Pooling knowledge and improving safety for contracted ... - IOS Press

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Work 51 (2015) 537–548 DOI 10.3233/WOR-141940 IOS Press

Pooling knowledge and improving safety for contracted works at a large industrial park Patrizia Agnello∗ , Silvia Ansaldi and Paolo Bragatto INAIL Italian Workers’ Compensation Authority, Research, Certification and Verification Area, Centro Ricerca, Monte Porzio Catone, Italy

Received 18 May 2013 Accepted 10 October 2013

Abstract. BACKGROUND: At a large chemical park maintenance is contracted by the major companies operating the plants to many small firms. The cultural and psychological isolation of contractor workers was recognized a root cause of severe accidents in the recent years. That problem is common in chemical industry. OBJECTIVE: The knowledge sharing has been assumed a good key to involve contractors and sub contractors in safety culture and contributing to injuries prevention. The selection of personal protective equipment PPE for the maintenance works has been taken as benchmark to demonstrate the adequateness of the proposed approach. METHOD: To support plant operators, contractors and subcontractors in PPE discussion, a method has been developed. Its core is a knowledge-base, organized in an Ontology, as suitable for inferring decisions. By means of this tool all stakeholders have merged experience and information and find out the right PPE, to be provided, with adequate training and information package. RESULTS: PPE selection requires sound competencies about process and environmental hazards, including major accident, preventive and protective measures, maintenance activities. These pieces of knowledge previously fragmented among plant operators and contractors, have to be pooled, and used to find out the adequate PPE for a number of maintenance works. CONCLUSIONS: The PPE selection is per se important, but it is also a good chance to break the contractors’ isolation and involve them in safety objectives. Thus by pooling experience and practical knowledge, the common understanding of safety issues has been strengthened. Keywords: Personal protection equipment, ontology, cognitive ergonomics

1. Introduction 1.1. The industrial park The case study is a large industrial park, featuring some 200 enterprises and 5000 employees. In the park there are large petrochemical and power plants, operated by six major national and international companies. The park hosts a number of small firms, which supply the major companies with mechanical and chemical ∗ Corresponding author: Patrizia Agnello, INAIL Ricerca, Dipartimento Innovazione Tecnologica, via Fontana Candida 1, I – 00040 Monte Porzio Catone, Italy. E-mail: [email protected].

goods, and produce plastic products for the consumer market. Most industrial services, including docks operation, internal transport, interconnecting, logistic, security and cleaning, are outsourced to the small companies. All maintenance and revamping works are contracted (and even subcontracted) to small companies in the area. In five establishments the legislation for the control of major accident hazard or “Seveso Legislation” is enforced, due to the amounts of processed and stored hazardous materials. In the safety reports, required by the Seveso legislation, some fifty major scenarios have been considered, including pool fires, flash fires, jet fires, vapour explosions. Some 400 ha are included in potential damage area.

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P. Agnello et al. / Pooling knowledge and improving safety for contracted works at a large industrial park

1.2. The issue of a safer maintenance In the period 2008–2010 at the park were recorded three occupational accidents, with two casualties and five severe injuries. All accidents were related to the maintenance activities and all victims were contractor workers or individual subcontractors. Due to the wide variety of tasks, their heterogeneity and non-systematic frequency, there are no “permanent” workers in charge of maintenance. Maintenance workers have frequently to change work environment, they do not have the same training as permanent workers on the risks inherent in that type of plant and are only aware of those risks related to maintenance tasks. Maintenance workers usually operate alone, often under time pressure and in isolation; furthermore activities are often carried out in unfavourable conditions, such as night or weekend work. Even though major companies adopt advanced procedures to promote safety culture, maintenance workers are not involved because the duration of activities is often too short. Thus they feel completely alienated than other workers. These problems are not specific of the studied park; but they are well known in all process industries (chemical and power), where most maintenance is contracted (and subcontracted), as shown by recent reviews such as EU-OSHA [1] and Nenonen [2]. 1.3. The cognitive approach to promote safety After the accidents, the promotion of a safer maintenance has become a priority both for the park Companies and the Occupational Safety and Prevention Service of the Local Health Agency, which, according to their mission, encourage a lively safety culture. Thanks to a research project, funded by the Italian Ministry of Welfare, a study has been promoted, where parks operators, contractors and Local Health Agency have been involved. In order to reduce accidents two leverage could be used: the prescriptive and the behavioral. As discussed by Tazi [3], the first approach requires many procedures to be enforced, with a lot of meetings and a lot of documents. This model doesn’t promote the adaptive capacities of contractors and subcontractors because it does not allow them to learn especially through errors, even if these adaptive capacities are a request from the client. Subcontractors don’t participate and their expertise doesn’t rise with this program. The behavioral approach, on the other hand, is based on employee observation cycles, which are too long compared to the duration of maintenance. Fur-

thermore contractors and subcontractors are not part of the team and do not have an internal person to report to. For those reasons an alternative to prescriptive and behaviour approaches was investigated. Promoting safety by means of knowledge pooling between clients, contractors and subcontractors. The clients that operate the plant must transfer to the contractors the knowledge about the risks arising from plant processes, the preventive and protective measures, and the emergency planning. Contractors must transfer to the contractors the expertise about task related risks and the relevant protective equipment and the problem deriving from personal protective equipment. At major companies operators are used to have a number of formal document where knowledge has a explicit form. For contractors most knowledge is, instead, implicit, more for individual subcontractors. The responsibilities for occupational safety are, furthermore, spread among a large number of duty holders, including Major Companies, Contractors and Subcontractors. All these issues hinder the diffusion of knowledge among the workers, and this is a potential cause of accidents specially in the team work, as demonstrated by Sasou and Reason [4]. 1.4. The issue of PPE The resources for the project were not sufficient for all issues relevant to a safer maintenance in the park thus a subject was selected to experiment the potential of the cognitive approach. Thus the scope of the research was limited to the optimal choice of Personal Protection Equipment (PPE) in maintenance works, because the misuse of PPE has been recognized a major cause of injuries. The choice of PPE is essential for preventing injuries, but it is difficult, because a wide range of equipment must be considered to meet the concurrent objectives of reducing task risks and interfering risks. In such a difficult situation, the client company has to make sure that the worker adopts the appropriate personal protective equipment by providing complete information and training on environmental risks, taking into account the hazards related to the maintenance task, but also ensuring that the PPE does not interfere with activity. Since the correct use of PPE is a key issue in the safety culture, all involved workers, both internal employees and external workers (contractors and subcontractors), must pursue the same level of safe work. For this aim, it has been recognized the need of a tool to identify the right PPE taking into account the different roles of people involved, sharing the


knowledge on risks. This shared decision process is a very good way to promote collaboration between operators and contractors. PPE choice is essential for the “Permits to Work” (PTW) system. PTW is a formal document that must be shared by the contracting company and the contractor before starting any works, aiming to define the PPE and the other technical and procedural measures that must be adopted to work safely and avoid accidents. In the chemical-industrial workplace all maintenance works, which are typically controlled by “permits to work” PTW system [4]. It has been a pillar of safety in the process industry for twenty years and, in a few countries, including Italy, it is even mandatory, in the framework of Seveso legislation.

2. The state of the art As the two main focuses of the research are PPE management and Knowledge pooling a short review about these two subjects is presented here. 2.1. PPE management in scientific literature The PPE matter is regulated by a number of national and international regulations, standard codes and good practices, which rule all technical requirements. Organizational aspects of PPE are, instead, ruled just by a couple of guidelines and standards, in the framework of SMS (Safety Management System) standardization. In the International Labour Organization guidelines [6] PPE management is included in the chapter on “Hazard prevention and control measures”. In the British standard code OHSAS 18001 [7] the subject of PPE is included in hazard identification, risk assessment and determining controls. PPE and interfering risks are discussed in many international and national guidelines, such as EU Guidelines [8]; the British guidelines [9]. In every single PTW all protective item must be indicated by their identification code, according to the CEN standard. Whilst PPE technical aspects are discussed in a number of papers in scientific journals, there are just a few papers on its management. Burtch and Sajadi [10] demonstrated for the chemical industry that safety culture and safety leadership are essential to make good use of PPE and to consequently reduce injury rates. According to Olson et al. [11] safety leaders were shown to be essential for promoting PPE use. In the case of contracted works there are many safety managers and shared knowledge and shared culture are essential to promote a recognized safety leadership in the park working community.

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2.2. Ontologies and taxonomies for safety knowledge As explicit and implicit knowledge on risk and PPE are definitely scattered among a number duty-holders (major and minor companies, contractors and subcontractors), the main problem to face has been the collection and management of such a fragmented knowledge. An intriguing approach in the field of knowledge engineering is the “ontological” approach and, consequently, in this chapter there is a special focus on “ontology” and its potential for improving SMS. The ontology approach was introduced for Knowledge Management in the Nineties [12] In many fields, including engineering and medicine, “Ontologies” have been proved suitable to capture and structure knowledge about some domain of interest. They are able to link taxonomies and infer decisions. Taxonomies, are commonly used as a starting point in ontology design. “Ontologies” describe the concepts in the domain of interest and also the relationships hold between those concepts. The use of ontologies for safety knowledge management has appeared in a few recent papers. The first and natural use of ontologies in safety engineering was for improving searches in accident databases. Ontology engineering was used by Suzuki et al. [13] to extract knowledge directly from databases while reducing the number of mismatches. Batres et al. [14] demonstrated the potential of ontologies for expanding the underlying database schema if, for example, new causes are identified. The design and development method of an ontology is illustrated in a reference by Noy and McGuinnes [15]. In the literature a few papers may be found about the use of ontologies for improving well-known hazard identification and analysis methods. An ontologybased application was developed by Zhao et al. [16] to improve HAZOP. FMEA ontology has been proposed by Ebrahimipour et al. [17]. Ontologies were also proposed for improving safety performances in the construction industry. Yurcyshyna and Zarli [18] presented an ontology-based method for the formalisation and application of effective code conformance checking. Tserng et al. [19] presented a study of ontology-based risk management (ORM) for contractors. In Wang and Boukamp [20] knowledge engineering has been exploited for improving Job Hazard Analysis. Camossi et al. [21] proposed an ontology-based method for addressing Safety certification of Pressure equipment. In that paper, the “ontology” includes the “taxonomy” of pressure vessels, the rules for the safe design, construction and operation, the inference rules and the logical axioms.

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3. Objectives The main goal is to demonstrate how plant operators and contractors may improve safety management by merging their different experience and information on risks and relevant protective equipment; even in a complex system, such as an industrial park. The objective of the research is to develop and test at a large chemical park with hundreds of contractors, a method to share knowledge on PPE and to make decisions on PPE for contracted maintenance work. A software tool, implementing the method, is the main deliverable of the research. This knowledge based system supports the process of PPE selection for outsourced and contracted works in the studied industrial park. It is aimed to assist the dialogue between client and contractors for a safer maintenance. As the study case is representative of many chemical establishments, a further objective is to export the developed solution to other industrial parks, featuring many interfering hazards and many duty holders. In order to promote safety in these sites it is essential to constitute a community of knowledge, participated by all workers, operators and contractors. 3.1. Target The potential users of the developed solution are the safety managers. They need a tool for selecting, from a huge number of PPE products, the right items, on the basis of direct and interfering risks. The optimal PPE will be indicated in the PTW to the workers. The software developers have also been required to provide a user-friendly graphical user interface, but the very core of the system is the PPE ontology, which is required to consider all the facets of problems and the relations among them, such as the risks to be covered and those arising from the equipment and its use, the body parts to be protected, the PPE reliability and compatibility with respect to work activities and conditions. A few brainstorming sessions with plant operators and contractors have been essential to fill up the ontology with all information about task risks and interfering risks. In this way two goals have been met: to have a highly specialized system and to involve all parties. 3.2. Domain of the method This method considers the PPE to be defined in the PTW. PPE includes equipment for protection on work operations, such as goggles, face-shield, masks,

gloves, boots, earmuffs, safety helmets, taking into account both task related and working environment related risks. PTW may require some protection for emergencies, for instance the “quick-escape-mask”. It has to be stressed that in the event of an accident the works have to be suspended and maintenance workers must reach a safe point. It is in any case essential that a fast and safe escape is not hindered by inadequate equipment (e.g. something that is incompatible with “quick-escape-mask” or too heavy). It is assumed that each maintenance work is contracted out by a single operator and is performed by a single company in a single unit or installation. The PPE for safe maintenance works must be selected, taking into account the risks related to the task to be performed, the risks related to the plant unit where the work is to be done, the exposure to major accident scenarios or other environmental hazards, the risks posed by the equipment itself.

4. The knowledge based model The developed model has two parts: the PPE ontology (Onto-PPE), the true “engine” described in the first paragraph, and the user-interface, briefly described in the second paragraph. An ontology is described by means of a knowledge representation language, such the Web Ontology Language [22] developed by the W3C. Onto-PPE has been modeled by using Protégé, developed by the Stanford Centre for Biomedical Informatics Research at Stanford University [23], one of the most popular ontology editors. This system supports the design of ontology, providing suit tools for validating and enquiring operations, and automatic generation in OWL. 4.1. Onto-PPE: The PPE ontology Onto-PPE is the representation, by means of a sophisticated formalism, of all the knowledge on the matter. The design of Onto-PPE ontology has been defined mainly applying a bottom-up approach, in order to enumerate important terms of ontology and define the classes, their properties and relationships. Each concept has been described and organized into appropriate classification, therefore in Onto-PPE the following taxonomies have been developed: – the personal protective equipment; – the hazards, from which the worker has to be protected and those arising from the equipment and their use;


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inv_has Safety Criteria Safety Criteria has Safety Criteria has Safety Criteria is Migated By Hazards to be Standard covered Codes protects By Hazard is Protected By PPE arises Hazard Parts of Body

Task Acvity has Hazard

inv_arises Hazard Hazards from PPE inv_has Safety Req

protects Part

has Safety Req Safety Requirements Fig. 1. Example of relations among taxonomies. Each rectangle contains a taxonomy root, arcs the main relationships.

– the safety and performance criteria, that are the requirements driving the selection. Every taxonomy is classified and organized into hierarchical structures of classes, which represent the domain concepts. The parent-child relationships enable property inheritance (is-a) among the classes involved. Furthermore, each class designed in the taxonomies can have properties: – attributes or simple data, e.g. hasName is the name of a PPE, – relations for mapping individuals contained in classes which may also belong to other taxonomies, e.g. protectsThePart is the relation between PPE and body part instances, – restrictions on the classes, that are designed by applying some mathematical properties, such as cardinality, existential or universal quantifiers to the relations. Onto-PPE is the representation of those taxonomies and their relationships, and opportune restrictions are rules derived by the technical normative. A simplified schema, reporting the main concepts, is shown in Fig. 1. In Onto-PPE, the Hazard_ToBe_Covered taxonomy describes the most common risks against which PPE is required to protect one of the body parts. Figure 2 shows the hierarchical structure of hazard classification, where the rectangles correspond to the classes and the arcs define only is-a property relations. Each bottom level of classes contains the instances that specify the hazards. For the benefit of readability, only the thermal hazard class is fully represented in figure. Those risks are related to the working activities, but they can also be considered as environmental or ex-

ternal risks, which take into account the circumstances and the conditions in which the worker operates. Another taxonomy takes into account the discomfort that can be generated by a PPE and its use, the problems of interference with working activities that may arise, the situations that may increase accidents and health hazards, or the effects that may be caused by their aging. In the same way, taxonomy based on safety and performance criteria for driving the PPE selection has been developed. The aim is to identify the characteristics that a PPE should have for contrasting hazards. The principles adopted for defining this taxonomy are related to the PPE capacity to protect the worker. For example, let consider the choice of the protective shoes. The resistance to shots and the absorption of impact are criteria to be analyzed in order to contrast object falling hazard and they are directly related to physical characteristics, e.g. the type of material of which the shoe is made. To formalize the concept “to protect from falls and impact to the heel, the safety shoes must have the energy-absorbing capacity of the heel” the following formula may be used. Impact_to_heel hasCriteria_toProtect

(1)

Energy_absorbing_of_heel where hasCriteria_toProtect is the relation, while Impact_to_heel and Energy_absorbing_of_heel are individuals of Hazard_ToBe_Covered and Criteria_To_ Protect, respectively. Furthermore a taxonomy classifies the requirements for avoiding that PPE, directly or not, be inadequate for protection, or even be the cause of health problems or accidents, for instance by limiting working capabil-

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Hazard to be covered Is-a Chemical

Is-a

Is-a

Is-a

Physical

Biological

Other

Is-a Mechanical Is-a

Is-a

Aack Surface Mech Abrasion

Is-a Radiaon

Tear

Is-a

Is-a

Electrical

Thermal

Is-a

Falling From Height

Is-a

Slip

Is-a

Mech Vibraon

Step On Sharp Objects

Blade Cut

Is-a Noise Is-a

Heat

High Temp.

Cold

Molten metal

Fire

Fig. 2. A Risk taxonomy.

PPE Is-a PPE Upper limb Is-a

Is-a

PPE Hand Is-a Gloves

PPE Eye Face Is-a Mask

Is-a

Is-a

PPE All Head Is-a

PPE Lower limb

Is-a

PPE Ear

Is-a

PPE Breath

Is-a

Is-a

Glasses

Face Shild

PPE Head

Is-a Helmet

Is-a PPE Foot Is-a

Is-a Bump Cup

Safety Foot wear

Is-a Protecive Footwear

protects By Hazard Hazard To Be Covered has Value Falling Objects Fig. 3. Example of PPE taxonomy.

ities. In this case, the adopted principles are: avoid discomfort to the worker, avoid interference with work, do not decrease the protection limit. The protection equipment taxonomy is conceptually the hierarchical structure of classes whose individuals are devoted to protect a certain part of the body. This classification is based on the part of the body to be protected, e.g. hands, head, feet, whole body, eyes, ear, through a relationship, “ProtectsThePart”, and specific restriction. For example, the class of head protective equipment is defined by the following restriction: ProtectsThePart hasValue Head

(2)

The further classification criteria to discriminate protective equipment is the hazards to be covered. An ex-

ample is shown in Fig. 3; the industrial safety helmet (Helmet) and the bump cap (BumpCap) are both head protective equipment, but they cover different hazards: the former protects from falling or flying objects, the latter only from head bumping. In PPE ontology, these concepts correspond to the definition of two subclasses of PPE_Head_Protection class, where Helmet class is implemented by defining a restriction of the inherited property protectsByHazard only to specific subclasses of Hazard_ToBe_Covered, e.g. objects falling. Other restrictions are added to avoid ambiguities among classes. For instance, the PPE_Head_Protection and PPE_Foot_Protection are declared disjoint classes, which is equivalent to say that an object cannot belong to both classes, obvious for common sense, but neces-


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Table 1 PPE Standard Codes included in OntoPPE Code EN 140 EN 142 EN 149 EN 166 EN 170 EN 340 EN 342 EN 343 ISO 20344 ISO 20345 ISO 20346 ISO 20347 EN 352-1 EN 352-2 EN 352-3 EN 352-4 EN 352-5 EN 352-6 EN 352-7 EN 374-1 EN 374/2 EN 374/3 EN 388 EN 407 EN 420 EN 511 ISO 10819 EN 397 EN 812 ∗ The

Year∗ 1998 2002 2009 2001 2002 2003 2004 2009 2007 2007 2007 2007 2002 2002 2002 2005 2005 2002 2002 2003 2003 2003 2003 2004 2009 2006 1996 2000 2001

Subject Respiratory protective dev. – Half masks and quarter masks Respiratory protective dev. – Mouthpiece assemblies Respiratory protective dev. – Filtering half masks to protect against particles – Personal eye –protection – Specifications Personal eye –protection – Ultraviolet filters – Transmittance req. Protective clothing – gen. req. Protective clothing – Ensembles & garments for protection against cold Protective clothing – Protection against rain Personal protective equipment – Test meth. for footwear Personal protective equipment – Safety footwear Personal protective equipment – Protective footwear Personal protective equipment – Occupational footwear Hearing protectors – Part 1: Ear – Muffs Hearing protectors – Part 2: Ear – plugs Hearing protectors – Part 3: Ear – muffs attached to an industrial safety helmet Hearing protectors – Part 4: Level – dependent ear – muffs Hearing protectors – Part 5: Active noise reduction ear – muffs Hearing protectors – Part 6: Ear – muffs with electrical audio input Hearing protectors – Part 7: Level – dependent ear – plugs Protective gloves Chemicals/microrganisms – Part 1: Terminology Protective gloves Chemicals/microrganisms – Part 2: resistance to penetration Protective gloves Chemicals/micrrganisms – Part 3: resistance to permeation Protective gloves against Mech. risks Protective gloves against thermal risks (heat &/or fire Protective gloves – gen. req. & test meth. Protective gloves against cold Mech. vibration & shock – Hand – arm vibration – Transmissibility of gloves Industrial safety helmets Industrial bump caps

year of the amendment is reported.

sary in order to avoid unexpected results of deductive process. One of the advantages of using ontology is the possibility that many concepts can be inferred and deduced from the knowledge model defined. Furthermore, PPE taxonomy, based on requirements related to specific hazards, has been defined according to the technical contents of European Standards, as reported in PPE-GUIDELINES [8]. The standard codes reported in Table 1 has been included in Onto-PPE. In Onto-PPE, a specific taxonomy (Safety_Req) of both Safety Requirements and Codes has been modelled, where each Safety Requirement refers to one criterion, contained in the criteria taxonomy mentioned before, and Codes are an appropriate combination (intersection) of them. For example, EN 345-1 classifies safety footwear on the basis of some requirements into categories; a subset is shown in Table 2. The concept: “a footwear with S1 code means that it is antistatic and has energy absorbing seat region” is represented by the formula: S1_code = Symbol_A ∩ Symbol_E

(3)

Interesting results produced by this formula is that the classification based on safety requirements, compliant with European regulations, is automatically deduced by the taxonomy of personal protective equipment. In other words, each equipment defined into PPE ontology is automatically classified into the safety taxonomy. The overall picture is illustrated in Fig. 4. 4.2. The user interface The PPE-Choice user interface has been organized into one main “page”, as shown in Fig. 5, in which all the aspects related to PPE choice are available, including risks, requirements and criteria, parts of the body, PPE lists and their parameters. The page has been split into frames, each one corresponding to a specific concept represented in OntoPPE. All frames have buttons corresponding to classes of the ontology, while the lists or combo-boxes contain the individuals, which can be used for choosing the right PPE. There seven frames, respectively, for the occupational risks to be covered, the environmental risks,

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P. Agnello et al. / Pooling knowledge and improving safety for contracted works at a large industrial park Table 2 A subset of safety footwear classification EN 345-1 Symbol

Safety requirements

A E WRU P

Antistatic Energy absorbing capacity of heel Uppers resistant to water penetration / absorption Penetration resistant

∗ is

Codes – Footwear SB S1 S2 S3 ∗ X X X ∗ X X X ∗ ∗ X X ∗ ∗ ∗ X

optional; X is mandatory.

Shoes Codes Is-a

Is-a

Is-a

Symbol E

Symbol Cl

Symbol P

Is-a Symbol M

Is-a

Is-a

Symbol C

Symbol A

is Applicable To PPE

Hazards to be covered has Safety Criteria Safety Criteria has Value Insulated From Cold

Safety Shoes

Safety Boots

Is-a

Is-a

Is-a Symbol WRU

Is-a

Is-a

Symbol Cl

Symbol Hl

protects Part Body Parts has Value Feet

Safety Foot wear

Fig. 4. The safety footwear classification in Onto-PPE.

the environmental requirements, the risks arising from candidate PPE itself, the parts of the body to be covered, the lists of candidate personal protective equipment, the PPE parameters, depending on the type of PPE selected. Besides this page, two additional panels have been designed for describing and managing environment and work related risks. It has to be stressed that the goal of this application is to have not a single protective item, but a complete set of protective items, for all body parts. After this first phase a list of candidate items of personal equipment is extracted from the ontology, taking into account: task related and interfering risks, protective items features, equipment related risks. All the interactive actions generate queries to the Onto-PPE, whereas they are completely transparent to the final user. The ontology Onto-PPE contains 387 classes of which 316 are primitive classes, having only necessary conditions, the others are defined classes, having necessary and sufficient conditions. It includes 50 properties of which 10 are data type, there are 18 properties with an inverse specified. There are 274 restrictions applied to relationships: 78 are existential (someValuesFrom in OWL speak or some relation), 74 univer-

sal (allValuesFrom in OWL speak or only relation), 98 hasValue properties (describing individuals that have at least one relationship along a specific property to a specific individual), 24 cardinality restrictions. The ontology can be freely accessed to the following wep page: http://www.ispesl.it/prodotti/dpi_onto/. 5. Testing and evaluation of the developed tool A number of stakeholders, including plant operators, safety managers, maintenance contractors and safety inspectors, have cooperated and exchanged information and knowledge, by means of formal systems. The software tool is the final product of those meetings, a true “knowledge distillate”, which should be used even after the project end. In order to verify the achieved objectives, the method has been tested to select the complete personal equipment for a few maintenance works, which was ongoing at the time of the project. 5.1. A practical example In this example the PPE choice for the replacement of a section of a flanged pipe, inside the cracking plant,


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Fig. 5. A snapshot of PPE_Choice user interface in a working session. (Colours are visible in the online version of the article; http://dx.doi.org/ 10.3233/WOR-141940)

Fig. 6. Selecting a maintenance activity to know the associated risks. (Colours are visible in the online version of the article; http://dx.doi.org/ 10.3233/WOR-141940)

is described. The following figures show some snapshots of the PPE-Choice application, which should simulate the team discussion and the process followed for identifying the PPE that have to be adopted by the workers. The first step is to identify the hazards related to the activities, as shown in Fig. 6. For this activity many hazards have been identified, i.e. head bumping, slipping, possible presence of dangerous dust (e.g. rock wool or toxic substance), sharp or pointed objects. By considering hazards related to the maintenance activity, PPE-Choice provides preliminary lists of PPE. The second step is to identify the location, i.e. the plant and the unit where the activity has to be per-

formed. Figure 7 shows the panel that describes the industrial park with its plants, depots or storage units, and service areas; for each of them the operators have already identified the risks, which is the result of knowledge sharing previously discussed. In the example, the work is at the cracking plant, in a unit where the hazards identified are falling object and slipping, noise; hot sources; hazardous chemicals. The team may refine the PPE evaluation by considering further environmental criteria. As the working area is within the potential impact area of a toxic release, protective equipment must be compatible with the use of quick-escape mask, which has to be worn to leave the area in the event of an alarm.

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Fig. 7. Selecting the location where the maintenance activity will be carried out, to know the environmental risks. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/WOR-141940)

Fig. 8. Selecting PPE pertinent to risks and criteria. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/ WOR-141940)

Fig. 9. The definitive list of equipment, as presented in the permit to work. (Colours are visible in the online version of the article; http://dx. doi.org/10.3233/WOR-141940)


The final step is to consider further risks that arise from equipment itself or from its vulnerability. Ergonomic and comfort criteria restrict again the choice, to converge finally to a single decision, as shown in Fig. 8. 5.2. The final PTW It has to be stressed that often a PTW must be released in a very short time in order to face unexpected and potentially hazardous situations. The proposed system has been demonstrated able to give the best PPE in a very short time. In Fig. 9 is shown a piece of a PTW, which has been delivered for making another work (namely leak surveillance at a plant in service). The resulting equipment is described according the EN standard codes. 5.3. Evaluation In the testing phase, the software has been fed with specific knowledge and information. The developed user interface has been accepted positively by the user involved in the project, also in defining the practical rules that are on the basis of the inferring engine, which is true value of the tool, hidden behind it. The tool itself is not conclusive, the essential thing is the willingness to share knowledge. Due to the restricted set of user, the problem of usability was not deepened in a formal way. Ontology, which is known as a powerful tool for keeping alive and sharing knowledge and experience, has been demonstrated powerful for supporting decision making. The detailed PPE taxonomy, as present in the EN standards, has been a very sound base for building the ontology. The brainstorming with safety experts (operators, inspectors, contractors, regulators) has been highly valuable to understand in detail the task related and interfering risks, to specialize the ontology and to write the rules that link each other the ontology items and enable the inference of the adequate pieces of equipment.

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course, by connecting all pieces of knowledge, their value is multiplied! The test and evaluation phase has been completed at the same time the funded project has ended. As the first results are encouraging, the method is suitable to be used for many hazardous works inside chemical establishments, including non destructive controls, instrument calibrations, safety system testing, seal replacing, on demand repairs. Collective equipment, as highly standardized, could be included in the method. The method is also suitable for other industrial services, such as security, cleaning and logistic, which are outsourced to small enterprise and have the same problems of maintenance, even though the risk level is slightly lower. The software is adaptive and customization for new establishment requires just a number of brainstorming meetings with operators and contractors. The group of users, without the help of a software engineer, can add new PPE and new risks without changing the reference model. Thus, the tool can be adapted to other industrial parks or similar contexts (e.g. the industrial port). The interface, in terms of labels and language, can be changed only by a software engineer. If the group of user will increase, we should consider the usability in a formal way. This phase is essential to break the cultural wall between operators and contractors. The side effects of forcing contractors and operators to share knowledge are even more important than the PPE selection. By contributing to the pooled knowledge base, contractors improve also the self-perception and are consequently much more awarded for all safety issues. Furthermore the results of this shared effort are automatically transferred to the PTW system, which is an essential item of the SMS. In such a way even contractors may understand that SMS is not a bureaucratic burden, but a living engine which may support all workers (both employees and contractors) to stay safer.

Acknowledgements 6. Conclusion By exploiting the potential of the ontological approach, an advanced decision tool has been developed. It is basically a structured container of knowledge. The parties, which hold just separate fragments of knowledge, are involved in customization for each site. Of

Research partially funded by the Italian Ministry of Welfare – Grant PMS/40/06/P7 The authors are very obliged to the Service for Occupational Prevention and Safety of the Brindisi Local Health Agency (SPESALASL/BR) and to the association of the Brindisi entrepreneurs (Confindustria Brindisi) for their friendly and open collaboration.

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