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NEBOSH DIPLOMAIN OCCUPATIONAL HEALTH AND SAFETY

Unit C

Workplace and Work Equipment Safety

2

Licence details

RMS PublishingVictoria House, Lower High Street, Stourbridge DY8 1TA

© RMS Publishing.

Fifth Edition February 2014.

All rights reserved. No part of this presentation may be stored in a retrieval system, reproduced, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without either the prior written permission of the Publishers.This presentation may not be lent, resold, hired out or otherwise disposed of by way of trade in any form other than that in which it is published, without the prior consent of the Publishers.This presentation may not be reproduced in any form without prior consent of the Publishers other than a single copy thumbnail handout for immediate use by the tutor.

Whilst every effort is made to ensure the completeness and accuracy of the information contained herein, RMS can bear no liability for any omission or error.

Issued to: Single LicenceLicence No:

33

ELEMENT C6WORK EQUIPMENT (WORKPLACE MACHINERY)

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C6.1 Describe the principles of safety integration and the considerations required in a general workplace machinery risk assessment

C6.2 Describe, with examples, the principal generic mechanical and non-mechanical hazards of general workplace machinery

C6.3 Describe protective devices found on general workplace machinery

C6.4 Explain the principles of control associated with the maintenance of general workplace machinery

C6.5 Describe the requirements for information and warnings on general workplace machinery

LEARNING OUTCOMES

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C6.6 Explain the key safety characteristics of general workplace machinery control systems

C6.7 Explain the analysis, assessment and improvement of system failures and system reliability with the use of calculations

LEARNING OUTCOMES (CONTINUED)

6

C6.1 Safety integration and machinery risk assessment

C6.2 Generic hazards

C6.3 Protective devices

C6.4 Maintenance

C6.5 Information and warnings

C6.6 Machinery control systems

C6.7 Systems failures and system reliability

CONTENTS

Diploma Unit C - Element C6 - Workplace and Work Equipment Safety July 2014

Sample of PowerPoint presentation for NEBOSH National Diploma in Occupational Health and Safety 1

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C6.4 Maintenance




CONTENTS

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• The principles of safety integration from the Supply of Machinery (Safety) Regulations (SMSR) 2008

• Factors to be considered when assessing risk

• Purpose of CE marking and the relevance of the CE mark

• Conformity assessments and the use of harmonised standards

Safety integration and machinery risk assessment

9

• The Supply of Machinery (Safety) Regulations (SMSR) 2008 set out requirements to ensure that machinery is designed and constructed taking account of essential health and safety requirements (EHSRs)

• The term ‘machinery’ incorporates machinery; interchangeable equipment; safety components; lifting accessories; chains, ropes, and webbing; removable transmission devices and partly completed machinery

• The requirement applies to situations where machinery is manufactured for supply to another organisation and when a user manufactures their own machinery

THE PRINCIPLES OF SAFETY INTEGRATION FROM THE SMSR 2008


10

• Schedule 2, Part 1 of SMSR 2008, first principle of safety integration, requires that machinery be designed and constructed so that it is fitted for its function and can be operated, adjusted and maintained without putting persons at risk when the operations are carried out under foreseen conditions and taking account of reasonably foreseeable misuse



Machinery must be designed and constructed to be fit for purpose and to eliminate or reduce risks throughout the lifetime of the machinery

11

• Schedule 2, Part 1 of SMSR 2008, second principle of safety integration, requires the responsible person to apply specified principles of good practice when selecting the most appropriate methods to prevent risk and satisfy the essential health and safety requirements


The principles must be applied in order to eliminate or reduce risks as far as possible; take necessary protective measures where risk cannot be eliminated; and inform users of any residual risks


12

• Schedule 2, Part 1 of SMSR 2008, third principle of safety integration, establishes a duty to not rely on the specification of intended use for the machine when designing, constructing and drafting instructions


When designing and constructing machinery and when drafting the instructions: use and foreseeable misuse must be considered




13

• Schedule 2, Part 1 of SMSR 2008, fourth principle of safety integration, requires the design and construction of the machinery must take account of constraints to which the operator is subject as a result of foreseeable use of personal protective equipment


Take account of operator constraints due to necessary or foreseeable use of personal protective equipment


14

• Schedule 2, Part 1 of SMSR 2008, fifth principle of safety integration, requires that supply must ensure that all essential special equipment or accessories are provided to ensure machinery can be adjusted, maintained and used safely


Machinery must be supplied with all the essentials to enable it to be adjusted, maintained and used safely


15

• Persons at risk

• Severity of possible injury

• Probability of injury

‒ Technical/procedural/behavioural factors

• Need for access

• Duration of exposure

• Reliability of safeguards

• Operating procedures and personnel

FACTORS TO BE CONSIDERED WHEN ASSESSING RISK


16

FACTORS TO BE CONSIDERED WHEN ASSESSING RISK


Risk assessment

Source: Rockwell Automation.

17

• Provide a visible declaration by the manufacturer, or their authorised representative, that the machinery is in conformity with the applicable requirements set out in European Community harmonisation legislation relating to machinery, being the Machinery Directive 2006/42/EC and in the UK the SMSR 2008

• Machinery bearing the CE mark will be taken as meeting the requirements and thereby entitled to free circulation throughout the European Economic Area, provided that it does in fact satisfy those requirements

• "CE Marking" is now used in all EU official documents

• "CE Mark" is also in use, but it is NOT the official term

PURPOSE OF CE MARKING AND THE RELEVANCE OF THE CE MARKDeclaration of CE marking


18

PURPOSE OF CE MARKING AND THE RELEVANCE OF THE CE MARK


CE Mark

Source: Department of Business Innovation and Skills.



19

• Selection of work equipment

‒ The Provision and Use of Work Equipment Regulations (PUWER) 1998, Regulation 10 - Conformity with community requirements, places a duty on the employer to ensure that work equipment, including machinery, conforms to UK legislation that gives effect to EU Directives

• Integration of work equipment

‒ Work equipment obtained by an employer may be integrated with other work equipment to form an assembly of machines, for example, a packing machine combined with a labelling machine

PURPOSE OF CE MARKING AND THE RELEVANCE OF THE CE MARKSelection and integration of work equipment in the workplace


20

• Various product Directives are produced by the European Community to define and control the standards of products manufactured for use within the European Community.

• They do this by setting out ‘Essential Health and Safety Requirements’ (EHSR)

• The essential health and safety requirements of machinery are set out in Annex 1 of the EU Machinery Directive 2006/42/EC and are listed in Schedule 2 of the SMSR 2008

CONFORMITY ASSESSMENTS AND THE USE OF HARMONISED STANDARDS


Essential health and safety requirements for machinery

21

Responsible person under SMSR 2008

• The manufacturer of the machinery

• The manufacturer’s appointed representative in the community

• The person who first supplies the relevant machinery




22

Machinery under SMSR 2008

• These include circular saws (single or multi-blade), band saws and other sawing machinery, spindle moulding machinery, presses (including press-brakes), cartridge operated and other such dangerous machinery that requires special consideration when designing, building and applying the CE mark




23

• There are three methods of conformity assessment under the SMSR 2008

• With the choice of method available to the responsible person being dependent, for the most part, on whether the machinery in question falls within Schedule 2, Part 4 of SMSR 2008, which reflects Annex 4 of the EU Machinery Directive 2006/42/EC



Conformity assessments

24Source: Department of Business Innovation and Skills.



Procedures for conformity



25

• A responsible person, applying the general principles and having regard to standards, undertakes a risk assessment against the essential health and safety requirements (EHSRs), produces a technical file having applied the necessary internal checks, produces a Declaration of Conformity and affixes the CE marking to the product, thus declaring compliance to the SMSR 2008



Conformity assessmentsProcedure 1 - Assessment of conformity with internal checks on manufacture (self assessment) - Part 8 of Schedule 2 of SMSR 2008 (Annex VIII)

26

• Details of the manufacturer, or representative in the European Community, and place of manufacture

• A written declaration that the application has not been submitted to another notified body

• A technical file

• A representative example of the machine or a statement of where it may be examined



Conformity assessmentsProcedure 2 - European Community (EC) type-examination (declaration of type approval) - Part 9 of Schedule 2 of SMSR 2008 (Annex IX)

27

• For machinery referred to in Part 4 of the SMSR 2008 (Annex 4) a manufacturer that has a full quality assurance system such as BS EN ISO 9001:2008 may produce such machinery under the system and declare conformity

• The manufacturer must operate an approved quality system for design, manufacture, final inspection and testing



Conformity assessmentsProcedure 3 - Full quality assurance - Part 10 of Schedule 2 of SMSR 2008 (Annex X)

28Source: Rockwell Automation.



Overview procedure for the machinery directive

29

Harmonised standards

• These are non-binding technical specifications adopted by one of the European Standard Organisations (CEN, CENELEC or ETSI) on the basis of a remit issued by the European Commission

• These harmonised standards, that cover all the EHSRs, are published in the Official Journal of The European Communities

• Where these standards have also been published as identically worded national standards ('transposed harmonised standards') and machinery is made in conformance to them they will be presumed to comply with the EHSRs covered by the European harmonised standards



Use of harmonised standards

PART ONLY OF THE COMPLETE ELEMENT C6 – WORK EQUIPMENT (WORKPLACE MACHINERY)

30



31Source: RMS.



Planetary chart - A B and C standards

32

Conformity assessment for Annex IV machinery

• For listed machinery that is manufactured in conformity with transposed harmonised standards the responsible person may choose between:

– Procedure 1 - assessment of conformity with internal checks on manufacture

– Procedure 2 - EC type-examination

– Procedure 3 - Full quality assured



Use of harmonised standards

33

• Before machinery is placed on the market or put into service the responsible person must compile a technical file

• The technical file must demonstrate that the machinery complies with the provisions of the EU Machinery Directive 2006/42/EC

• It must cover the design, manufacture and operation of the machinery to the extent necessary for the purposes of conformity assessment



Technical file

34

Declaration of conformity

• The requirements for declaration of conformity are set out in Schedule 2, Part 2 “Annex II: Declarations” of SMSR 2008.

• The declaration of conformity and translations of it must be drawn up under the same conditions as instructions for the machinery and must be type written or hand written in capital letters

• The declaration relates to the condition in which the machine was placed on the market and excludes components and similar items added by the final user



Declaration of conformity/incorporation

35

Declaration of incorporation

• Where the machinery is intended for incorporation into other machinery or an assembly with other machines

• For example, an electric motor or a conveyor belt section, a declaration of incorporation is required

• The responsible person draws up a declaration of incorporation for each machine and no “CE” marking is applied to the machinery

• The declaration of incorporation states that the machinery must not be put into service until the machinery that it is incorporated into has been declared to be in conformity with the EHSR



Declaration of conformity/incorporation

36

Source: RMS.



EC declaration of conformity and incorporation



37




C6.4 Maintenance




CONTENTS

38

• Drills (radial arms, pedestal) - main hazard of entanglement

• Circular saws - main hazard of cutting

• Guillotines - main hazard of shear

• Paper shredders - main hazard cutting

• Photocopiers - main hazard drawing-in

• Disc sanders - main hazard abrasion

• Abrasive wheels - multiple hazards

• Lathes - main hazard entanglement

• Automatic doors and gates - main hazard crush or impact

• Mechanical and hydraulic presses - main hazard crush

COMMON MACHINERY HAZARDS IN A RANGE OF GENERAL WORKPLACES

Generic hazards

39


Generic hazards

Belt sander

Source: Clarke International.

40

• A huge variety of power tools is available, ranging from drills, grinders to more specialist equipment like diamond disc saws or petrol-driven strimmers/brush-cutters

• Typical injuries are cutting, stabbing, and eye injuries from waste material

• Portable tools include equipment powered by battery, petrol and compressed air


Generic hazards

Portable power tools

41

• Traditional engineering workshop machinery such as lathes and milling machines may be operated via computer numeric controls (CNC)

• Rather than relying on the skill of a human operator to control operating parameters and deliver precision products, processes can be partially or completely computerised

• Partial control includes microprocessor enhancements that control critical parameters, whilst leaving many control decisions in the hands of the operator


Generic hazards

CNC machines

42


Generic hazards

Example of a CNC machine

Source: cncmachine-details.info.



43

• The main hazards of robotics are associated with setting up and maintenance

• At setting up and maintenance the robotic equipment may make sudden unpredictable movements, leading to risks of impact, crushing, entanglement, shear, cutting, electric shock or burns

• At the time of dealing with breakdowns the main hazard is trapped potential energy, which might cause the equipment to cycle, even when isolated from external energy sources, resulting in any of the above injuries


Generic hazards

Robotics

44


Generic hazards

Summary - machinery hazardsExamples of mechanical hazards

Examples of machines with this mechanical hazard

Examples of non mechanical

Crushing Automatic doors and gates or presses Dust etc

Shear Guillotine, automatic doors and gates Radiation

Cutting/severing Circular saw, paper shredder Noise

Entanglement Drills, lathes Extremes of temperature

Drawing in/trapping Paper shredder, photocopier, abrasive wheel Vibration

Impact Automatic doors and gates or presses Electricity

Stabbing and puncture Drilling machine or sewing machine

Ejection Grinding wheel - disintegration or sparks, drills

Injection Hydraulic or pneumatic presses

Friction and abrasion Disc sanders, grinding wheels

Source: RMS.

45

Crushing

Shearing

Cutting/severing

Entanglement

Drawing in/trapping

Impact

Stabbing/puncture/ejection

Friction/abrasion

High pressure fluid injection

THE TYPES OF GENERIC MACHINERY HAZARDSMechanical hazards

Generic hazards

46

Source: RMS.

THE TYPES OF GENERIC MACHINERY HAZARDSBench cross-cut circular saw

Generic hazards

47

Source: RMS.

THE TYPES OF GENERIC MACHINERY HAZARDSShear

Generic hazards

48

THE TYPES OF GENERIC MACHINERY HAZARDSEntanglement in chuck of pedestal drill

Generic hazards

Source: RMS.



49

THE TYPES OF GENERIC MACHINERY HAZARDSAbrasive wheel

Generic hazards

Source: RMS.

50

Main types:

• Noise

• Vibration

• Electricity

• Thermal (high/low temperature)

• Radiation

• Hazardous materials and substances

Others:

• Falling

• Collision with equipment

• Neglecting ergonomic principles

• Pressure

Non-mechanical hazardsTHE TYPES OF GENERIC MACHINERY HAZARDSGeneric hazards

51

Influencing factors on modes of failureStress and strain

• The properties of stress and strain relate to the strength and stiffness of a material

• Stress is the load (force) per unit area:

• Where: S = stress, F = force, A = area

• The unit of stress is the Newton per square metre (N/m2) or the Pascal (Pa)

• Stress is a measure of the strength of a material

S = FA

THE TYPICAL CAUSES OF FAILURESGeneric hazards

52

Stress and strain

• Strain is a measure of the stiffness of a material:

• The property of the stiffness of a material is the extent to which a material resists being deformed by a force or how springy it is

• Note: strength and stiffness are not the same thing

Strain = change in lengthoriginal length

Influencing factors on modes of failureTHE TYPICAL CAUSES OF FAILURESGeneric hazards

53


Source: RMS.

Tension

54


Source: RMS.

Compression



55

Shear stress = shearing load

area being sheared

F

AMN m-2

Source: RMS.


Shear stress

56


Source: Ambiguous.

A tensile test-piece

57

• The amount of elastic deformation• This is reversible deformation• The degree of permanent plastic deformation• This is not reversible• The yield point at which plastic deformation is initiated• The stress at which a material breaks, called the breaking

stress• The maximum tensile stress that a material can support

without breaking, called the ultimate tensile strength


Influencing factors on modes of failureStress/strain relationships, yield point, breaking stress, ultimate tensile strength, elasticity and plasticity

58Source: Ambiguous.


Tensile stress-strain curve

59


Stress-strain curve for iron and glass

Source: Ambiguous.

60

The main modes of failure of structural components are:

• Metal fatigue

• Ductile failure

• Brittle failure

• Buckling

• Corrosion

• Wear

• Creep


Influencing factors on modes of failure



61

Source: RMS.


Metal fatigue

62

Source: Ambiguous.


Tensile stress and ductile failure

63

Source: Ambiguous.


Tensile stress and brittle failure

64

Source: Ambiguous.


Tensile stress and brittle failure

65

Source: RMS.


Scaffold standard

66

Source: 14 Bimetallic Corrosion, Dept of Industry in association with the Institution of Corrosion, Science and Technology.


Corrosion of galvanised iron pipe



67

Brent Cross, 20 June 1964Facts• The jib on a 15.2 tonne (15 ton) mobile crane failed and

fell onto a passing coach killing seven passengers and injuring a further thirty two

• At the time of the accident the crane was erecting a larger scotch derrick crane

FAILURE MODES AND PREVENTION IN RELATION TO MAJOR INCIDENTS

Generic hazards

68Source: HSE Report on Brent Cross Crane Failure.

Brent Cross, 20 June 1964 - crane failure


Generic hazards

69

Main factors

• Incorrect manufacture of the gate

• Incorrect positioning of the gate

• Failure to inspect

• Failure to notify designer’s limitations on use to the user

• Crane was operating on a 1:30 slope

• Estimated weight of load was wrong

• SWL exceeded

• The safe load indicator was defective

• Failure to test

Brent Cross, 20 June 1964


Generic hazards

70

Facts

• A single suspension rope of one of the hoist cages, in which nine men were travelling, broke

• The safety gear failed to operate and the cage plunged more than 30 metres to the bottom of a 60 metres shaft

• Four men were killed and five were seriously injured

Littlebrook D Power Station, 09 January 1978


Generic hazards

71

Main factors

• The hoist’s suspension rope broke at a part weakened by corrosion and lacking lubrication

• The deterioration took place over a relatively short period of time and was not detected

• Analysis of the water in the shaft showed that it contained salt and the corrosion was consistent with the rope having been impregnated with salt water

• Both clamping units of the cage safety mechanism were found to be corroded and coated with hard, cement like, material that prevented them from working

Generic hazards

FAILURE MODES AND PREVENTION IN RELATION TO MAJOR INCIDENTSLittlebrook D Power Station, 09 January 1978

72

Contributory factors

• The statutory six monthly examination of the hoist was overdue

• The weekly site inspection had failed to record any defects

• The maximum load for the hoist was eight passengers

• The maintenance of the cage safety mechanism had been inadequate to maintain it in good working order in the environment to which it had been exposed

Generic hazards

FAILURE MODES AND PREVENTION IN RELATION TO MAJOR INCIDENTSLittlebrook D Power Station, 09 January 1978



73

Generic hazards

Source: The hoist accident at Littlebrook ‘D’ Power Station, HSE Books.

FAILURE MODES AND PREVENTION IN RELATION TO MAJOR INCIDENTSGeneral layout of shaft hoist and tunnel

74

Facts• The day shift was being lowered at No. 3 upcast shaft at

Markham Colliery, Derbyshire on 30 July 1973

• A double deck cage containing 29 men crashed to the wooden baulks at the pit bottom killing 18 men and seriously injuring another 11

• The subsequent investigation found that:

1) There was a complete failure of the winding engine brake the centre rod in the spring nest had broken

2) The centre rod appeared to have failed due to fatigue

Markham Colliery, 30 July 1973

Generic hazards


75

Main factors• No provision had been made for non-destructive testing (NDT) of the centre rod

in the spring nest

• The centre rod was a ‘single line’ component and the safety of the cage was completely dependent upon it

• A similar rod had broken in Ollerton Colliery in January 1961, which was attributed to induced stresses

• The subsequent instruction to examine centre rods did not give any guidance as to the nature and frequency of examinations or the use of NDT

• Ultrasonic tests, which can be carried out in situ, would have revealed large cracks (~ 10 mm (3/8 “) depth) but would not have detected the small cracks in the rod

Generic hazards

FAILURE MODES AND PREVENTION IN RELATION TO MAJOR INCIDENTSMarkham Colliery, 30 July 1973

76

Facts• A passenger walkway collapsed killing six passengers and seriously

injuring seven more

• In the collapse, one end of the walkway fell 10 metres, embedding itself in the deck of the pontoon that had provided the floating seaward support for the structure

• The HSE investigation established that the immediate cause of the collapse was the failure of a weld in a safety-critical support element of the structure

• Further investigation revealed gross deficiencies in the design, which would have ensured failure of safety-critical elements within a fairly short part of the structure’s lifespan

Port Ramsgate, September 1994

Generic hazards


77

• Methods of identifying potential failure modes

– Identifying potential failure modes

– Use of fracture mechanics

• Related environmental factors

– Selection of materials

– Purpose of ‘safety factors’

• Quality assurance during manufacture and installation

• Testing during manufacture and installation

1) An inspection carried out on completion of the product

2) A last inspection carried out prior to dispatch

3) A last inspection the supplier carries out prior to transfer of ownership to the customer

FAILURE PREVENTION STRATEGIESGeneric hazards

78

FAILURE PREVENTION STRATEGIESGeneric hazards

Mode Possible indicators

Tensile fracture Local ‘necking’ or extension and decrease in sectional area in direction of load.

Shear fracture Friction marks with a new-moon shaped gap on the unloaded side of a bolt etc.

Brittle failure Clean break with no signs of necking. Surface has coarse, angular appearance with‘chevron’ markings pointing back to the starting point.

Wear Shiny new appearance, pitting and fretting of components.

Corrosion Pitting, colour changes (for example rust and tarnishing).

Fatigue crack ‘Beach’ or conchoidal marks.

Source: RMS.

Failure modesForensic examination of failed components



79

• Visual inspection

• Liquid dye penetrant inspection

• Magnetic particle testing

• Eddy current testing

NON-DESTRUCTIVE TESTING TECHNIQUESGeneric hazards

NDT techniques suitable for surface defects

80

• Radiography

– X-ray radiography

– Gamma ray radiography

– Neutron radiography

• Ultrasonic testing

– Ultrasound is defined as (sound) waves at frequencies beyond the upper limit that the human ear can detect (i.e. above 20 kHz)


NDT techniques suitable for sub-surface defects

81

• Acoustic methods

• Electromagnetic methods

• Leak-test methods

• Hydrostatic and pneumatic testing

• Cryogenic testing

• Tensile tests

• Hardness, impact and manipulating tests


Other NDT techniques• Corrosion tests

• Brittle (coating) lacquer testing

• Strain-gauge testing

• Electrical resistivity

• Thermography

• Holography

82




C6.4 Maintenance




CONTENTS

83

• A fixed guard is simple, and should be used where access to the danger area is not required during operation of the machinery or for cleaning, setting or other activities

• Where access to the danger area is not required during normal operation of the machinery, safeguards may be selected from the following:

– Fixed enclosing guard

– Fixed distance guard

– Interlocking guard

– Trip device

Factors affecting choice of safeguarding methodTHE MAIN TYPES OF SAFEGUARDING DEVICESProtective devices

84

• Where access to the danger area is required for normal operation, safeguards may be selected from the following:

– Interlocking guard

– Automatic guard

– Trip device

– Adjustable guard

– Self-adjusting guard

– Two-hand control device

– Hold-to-run control




85

Fixed enclosing guard constructed of wire mesh and angle section preventing access to transmission machinery

Source: BS PD 5304.

THE MAIN TYPES OF SAFEGUARDING DEVICESProtective devices

86

• Hierarchy of safeguarding methods (PUWER 1998 -Regulation 11 dangerous parts of machinery) as amended by the Health and Safety (Miscellaneous Amendment) Regulations (MAR) 2002

• Guard construction

– Any guard selected should not itself present a hazard such as trapping or shear points, rough or sharp edges or other hazards likely to cause injury

– Guard mounting should be compatible with the strength and duty of the guard

– Power operated guards should be designed and constructed so that a hazard is not created


87

• A fixed guard is a guard that has no moving parts.• If the guard can be opened or removed, this should only be

possible with the aid of a tool• Preferably the fastenings should be of the captive type• Ideally the removal of a single fixing with the appropriate

tool should give the access required• When in position, prevents access to a danger zone or

point by enclosure

CHARACTERISTICS, KEY FEATURES, LIMITATIONS AND TYPICAL APPLICATIONS

Protective devices

Fixed enclosed guards

88

• A fixed guard that does not completely cover the danger zone or point, but places it out of normal reach

• The larger the opening (to feed in material) the greater must be the distance from the opening to the danger zone or point

• A distance guard that completely surrounds machinery is commonly called a perimeter-fence type guard

Protective devices

Fixed distance guards


89Source: BS PD 5304.

Protective devices

Fixed distance guard fitted to a press brake


90

Anthropometric considerations

• General

– Guards should be designed and constructed with the object of preventing any part of the body from reaching a danger zone or point

• Openings in a guard

– Where it is necessary to provide an opening in a guard, it should be at a sufficient distance to prevent any person from reaching the danger zone or point

• Barriers

– Where it is not practicable to use enclosing guards, barriers may be used to prevent people reaching the danger zone or point

Protective devices

Fixed distance guards




91

• Functions of an interlock

– Interlocking media/methods

– Interlocking incorporating braking and/or guard locking

– Guard locking systems

• Types of failure of interlocking systems

• Failure monitoring of interlocking systems

Protective devices

Interlocked guards


92

Protective devices

Interlocking guard for positive clutch power press

Source: BS PD 5304.


93

Protective devices

Schematic representation of power and control interlocking

Source: Ambiguous.


94

Protective devices

Probable effect of a failure to dangerType of system Probable effect of a failure to

danger in a single channelAction

Single-control system interlocking without indication of failure.

Machinery will continue to operate normally.

Guarding system is ineffective.

Dual-control system interlocking without cross-monitoring, but provided with indication of failure.

Machinery will continue to operate normally. Guarding system remains effective only on one channel.

Note indication failure. Take necessary remedial action.

Dual-control system interlocking with cross-monitoring. Monitoring function self-checked.

Guarding system remains effective.

None.

Source: RMS.


95

Source: Paper D (S Tech); Q5; June 1996 Previous NEBOSH Diploma.

Protective devices

Interlocking system


96

• Choice of interlocking system

• Interlocking switch types

• Mechanical interlocks

• Cam-activated position switches and modes of operation

• Magnetic switches

Protective devices

Interlocked guards




97

Protective devices

Two position switches operating in opposite modes, mounted side by side, each actuated by its own cam mounted on the guard hinge

Source: BS PD 5304.


98

Captive and trapped key systems

• Captive key systems

– Captive key interlocking systems involve a combination of an electrical switch and a mechanical lock in a single assembly

• Trapped key system

– In a trapped-key system the guard lock and switch, which also incorporates a lock, are separate as opposed to being combined into a single unit as in the captive-key switch


Protective devices

Interlocked guards

99

Source: BS PD 5304.

Protective devices

Captive key switch


100

Source: Castell Safety.

Protective devices

Key exchange box system

1 Key, 3 keys trapped. Insert and turn free key, then turn and release trapped keys in sequence.

1 key is trapped, 3 keys released.


101

Source: BS PD 5304.

Protective devices

Practical application of the trapped-key control system


102

Source: BS PD 5304.

Automatic guard for a power press

Protective devices




103

• A guard which is moved into position automatically by the machine

• Removing any part of a person from the danger area

• In some applications this type of guard is known as ‘sweep away guard’ e.g. on a guillotine

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

• The movable part of the guard should be positively actuated by the movement of the dangerous part of the machinery

Automatic guards

Protective devices


104

• Mechanical actuated devices

– Pressure sensitive mat system

• Non-mechanically actuated devices

– Photoelectric safety systems

Trip devices

Protective devices


105

Trip device for drilling machines

Protective devices


Source: BS PD 5304.

106

Pressure sensitive mat safeguarding the clamping and bending jaws of an automatic horizontal tube bender

Protective devices

Source: BS PD 5304.


107

Source: HSG 129 Health and Safety in Engineering Workshops.

Protective devices

CHARACTERISTICS, KEY FEATURES, LIMITATIONS AND TYPICAL APPLICATIONSPhotoelectric safety system used as a presence sensing device inside distance guards fitted around a robot served pressure die casting machine

108

Hydraulic press brake using photoelectric safety system

Protective devices

Source: HSG 129 Health and Safety in Engineering Workshops.




109

Adjustable

• An adjustable guard is a fixed guard that incorporates an adjustable element for example on a pillar drill or circular saw

• An adjustable guard provides an opening to the machinery through which material can be fed

• The guard should be designed that the adjustable parts cannot easily become detached and mislaid

Adjustable/self-adjusting guards

Protective devices


110

Adjustable guard for a radial or pedestal drilling machine

Protective devices

Source: BS PD 5304.


111

Self adjusting

• Prevents accidental access by the operator

• Allows entry of the material to the machine in such a way that the material actually forms part of the guarding arrangement itself for example hand held circular saw

• Designed to prevent access to the dangerous part(s) until actuated by the movement of the workpiece

Adjustable/self-adjusting guards

Protective devices


112

Self-adjusting guard arrangement for snipper cross-cutting sawing machine

Protective devices

Source: BS PD 5304.


113

• A two-hand control device (2HC) is a device that requires both hands to operate

• Note that ‘2HC’ devices protect only the operator and then, only provided the assistance of a colleague is not solicited to activate one control

• Where guarding is impracticable two-hand controls offer a means of protecting the hands of the machine operator

• It may also be used as a hold-to-run control

Two-hand controls

Protective devices


114

Protective devices

Two-hand control device

Source: BS PD 5304.




115

• Mechanical restraints are devices that apply mechanical restraint to the dangerous part, which prevents it from moving:

– When the controls fail

– When the machine is inadvertently activated

Mechanical restraints

Protective devices


116

• Jigs are protection appliances that are used to hold or manipulate the workpiece in a way that allows people to keep their body away from the danger zone or danger point

• They normally need to be used in addition to guards

• Even when the best possible guarding is used, the operation of certain types of machines often involves considerable risk

• Wherever possible appliances such as jigs and holders should be provided and used

Jigs

Protective devices


117

• Push sticks are used to feed timber through bench mounted circular saws or food into a food processing machine

• The stick used with a circular saw is a short 12 to 24 cm length of wood used to move the last part of the timber to be cut past the blade

• The stick keeps the blade at a safe distance from the hands and the fingers

• Push sticks and jigs are defined as appliances within the scope of hierarchy of Provision and Use of Work Equipment Regulations (PUWER) 1998 for safeguarding machinery

Push sticks

Protective devices


118




C6.4 Maintenance




CONTENTS

119

• Essential to have a balanced strategy of integration of technical, procedural and behavioural controls in order to achieve safety with machinery

• This means not having an over reliance on any one control but ensuring that they are integrated and complement each other

• The principle of taking a risk based approach is essential

• This will mean using more of the control options the higher the risk

THE MEANS BY WHICH MACHINERY IS SAFELY SET, CLEANED AND MAINTAINEDSafe systems of work

Maintenance

120

Format

• A permit-to-work is a document that:

‒ Specifies the work to be done and the precautions to be taken

‒ Predetermines a safe procedure

‒ Provides a clear record that foreseeable hazards have been considered in advance

Permits

THE MEANS BY WHICH MACHINERY IS SAFELY SET, CLEANED AND MAINTAINED

Maintenance



121

Major features of permit-to-work systems

• Identifying need

• Identifying hazards

• Implementation

• Key points of a permit-to-work

Permits


Maintenance

122

• Regulation 19 of PUWER 1998 deals with isolation from sources ofenergy“(1) Every employer shall ensure that where appropriate work

equipment is provided with suitable means to isolate it from all its sources of energy

(2) Without prejudice to the generality of paragraph (1), the means mentioned in that paragraph shall not be suitable unless they are clearly identifiable and readily accessible

(3) Every employer shall take appropriate measures to ensure that re-connection of any energy source to work equipment does not expose any person using the work equipment to any risk to his health or safety”

Isolation


Maintenance

123

• Setting

‒ The process by which cutting tools etc. are replaced or adjusted on a machine to suit the work to be done

• Cleaning

‒ The process by which the cutting tools etc. are cleaned of waste materials

• Maintenance

‒ Any maintenance work, including setting and cleaning, should only be done when the machine is isolated from all sources of power

Procedures for working at unguarded machinery


Maintenance

124

• Isolation means establishing a break in the energy supply in a secure manner

• It is important to identify the possibilities and risks of reconnection as part of the risk assessment process

• If work on isolated equipment is being done by more than one worker, it may be necessary to provide a locking device with multiple locks and keys

• For safety reasons sources of energy may need to be maintained when the equipment is stopped

• Isolation could lead to consequent danger, so it will be necessary to take appropriate measures to eliminate any risk before attempting to isolate the equipment

THE MEANS BY WHICH MACHINES ARE ISOLATED FROM ALL ENERGY SOURCES

Maintenance

125

• Isolation of electrical equipment is dealt with by regulation 12 of the Electricity at Work Regulations (EWR) 1989

• Note that these Regulations are only concerned with electrical danger and do not deal with other risks (such as mechanical) that may arise from failure to isolate electrical equipment

• Regulation 19(3) of PUWER 1998 also requires precautions to ensure that people are not put at risk following reconnection of the energy source


Maintenance

126


Maintenance

Physical isolation of valve

Source: RMS.



127


Maintenance

Multiple (padlock) lock off device

Source: RMS.

128




C6.4 Maintenance




CONTENTS

129

• As part of the requirements set out in Part 1 (Annex I) subparagraph 1.7 of Schedule 2 of SMSR 2008, concerning how essential health and safety requirements are dealt with, manufacturers must provide comprehensive information regarding the safe operation and use of machinery

• Instruction manuals provided with machinery by manufacturers or suppliers must be in one or more official European Community languages

• The words “Original Instructions” must appear on the language versions and this must be verified by the “Responsible Person”

THE SCOPE OF INFORMATION REQUIRED FOR THE SAFE USE AND OPERATION OF MACHINERY

Information and warnings

130

• The EU Machinery Directive 2006/42/EC and SMSR 2008 require that information and instructions provided by the responsible person, for example the manufacturer, regarding the operation and use of machinery must be comprehensible to those concerned

• In addition, PUWER 1998, Regulation 8, requires that:

‒ “(4) Information and instructions required by this regulation shall be readily comprehensible to those concerned”

INFORMATION AND INSTRUCTIONS REGARDING THE OPERATION AND USE OF MACHINERY


Comprehensible information and instructions

131

PUWER Regulation 23 - Markings

• PUWER 2008, Regulation 23 requires that employers ensure that work equipment is marked in a clearly visible manner with any marking appropriate for reasons of health and safety

PUWER Regulation 24 - Warnings

• PUWER 2008, Regulation 24 requires that employers ensure that work equipment incorporates any warnings or warning devices that are appropriate for reasons of health and safety

INFORMATION AND INSTRUCTIONS REGARDING THE OPERATION AND USE OF MACHINERY


Markings and warnings

132




C6.4 Maintenance




CONTENTS



133

The machinery control system should:

• Make allowance for the failures, faults and constraints to be expected in the planned circumstances of use

• Not create any increased risk to health or safety

• Faults or damage to the control system or the loss of energy supply must not result in additional risk to health or safety

• Not impede the operation of any stop/energy stop controls

THE KEY SAFETY CHARACTERISTICS OF MACHINERY CONTROL SYSTEMS

Machinery control systems

General requirements

134

• Any change in the operating conditions should only be possible by the use of a control, except if the change does not increase risk to health or safety

• Examples of operating conditions include speed, pressure, temperature and power



Controls for starting or making a significant change in operating conditions

135

• Stop controls must be placed so that they are readily accessible to the user

• Therefore it is important to consider the activities the user may be involved in and ensure the controls are available to them while they are doing this work

• This may include providing supplementary stop controls at points where material is fed in or taken out of machinery as well as the primary operating position



Stop controls readily accessible and leads to a safe condition

136

• The function of an emergency stop control device is to provide a means to bring a machine to a rapid halt

• It is provided in such circumstances where it would be of benefit and should be readily available to the operator and/or others

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



Emergency stop controls provided and to be readily accessible

137

• It should be possible to identify easily what each control does and on which equipment it takes effect

• Both the controls and their markings should be clearly visible

• As well as having legible wording or symbols, factors such as the colour, shape and position of controls are important

• Warnings given in accordance with PUWER 1998, Regulation 17(3)(c), should be given sufficiently in advance of the machine starting to give those at risk time to get clear

• As well as time, suitable means of avoiding the risk should be provided



Position and marking of controls to be visible and identifiable

138

Ergonomic principles

• Ergonomic considerations involve the study of the person-equipment interface

• The aim of ergonomic principles is to ensure controls suit a variety of individual sizes of worker and work positions in order to provide machinery control systems that are suitable and can be operated effectively



Consideration of ergonomic principles



139


Practical application of ergonomic principles to machine design

Source: Guide to the Machinery Directive.


140

Stability

PUWER 1998 - Regulation 20 - “Stability” requires:

• “Every employer shall ensure that work equipment or any part of work equipment is stabilised by clamping or otherwise where necessary for purposes of health or safety”




141

Lighting

PUWER 1998 - Regulation 21 - “Lighting” requires:

• “Every employer shall ensure that suitable and sufficient lighting, which takes account of the operations to be carried out, is provided at any place where a person uses work equipment”




142




C6.4 Maintenance




CONTENTS

143

• Meaning of the term ‘system’

• Principles of system failure analysis

• Use of calculation in the assessment of system reliability

• Methods for improving system reliability

Systems failures and system reliability

144

• A system is a set of inter-related elements that starts with an input

• That undergoes some process and results in an output

• Which has a monitoring (feedback) loop that evaluates the input, process and output

• In order to make adjustments that ensure the intended resultant output is provided

MEANING OF THE TERM ‘SYSTEM’Systems failures and system reliability



145

Source: RMS.

MEANING OF THE TERM ‘SYSTEM’Systems failures and system reliability

System

146

• The holistic approach examines the system as a whole

• The reductionist approach to analysis of any system involves dividing the system into its individual component parts

PRINCIPLES OF SYSTEM FAILURE ANALYSISSystems failures and system reliability

Holistic and reductionist approaches

147

• Systemic: of the body as a whole

• Systematic: methodical; according to plan, not casually or at random

• A systemic analysis considers the whole system whereas a systematic analysis considers the component parts of the system in a logical, methodical way that considers each stage of the system in turn

• Systemic analysis allows for an intuitive approach that may perceive relationships in an apparently unconnected array of activities


Differences between systemic and systematic analysis

148

• An analysis of the system and sub-system would have shown the probability of a failure of a weak temporary link (solvent pipeline) between vessels at Flixborough, where a major flammable chemical explosion occurred

• The Piper Alpha explosion was due, in part, to management failure within a permit-to-work system

• If a car and passenger ferry such as the Herald of Free Enterprise leaving port is considered as a system, then for the numerous problems that developed, for example, management attitude ‘to turn the ship around quickly’, failure to follow standard procedures in the sub-systems inevitably led to disaster


Application to actual examples

149

USE OF CALCULATION IN THE ASSESSMENT OF SYSTEM RELIABILITY


General points• System reliability calculations are based on two important

operations:

– As precise as possible a measurement of the reliability of the components used in the system environment

– A calculation of the reliability of some complex combinations of these components

150

A BSource: RMS.


Series system


Series systems



151

A

B


Parallel system


Parallel systems

Source: RMS.

152

A

B

C


Three components in parallel


Parallel systems

Source: RMS.

153


The reliability of a mixed system (series and parallel)


Mixed systems

Source: RMS.

154

A

C

B

D

E


Mixed system


Mixed systems

Source: RMS.

155


Mixed systems• In the mixed system, the two equal paths, A-D and B-E,

operate in parallel so that if at least one of them is good, the output is assured

• But, because units A and B are not reliable enough, a third equal unit, C, is inserted into the system so that units D and E are supplied with the necessary input

• Therefore, the following operations are possible:


156


Common mode failures• Failure can occur when an external factor affects the systems

• For example, in 1980 a leg sheared off an oil platform (rig), the platform tilted and the generator was knocked off

• The generator supplied all the electrical power

• The rig was plunged into darkness, the resulting fire could not be dealt with and there was no means of escape

• The systems for dealing with the various emergency situations should have been so completely apart from each other that the risk of them all being affected by the same external factor could have been avoided




157


Principles of human reliability analysis• Human behaviour

• Examples of errors

• Applications of human reliability analysis

• Implementation of human reliability analysis

• Type and nature of results


158

METHODS FOR IMPROVING SYSTEM RELIABILITYSystems failures and system reliability

• Three risk factors need to be considered if the testing of systems is carried out more frequently:

1) Continuance of plant operation whilst protective devices are removed for testing

2) The likelihood of error/damage in removal/replacement of equipment by test engineers

3) Potential exists to replace a good component with a component that is defective

General points

159


1984 Bhopal, India

• A major disaster occurred to the local population following the uncontrolled release of highly toxic vapour

• When a storage tank containing methyl isocyanate was contaminated with water (major respiratory injury results at exposure to levels at parts per billion)

• 2,500 people were killed and it is estimated that approaching 500,000 people were injured from the release

General pointsMETHODS FOR IMPROVING SYSTEM RELIABILITY

160


• By considering the data available, the most reliable components can be chosen

• The most expensive may not always be the most suitable

• For example, the reliability of a system may be lessened because a valve has a probability of failure of 0.05

• Using the same level of quality valve, a second valve can be placed in parallel so if one fails the other will come into use

• This means, for a dangerous situation to arise, both valves will have to fail together, the probability of which is 0.05 X 0.05 = 0.0025

• The probability has gone from 1 in 20 to 1 in 400

Use of reliable componentsMETHODS FOR IMPROVING SYSTEM RELIABILITY

161


• Components that are made to a specification within a quality assurance system

• Where rigorous testing is carried out are more likely to be reliable

• It is important that reliability is built in from the design stage, through manufacture, through the building of the system, its use, making changes, and maintaining the system and its component parts

Quality assuranceMETHODS FOR IMPROVING SYSTEM RELIABILITY

162

METHODS FOR IMPROVING SYSTEM RELIABILITYSystems failures and system reliability

• System reliability can be improved by duplication of critical components in parallel

• When one component fails (becomes redundant) the other operates to maintain control for example dual braking fitted to a road vehicle

• When designing parallel systems consideration should also be given to diversity

• Which is where alternative mechanisms provide the desired action

• For example a pneumatic system may be provided in parallel to support an electronic system

Parallel redundancy



163


• A stand-by system is where a component or unit is operating and one or more units are standing by to take over the operation, should the primary one fail

• The supporting components or units are normally idle and begin to operate only when the primary unit fails

• An example of this is a second water supply pump at a water treatment plant provided to be available by valve switching when required following a failure or maintenance of the primary pump

Standby systemsMETHODS FOR IMPROVING SYSTEM RELIABILITY

164


• A design consideration at the HAZOP stage

• Requires consideration of the operation of safety critical equipment and devices at the time of failure of the device, detector communication link or responder

• Consider a remotely operated steam control valve to a reactor

• Such valves are usually controlled using compressed air operating the valve against a spring

• A typical arrangement would be that the valve closes at zero supply pressure and opens when compressed air at a known pressure is applied

Minimising failures to dangerMETHODS FOR IMPROVING SYSTEM RELIABILITY

165


• Diversity is concerned with the identification of common mode failure

• Common mode failure may cause a parallel system failure

• For example if the parallel system requires compressed air and both components are supplied from the same air supply, then failure of the air supply will result in the failure of both components in the parallel system

• A single failure of electrical supply may affect many different supply voltages to a plant

• Care needs to be taken when considering the need for either redundancy or diversity

DiversityMETHODS FOR IMPROVING SYSTEM RELIABILITY

166

Pneumatic

Electric

MechanicalSource: RMS.


Diverse systemMETHODS FOR IMPROVING SYSTEM RELIABILITY

167

Plant maintenance systems

• It is important therefore to have a suitable system for emergency maintenance in place

• This may be achieved through the use of:

– Contingency plans

– Model (or generic) risk assessments

– Safe systems of work (for example permit to work system)

– The provision of appropriate skills and training


Planned preventive maintenanceMETHODS FOR IMPROVING SYSTEM RELIABILITY

168

The role of statutory examinations of plant and equipment

• The Lifting Operations and Lifting Equipment Regulations (LOLER) 1998 provide that operational lifting equipment is to be thoroughly examined:

– At least every 6 months for lifting equipment for lifting persons or lifting accessories

– At least every 12 months for other lifting equipment

– In either case, in accordance with an examination scheme

– On each occurrence of exceptional circumstances liable to jeopardise the safety of the lifting equipment


Planned preventive maintenanceMETHODS FOR IMPROVING SYSTEM RELIABILITY



169

• Human reliability analysis (HRA) can be used to develop training schemes for skill based behaviour and associated physiological factors, the design of controls, workplace, buildings, environmental conditions, transportation, and communications

• A good example is the design of aircraft cockpit control layouts in which human performance at the operator level reaches the highest levels of criticality

• The concept of HRA could be used by management to devise management controls


Minimising human errorMETHODS FOR IMPROVING SYSTEM RELIABILITY

170


Error rates for a control roomMETHODS FOR IMPROVING SYSTEM RELIABILITY

Error rate Situation

1 in 1 Impending disaster, rapid action needed, panic

1 in 10 No impending disaster apparent, busy, signals, alarms

1 in 100 Quiet but busy, relaxed

1 in 1000 Familiar, routine tasks

Source: RMS.

171

• Provision and Use of Work Equipment Regulations (PUWER) 1998 (Regulations 10-19)

• Supply of Machinery (Safety) Regulations (SMSR) 2008 -Schedule 2

• Workplace (Health, Safety and Welfare) Regulations (WHSWR) 1992

RELEVANT STATUTORY PROVISIONS

172




C6.4 Maintenance




CONTENTS

173173

ELEMENT C6WORK EQUIPMENT (WORKPLACE MACHINERY)

174174

NEBOSH DIPLOMAIN OCCUPATIONAL HEALTH AND SAFETY

Unit C

Workplace and Work Equipment Safety



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