Safety.

Safety

Most industrial plant has the capacity to maim or kill. It is therefore the responsibility of all people, both employers and employees, to ensure that no harm comes to any person as a result of activities on an industrial site.

Not surprisingly, this moral duty is also backed up by legislation.

It is interesting that most safety legislation is re-active, i.e. respond­ ing to incidents which have occurred and trying to prevent them happening again. A prime example of this is the CDM regulations which arose because of the appalling safety record in the construction industry.

Safety legislation differs from country to country, although harmonization is underway in Europe. This section describes safety from a British viewpoint, although the general principles apply throughout the European community and are applicable in principle throughout the world. The descriptions are, of course, a personal view and should only be taken as a guide. The reader is advised to study the original legislation before taking any safety-related decisions.

Most safety legislation has a common theme. Employers and employees are deemed to have a Duty of Care to ensure the Health, Safety and Welfare of the employees, visitors and the public. Failure in this duty of care is called Negligence. Legislation defines required actions at three levels:

Shall or Must are absolute duties which have to be obeyed without regard to cost. If the duty is not feasible the related activity must not take place.

If practicable means the duty must be obeyed if feasible. Cost is not a consideration. If an individual deems the duty not to be feasible, proof of this assertion will be required if an incident occurs.

Reasonably practicable is the trickiest as it requires a balance of risk against cost. In the event of an incident an individual will be required to justify the actions taken.

There is a vast amount of safety legislation with varying degrees of authority. Acts (e.g. the Health and Safety at Work Act (HASWA)), are statutes passed by full parliamentary procedures and are enforced by criminal law. Often acts such as HASWA (called Enabling Acts), are arranged to allow supplementary regu­lations to be made by the Secretary of State without going through the full parliamentary procedure.

Regulations are introduced under an enabling act. They have the same power and status as acts. Most British safety regulations have

been made under the Health and Safety at Work Act 1974.

Approved Codes of Practice (ACOPs) are documents written to define safe working methods and procedures by organizations such as CENELEC and British Standards Institute. They are approved by the Health and Safety Commission. Whilst they are not mandatory (i.e. there can be no prosecution for not following them), failure to follow ACOPs may be viewed as a contributory factor in investigations of an incident.

Codes of Practice are guidance codes provided by trade unions and professional organizations. These do not have the semi-legal status of ACOPs, but contain good advice. Again, though, imple­ mentation or otherwise can be given in evidence in court.

In Europe there is a serious attempt to have uniform legislation throughout the EC. At the top level is EC Regulations which over­ ride national legislation. Of most relevance are EC Directives which require national laws to implemented.

In Britain the primary legislation is the Health & Safety at Work Act 1974 (HASWA). It is an enabling act, allowing other legislation to be introduced. It is wide ranging and covers everyone involved with work (both employers and employees) or affected by it. In the USA the Occupational Safety and Health Act (OSHA) affords similar protection.

HASWA defines and builds on general duties to avoid all pos­sible hazards, and its main requirement is described in section 2( 1) of the act:

It shall be the duty of every employer to ensure, so far as is reasonably practicable, the health, safety and welfare at work for his employees This duty is extended in later sections to visitors, customers, the general public and (upheld in the courts), even trespassers. The onus of proof of Reasonably Practicable lies with the employer in the event of an incident.

Section 2(2) adds more detail by requiring safe plant, safe systems of work, safe use of articles and substances (i.e. handling, storage and transport), safe access and egress routes, safe environ­ ment, welfare facilities and adequate information and training.

If an organization has five or more employees it must have a written safety policy defining responsibilities and employees must be aware of its existence and content (section 2(3)) Employers must consult with worker safety representatives The act is not aimed purely at employers, employees also have duties described in sections 7 and 8 of the act. They are responsible for their own, and other’s safety and must co-operate with employ­ers and other people to ensure safety, i.e. they must follow safe working practices. They must not interfere with any safety equip­ment (e.g. tampering with interlocks on movable guards).

The act defines two authorities and gives them power for the enforcement of the legislation (sections 10-14 and 18-24). The Health and Safety Commission is the more academic of the two, and defines policy, carries out research, develops safety law and disseminates safety information. The Health & Safety Executive (HSE) implements the law by inspection and can enforce the law where failings are found. Breaches of HASWA amount to a indictable offence and the HSE has the power to prosecute the offenders.

The power of HSE inspectors are wide. They can enter premises without invitation and take samples, photographs, documents, etc. Breaches of HASWA amount to a indictable offence and the HSE has the power to prosecute the offenders. People, as well as organisations, may be prosecuted if a safety failing or incident arises because of neglect by a responsible person.

The HSE also has the power to issue notices against an organisation. The first, an Improvement Notice, is given where a fairly minor safety failing is observed. This notice requires the failing to be rectified within a specified period of time. The second, a Prohibition Notice, requires all operations to cease immediately and not restart until the failing is rectified and HSE inspectors withdraw the notice.

It is all but impossible to design a system which is totally and absolutely fail-safe. Modem safety legislation, such as the Six Pack, recognises the need to balance the cost and complexity of the safety system against the likelihood and severity of injury. The pro­ cedure, known as Risk Assessment, uses common terms with specific definitions:

image

Risk assessment is a legal requirement under most modem legisla­ tion, and is covered in detail in, standard prEN 1050 ‘Principles of Risk Assessment’.

The first stage is identification of the hazards on the machine or process. This can be done by inspections, audits, study of incidents (near misses) and, for new plant, by investigation at the design stage. Examples of hazards are: impact/crush, snag points leading to entanglement, drawing in, cutting from moving edges, stabbing, shearing (leading to amputation), electrical hazards, temperature hazards (hot and cold), contact with dangerous material and so on. Failure modes should also be considered, using standard methods such as HAZOPS (Hazard & Operability Study, with key words Too much of and Too little of), FMEA (Failure Modes and Effects Analysis) and Fault Tree Analysis.

With the hazards documented the next stage is to assess the risk for each. There is no real definitive method for doing this, as each plant has different levels of operator competence and maintenance standards. A risk assessment, however, needs to be performed and the results and conclusions documented. In the event of an accident, the authorities will ask to see the risk assessment. There are many methods of risk assessment, some quantitative assigning points, and some using broad qualitative judgements.

Whichever method is used there are several factors that need to be considered. The first is the severity of the possible injury. Many sources suggest the following four classifications:

image

Linked to this is how long the exposure lasts. Is the person exposed to danger for a few seconds per event or (as can occur with major maintenance work), several hours? There may also be a need to consider the number of people who may be at risk; often a factor in petro-chemical plants.

Where the speed of a machine or process is slow, or there is a lengthy and obvious (e.g. noisy) start-up, the exposed person can easily move out of danger in time. There is obviously less risk here than with a silent high speed machine which can operate before the person can move. From studying the machine operation, the proba­bility of injury in the event of failure of the safety system can be assessed as:

Certain, Probable, Possible, Unlikely

From this study, the risk of each activity is classified. This classifi­ cation will depend on the application. Some sources suggest apply­ ing a points scoring scheme to each of the factors above then using the total score to determine High, Medium and Low risks. Maximum Possible Loss (MPL) for example uses a 50 point scale ranging from 1 for a minor scratch to 50 for a multi-fatality. This is combined with the frequency of the hazardous activity (F) and the probability of injury (again on a 1-50 scale) in the formula:

risk rating (RR) = F x (MPL + P)

The course of action is then based on the risk rating.

An alternative and simpler (but less detailed approach) uses a table as Figure 8.1 from which the required action can be quickly read.

Safety, fault-finding and maintenance-0217

There is, however, no single definitive method, but the procedure used must suit the application and be documented. The study and reduction of risks is the important aim of the activity.

The final stage is to devise methods of reducing the residual risk to an acceptable level. These methods will include removal of risk by good design (e.g. removal of trap points), reduction of the risk at source (e.g. lowest possible speed and pressures, less hazardous material), containment by guarding, reducing exposure times, provision of personal protective equipment and establishing written safe working procedures which must be followed. The latter implies competent employees and training programs.

There is a vast amount of legislation covering health and safety, and a list is given below of those which are commonly encountered in industry. It is by no means complete, and a fuller description of these, and other, legislation is given in the third edition of the author’s Industrial Control Handbook. An even more detailed study can be found in Safety at Work by John Ridley, both books pub­ lished by Butterworth-Heinemann.

Commonly Encountered Safety Legislation:

Health & Safety at Work Act 1974 (the prime UK legislation) Management of Health & Safety at Work Regulations 1992 Provision & Use of Work Equipment Regulations 1992 (PUWER) Manual Handling Regulations 1992 Workplace Health, Safety & Welfare Regulations 1992 Personal Protective Equipment Regulations 1992 Display Screen Equipment Regulations 1992 (the previous six regulations are based on EC directives and are known collectively as ‘the six pack’) Reporting of Injuries, Diseases & Dangerous Occurrences Regulations (RIDDOR) 1995 Construction (Design & Management) Regulations (CDM) 1994 Electricity at Work Regulations ( 1990) Control of Substances Hazardous to Health (COSHH) 1989 Noise at Work Regulations 1989 Ionising Radiation Regulations 1985 Safety Signs & Signals Regulations 1996 Highly Flammable Liquids & Liquefied Petroleum Gas Regulations 1972 Fire Precautions Act 1971 Safety Representative & Safety Committee Regulations 1977 Health & Safety Consultation with Employees Regulations 1996 Health & Safety (First Aid) Regulations 1981 Pressure Systems & Transportable Gas Containers Regulations 1989

As hydraulic systems are nowadays invariably linked to Programmable Controllers (PLCs), the reader should also consult the occasional paper OP2 ‘Microprocessors in Industry’ published by the HSE in 1981 and the two later booklets ‘Programmable Electronics Systems in Safety Related Applications’, Book 1, an Introductory Guide and Book 2, General Technical Guidelines both published in 1987.

Electrical systems are generally recognised as being potentially lethal, and all organisations must, by law, have procedures for isolation of equipment, permits to work, safety notices and defined safe-working practices. Hydraulic and pneumatic systems are no less dangerous; but tend to be approached in a far more carefree manner. High pressure air or oil released suddenly can reach an explosive velocity and can easily maim, blind or kill. Unexpected movement of components such as cylinders can trap and crush limbs. Spilt hydraulic oil is very slippery, possibly leading to falls and injury. It follows that hydraulic and pneumatic systems should be treated with respect and maintained or repaired under well defined procedures and safe-working practices as rigorous as those applied to electrical equipment.

Some particular points of note are:

• before doing anything, think of the implications of what you are about to do, and make sure anyone who could be affected knows of your intentions. Do not rush in, instead, think;

• anything that can move with changes in pressure as a result of your actions should be mechanically secured or guarded. Particular care should be taken with suspended loads. Remember that fail open valves will tum on when the system is de­ pressurised;

• never disconnect pressurised lines or components. Isolate and lock-off relevant legs or de-pressurise the whole system (depend­ ing on the application). Apply safety notices to inhibit operation by other people. Ideally the pump or compressor should be iso­ lated and locked off at its MCC. Ensure accumulators in a hydraulic system are fully blown down. Even then, make the first disconnection circumspectly;

• in hydraulic systems, make prior arrangements to catch oil spillage (from a pipe-replacement, say). Have containers, rags and so on, ready and, as far as is possible, keep spillage off the floor. Clean up any spilt oil before leaving;

• where there is any electrical interface to a pneumatic or hydraulic system (eg, solenoids, pressure switches, limit switches) the control circuits should be isolated, not only to remove the risk of electric shock, but also to reduce the possibility of fire or acci­ dental initiation of some electrical control sequence. Again, think how things interact;

• after the work is completed, leave the area tidy and clean. Ensure people know that things are about to move again. Check there is no one in dangerous areas and sign-off all applied electrical, pneumatic or hydraulic isolation permits to work. Check for leaks and correct operation;

• many components contain springs under pressure. If released in an uncontrolled manner these can fly out at high speed, causing severe injury. Springs should be released with care. In many cases manufacturers supply special tools to contain the spring and allow gradual and safe decompression.

Incoming search terms:

Related posts:

Control principles for variable speed pumping:Soft starting and stopping
Engineering Data:Graphical symbols for pneumatic systems and components
Engineering Data:Standards and publications
Pipelines and valves:Valves and Discharge valves
Health and safety:Conveying operations
Review of pneumatic conveying systems:Material property influences
Conveying characteristics:The determination of conveying characteristics
RESERVOIRS, STRAINERS, FILTERS, AND ACCUMULATORS:fiLTRATION
BASIC HYDRAULICS:USE OF HYDRAULICS
Applications of hydraulic systems:Advantages of hydraulic systems
LINES, FITTINGS, AND SEALS:Hose Connection Side of Hose Fittings.
Fundamental Principles:Fundamental Principles
INTRODUCTION AND OVERVIE:HEAT TRANSFER
BASICCONCEPTS OF THE RMODYNAMICS:FORMS OF ENERGY
INTRODUCTION TO FLUID MECHANICS:CLASSIFICATION OF FLUID FLOWS

Leave a comment

Your email address will not be published. Required fields are marked *