HAZOP method effectiveness

Process Hazards Analysis. Analysis of processes for unrecogni2ed or inadequately controUed ha2ards (see Hazard analysis and risk assessment) is required by OSHA (36). The principal methods of analysis, in an approximate ascending order of intensity, are what-if checklist failure modes and effects ha2ard and operabiHty (HAZOP) and fault-tree analysis. Other complementary methods include human error prediction and cost/benefit analysis. The HAZOP method is the most popular as of 1995 because it can be used to identify ha2ards, pinpoint their causes and consequences, and disclose the need for protective systems. Fault-tree analysis is the method to be used if a quantitative evaluation of operational safety is needed to justify the implementation of process improvements. 

The standard lists six different methods for conducting a hazards analysis. It also provides for the use of other methods that are not hsted in the regulation. The key point is that the regulation permits a great deal of flexibility regarding the choice of method. In particular, there is no requirement that the HAZOP method always be used. The onus is on the facility s management to choose the techniques that most effectively reduce risk. 

Methods for performing hazard analysis and risk assessment include safety review, checkhsts, Dow Fire and Explosion Index, what-if analysis, hazard and operabihty analysis (HAZOP), failure modes and effects analysis (FMEA), fault tree analysis, and event tree analysis. Other methods are also available, but those given are used most often. 

The cost of performing the hazard identification step depends on the size of the problem and the specific techniques used. Techniques such as brainstorming, what-if analyses, or checklists tend to be less expensive than other more structured methods. Hazard and operability (HAZOP) analyses and failure modes and effects analyses (FMEAs) involve many people and tend to be more expensive. But, you can have greater confidence in the exhaustiveness of HAZOP and FMEA techniques—their rigorous approach helps ensure completeness. However, no technique can guarantee that all hazards or potential accidents have been identified. Figure 8 is an example of the hazards identified in a HAZOP study. Hazard identification can require from 10% to 25% of the total effort in a QRA study. 

The what-if analysis is a creative, brainstorming examination of a process or operation conducted by a group of experienced individuals able to ask questions or voice concerns about undesired events. It is not as inherently structured as some other methods, such as the hazard and operability (HAZOP) study or a failure mode and effects analysis (FMEA). 

V Process hazard analysis (PHA) must be performed by a team of experts, including engineers, chemists, operators, industrial hygienists, and other appropriate and experienced specialists. The PHA needs to include a method that fits the complexity of the process, a hazards and operability (HAZOP) study for a complex process, and for less complex processes a less rigorous process, such as what-if scenarios, checklists, failure mode and effects analysis, or fault trees. 

Detonation arresters are typically used in conjunction with other measures to decrease the risk of flame propagation. For example, in vapor control systems the vapor is often enriched, diluted, or inerted, with appropriate instrumentation and control [5]. In cases where ignition sources are present or predictable (such as most vapor destruct systems), the detonation arrester is used as a last-resort method anticipating possible failure of vapor composition control. Where vent collection systems have several vapor/oxidant sources, stream compositions can be highly variable and this can be additionally complicated when upset conditions are considered. It is often cost-effective to perform hazard analyses such as HAZOP or fault... 

For larger or more complex facilities, a systematic approach to identifying incompatibility scenarios and analyzing their severities and likelihoods may be warranted. A process hazard analysis (PHA) approach such as a hazard and operability (HAZOP) study can be an effective tool to facilitate such an effort, and may be required by regulation if the process falls within the scope of regulations. These methods are discussed in Section 4.5. 

Failure Modes and Effects Analysis (FMEA). FMEA is a systematic, tabular method for evaluating the causes and effects of component failures. It represents a bottom-up approach, in contrast with a fault tree, where the approach is top-down. In large part, HAZOP is a well-developed form of FMEA.2... 

HAZOP and What-If reviews are two of the most common petrochemical industry qualitative methods used to conduct process hazard analyses. Up to 80% of a company s process hazard analyses may consist of HAZOP and What-If reviews with the remainder 20% from Checklist, Fault Tree Analysis, Event Tree, Failure Mode and Effects Analysis, etc. An experienced review team can use the analysis to generate possible deviations from design, construction, modification, and operating intent that define potential consequences. These consequences can then be prevented or mitigated by the application of the appropriate safeguards. 

This publication is intended to provide guidance to HAZOP (Hazard and Operability) and What-If review teams associated with the petroleum, petrochemical, and chemical industries. It describes the nature, responsibilities, methods and documentation required in the performance of such reviews. This ensures the reviews are conducted in a timely, effective and professional manner as may be prescribed by a company s Process Safety Management (PSM) Policy. 

The first task is crucial in process system safety analysis, because the effectiveness of the other two tasks depends on it. The technique of hazard and operability (HAZOP) study is a systematic approach to identifying most potential hazards and operating problems. The technique in contrast to the traditional methods is simple, creative, and flexible. 

Batch reactor, typical, DACSL kinetic and reactor modeling, 94 Benefits, HAZOP study, 37 Benson s second-order group additivity method, CHETAH program, 82 Benzoyl peroxide (BPO), effect of dilution with xylene, CHETAH program, 87... 

What-if method, hazard and operability (HAZOP) study, failure mode and effects analysis, and fault tree analysis. 

Prior to stan-up of i production campaign, a process hazards analysis (PHA) should be conducted. A common and generally accepted PHA technique is the HAZOP (Hazard and Operability) method, although alternate teehniques can he equally effective 113.14,l.s, The purpose of the PHA is to evaluate the maiuiltictiiring prtteess to identity aiul address potential safely issues prior to start-up. 

There are various types of analyses that are used for a process hazard analysis (PHA) of the equipment design and test procedures, including the effects of human error. Qualitative methods include checklists, What-If, and Hazard and Operability (HAZOP) studies. Quantitative methods include Event Trees, Fault Trees, and Failure Modes and Effect Analysis (FMEA). All of these methods require rigorous documentation and implementation to ensure that all potential safety problems are identified and the associated recommendations are addressed. The review should also consider what personal protective equipment (PPE) is needed to protect workers from injuries. 

One effective systematic method, a variation on which will be outlined further in this book, is the SWIFT or Structured What-If Technique. SWIFT is a systems-based risk identification technique that employs structured brainstorming, using pre-developed guidewords or headings in combination with prompts elicited from participants (which often begin with the phrases What if... or How could... ), to examine risks and hazards at a systems or subsystems level [1]. The technique was originally developed as a simpler alternative to HAZOP (see Sect. 13.6.2). 

An inductive analysis works bottom upwards. A failure event is postulated. The analysis team then determines what effect this failure could have on the overall system. The HAZOP and Event Tree Analysis methods are both inductive. 

First, the importance of learning lessons from past process safety incidents is highlighted in Section 3.2. The subsequent section presents preliminary hazard review procedure, risk matrix, what-if method, plot plan and layout review, pressure relief system review and fire safety design aspects. Section 3.4 presents PHA techniques and procedures hazards and operability analysis (HAZOP), failure modes and effects analysis (FMEA), instrumented protective system (IPS) design, fault trees, event trees, layer of protection analysis (LOPA) and finally SIS life eyele. The importanee of revision of PSI is highlighted in Seetion 3.5. 

Proper application of hazard analysis methods and PHA (What-if, HAZOP, FMEA) in pre-FEED and FEED stages is very important to develop safer and cost-effective designs... 

HSE assessments have a long tradition within the oil-and gas industry. These assessments use a wide range of methodologies, from the strict quantitative methods such as QRA (Quantitative Risk Analysis) and FMECA (Failure Mode Effect and Criticality Analysis) to the more qualitative methods such as HAZOP (HAZard OPerability analysis). Most methods combine qualitative and quantitative data and approaches. For example, an FMECA basically uses generic failure data, expert judgments are likewise important. 

In 1985, the American Institute of Chemical Engineers (AIChE) initiated a project to produce the Guidelines for Hazard Evaluation Procedures. This document, prepared by Battelle, includes many system safety analysis tools. Even though frequently identified as hazard and operability (HazOp) programs, the methods being developed by the petrochemical industry to use preliminary hazard analyses, fault trees, failure modes, effects, and criticality analyses, as well as similar techniques to identify, analyze, and control risks systematically, look very much like system safety efforts tailored for the petrochemical industry (Goldwaite 1985). 

Chapter 3 presents introductory aspects of safety and human factors. Chapter 4 is devoted to methods considered useful to perform patient safety analysis. These methods include failure modes and effect analysis (FMEA), fault tree analysis (FTA), root cause analysis (RCA), hazard and operability analysis (HAZOP), six sigma methodology, preliminary hazard analysis (PFfA), interface safety analysis (ISA), and job safety analysis (JSA). Patient safety basics are presented in Chapter 5. This chapter covers such topics as patient safety goals, causes of patient injuries, patient safety culture, factors contributing to pahent safety culture, safe practices for better health care, and patient safety indicators and their selection. 

Use of analytical methods such as hazard and operabiUty analysis (HAZOP), failure mode, effect analysis (FMEA) , and master logic diagrams ... 

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