Hazard Identification Techniques In Industry 4d14m

HEALTH AND SAFETY IN INDUSTRIAL PLANTS TCE 3208

HAZARD IDENTIFICATION TECHNIQUES

Identification of hazards is a major component of safety risk assessment in a system. A hazard can be considered as a dormant potential for harm which is present in one form or another within the Industry. The Identification of hazards associated with the day-to-day operations of an organisation, or associated with changes to the operations of an organisation; the assessment of the risks associated with those hazards; and the implementation and management of measures to reduce those risks to an acceptable level (hazard removal; or the application of barriers and/or mitigations – i.e. risk control). Tools and techniques used in hazard identification It should be ed that any system or operation comprises:    

People Procedures Equipment and An environment of operation

1. The Hazard Operability (HAZOP) Study HAZOP is a systematic and structured approach that uses parameter and deviation guidewords. HAZOP relies on a very detailed system description being available for study and usually involves breking down the system into well defined subsystems and functional or process flows between subsystems. HAZOP can be used at varying times during the life cycle of the process, from process development through to the closure of the plant, including hazard assessment of any modifications proposed during the operational life span.

1|Page

The details and information requirements can entail provision of P&I drawings Flow charts Process description Operating manuals. The study is usually conducted by a multidisciplinary group of experts led by a Chairman with experience in performing safety studies. An officer from the Loss Control Department is normally designated to be the Secretary. In the Chemical Process Industry ( I) the typical composition of the HAZOP Study team would compose of the following Departments : PRODUCTION MECHANICAL ENGINEERING ELECTRICAL EGINEERING INSTRUMENTS ENGINEERING TECHNICAL SERVICES LOSS CONTROL DEPARTMENT; and LABORATORY Ideally the Chairman should be from the Technical Services Department. To produce a a comprehensive evaluation of the process a number of GUIDEWORDS (typically no/not/none; more, less, part of, reverse ,other than, as well as) are combined with parameters (flow, pressure, temperature, reaction, level, composition) and systematically applied to each pipe and vessel of the process. The records produced by the study group should indicate the following: (i) The design intent of the pipe or vessel (ii) Any notable deviations from the intent (iii) Possible causes of the deviation (iv) Possible consequences of the deviation if it occurs (v) Additional action that can be performed to minimise the hazard associated with the deviation, if practicable. In recent years computer packages are now available to aid HAZOP Studies.

2|Page

2. What if ? analysis The method uses a creative brainstorming methodology and can be used to evaluate any aspect of a process. For a simple project only 1 or 2 people are required, though with increasing complexity the group size will need to be increased. The examiners are required to be experienced in performing such studies as it can be easy to miss hazards and hence the evaluation would be incomplete. Examples of questions: What if the raw material is of wrong concentration? What if the flow of the feed into the reactor is doubled? Before the study begins a certain level of process information is required. This includes a description of the process, the process drawings, the operating procedure. If the study is being done on an operating plant then interviews with the operating staff can be performed along with a site visit.

Event Tree Analysis (ETA) An event tree is a graphical representation of the logic model that identifies and quantifies the possible outcomes following an initiating event. Event tree analysis provides an inductive approach to reliability assessment as they are constructed using forward logic. Fault trees use a deductive approach as they are constructed by defining TOP events and then use backward logic to define causes. Event tree analysis and fault tree analysis are, however, closely linked. Fault trees are often used to quantify system events that are part of event tree sequences. The logical processes employed to evaluate event tree sequences and quantify the consequences are the same as those used in fault tree analyses.

Fault Tree Analysis ( FTA) Fault tree analysis techniques were first developed in the early 1960’s. Since this time they have been readily adopted by a wide range of engineering disciplines as one of the primary methods of performing reliability and safety analysis. Fault trees graphically represent the interaction of failures and other events within a system. Basic events at the bottom of the fault tree are linked via logic symbols (known as gates) to one or more TOP events. These TOP events represent identified hazards or system failure modes for which predicted reliability or availability data is required. Typical TOP events might be:   

Total loss of production Safety system unavailable Explosion

3|Page

Preliminary Hazard Analysis (PHA) PHA is used as an early means of hazard identification during the design and development of the process. It follows an approach quite similar to that of HAZOP, though the process is split into larger sections – generally major process items and associated lines and Heat Exchangers. The Technique requires a minimum level of knowledge before it can be performed. For example: (i) (ii) (iii) (iv) (v) (vi) (vii) (viii)

Notes on dangerous reactions and side reactions Data on hazardous materials Equipment specification sheets Notes on inventory levels Any available operating information Disturbances resulting in rupture or exceeding mechanical limits Critical defects in construction Flow through abnormal openings

N.B.

ADVANTAGES OF STANDARDS / CODES OF PRACTICE

Standards and Codes of practice provide authoritative guidance on design criteria and possible hazards. The standards and codes of practice provide minimum safety considerations for the process and recommended working practices. Failure Modes and Effects Analysis ( FMEA) FMEA is a bottom up technique. It considers ways in which the basic components of a system can fail to perform their design intent. This could either be at equipment level or at functional level. The technique relies on a detailed system description and considers the ways in which each sub-component of the system could fail to meet its design intent and what the consequences would be on the overall system. For each sub-component of a system FMEA considers:    

All the potential ways that the component could fail The effect that each of these failures would have on the system behavior The possible causes of the various failure modes How the failures might be mitigated within the system

4|Page