It’s a tough job but someone’s got to do it.  Service is about dealing with clients and customers.  It is working with panics, tempers, expectations and misunderstanding, dealing with personalities and human beings.  On top of this, there is the safety aspect – not from people, though that can be bad enough, but from the equipment and environment.  By definition, when service intervention is needed, the equipment has stopped working normally.  The operation involved will often require many of the safeguards designed for protecting users during normal operation of the machine, over-ridding or removing, which leaves the service engineer to work in an environment of heightened risk. 

Within the European Union, Directives have been embodied in National Regulations, to ensure that work equipment does not result in health and safety risks regardless of age, condition or origin.  Emphasis is placed on Safety Management through effective organisation, planning, performance measurement and audit together with reviews to achieve continual improvement.  As a result, many organisations are establishing a culture that promotes worker involvement and commitment at all levels and emphasises the unacceptability of deviating from the established safety standard.

Within the service organisation environment, Customer demands are making it essential for service organisations to make preparations before attending a work site and even before negotiating the service contract.  The days when the service engineer turns up and assesses the situation “on the hoof” are drawing to a close.  Professionalism is being measured by the preplanning that is done.  This often has a major effect on reducing equipment downtime so it makes commercial sense as well.  However the only way that this can be carried out successfully and consistently is by documenting the work methods to a level of detail sufficient to demonstrate competence and a systematic approach to the quality of safety management in dealing with the risks.

Those who own or operate the laser equipment to be serviced also have responsibilities. It is they who have control of the workplace and it is they who work in it.  Customers are responsible for ensuring that their safety culture is known and understood by the service organisation so that their controls within the organisation are not compromised. This culture awareness can only be made known by good communication and the cooperation of the workforce, who themselves should have good attitudes and behaviour towards safety management.

In practical terms, the Customer needs to spell out all specific safety requirements and procedures that the service organisation or engineers are expected to follow. There is great advantage to be had if these requirements are well known before any actual service intervention activity is commenced as the service activity itself can be planned with these local requirements in mind. The major topics to be defined are include:

• Local safety rules regarding access to factory or operating areas, fire and evacuation procedures, special hygiene and PPE requirements, location of responsible persons in case of emergency, etc.;
• Control of the local area around the laser equipment and limits of any transfer of responsibilities;
• Control and authorisation of personnel within the area and especially of spectators;
• Methods related to withdrawal of laser equipment from production and the constraints that this may have on the rest of the plant;
• Control of the equipment so preventing unauthorised operation during the service period;
• Provision of sufficient space to allow work to be carried out safely.  This is particularly important if the laser equipment contains high voltage equipment.  There may be local Regulations that apply and require work areas to be defined under these circumstances;
• Anticipated timescales and other time constraints.

Service Organisations have responsibilities to ensure that their workers are adequately prepared to meet the challenges that face them when they arrive at the Customers premises and to do so in a way that does not place them or anybody else in jeopardy.  Preparation is really a demand for competence and thus for continual training.  Customers are increasingly asking for some documentary confirmation of competence as part of their safety management system requirements.  Similarly the Service Organisation must provide the correct tools and equipment to allow work to be conducted safely.  Establishing the safe working practices and methods before hand, not only defines the predicted way of working but also establishes the equipment that is needed. 

In addition to safety benefits, the use of the correct equipment for servicing means that the job gets done correctly, effectively, consistently, more quickly giving greater cost effectivity and better margins.  It is a win-win situation every time.  Yet time and time again, service engineers can be seen struggling with inadequate equipment and generally having to compromise safety to resolve the work around.  As important is establishing, before hand, the safe working practices and methods.  This not only defines the predicted way of working but also establishes the equipment that is needed.

The person generally at risk from any latent hazards is the service engineer him or herself.  In make-or-break situations, they can often be the people whose quality of service forms the measure used by the Customer to judge the whole service organisation.  Working safely is very high on many Customers priorities (though at the scene of activity, time may seem to be more important!).  

SAFE SERVICE PRACTICE
Local enclosure
Preventing human access to the laser hazard during laser service is a primary requirement but under service conditions, is often difficult. It should not be underestimate what can be achieved, and suggesting that this strategy is “impossible” should not be accepted.

Laser designers can perhaps contribute most but seem in many cases to be completely blind to the situation.  For example, only a small number of industrial laser models are modularised so that service intervention on the factory floor amounts to little more than simple substitution of the modules.  These modules are pre-aligned and need no further (or very minimal) optimisation once fitted.  This means that service can be completed with complete safety and the possibility of exposure to laser radiation eliminated.  Additional benefits often include improved lifetime of components and consistency of laser performance.  The majority of lasers, however, are not designed like this and thus additional engineering measures may have to be limited by what is reasonably practicable.  Where a good level of protection is not achievable, access may need to be prevented by appropriate use of barriers, beam tubes and local enclosures allowing access only to the areas where it is essential to the service operation.

Peripheral enclosure
Whenever laser radiation presents a reasonably foreseeable risk of harm, a laser-controlled area should be established to enclose the hazards.  The area needs to be very clearly delineated, with access strictly limited to authorised persons only.   The authorised persons should either have adequate safety awareness training to ensure that they are able to deal with the heightened risk correctly or be under very close control and supervision.

The boundaries of the laser controlled area need to be well defined.  Warning signs should be clearly displayed on the outside of the laser-controlled area using the laser hazard warning symbol and stating the restrictions imposed together with the precautions to be adopted on entry. Complete enclosure of laser-controlled area is desirable but may not always be necessary provided that access into the area is adequately controlled and no unreasonable risks exist to persons outside the area. 

Interlocks
Industrial machines often employ interlocks on the laser enclosures - IEC60825-4 gives guidance.  This method of protection provides an excellent method of mitigating the laser hazard especially for machine operators.  During the service activity, these interlocks may have to be over-ridden to allow operation during establishing (or proving) a repair.   In these situations it is important to use only the minimum of over-rides and to limit the over-ride condition to a minimum, removing over-rides as soon as their use is no longer required and not simply leaving them on until it is convenient to remove them.  A record of all interlocks that have been over-ridden should be maintained so that the service engineer can immediately gain an overall view of the situation.

Administrative control
Where there is risk of injury within the laser controlled area but where it is not practicable to control access by engineering means, then administrative procedures may be necessary.  Signage becomes very important with illuminated warnings preferable, to indicate when it is safe and when it is not safe to entry the area.  The installation of conventional Emergency Stop actuators on the inside of the laser-controlled areas provides additional means of terminating emission in the event of an emergency.
Any administrative controls require inclusion in the local information to ensure that local workers understand and abide by the controls implemented.  This information should be reviewed on a regular basis to ensure continued relevance. This information should include:

• Description and purpose of the equipment;
• Name and contact point of the local Laser Safety Officer;
• Name of person authorised and in control of the service work;
• Working procedures to be adopted when inside the laser controlled area
• Actions to be taken in the case of an emergency, such as an equipment failure of a suspected accident;
• Details of requirements for authorisation of hazardous operations, such as procedures that may required a local “permit to work”

Working with administrative controls in place, inherently means that the risk of injury is heightened.  Additional steps need to be taken – these include:

• Providing adequate training to all personnel involved;
• Ensuring the security of all laser components;
• Using adequate beam stop methods to prevent inadvertent beam paths;
• Using enclosures (even temporary ones) to encase the laser beam path and to extend this encasement as far as reasonably practicable;
• Confining the beam with well-defined areas;
• Using screens or curtains to contain the laser radiation (N.B. The standard IEC 60825-4 gives guidance on this subject);
• Minimising the risk of specular reflections by careful control of all objects with shiny surfaces (tools, jewellery etc) used or worn around the beam path.

Personal protective equipment
If the risk assessment and the engineering means cannot prevent access to the laser radiation hazard, then the use of personal protective equipment (PPE), i.e. laser protective eyewear, is essential.  PPE should not be used in place of other controls, but in addition to them.

In some cases (e.g. when servicing UV Laser sources) it may be necessary to provide wear other protective clothing when working in a laser-controlled area.  Masks, gloves and occasionally whole body protection may be required.

Records
As part of any risk assessment undertaken prior to the commencement of service work, any classification change to the laser that the removal of protective covers may make should be noted; together with disabling any protective features may cause a change to the performance of the laser product thereby increasing the risk of injury. Thus it is important to keep a record of all service activities and operations and any resulting changes to the performance of the laser equipment.

Beam path alignment
Servicing embedded laser products can greatly increase the risk of injury.  Additional controls to reduce the likelihood of an errant laser beam should be put into place during beam alignment and other such beam path operations including:

• Limiting the range of movement of beam steering components
• Checking beam alignment close to the laser before allowing the beam to travel into the full beam delivery system;
• Using large area beam stops to allow for misalignment;
• Using visualising alignment aids such as cameras or fluorescent or heat sensitive screens;
• Using non-reflective coating or diffusely reflecting surfaces on tools in addition to the best practice of being very tidy and keeping all tools away from the beam path area.

EXAMPLES OF SERVICE IMPORVEMENTS
During the authors’ years of experience with laser use and laser servicing, many examples have arisen where the above principles have not been considered sufficiently and situations have resulted in distress or injury.  Below are a few selected examples, which act as illustrations of how it could have been done better:

Example 1
This example involves a high power (several kilowatts) CO2 laser, which generated a beam travelling horizontally 3 m above the floor level.  The beam was projected horizontally through a beam tube to a turning mirror that directed the beam vertically downwards to the focus device and thence onto the workpiece being processed.  The whole of the beam path was enclosed, but on one occasion the beam path had to be adjusted and the turning mirror had been removed to allow this work.  There was some confusion about the process and the laser was energised.  The beam was now directed not at the workpiece but at part of the roof structure, which caught fire.  This accident caused more embarrassment than injury but was serious none the less.  The mirror assembly was interlocked but the interlock took the form of a water pressure switch on the water cooling to the mirror assembly.  If the mirror were removed, the cooling water supply pressure would change and the interlock (switch) would operate to prevent laser action.  However on this occasion the mirror was only displaced a small distance and the water was not disconnected.

The lessons derived from this event are twofold.  Firstly, the physical position of the mirror assembly should have been monitored directly and not indirectly and suitable interlocks (i.e. fail safe, proven design) introduced.  Secondly, the administrative controls put in place were not sufficiently well thought out, recorded or understood. (Nevertheless, a beam stop was fixed to the roof structure should a repeat of the event occur!)

Example 2
Here, a high power CO2 laser where the laser was mounted remote to a flat bed sheet metal cutting machine.  The beam was emitted horizontally from the laser at about 1.8 m above the floor level.  The beam path between the laser and the machine was contained within a substantial tube during normal operation.  Beam alignment necessitated the tube to be removed.  The service engineer had taken all the precautions that he thought reasonable by indicating that the laser was being serviced and by restricting access to the area where the laser machine was situated.  Both barriers and signs were put at the entranceways.  Next to the laser was a bench with a kettle and tea making equipment (cups and tea bags).

During the service activity the laser was operated with the beam path tube removed and when a work break was taken the laser was left energised with the machine unmanned.  During this period, another worker deciding that it time for a cup of tea and with the beam tube removed, he now had a clear path to the bench where the kettle and cups were kept. The worker disregarded the barriers and signs and walked through the laser beam, receiving a burn on his neck from the laser beam.  Not only did the man suffer a serious burn and had to laid off work, but because the period of sickness was greater than three days, a report had to submitted to the local Health and Safety Executive office.   In addition to the cost and time consumed in having the worker injured, the employer had a significant amount of grief from the government enforcement agency.

The lessons learnt included identifying and preventing secondary activities within the hazard controlled area (removal of the kettle and tea making facilities), the installation of improved barriers, modifications to the laser machine interface that allowed the beam tube to be removed from its normal position to a temporary position that still offered some protection from accessing to the beam, laser safety awareness training to all staff who may have access to the laser system, and improved safety awareness training throughout the Company.

Example 3
This example did not involve an injury, but the service situation was extremely costly from a production point of view.  A high power Nd:YAG laser formed part of a laser process machine.  The beam delivery system used an optical fibre to deliver the laser output to the focus lens assembly.  The machine was situated in the centre of a production line and about 60 workers worked in the immediate area.  The factory worked 24/7 manufacturing parts for the automotive industry.  The laser worked well and a problem was only evident when the laser required planned service.  During such servicing the design of the laser was such that the protective housings had to be removed and alignment aids, held on retort stands, were erected.  In the absence of effective peripheral guarding, all workers on the production line to be evacuated and hence the production line stopped, placing the service engineer under extraordinary pressure to finish quickly and get the production line running again. 

The driver for improved safety during service was the elimination of production downtime.  Service engineers said that it could not be done and surprisingly, the laser manufacturer was not really interested in helping.  Nevertheless, the user company put together a team and adopted a structured problem solving approach.  The team was made up of the service engineers, the machine operators and production engineers aided by a facilitator. Their excitement was the result of actually being asked to solve the problem! They produced a solution in the form of a small amount of specialised tools and some jigs together with some carefully worked out procedures. Their implementation allowed production to continue during the laser service activity and produced more reliable and repeatable laser operation.  All costs were set aside the first time the laser was serviced because production continued.

CONCLUSIONS
During service activities, key hazard controls fall into three main categories.  All these categories need addressing.  The categories are:

• Organisational (involving risk assessment, training and supervisor control),
• Procedural (including definition of working methods) and
• Equipment (including necessary tooling and jig, temporary guards or screens and signage).

Consideration of these key hazard control categories together with establishing an environment that encourages well-defined good practices and continual improvement, significantly reduces the risks to all those involved in service activities.  As a bonus, significant improvements in laser performance and reliability can be achieved at no increased cost.