1          General principles

1.1      Introduction

If the assessment of compliance with the minimum requirements and general occupational safety and health requirements (OSH requirements) fails to confirm the fulfilment of the requirements and an answer obtained is negative, the use of appropriate safety measures is required. The application of these measures should lead to achieving the compliance with the OSH requirements. This may require the machine user to repair machine components and/or safety equipment, upgrade or modify the machine and/or safety equipment (provide additional safety measures, change technology and manufacturing conditions, etc.), change the machine operation environmental conditions (improvement of ambient lighting) and, in extreme cases, when there are no acceptable solutions for solving the problem, it would require a decision to decommission the machine (e.g. when the risk assessment results indicates its unacceptable level). After the application of safety measures meeting the specified requirement, this risk should be reduced to a level corresponding to at least the legal requirements with regard to the current state of the art.

1.2      General principles of risk reduction through the application of safety measures

For risk reduction, the following order of precedence of activities shall apply [1].

1.2.1    Inherently safe design solutions

Inherently safe design solutions eliminate hazards or reduce the risk by appropriate selection of the design characteristics of the machine itself and/or interaction of people exposed and the machine.

1.2.2    Engineering control measures and/or supplementary protective measures

Considering the use of the machine in accordance with the intended purpose and foreseeable inappropriate use, engineering control measures or complementary protective measures are used to reduce the risk, if it is not possible to eliminate the hazard or sufficiently reduce the associated risk using inherently safe design solutions.

1.2.3    Information on the use

Information concerning the use, in terms of the identified residual risks should include in particular:

-          machine operating procedures appropriate for the personnel who will operate the machine or other persons potentially exposed to the hazards posed by the machine,

-          recommended safe methods to use the machine and related requirements for required training,

-          relevant information, including a warning about residual risks occurring at different stages of machine life

-          description of the recommended personal protection equipment, stating the necessity for its use and provision of training in its use.

Adoption of abovementioned measures should lead to achieving a sufficient risk reduction, which is the condition in which:

-          all types of work and methods of interaction are taken into account,

-          all hazards were eliminated or risks caused by them were reduced to the lowest level possible in practice,

-          all new hazards that have emerged along with the protective measures were properly demonstrated and appropriate protective measures were used,

-          users were fully informed and warned of the residual risks,

-          mutual compatibility of protective measures used was achieved,

-          protective measures taken do not adversely affect the working conditions of the operator or the usefulness of the machine

Protective measures must permit easy use of machines in accordance to their intended purpose, so that users do not attempt to defeat or circumvent the actions of those measures. Such actions may occur when a safety measure:

-          slows down the production process

-          conflicts with another activity

-          interferes with the user’s preferences;

-          is difficult to use

-          engages persons other than the operator

-          is not recognised by the user

-          is not accepted as appropriate to the implementation of the intended function.

1.3      Ensuring the compliance with minimum safety requirements through the use of appropriate safety measures

The operation of machines and equipment requires the fulfilment of minimum safety requirements, which sometimes involves the necessity for upgrading works. The employer often has to interfere with the machine structure and also handles other maintenance tasks (such as repair, refurbishment, maintenance, etc.). However, if the user makes changes to increase the production efficiency and quality, or a change in the scope of use of machines and equipment, the applicable European interpretation “a product which after commissioning has been changed considerably altered by upgrading (modification) is considered to be a new product”.

To assess and maintain the condition of operated machines and equipment, it is essential to pay attention to the following aspects, as defined in the regulation [2]

1.3.1    Control elements

Table 1.1 Features of control elements

Item	Feature considered	Fulfilment of the required feature
1	Marking method	·       clearly legible letters in Polish ·       with use of intelligible symbols
2	Location of labelling of control elements	·       on the elements ·       above the elements ·       under the elements
3	Colours of control elements	·       start (enable) – green or white (grey or black is also acceptable) ·       stop (disable) – red or black (white or grey is also acceptable) ·       emergency stop – red on a yellow background, distinguished by shape (mushroom-shaped button).
4	Location of control elements	·       preventing operator from a contact with hazardous elements of machines and equipment: - moving parts of the drive - tools - sharp edges and corners - live parts - hot surfaces - aggressive chemicals

Features of operational safety-related control devices are shown in Table 1.1.

Control elements should also be protected against accidental change of position. The methods to meet this requirement are shown in table 1.2.

Table 1.2. The method of protecting control elements against accidental change of position.

Item	Protection against accidental activation	Method of protection
1	Mounting and location	·       placing buttons in cabinet depressions or in flanges ·       maintain a sufficient distance between controls (to prevent unintentional start-up of a few of them) ·       enclosing of the pedals
2	Application of solutions forcing a deliberate operators’ action on control elements	·       assurance of adequate minimum activation force (5 N) ·       application of a double-acting control lever (performing two different movements is required to enable) ·       use of a confirming button (manual or foot control) ·       mechanical lockout position interlock (e.g. locks, key locks).

 

1.3.2    Visibility of danger zones from the operator station

The control panel shall be located so as to provide the operator with a possibility of observing all places of work. The operator must be able to verify if no person is present in hazard zones.

If the operator is unable to do so, before the machine is started, the safety system should automatically send an audible or visual warning signal, which should be received at all machine operator stations. The time between the transmission of the signal and the start-up should be long enough so that the person exposed can avoid the hazard (leave the danger zone or prevent the machine start-up (emergency stop buttons at the work station).

1.3.3    Control systems

An appropriate control system should be provided to prevent dangerous operation of the machine and keep safety features across the range of works and machine operating conditions (temperature, humidity, vibration, impacts, electromagnetic fields, etc.). Control elements directly performing safety functions should be appropriately fail-safe (e.g. power failure or fluctuations, short circuit between conductors, contactor failure, relay or distributor failure, safety switch disconnection failure, broken spring, software malfunction).

1.3.4    Starting up the machine

The design of the control system is to prevent the machine from starting in an unpredictable and spontaneous manner in hazardous conditions (movement of tools, workpieces, etc.). Unexpected start-up shall be prevented in the following circumstances:

-          after rectification of a control system fault

-          after power is supplied following a power failure

-          following an emergency stop

-          after activation of electro-sensitive protective equipment in hazardous conditions (interlocking, electro-sensitive protective equipment)

-          after closing of interlocking movable guards in hazardous conditions

-          Immediately after connecting the machine to a power source (without activating a start-up signal via a control element).

1.3.5    Normal stop

Machines should be fitted with a control system designed to stop them completely and safely. Depending on the type of hazard at the work station there should be controls intended to stop the whole machine or some parts of it, so that the machine remains safe. Power supply of relevant drives of the machine is disconnected in the case of stopping the machine or its dangerous parts.

Control elements should be located so that the operator can see the stopped elements. The stop function (STOP) should have a priority over the start function (START). This means that with the simultaneous operation of the control element for starting and stopping, the machine cannot be started and during operation it should stop.

Activation of the machine stopping system should not cause any hazard, e.g. effects of rapid action of inertia forces, as well as the presence of other residual energy (loosening, tools and objects slipping in holders, breaking of tools, collision of materials and workpieces, loss of stability of workpieces, etc.).

1.3.6    Emergency stop

Due to hazards posed by moving machine parts, its drives or moving tools or processed materials and depending on their stopping time, machines is fitted with an emergency stop device. Emergency stop controls should be:

-          easily accessible

-          located in all places and positions occupied by operators (i.e. the control panel, the place of feeding and receiving materials),

-          located in places which are not visible from operator stations.

The emergency stop device should efficiently shut down all of its hazardous movements regardless of the type of machine operation.

1.3.7    Emission or ejection of substances, materials

Due to a possible emission or ejection of its substances and materials by the machine, the personnel shall be protected against mechanical injuries and thermal impact. Sources of hazards in this case may be, for example containers of liquids or gases and pressurised lines (rigid, flexible and connecting tanks and equipment).

Protection against hazards can be provided by:

-          relocation of work stations considering sources of hazards

-          the use of guards, insulation, etc.

-          proper fastening of lines conveying media under pressure (e.g. using hangers, hooks, supports, etc.).

-           use of enclosures, screens, panels in places of expected ejection of steam, water, liquid metals, plastics and other media under pressure.

1.3.8    Falling or ejected objects

To provide protection against falling or ejected objects:

-          clamp tools and work pieces in suitably selected holders, fixtures or tables with mounting holes.

-          use guides and rests for work pieces.

-          fit the machines with suitable devices to prevent work piece ejection

-          use position stops protecting against crossing the extreme positions and falling of machine and equipment parts (from slides, guides, etc.)

-          use position stops of handled materials and products (moved from conveyors, cranes, etc.).

-          provide appropriate mechanical strength of guards, screens, enclosures of hazard zones (allowing absorption of the energy of ejected objects and tools).

1.3.9    Emission of gases, vapours, liquid or dust

In order to reduce emissions of harmful agents in the work environment it is necessary to use enclosures, hoods, suction cups and other devices (extracting agents harmful to health) located near the sources of emissions and interoperating with local exhaust system devices.

1.3.10 Detachment or disintegration of machine parts

Detachment or disintegration of machine parts can be prevented by selection of appropriate materials for their construction, characterised by:

-          appropriate mechanical properties,

-          resistance to corrosion, abrasion resistance, etc.

-          suitability for the existing conditions (pressure, speed, temperature, humidity, etc.),

and appropriate selection of guard designs in places of anticipated zones of separation or disintegration of parts of machines.

1.3.11 STABILITY

The machine exposed to overturning or execution of unintended movements under the influence of external and internal forces (e.g. wind pressure, vibration, shock, load) should be anchored to the ground. For this purpose holders, anchors, bolts can be used.

1.3.12 Moving parts

Use (fixed or movable) guards or other safety devices (non-barrier engineering control measures) to prevent contact with hazardous moving parts, i.e. power transmission elements (shafts, couplings, gears, belt or chain transmissions, etc.) and elements in the work zone (tools, workpieces).

Guards should meet the following requirements:

-          use of materials suitable for the process conditions (resistance to temperature, corrosion, abrasion, suitable strength, impact resistance, etc.).

-          no sharp edges and corners

-          reliable connection with the machine during its operation (protection against unexpected opening, falling away, repositioning, etc.)

-          location relative to a danger zone (movable parts) maintaining the safety distance specified in the Polish Standard

-          a possibility of convenient observation of the work process (selection of the appropriate shape and position, use of transparent materials or openings in the guard)

-          selection of the guard type depending on the frequency of access to the danger zone (fixed guard, movable interlocking guard, movable locking guard, movable automatic, controlling guard)

-          matching to the number and location of danger zones (local guard, full barrier guard).

1.3.13 Lighting of places where work is performed

Ensure local lighting (where ambient lighting does not provide appropriate lighting parameters for work zones and places where adjustment, maintenance and repair activities are performed) and the type of light sources which is appropriate to the type and location of the activities carried out (incandescent, discharge lamps) and luminaries (conforming with regulations and standards and lighting measurement results).

1.3.14 Extreme temperatures

Human contact with elements of a very high or very low temperatures (flame, hot products and waste, tools, installations) should be prevented. For this purpose the following can be used:

-          guards, covers or screens

-          insulation materials (inside or outside the equipment).

Machines should be arranged so as to eliminate the necessity for the operator’s presence at the place of exposure. Zones (surfaces) posing a hazard should be appropriately labelled.

1.3.15 Warning signals

Light and/or acoustic signals to indicate hazardous situations (machine start-up, change of parameters, failure), should be selected so that the generated signals are unambiguous and can be easily noticed and distinguishable from other signals.

For this purpose, the following should be used:

-          an intermittent (flashing) light signal to indicate a higher risk or a more urgent need for action

-          a continuous signal to indicate a lower hazard

-          a sound signal with modulated frequency to indicate a higher risk or a more urgent need for action

-          a fixed frequency signal to indicate a lower hazard

-          a continuous warning signal to call for evacuation.

Light warning devices should be located in highly visible places and selected depending on the emitted signal colour, i.e.:

-          red – failure, malfunction (emergency)

-          yellow – warning (abnormal condition, imminent emergency)

-          green – safe condition (normal condition)

-          blue – a condition in which the operator action is necessary (indicating about the necessity for action by the operator).

1.4      Use of machines

Machines and equipment should be used in accordance with the guidelines and recommendations specified by the machine manufacturer in the user’s manual. During the use of machines and equipment particularly dangerous works may be carried out. These works referred to in the regulation [3] and other regulations on occupational health and safety or operating instructions of machines and equipment. They may also be works determined by the employer as works with an increased hazard level or performed in more difficult conditions.

The employer is obliged to determine and update the list of particularly hazardous activities carried out in the workplace The employer should determine the specific requirements of occupational health and safety when performing works which are particularly dangerous, and in particular ensure:

-          direct supervision of these works by designated persons

-          appropriate engineering control measures

-          employee training, including in particular personal division of works, the sequence of task completion, requirements for safety and health at the individual activities.

The employer shall also ensure that access to places where particularly hazardous work is carried out is restricted only to authorised and properly trained personnel.

It is important for safe operation of machines and equipment to carry out a suitable occupational risk assessment for all activities performed by employees. The risk assessment for all works performed by employees can also identify all hazards and raise awareness of their occurrence among employees, supervisors and the employer, and therefore the required application of appropriate engineering controls and organisational measures.

Works should also be properly arranged, taking into account:

-          ensuring appropriate access to work stations, i.e. appropriate distances of passageways between machines, and between machines and room furnishings

-          providing access, including access paths to places where operation activities are carried, appropriate to the anthropometric dimensions of the operator, type of activity and the tools used to achieve an acceptable level of risk

The employer may also not permit an employee to do work, for which the employee did not acquire sufficient knowledge of the health and safety regulations and rules. The employer should inform employees about the risks associated with machines located in the workplace or its environment, and any changes made in this respect to the extent to which these changes can have an impact on safety, even when the employees do not directly use these machines. The employee shall confirm in writing that he/she has read the regulations and occupational safety and health rules.

The employer should provide personnel with up-to-date safety instructions for permanent use.

In addition to the condition of machines and equipment, appropriate selection and adaptation to the type of work is essential for the safety of personnel. While selecting the user (employer) should take account the specific conditions and type of work. It is also important to identify the hazards existing in the plant or in the workplace. While selecting of machines and equipment the following aspects are particularly importance: the range of applications specified in the operation and maintenance manual (O&M manual), potential risks resulting from the operation in a particular environment, spatial and power supply on-site, safe supply and/or discharge of energy and raw materials and products, appropriate space (to carry out operation activities, cleaning, repairs and maintenance), machine or equipment technical parameters, requirements for operators (e.g. qualifications, experience, physical fitness and motor skills, occupational psychological fitness).

1.5      Personnel training and qualifications

Personnel should be provided with appropriate qualifications and licences         necessary for operation of certain groups of machines and equipment, if operation, repair, refurbishment or maintenance cause a hazard to the personnel safety or health. Required qualifications are set out in the applicable industry regulations and depend on the type of work equipment and its parameters, e.g. maintenance and driving motor-driven forklift trucks and replacement of gas cylinders in forklift trucks fuelled with gas, in accordance with the regulation of the economy minister on occupational health and safety in the use of forklift trucks [4].

It is the duty of the employer to provide training for personnel on occupational safety and health [5] before permitting them to work (initial training) and to conduct periodic safety training. The initial training consists of the general initial training, so-called general induction training and on-the job training, so-called toolbox training. In the course of the general induction training the employee should become familiar with the basic rules of occupational safety and health contained in the Labour Code, collective agreements or employee handbook, with the effective occupational safety and health rules and regulations at the workplace, as well as the principles of first aid in case of emergency. The toolbox training should ensure that the workers become acquainted with safe work methods with the use of machines, including the common environmental factors occurring at the work station, occupational hazards associated with their work and methods to protect against hazards. The toolbox training ends with a test of knowledge and work skills in accordance with the provisions and rules of occupational health and safety. Completion of the general initial training and the on-the-job training shall be confirmed by the employee in writing on the initial training sheet, which is stored in the employee personal records. Periodic employee training in the operation of machines and equipment (employed as workers) shall be carried out not less than once every 3 years, and for job where particularly dangerous works are carried out, at least once a year [5]. The purpose of this training is to update and refresh occupational safety and health knowledge and skills and to familiarise employees with the new engineering and organisational solutions in this area. Periodic training ends with a test to verify the knowledge acquired covered by the training programme. The training provider shall confirm its completion by an appropriate certificate, which is stored on file in the employee’s personal records.

Personnel should be made aware of the hazards related to the machines and other equipment located in the workplace or its vicinity and any changes in this respect to the extent to which these changes affect machines and other equipment located directly in the workplace and its vicinity, even when the employees do not directly use these machines. During the personnel training the employer shall implement solutions which ensure that:

-          employees whose duties include the operation of machines, have been suitably trained, which also includes all the risks associated with the use of these machines taking into account unusual (abnormal) situations

-          personnel performing repairs, upgrades or maintenance have been trained in this respect.

1.6      Maintenance works

Maintenance (lubrication, adjustment, replacement and refilling with operating fluids) should be performed during machine downtime. Appropriate control device should be used (if it is not possible to perform the work during downtime), such as a limited movement control device allowing to reduce the distance by which a hazardous item moves, a hold-to-run control device allowing for movement of the hazardous item only during the control button on-time). During maintenance works mechanical devices should be used to prevent unintended change of position of dangerous parts of the machine (e.g. by gravity, spring action), such as wedges, supports, struts, holders, etc. In order to record any repairs, maintenance, replacement of fluids a maintenance log should be maintained.

1.7      Isolation of energy sources

Means for disconnecting electricity (e.g. disconnectors, circuit breakers, plug-socket sets) should be applied and properly labelled. For electric machines with a power below 1 kW and current value of less than 16 A a plug-socket system may be used in this case. Machines and equipment should be fitted with devices for shutting off the flow of gas, liquid, process steam and other energy carriers including appropriate labelling. Positions of the power supply shutting of components should be labelled to identify the “on/off” status. Devices for disconnection from power sources should be key lockable in the lock out position (e.g. a padlock).

1.8      Signs and other safety labelling

If hazards cannot be eliminated by any other protective measures, use signs and/or safety colour coding and other marking (pictograms, notices). Safety signs (prohibition, warning, mandatory signs, escape and information signs) should be compliant with the templates specified in the Polish Standards. Safety marking should be placed in locations of an identified hazard or in its immediate vicinity. Places where there is a risk of collision with obstacles, falling or of objects falling downs should be marked with safety colour codes – alternating yellow and black or red and white diagonal stripes (stripes at an angle of approx. 45° of similar dimensions).

1.9      Access to places where machines and equipment are used

Appropriate space should be provided for walking or standing, reducing the risk of falling and slipping (e.g. chequered plate, steel grating, non-slip mats). Access to work areas located at different levels should be safe. This can be ensured by the use of stairs, ladders and access walkways fitted with protective railing with a height of 1.1 m. Where work at height is carried out, install anchor points for personal protective equipment providing protection against falls from height.

1.10   Fire, explosion and electric shock

Electrical cables, lines for transmission of gas, liquid and other media should be protected against mechanical damage, effects of fire and other factors (by running cables in floors, pipes, suspended, etc.). Use systems and electrical equipment versions which are suitable for the existing hazards (e.g. explosion proof). Work stations should be fitted with devices for inspecting and maintaining an appropriate level of operating parameters (temperature, pressure, voltage and current, etc.). Protection against fire, explosion and electric shock is provided with the use of engineering measures which eliminate electricity-related risks or such risks can be prevented (e.g. by application of electrical safety measures, if direct and indirect contact is possible, or by enclosing electrical equipment in order to prevent access to them). Solutions should also be applied to prevent or limit a possibility of generation of dangerous electrostatic charges or means for their discharge (prevention of the accumulation of charges or their discharge).

1.11   Bibliography

1.    PN-EN ISO 12100: 2011 Safety of machinery – General principles for design – Risk assessment and risk reduction

2.    Regulation of the Minister of Economy of 30 October 2002 on the minimum requirements concerning the occupational safety and health while using engines at work. Journal of Laws No 191, item 1596 (as amended).

3.    Regulation of the Minister of Labour and Social Policy of 26 September 1997 on general health and safety rules (consolidated text). Journal of Laws of 2003, No. 169, item 1650 (as amended).

4.    Regulation of the Minister of Economy of 10 April 2002 on occupational safety and health when operating forklift trucks. Journal of Laws No. 70, item 650 (as amended).

5.    Regulation of the Minister of Economy and Labour of 27 July 2004 on training in respect of occupational safety and health. Journal of Laws No 180, item 1860 (as amended).

1          Methodology of periodical inspections of protective devices and guards for machines

1. Introduction.

To understand the need to systematize the issues related to the inspection of protective devices, one has to realize how important they are for the industry.

As a result of the industrial revolution, more powerful and universal machines were created, powered by new energy sources such as electric motors or steam engines. The quality and productivity of work increased, but also new threats occurred that had not existed before. Bigger and faster movable parts of machinery posed a growing hazard to their operators. Thus, along with the importance of technological development, the importance of the problem of effective employee protection without limiting their productivity increased. The first and easiest solution was the attempt to fence off the machine operator from dangerous movable parts. It is possible especially in the case of movable parts of power transmission system. However, it becomes a big problem when it concerns operating parts. Due to technological reasons, at least a temporary intervention in the workspace is often necessary, e.g. in order to supply material or receive manufactured parts. At the same time, technological requirements and demand for maximum productivity made the work of operating the machine increasingly monotonous and uniform. It is known that progressing fatigue in an employee causes loss of concentration and increases the likelihood of improper activities, which might result in a dangerous accident. Therefore, it was necessary to introduce technical solutions that would allow for automatic control of the location of the operator in relation to hazardous zones. Historically, the first such devices were two-hand control devices applied to presses. With the development of technical capabilities, especially the common development of computerization, created devices were more and more effective. At the same time, the importance of proper use of protective equipment was increasing, so that they can provide designed functions as effectively as possible.

Protective devices implement their functions well only if they are in proper working order. Correct operation of these devices is guaranteed not only by their proper design and installation, but also adequate controls. Principles of conducting controls are regulated by law. The current legislation is listed and discussed below.

3.1. Initial inspections

Initial inspection is a control which takes place after installation and before putting a device into service for the first time or after installation on a different working station or working area. The scope of this inspection mainly includes validation of the safety function (presence detection or intrusion detection function [Table 1]). Therefore, tests should be performed to check whether:

1.    None of the dangerous parts of the machinery can be activated if a person (or any part of their body) is in a position that activates the protective device.

2.    Starting the protective device while the machine is operated and performs a hazardous work should result in switching the machine into a safety mode before any part of the human body appears in the risk zone. The hazardous operating mode cannot be restarted until the the protective device is restored to its normal conditions, and the machine is manually restarted.

 

Table 1 The scope of initial inspection.

 

In addition, the scope of initial inspection guards the following tests:

1.    Check whether the protective device is in the correct distance from the danger zone, specified by the manufacturer

2.    Check whether there the additional protective measures were undertaken (if necessary) to provide access to the danger zone which is unprotected by the protective device.

3.    Check (measure), whether the total time of reaction / response of the protective device is equal to / less than the time stated by the manufacturer.

4.    Verify whether a person cannot stay between the danger zone and the detection zone.

5.    Check the operation of the protective system in accordance with the manufacturer's instructions.

6.    Check whether the protective device has a reflective surface that could reduce the device's detection capabilities.

7.    Check whether the manufacturer's requirements of the machine and the protective device are compatible (within the control and connection areas).

8.    Check the monitor that shall indicate the necessity to stop (if applicable); whether it is well-placed and tuned and whether it works in accordance to the supplier's instructions. Check whether the the means by which it is indicated to stop the system can be assessed by the operator correctly (whether they are legible to the operator).

9.    Check how the ”muting“ (shadowing) and suppression (if applicable) functions work. Check whether the device is properly protected against unauthorized use of these functions.

10. If your device has two channels, please check both.

11. Check whether the device is protected against unauthorized use with a password, key or dongle.

12. Check whether all functions, including start-up and restart, are available

a.    The protective device works in all the important and relevant modes of the machine.

b.    If it is possible to turn off of the protective device, the machine should complete the hazardous operation at a given time.

13. The device for protection against overvoltage should be connected in parallel to the load, and not parallel to the output circuits.

14. Monitoring safety relays should be tested in accordance with IEC.

15. Check whether safety is maintained during the operation of functions such as muting, blanking

16. Check the brakes and clutch (if applicable) in accordance with the manufacturer's instructions.

Table 2 The scope of initial inspection.

 

3.2. Periodical inspections

Periodical inspections verify whether the operation of the protective device has damaged it or not.

Table 3 The scope of periodical inspection.

 

The scope of periodical inspections (except inspectioning whether the device meets the requirements specified by initial inspection) includes the following tests:

1.    Check whether the the protective device is properly installed in the location designated / confirmed during installation and commissioning.

2.    Check whether  the additional protective measures were undertaken (if necessary) to provide access to the hazard zone which is unprotected by the protective device.

3.    Check whether the requirements regarding stopping the machine are met in a satisfactory manner

4.    Ensure that a person cannot stay between the danger zone and the detection zone (hazardous), except for the restart interlock state.

5.    Check whether the main control elements of the machine work properly and it they require maintenance or replacement or not

6.    Check the machine to make sure that there are no other mechanical or structural aspects which would prevent stopping the machine and whether there are no other situations that require any additional protection measures.

7.    Check the control system and the connection of the machine with the protective device to ensure that there no modifications have been made which could affect the safety system.

8.    If possible, check the cycle of preparations for re-start

9.    Perform functional tests (listed below as well as the ones recommended by the manufacturer)

3.3. Functional check

Functional checks should be carried out every day by an employee that operates the particular working station. The scope of functional check guards the following tests:

1.    Check whether protective equipment (including muting sensors, if applicable) is securely mounted and there are no signs modification, destruction or relocation.

2.    Check whether the access to hazardous parts of the machine is possible from any side unprotected by the protective device and if the additional mechanical protection such as side and rear guards are in the right place and are not destroyed.

3.    Check whether it is possible for a person to stand between the sensitivity (sensor) zone and the hazardous zone of the protective equipment .

4.    Check the effectiveness of protective equipment with the power on, but with the machine at rest.

·         Check whether the protective equipment is working by checking the status of relevant indicators and ensuring that protective equipment is not in the muting mode.

·         Insert the appropriate testing cylinder testing in the sensitive zone of the protective device.

–     In the case of light curtains, the testing cylinder should be moved down slowly (e.g. safety light curtain) close to one column of detectors, then close to the second column, and midway between the detectors. When the testing cylinder leaves or enters a light curtain, the light indicator that indicates activation of the device should change the status, and when the "test piece" remains in the detection zone – it cannot change its status.

–     In the case of pressure-sensitive devices, activate the mat / floor in several locations (using  the weight specified by the manufacturer) and check its function (e.g. by observing the light indicators). Check whether the mat detects the absence of human presence on it.

–     In the case of laser scanners, place the testing cylinder in the detection zone in several locations along the border. When the the testing cylinder leaves or enters a light curtain, the light indicator that indicates activation of the device should change the status, and when the "testing cylinder" remains in the detection zone – it cannot change its status. This must be checked for all available detection zones.

·         When the device uses the trip time timer function, you must start the machine and then put the testing cylinder in the protective device at such angle so that it interferes the least with the detection zone. Under no circumstances should you enter the danger zone. As a result of placing the testing cylinder in the detection zone, the machine shall switch to a stand-by mode or any other safe mode with no perceptible delay.

·         When the device uses the presence detection function, place the testing cylinder in the detection zone of the protective equipment and try to switch the machine on. Under no circumstances should you enter the danger zone. It should not be possible to initiate such hazardous operation when the  protective equipment works. For testing the protective mat / floor, such weight should be used so as to avoid standing near the danger zones.

5.    Check whether when the protective device is in the muting mode, the machine is not dangerous or safety is provided by other measures. Check whether the muting lights (if any) switch on when the device is muted.

6.    Check the detention effectiveness controller (if applicable),  whether it is well-placed and tuned and whether it works in accordance with the supplier's instructions. Check whether the means by which it is indicated to stop the system can be assessed by the operator correctly.

7.    Check whether the cabinets with electrical equipment / electronics are locked and the key is kept by a competent person.

8.    Check whether no physical indications occur of destruction of equipment or cabling.

Table 4 The scope of functional check.

 

3.4. Methods of  carrying out the inspection of protective devices

Depending on what should be checked, the inspection may just be a visual examination, it may require inducing the safety function, but it may  also require the parameter measurements of the device and the machine.

As already stated, many inspections are based on a visual check, such as checking whether the machine is in the correct position or has been moved as well as whether there are all of necessary protection guards or other additional protective devices. During the examination you can also observe the evidence of damage in equipment or wiring.

More advanced tests require interaction with the protective device, which usually is inducing the safety function. For light curtain or laser scanner the manufacturer usually provides adequate testing probe used for examinating the borders of the detection zone. Optoelectronic protective devices are equipped with an optical indicator indicating that the detection zone has been breached, making it easier to test. For light curtain, it is important not to carry out the test too quickly and to double check if any interruption of the light beam produces response of the device. Another thing is to keep in mind is that the device should change the status in the event of a breach of the detection zone, but it cannot change it when the testing probe remains in the zone. For testing of pressure sensitive mats, the zone breach occurs through entering the mat.

Fig. 1. Example of a measurement report on distance and the speed of clamping of the actuator using stopping time and machine diagnosis tool.

The test that is the most difficult to perform is to measure the stopping time. It is performed for curtains and light beams, laser scanners, two-hand control devices as well as pressure-sensitive mats. From the security perspective it is a very important test, because the protective device with the machine can perform the safety function, e.g. stop dangerous movements when it detects a breach of the detection zone, but it can do it too slowly. In the case of the press, failure to stop the plunger within a reasonably short time can result in e.g. crushing a hand. The distance in which the protective device is set or the detection zone borders are associated with the machine stopping time by its speed. Hence, the protective device performs its function as long as both borders and time zones do not change. The response time consists of a protective device response time and stopping time of the machine, the response time of the protective device is typically of a magnitude of single millisecond and it is the stopping time of the machine that is really essential (fractions of a second, seconds). Since these times are so short, considering human reaction time, they are difficult to measure accurately e.g. with a stopwatch. A more accurate tool for this purpose is a stopping time and machine diagnosis tool. Fig. 1 shows an example of a report generated by this device. It measures the displacement and speed of the links attached to the movable element of the machine of which the stopping time we want to measure. Delivery of the measurement can occur simultaneously with activating the two-hand control device (by adding a button) or simultaneously with breaching the detection zone of the safety light curtain or the laser scanner. The diagram below shows the movement of the links of the stopping time and machine diagnosis tool (green line, right-hand scale) and its velocity (dark blue line, left scale). The horizontal axis presents the time.

The diagram allows you to analyse and measure the time that has elapsed since pressing the button (or breaching the safety zone) until the movable part of the machine slows down and reaches a speed of 10 mm/s, 5 mm/s, etc. to a complete stop. The diagram allows you to see a change of direction in movement of the movable part. In cases where the machine stopping time is short, the device allows, and sometimes makes it possible to correct its measurement.

4. Principles for determining the schedules of periodical inspections

Having information about the protective device gathered in its characteristics card you can determine or modify the schedule of inspections.

 

Conditions for initial and special inspections are clearly specified in the Directive 2009/104/EC.

Initial inspection is to be carried out after installation and before putting the device into service for the first time and after installation on a different working station or working area.

The special inspection (of which the scope is the same as the initial inspection) should be carried out when there is a possibility of deterioration of safety associated with the machinery as a result of: modification works, natural phenomena, extended shut-down time, hazardous failures and accidents at work.

Most of the difficulties come with determining / modifying the schedule periodical inspections. To do so, you need to analyse the installation data contained in the documentation of the protective device. Particular attention should be paid to:

1.    The risk level limited by a particular safety function.

2.    The intensity of use of the machine.

3.    The conditions of the machine's operation. Determine whether these conditions (dust, moisture, chemical vapours) may have an impact on faster wear of the parts of the machine that implement safety functions.

4.    Wearing parts of machinery and their impact on the implementation of safety functions (brakes, suppressors systems, transmitters) and manufacturer's instructions regarding the operation of these components.

When we determine the schedule of periodical inspection of the protective device for the first time and there is a high probability of loss of safety functions, the machine is heavily used, the loss of the safety function is associated with some serious consequences, the machine operates under conditions conducive to faster wear of the parts of a machine that implement the safety function, we should consider a shorter period of time between the inspections (e.g. half a year). However, if none of these conditions occur, the time between the inspections can be prolonged to one year. For subsequent inspections, verify whether these conditions and the intensity of use of the machine have changed and analyse the results of periodical inspections. If the operating conditions of the machine and the protective device have not changed and tests of the protective device have shown that it works correctly (no dislocation, no prolongation of the stopping time of the machine, etc.), you can extend the time between inspections. However, if there has been a significant deterioration in the operation of the protective device (e.g. the stopping time became significantly longer), you should reflect on the cause of this and, possibly, shorten the time between inspections.

Similar caution should be exercised while modifying schedules when the conditions of the machinery and device operation change, and in such cases the time between the inspections should be rather shortened.

After determining the schedules of inspections for individual machines, you must specify the schedule of inspection for the entire plant taking into account the frequency of inspections for individual machines.

As already stated, specifying the inspection schedules and scopes for protective devices is an ongoing process. These schedules and scopes can and should be reviewed and modified, because due to the huge number of possible applications of protective devices in machines, they cannot be predicted in advance and schedules and scopes of inspection cannot be strictly determined.

The proposed procedure for determining the schedules of periodical inspections for protective devices is shown in Fig. 1.

When determining the schedules of periodical inspections, it is advisable to conduct an assessment of the risk which is reduced by the individual protective device. The general rule is that in the case of devices, which are responsible for reducing high risk, inspections should be carried out more frequently than when the risk is lower, the possibility to avoid the damage is greater or duration of exposure to the risk is short. Thus, in case of high risk reduction the primary period of time between the inspections should not be no longer than 6 months, if the machine manufacturer had not specified otherwise. In the case of low-risk inspections may be conducted less frequently.

5. Methods of documenting the inspection of protective devices

The results of inspections collected by the employer are also the basis for determining the scopes and schedules of inspections of protective devices, as well as their verification. The regulation does not specify how to document the results of the inspections, but the more detailed information on the installation of the protective device is in the reports, the easier it is to use this knowledge to create the next schedule and to verify the current one. It should also be stated that the schedule of inspections should not be set with the assumption that  it remains unchanged for the particular installation. Along with gaining experience, the schedule and the scope of inspection can and should be modified.

To efficiently conduct periodical inspections of protective devices it is necessary to define scopes and schedules of these inspections. Schedules should be of two kinds. Firstly, the general the schedule should be drawn up (for the entire plant, hall or production line) including all safety devices installed there. This will allow to plan the order of inspection of individual devices, so that these inspections do not cause too long work stoppage. Secondly, scopes and detailed schedules must be specified that will provide detailed information on the status of each protective device.

5.1. Inventory of protective devices

Table 5 Inventory of protective devices on the production stations (example)

List of protective devices (example)
Name of the hall / working station:
Name and signature of the signatory:				Date
No	Type and number of protective devices	The safety functions and the level of reduced risk	The date of initial inspection.	Comments on initial inspection

You should start with an inventory of protective devices at the plant, which then to order and facilitate the work can be divided into groups. The inventory of protective devices is also aimed at creating the schedule of inspection of equipment throughout the plant, so that the inspections do not disrupt the work. For this purpose you can use a table similar to the one shown below.

5.2. Documenting data on the protective device

Table 6 Data on the protective device (example)

Protective Device Sheet
Data on the protective device and the machine on which the protective device has been installed
No	Verified characteristics	Comments:
1	Name, type, ID number and location of the protective device
2	Risk level reduced by the safety function
3	Safety category or performance level of the protective device
4	Safety distance specified when designing the system.
5	The response time of the protective device and machine stopping time specified when designing the system.
6	Other safety-related parameters - list them
7	Give category of machine stopping (if applicable)
8	Implementation of the safety functions
9	Do the safety functions involve brakes (yes / no)?	Specify the manufacturer's instructions for operation and control of the brake wear
10	Does the safety function involve transmitters (yes / no)?	Specify the manufacturer's instructions for operation and control of the transmitters wear
11	Other devices that might influence the implementation of the safety function (despite protective devices)	Specify the manufacturer's instructions for operation and control of the wear of other devices that might influence the implementation of the safety function
12	Specify the intensity of use of the machine.
13	Specify the operating conditions (dust, moisture, fumes, etc.)

The safety functions are usually implemented in connection with a machine (not by the protective device alone), so when determining the scopes of inspection you should take into account the recommendations and manuals from both the protective device manufacturer and the manufacturer of the machine. Particular attention should be paid to the time of trouble-free operation of individual parts and components declared by the manufacturer (brakes, transmitters, couplings), because their efficiency is crucial for the proper operation of the safety function.

 Explanations to Table 6

Annotation 1 It often happens that similar devices are installed in different machines, working under different conditions or are older, operated more heavily, etc. Therefore, each of them must be treated individually. This is why they need to be identified.

Annotation 2 We assume that the risk level reduced by the safety function has been specified during the design of the protective device system.

Annotation 3 Please check to which safety category can you qualify the tested protective device. Sometimes the standard permits a lower safety category if additional requirements are met (e.g. controls). If the device was conditionally qualified to a particular safety category, this should be taken into account during the inspection. Instead of the safety category, the provided safety level can be considered.

Annotation 4 and 5 Parameters relevant to safety shall be noted so that during the next inspection it is possible to verify them.

Annotation 4 and 6  List other parameters related to safety which should be checked (e.g. angle of rotation of rolls before stopping, force of activation the pressure-sensitive device, location of the protective device, etc.).

Annotation 7  The PN-EN 60204-1 standard specifies three categories of stopping for drive systems:

Category 0 - stopping by the immediate disconnection of the power supply the machine drive (uncontrolled stop)

Category 1 - a controlled stop when the power supply is provided to the machine drive until it stops and then it is disconnected, when the machine has already stopped

Category 2 - a controlled stop when the power supply is provided to the machine drive in a continuous manner

Annotation 8 Describe how the safety function is implemented by attaching drawings of safety and risk zones (if applicable). Awareness of how the safety function works is clearly necessary to be able to test the protective device. Furthermore, sometimes it happens that the on the working station where the safety light curtain has been installed, the safety laser scanner is mounted in order to improve the safety level, but it results in the fact that safety functions of protective devices are duplicated and it does not enhance the safety but only increases the number of checks necessary to conduct. Thus, inspections of protective devices are a good opportunity to rethink the protection used in the plant, which can and should lead to the removal of some of the protective devices as well as to installing the new ones.

Annotation 9-11 As already mentioned, protective devices perform safety functions only in connection with the machine. Therefore proper implementation of the safety function can be affected by a number of parts of the machine itself (e.g. brakes, transmitters, valves, etc.). During the inspection of protective devices you should also pay attention to these elements, as well as manufacturer requirements for their operation, maintenance and replacement.

Annotation 12 Enter the estimated number of hours worked per week, as well as give the number of times per hour or per shift that the safety function is referred to.

Annotation 13 Specify conditions that could affect the consumption of parts of the machine affecting its safety.

5.3. Documenting the inspection of protective devices

To fill in the sheet with all the inspections results should be the next step. This inspection sheet will vary depending on the device and inspection type (initial, periodical, special). When defining the scope of periodical inspections you must meet the recommendations of the technical specifications: IEC/TS 62046: 2008 - Safety of machinery - Application of protective equipment that detect the presence of persons. The example of the inspection sheet is shown in Table 7.

Explanations to Table 7

Annotation 1 - 10. These points include tests to be carried out in the assessment process, the scope which is set out in the first stage of the task and is dependent on the type of protective device and type of inspection (initial, periodical, special). Having collected detailed data on each protective device, you are ready to determine the scopes and schedules of inspections (initial, special and periodical) for each device. When determining the schedule of periodical inspections (frequency of inspections) use the following table which contains detailed data on the device.

Table 7 Results of inspection of the protective device (example)

II Results of inspection of the protective device
1	Type of inspection
2	Date of inspection
3	Does the implemented safety function work properly? (yes/no)
4	Has the distance between the risk zone and the device changed? (yes/no)
5	Inspection additional protective measures (e.g. fixed guard), if it is required by the given application of the device? (yes/no)
6	Measure the stopping time. Compare it with the stopping time measured when the device was installed.
7	Is there any other equipment within the device that would reduce its detection capability? (yes/no)
8	Check the detention effectiveness controller operation (if applicable). Is it securely seated and tuned? Does it operate in accordance with the recommendations of the supplier and whether the means by which the system is stopped are indicated to the operator in a clear and unambiguous way? (yes/no)
9	If the device is equipped with muting and blanking features, check these functions, and check whether they are properly secured against unauthorized use? (yes/no)
10	Other safety-related parameters
III Conclusions of the inspection
11	Have the working conditions changed since the last inspection?
12	Have any non-conformities in the machinery operation been detected?
13	Is it reasonable to extend / shorten the interval between inspections?
14	Proposed changes in the inspections schedule.
15	Signature of the auditor

6. Summary

Properly specified schedules and scopes of inspections of protective devices is a decisive element for the fact that these inspections will be carried out efficiently and correctly. The important thing here is not only to identify the characteristics that are to be inspected and the intervals at which these features are to be controlled, but the organization of the inspections so as not to disrupt the work at the plant. Despite the formal requirements specified in the regulations on safety at work, planning periodical inspections of protective devices poses a problem for machine operators, especially due to the lack of more explicit guidelines and recommendations in this regard. As shown by the analysis carried out as part of the implementation of this task, this applies to basically all countries of the EU. We hope that presented rules of conduct will help to reduce these problems.

7. Literature

1.    PUWER 98 (Provision and Use of Work Equipment Regulations) – provisions implementing the Machinery Directive in England, published by HSE (Health and Safety Executive)

2.    ZH 1/281 - Sicherheitsregeln für berührungslos wirkende Schutzeinrichtungen an kraftbetriebenen Pressen der Metallbearbeitung – provisions issued by Der Hauptverband der gewerblichen Berufsgenossenschaften

3.    EN ISO 12100-1: 2005 - Safety of machinery - Basic concepts, general principles for design - Part 1. Basic terminology, methodology

4.    EN 61496-1: 2004 - Safety of machinery - Electro-sensitive protective equipment - Part 1: General requirements and tests.

5.    EN 61496-3: 2004 - Safety of machinery - Electro-sensitive protective equipment - Part 3: Particular requirements for active opto-electronic protective devices responsive to diffuse reflection (AOPDDR).

6.    IEC / TS 62046: 2008 - Safety of machinery - Application of protective equipment that detect the presence of persons.

1          Inspections of integral lighting of the equipment

The main parameters which determine lighting both on its quality and occurrence of occupational risks are:

·         light intensity

·         lighting uniformity

·         the occurrence of glare

·         flickering and stroboscopic effects

·         colour rendering index.

The main parameter that should be assessed within the task area of each machine on which the visual work is performed is the level of intensity and its uniformity. To do so, we need to measure the lighting brightness and determine its uniformity. The results shall be related to the general requirements for lighting of the equipment included in the EN 1837+A1 standard: 2009. Safety of the equipment. Integral lighting of the equipment. When selecting lighting requirements, you can also use the EN 12464-1: 2012 Light and lighting standard. Working stations lighting. Part 1: Indoor working stations where the performed work requirements include the difficulty of the visual work while operating various types of machinery and equipment (tables 5.8 to 5.25).

In the case of underexposure, it is necessary to use spot lighting fixtures. Some manufacturers equip a standard machine in the spot lighting fixtures that can be integrated into its structure or form a separate part.

If you use spot lighting fixtures, check as well, based on the performed measurement, whether the applied luminaire provides a good degree of lighting of the working area of the machine on which the visual work is performed. Such a fixture should also provide a good degree of illumination of zones where adjustment, setting and frequent maintenance are carried out.

Another parameter that is evaluated is the distortion of colours of observed details by the light source installed in the luminaire. This parameter applies to fluorescent and LED light sources and is placed on them as a numeric code. When using fluorescent and LED light sources, it should also be assessed whether the colour of emitted light is pleasant. It should be warm (yellow, within the range of 2,700 ÷ 4,000 K), not cold, bluish white. This parameter is also placed on the light sources as a numeric code.

   It is important to determine whether the stroboscopic effect is possible to occur on the equipment when the spot light fixture is on. If so, in the case of spot lighting fixtures used with fluorescent lamps, the type of the ignition system should be checked. If there is a magnetic system, it must be replaced with an electronic ignition system. In situations where spot lighting luminaire does not cause the stroboscopic effect, verify whether the occurrence of the flickering effect and ripple of light can be noticed. If so, you should check the technical condition of the ignition system and the light source and, if necessary, replace them with new ones.

   Furthermore, the machine operator needs to determine whether the applied spot lighting luminaire does not result in a direct glare (light source does not shine into the eyes of the employee when working) or a reflective glare – by the reflection of light from the glossy structural elements of the machine. If it is found to be the case, change the position of the lighting fixture or dull these surfaces.

   Within the working area of the machine on which the visual work is performed, underexposed places or formation of dangerous shadows caused e.g. by means of the design of the machine and/or its covers must not be present. Then you should change the location of spot lighting fixtures or use the luminaire with e.g. longer arms.

   In terms of safety, it is also important to check whether the power supply and switching of the fixture is constructed in a way that is safe for the user. Electric power supply cables must not be e.g. frayed, and the switch must not be damaged.

   Also the assessment of functionality of the spot lighting fixture is of great importance when operating it. Therefore, you should check whether the position of the light fixture with the light source is adjustable at all, and if so, whether this adjustment is easy and does not require any tools. Furthermore, the adjustment of the lighting fixture position must not cause any risk to people who do the adjustment (burns caused by a hot luminaire, scratches, etc.). If operating the machine requires the use of protective shields, then you should check whether the level of light intensity was increased in proportion to the degree of suppression of light by this cover.

These aspects have been included in the questionnaires comprised in the developed check lists. All of these issues are included in a list intended for the periodic inspection. The lists intended for preliminary inspection and special inspection are slightly shortened, but contain the most important elements affecting the quality of lighting equipment.