarding

Mechanical Hazards

• Entanglement – caused by revolving parts of machine. Risk increased by loose clothing, jewellery, long hair etc. E.g. couplings, drill chucks/bits, flywheels, spindles and shafts (especially those with keys/bolts)

• Drawing in/trapping – caused when a belt runs round a roller e.g. conveyors

• Impact – caused by objects which strike the body but do not penetrate

Guarding on a chainsaw source Health & Safety Executive

Circular saw

Width setterShrouded on-off switches

Blade guard

Abrasive wheel

Lathe

Mechanical Hazards

• Stabbing/puncture/ejection – The body may be penetrated by flying objects such as broken pieces of machinery or sharp pieces of machinery (drill bits) or ejection of material (swarf/sparks)

• Friction/abrasion – Friction burns or abrasion injuries can be caused by coming into contact with smooth surfaces moving at high speed (grinding wheel)

• High pressure fluid injection – Injection of fluids through the skin. Air or hydraulic oil entering the blood stream through the skin may be fatal. Immediate medical assistance is essential

Protection against Mechanical Hazards

Fixed distance guard

• Does not completely cover the danger point but puts it out of normal reach

• A distance guard which completely surrounds machinery is commonly called a perimeter-fence type guard (1.8m high)

Fixed enclosing guardFine mesh prevents fingers reaching moving parts

Moving parts visible

Ventilation prevents overheating

Doesn’t stop noise

Should contain broken belt and fragments

Tools needed to remove guard

Belt tensioner and drive motor•fixed perimeter fence•access via interlocked door•residual risk of falling in from above

Protection against Mechanical Hazards

Anthropometric considerations

• Guards should be designed and constructed with the object of preventing any part of the body from reaching a danger point or area. They should take account of the physical characteristics of the people involved, and their abilities to reach through openings, over or around barriers or guards

Protection against Mechanical Hazards

Key Dimensions

Protective Structure

Danger zone

Reference planea b

c

.a Height of danger zone

.b Height of protective structure

.c Horizontal distance to danger

Protection against Mechanical Hazards

Interlocked guards• Similar to a fixed guard but has a movable

(usually hinged) part connected to the machine controls so that if the movable part is open/lifted, the dangerous moving part at the work point cannot operate.

• Until the guard is closed the interlock prevents the machine from operating

• Or the guard remains closed until the risk of injury has passed

Perimeter fence 2.4m high

Door with interlocks

Protection against Mechanical Hazards

The four media for interlocking guards are electrical, mechanical, hydraulic and pneumatic

Guard locking systems • motion or position sensing devices – photoelectric

beam• Timing devices – delay relay, mechanical, electric

or electronic clocks• Guard locking devices – captive key/trapped key

Dual Electrical Interlock with cross-monitoring

Protection against Machinery Hazards

Automatic guards• Moved into position automatically by the machine

thereby removing any part of a person from the danger area sometimes known as a ‘sweep away’ guard.

• Operates by physically removing from the danger area any part of a person

• It can only be used where there is adequate time for such removal to take place without introducing any further danger

Protection against Machinery Hazards

Trip devices• A trip device is a device which causes working

machinery to stop or assume an otherwise safe condition while a person remains within the danger area

• Designed to ensure that an approach to a dangerous part beyond a safe limit causes the device to operate and the dangerous part to stop

• May be reset automatically or manually after operation

Protection against Machinery Hazards

Pressure sensitive mat system• Contains sensors which operate when a

person or object applies pressure to the mat. • May be exposed to potential damage which

can result in failure.• Dimensions should take account of speed of

approach, length of stride and overall response time

Protection against Machinery Hazards

Adjustable guard

• A fixed guard which incorporates an adjustable element (which remains fixed for the duration of a particular operation) e.g. on a pillar drill or circular saw

• Opening may be adjusted to accommodate material

Adjustable guard

Riving knifeFixed enclosing guard

Guarding a circular saw. Power takeoff (PTO) should also be guarded

PTO

Protection against Machinery Hazards

Self-adjusting guard• Prevents accidental access by the operator but

allows entry of the material in such a way that the material actually forms part of the guarding arrangement e.g. hand held circular saw

• Opened by passage of the workpiece• Returns to safe position on completion of the

operation

Protection against Machinery Hazards

Two hand controls

• A device which requires two hands to operate and therefore protects the hands of the operator

• Protects only the operator

Protection against Machinery Hazards

Emergency stop devices• The function of an emergency stop device is

to provide a means to bring a machine to a rapid halt.

• It should be easy to operate and clearly discernible from other controls

• Should be readily available to the operator and/or others

Light curtains

Emergency stops

Provision and Use of Work Equipment Regulations

Regulation 11 – Dangerous parts of machinery (hierarchy of control)

• Fixed guards

• Other guards or protection devices

• Provision of jigs, holders, push-sticks or similar protection appliances

Push stick

Non-mechanical hazards

• Electricity – power generated at a variety of voltages, alternating/direct current, stored energy, static electricity, batteries (chemical)

• High/low temperature – Many processes rely on the input of high or low temperature as part of the process or process may evolve high or low temperatures

Non-mechanical hazards

• Radiation – may be ionising or non-ionising

• Hazardous substances – may be part of the process, evolved or introduced along with materials by mistake e.g. vapours released or substances carried on materials from a prior process

Non-mechanical hazards

• Noise – noise sources from equipment may be from such things as bearings that are loose or worn, materials falling into or out of equipment or from air exhausted from equipment

• Vibration – vibration may be designed as part of the process or a result of moving parts of the equipment such as conveyor systems and rotating parts