Safety, Fault-Finding and Maintenance: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 reactive, i.e. responding 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 the British Standards Institute. They are approved by the Health and Safety Com- mission. 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 fac- tor 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, implementation or otherwise can be given in evidence in court.

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

In Britain the primary legislation is the Health and 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 environment, welfare facilities and adequate in- formation 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 de- scribed in sections 7 and 8 of the act. They are responsible for their own and others’ 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 and Safety Executive (HSE) implements the law by inspection and can enforce the law where failings are found. Breaches of HASWA amount to an indictable offence and the HSE has the power to prosecute the offenders.

The powers of HSE inspectors are wide. They can enter premises without invitation and take samples, photographs, documents, etc. People, as well as organizations, 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 organization. The first, an Improvement Notice, is given where a fairly minor safety failing is ob- served. This notice requires the failing to be rectified within a specified period of time. The second, a Prohibition Notice, requires all operations to cease imme- diately 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. Modern safety legislation, such as the Six Pack, recognizes the need to balance the cost and complexity of the safety system against the likelihood and severity of injury. The procedure, known as risk assessment, uses common terms with specific definitions:

Hazard The potential to cause harm

Risk A function of the likelihood of the hazard occurring and the severity Danger The risk of injury.

Risk assessment is a legal requirement under most modern legislation, and is covered in detail in standard prEN1050 ‘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, tempera- ture hazards (hot and cold), contact with dangerous material and so on. Failure modes should also be considered, using standard methods such as HAZOPS (Hazard and 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 judgments.

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

Fatality One or more deaths.

Major Non-reversible injury, e.g. amputation, loss of sight, disability. Serious Reversible but requiring medical attention, e.g. burn, broken joint. Minor Small cut, bruise, etc.

The next step is to consider how often people are exposed to the risk. Sugges- tions here are:

Frequent Several times per day or shift. Occasional Once per day or shift.

Seldom Less than once per week.

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 h? There may also be a need to consider the number of people who may be at risk, often a factor in petrochemical 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 classification will depend on the application. Some sources suggest applying a points scor- ing 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 × (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 in Figure 9.1 from which the required action can be quickly read.

Safety, Fault-Finding and Maintenance

Safety, Fault-Finding and Maintenance-0201

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 ac- ceptable 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 published by Butterworth-Heinemann.

Commonly encountered safety legislation:

Health and Safety at Work Act 1974 (the prime UK legislation) Management of Health and Safety at Work Regulations 1992 Provision and Use of Work Equipment Regulations 1992 (PUWER) Manual Handling Regulations 1992 Workplace Health, Safety and 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’) Machinery Directive 2006/42/EC (see note below) EN 286-1:1998 +A2:2005 Simple pressure vessels designed to contain air or nitrogen BS EN574:1996 +A1:2008 Two handed control EMC Directive 1993 Electromagnetic interference Low Voltage Directive 73/23/EEC and 2006/95/EC Safety of Fluid Power Systems, Hydraulics. EN982 1996 (see note below) Safety of Fluid Power Systems, Pneumatics. EN983 1996 (see note below) Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR) 1995 Construction (Design and 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 and Signals Regulations 1996 Highly Flammable Liquids and Liquefied Petroleum Gas Regulations 1972 Fire Precautions Act 1971 Safety Representative and Safety Committee Regulations 1977 Health and Safety Consultation with Employees Regulations 1996 Health and Safety (First Aid) Regulations 1981 Pressure Systems and Transportable Gas Containers Regulations 1989 The Machinery Directive (formerly 98/37/EC) is implemented in the UK as the Supply of Machinery (Safety) Regulations 1998 and requires manufacturers of ready to use equipment, machine or plant to state the equipment meets all the Essential Health and Safety Requirements (ESHR) of the relevant directives and legislation. The manufacturer gives the equipment a CE conformity mark. Note that compliance is a lot more than assembling pre-made units which are individually CE marked; CE plus CE does not make CE. Generally the manufacturer will provide a file showing compliance and listing safety procedures, safe ways of working etc.

The Health and Safety Executive website has many excellent publications which can be downloaded free as PDF files. The important EN982 and EN983 books and others can be found here:

http://www.hse, British Standards can also be found on the British Standards website:

As hydraulic and pneumatic 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 Techni- cal Guidelines, both published in 1987. These also can be found on the HSE website.

Electrical systems are generally recognized as being potentially lethal, and all organizations 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 veloc- ity 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 turn on when the system is depressurized;

• never disconnect pressurized lines or components. Isolate and lock-off relevant legs or depressurize the whole system (depending on the application). Apply safety notices and locks to inhibit operation by other people. Ideally the pump or compressor should be isolated and locked off at its MCC. En- sure 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 (e.g. 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 accidental 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.

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