Implementing Hazard & Operability (HAZOP) Studies Throughout the Project Life Cycle

Transcription

1 Implementing Hazard & Operability (HAZOP) Studies Throughout the Project Life Cycle Vivian Papen Sound Transit Seattle, WA Ronald Harvey Sound Transit Seattle, WA Hamid Qaasim Sound Transit Seattle, WA Peregrin Spielholz Sound Transit Seattle, WA ABSTRACT Rail Systems provide an efficient, safe, convenient, and environmentally - friendly transportation means to the public. Emphasis on including operability in the design is critical to provide safe, user-friendly and reliable rail systems to both the public and the operators. Hazard & Operability (HAZOP) studies were initially developed to systematically examine the design of chemical processes, but have been extended to other systems which have complex operations. Professionals using HAZOP studies can review individual system and subsystem designs, discover possible causes of deviations from the intended functions, identify potential hazards or operability problems due to these deviations; and thereby recommend mitigation measures as appropriate. Several prerequisites are required for HAZOP Studies to achieve effective and useful outcomes in improving system design and operability of rail systems. This paper will explain the advantages of implementing HAZOP studies throughout the project life cycle and while the system is being operated; provide details of planning and preparing HAZOP studies at different project phases, and managing the results from HAZOP studies until the end of the project life cycle. It will describe how HAZOP studies can be used to provide the best practical assessment on potential operational or design changes. INTRODUCTION Every day, thousands of patrons rely on commuter rail, light rail, and street cars to travel to and from home. During special events, many spectators, audiences and attendees are taking advantage of an efficient, reliable, economical and hassle-free rail system to go to the venue. A rail system requires engineering, operational, maintenance, human factor, and public inputs to build a safe, reliable, user-friendly system. In the last decade, human factors, including operator error, improper maintenance work, and design modifications were the primary contribution of all the recent railway accidents. Studies also show the lack of communication between system design modifications, operation department, and maintenance department. Hazard & Operability (HAZOP) studies provide a guideline to System Safety & Assurance engineer to perform hazard analyses, which consider design, operations, maintenance and human factors, during the design, construction and testing phases. As the railway system is operating, the System Safety & Assurance Department can utilize HAZOP studies to review any design modification, operational and maintenance issues, and provide any recommended mitigation measures to reduce the risk of the potential hazards. HAZOP studies require multiple departments to participate and have regular meetings through the whole project life cycle. Since HAZOP studies are a new methodology for the System Safety & Assurance Department to implement, the transit authority needs to understand the advantages of implementing HAZOP and encourage all departments to participate. Training should be conducted by an experienced HAZOP professional. When transit agency understands the advantages of implementing HAZOP, the System Safety and Assurance Department can then plan and prepare all the necessary documentation with different departments at different project phases, develop a management system to monitor all the results from HAZOP, and implement a committee that meets regularly to review any concerns or potential problems when the railway is operating. ADVANTAGES OF IMPLEMENTING HAZOP STUIDES Traditional System Safety & Assurance Analyses can be performed by the specialist only when all the relevant documentation has been assembled. He/she then bases 1

2 these analyses on his/her previous experiences and historical data to produce the intended result. Even then sometimes, the results don t cover all different perspectives of the system. HAZOP studies have been used in the chemical process industry for many years. However, it is not as well known within the transit industry. Knowing the advantages of HAZOP studies can help all the key departments to understand how to design and operate a safe, reliable, and user-friendly railway system. The advantages of a HAZOP study affects the employees approach to identify the situations which require the resolution of any hazardous issues in the system. A structured and systematic approach is one of the crucial skills in HAZOP studies to identify potential hazardous situations or unintended design functions in the system. HAZOP studies procedures using the description of a system and systematically applies certain questions, i.e. operation modes, scenarios, and what if statements to each subsystem/part/element in order to discover how deviations from the intended designed can occur and whether that deviation will rise to hazards or operability issues. All operation modes, Normal, Degraded, Emergency, will be considered systematically with a combination of possible scenarios. In addition to the operation modes and scenarios, guide words are used along with appropriate parameters, to identify deviations of the intended design functions. A combination of guide words can be used if it is meaningful to the design function. The discussion of each combination of operation mode, scenario, and guide words will not be exhausted until all HAZOP study meeting participants agree that no more hazardous situations, unintended design functions, and operability issues can be identified. Table 1 shows examples of guide words for transit system: Deviation Guideword Example interpretation for process industry Negative NO No part of the intention is achieved. Quantitative modification Qualitative modification Example interpretation for a Programmable Electronic System, PES No data or control signal passed MORE A quantitative increase Data is passed at a higher rate than intended LESS A quantitative decrease Data is passed at a lower rate than intended AS WELL AS PART OF Impurities present Simultaneous execution of another operation/step Only some of the intention is achieved, i.e. only part of an intended fluid transfer take place Substitution REVERSE Covers reverse flow in pipes and reverse chemical reactions OTHER A result other than the original THAN intention is achieved, i.e. transfer of wrong material Time EARLY Something happens early relative to clock time LATE Something happens late relative to clock time Order or BEFORE Something happens too early in a sequence sequence AFTER Something happens too late in a sequence Some additional or spurious signal is present The data or control signals are incomplete Normally not relevant The data or control signals are incorrect The signals arrive too early with reference to clock time The signals arrive too late with reference to clock time The signals arrive earlier than intended within a sequence The signals arrive later than intended within a sequence. Table 1. Example of deviations and the associated generic list of guide word 1 HAZOP study meetings require a team of people with different areas of expertise to identify possible hazardous situations from multiple perspectives. HAZOP study meetings are carried out by a team because the team members can inspire each other and develop from each other s ideas. HAZOP study meetings help the operators and maintainer to understand the reasons for different design features and help them prepare operational and maintenance documentation (operation / maintenance plan, procedures and rule books). In addition, Designers or Engineers have the opportunity to be aware of any operational or maintenance issues identified in the past so that they can modify the design without jeopardizing the operators and maintainers performances. System users behaviors can also be discussed candidly to design a userfriendly system. If any design or operational issues are identified after the system is being operated, HAZOP studies assist engineers / designers, operators, and maintainers to review the situation and recommend any mitigation measures which will comprise of the inputs from Design / Engineering Department and Operational & Maintenance Department. Interfaces are sometimes neglected which can lead to inter-operability issues. The inter-operability issues may not be identifiable until all the systems / subsystems are installed and tested. HAZOP study meetings require multiple disciplines to review or analyze the intended design functions. Functional block diagrams are necessary to ensure that a structured and systematic approach is being performed and it does not overlook any design parameters. Functional block diagrams help the HAZOP study meeting team members to understand the intended design functions and all the interfaces (internal and external) that apply to the System. Multiple engineers or designers, responsible for different systems / subsystems, will be able to discuss their interfaces to ensure the intended design functions are not altered. At the same time, testing and commissioning documentation can be prepared regarding these interfaces. With the understanding of the advantages of implementing HAZOP studies, changes can be implemented within the transit agency to ensure the railway is designed with the intended functions, highquality of operability and that it is a user-friendly system. Planning and Preparing HAZOP Studies 1 IEC Hazard and operability studies (HAZOP studies) Application guide, International Electrotechnical Commission,

3 HAZOP studies require multiple departments to participate and provide their expertise in system design, operation procedures and maintenance procedures. Well organized HAZOP study meetings with participants who are well trained and have good knowledge of HAZOP methodology is important to implement HAZOP study Meetings in a timely manner with good and valuable results. Training, defining, planning, preparation and examination are essential steps before HAZOP study meetings can be organized by System Safety and Assurance Department. HAZOP studies are an intuitive and simple risk management tool but its use is not commonly known or team members often have not had prior experience in HAZOP study meetings. The System Safety and Assurance Department is ideal to provide training for HAZOP study meeting team members and transit authority management. In the training, the HAZOP study concept can be introduced, all the necessary steps which are required for performing effective HAZOP studies can be discussed and the post-meeting follow-up and documentation can be suggested. In addition to introducing the necessary steps, a mock HAZOP study meeting is recommended to provide up-front experience and expectations in the upcoming HAZOP study meetings. It is recommended to organize HAZOP study training for those who are specifically involved in the HAZOP study meetings a month or so before every HAZOP study meeting to insure team members are prepared and reduce the probability of explaining the methodology during the study. System Safety and Assurance Department is required to work closely with Engineering department s person-incharge to plan and define the scope and objectives of the upcoming HAZOP study meeting(s). At different project phases, different system/subsystem/elements/interface functions will be chosen to be reviewed and discussed in the meeting. Positive and constructive attitudes are important to have a successful HAZOP study meeting. The team should not be too large, ideally between four to eight technical members consisting of personnel who provide jointly or individually with (1) Practical experience of HAZOP technique in organizing and leading HAZOPs, (2) Complete knowledge of the system under consideration including associated hazards of the operations concerned, (3) Sufficient seniority and authority to minimize the referral of decisions outside of the meeting. The HAZOP Chairman should not have been closely associated with the design, should have extensive experience in HAZOP technique, experienced with system safety and assurance analyses, and have significant management and organizational skills to handle and motive the rest of the team. A HAZOP secretary is required to assist organizing HAZOP study meetings, take clear and precise notes from the meeting and record all the details on HAZOP form. In addition, team members with extensive knowledge in the design, operating, maintaining of the function(s) should be included the meetings. The System Safety and Assurance Department will prepare the HAZOP Studies Plan, which includes the schedule of all the upcoming HAZOP study meetings, the scope and objective of individual meeting, the estimated time duration, and the style of recording HAZOP studies meeting results. Individual HAZOP study meeting member s pack, should include Functional Block Diagrams for the specific system function, system description provided by the Engineering department, historical data if applicable, operation modes, agreed guide words, HAZOP Studies recording format, date, time, and the location of the meeting. It should be issued to individual team members to review and prepare before the HAZOP meetings. The HAZOP Study Meeting Member Pack is required to be issued to all the team members a minimum of three weeks before the meeting. This is to ensure any recent design changes are known and give time to contact other experienced persons if they are needed at the meeting. In addition, team members will have time to discuss the scope and objective of the meeting should any further modifications of the process be required. In the HAZOPs meetings, team members will examine the physical systems which are related to the specific system functions. When the physical systems are identified, the systems are required to be broken down into smaller parts or elements. The HAZOP Chairman will lead the HAZOP study process. The designer / engineer is recommended to provide description of the function, systems, parts and elements. Detailed functional block diagrams for each level (system, parts, and elements) are recommended to be provided in the meetings. If the detailed functional block diagrams cannot be provided, conceptual drawings can also help the process. Pre-identified guide words, operation modes, and scenarios are applied to each of the parts or elements to identify any potential deviation systematically. It is important to be aware that not all combination of guide words and parts or elements is expected to generate possible reasonable or credible deviations. In general, it is best to list all the conditions to identify any potential hazardous situations or operability issues even if they may 3

4 not be a credible situation. When any potential noncredible situation is identified, it should be further assessed in the meeting to determine if it in fact has some credible component. However, it is not necessary to record the instances when the combinations of guide words, operation modes and scenarios do not yield any credible deviations. The HAZOP Secretary will record the combination as a checklist to ensure all combinations have been examined. Well trained HAZOP study meeting team members and well organized meetings generate useful recommended mitigation measures to modify system design and provide inputs to create better operational and maintenance procedures that assist to reduce the probability of hazardous situations or operability issues. 4

5 Figure 1. Flow Chat of the HAZOP examination procedure Guideword 1 1 IEC Hazard and operability studies (HAZOP studies) Application guide, International Electrotechnical Commission,

6 Figure 2. Flow Chat of the HAZOP examination procedure Element 1 1 IEC Hazard and operability studies (HAZOP studies) Application guide, International Electrotechnical Commission,

7 Post-HAZOP Studies Meetings and follow-up HAZOP study meetings review system design functions systematically to identify any potential hazardous situations or operability issues. All the identified hazardous situations and operability issues are required to be reviewed, revised if necessary, updated, and monitored regularly until the end of the project life cycle. After the HAZOP study meeting, all hazard entries are required for review by all the team members in order to agree with the entries description, recommended mitigation measures, and risk ranking identified by System Safety and Assurance Department. All the hazard entries should be reviewed within two weeks after the meeting. Any team member can provide additional documentation for the design, any changes that have been made on the design since the meetings, and delete any hazard entries which are not relevant to the system anymore due to design changes. If any major design changes have happened since the meeting, an additional HAZOP study meeting will be required to review the system functions and identify any potential hazardous situations or operability issues. HAZOP study meeting reports will be prepared by the System Safety and Assurance Department and issued to all team members and the director of engineering/ designer, director of operation and director of maintenance as reference. The System Safety and Assurance Department will transfer all the agreed hazard entries from HAZOPs meetings to Hazard log / Hazard management system to monitor all the hazard entries regularly throughout the project life cycle. The System Safety and Assurance Department will arrange quarterly safety review group meetings with different system/subsystem engineers/designers to review all the related hazard entries and update individual mitigation measures with documentation references accordingly. Any hazard entries related to operation and maintenance will also be reviewed with the operators and maintainer to confirm all the mitigation measures are implemented in the procedures or plans with reference to the specific documentation. Updating hazard entries require multiple departments to work together. System Engineers / Designers, Operation team, and Maintenance team are recommended to submit a Hazard log / Hazard management system report monthly to System Safety and Assurance Department for the updates of all their assigned hazard entries. All hazard entries will be monitored, updated, reviewed, and revised if necessary until the system is opened for the public. All hazard entries will be stored in the hazard log / hazard management system for any future reference if any similar hazardous situations or operability issues are identified after the system is in operation. Regular HAZOP study meetings are recommended during the System operation phase to review any systems, operational, and maintenance concerns. If any new hazardous situations or operability issues are identified, further HAZOP study meetings assist in reconvening the engineers and specialists. They will follow the same process to review the hazardous situations or operability issues, provide recommended mitigation measures according to the actual operating modes for which the incidents happened. Appropriate recommended mitigation measures will be provided for all departments to review and agree. The System Safety and Assurance Department will assist engineers/operators/maintainers to implement the recommended mitigation measures into the design changes, operational procedures, and maintenance procedures. In addition, the HAZOP study meeting results can assist obtaining support from the management to perform any changes in the system. Post HAZOP efforts are very important for successful HAZOP study. It will affect whether the hazardous situations have been reduced or eliminated from the system. Implementing HAZOP study meetings and review of the existing HAZOP study entries with similar hazardous situations in the operation phases can help to mitigate any incidents without jeopardizing the existing system design functions, operators and maintenance procedures / rules. CONCLUSION A safe, reliable, and user-friendly rail system requires multiple disciplines to design, operate and maintain properly. HAZOP Studies use a different methodology than traditional System Safety and Assurance Analyses, which largely rely on individuals working on desktop scenarios. Through collaborative effort of multiple individuals with multiple perspectives, many potential hazards and operational issues may be prevented. It creates a brain-storming environment which allows all participants to discuss potential hazards and operational issues systematically. Through the use of guide words in reviewing intended design functions, HAZOP Studies help participators identify situations that otherwise would be difficult to detect, analyze and predict. The output of HAZOP Studies meetings provide mitigations to modify existing or future systems, and provides guidelines to 7

8 development operation/maintenance procedures and design criteria for future projects. In conclusion, HAZOP Studies should be considered as one of the primary methodologies for System Safety and Assurance Department to utilize for a complete overview of hazard analysis from multiple perspectives. REFERENCE Engineering Safety Management (The Yellow Book), Rail Safety and Standards Board on behalf of the UK Rail industry, 2007 IEC Hazard and operability studies (HAZOP studies) Application guide, International Electrotechnical Commission, 2001 Keltz, Trevor, Hazop and Hazan: Identifying and assessing process industry hazards. United Kingdom: Institution of Chemical Engineers Ministry of Defense, Defense standard 00-58, HAZOP studies on Systems Containing Programmable Electronics, 19 May