HIRARC: HAZOP

HAZOP is an acronym for HAZard and OPerability studies. The term 'HAZOP' originated in ICI and first appeared in the literature in the early 1970s.

Skelton, B, (1997) defined it as a formal, systematic, critical, rigorous examination to the process and engineering intentions of new and existing facilities to assess the hazard potential of mal-operation or mal-function of individual items of equipment and the consequential effects. Wells, G, (1996),  HAZOP is formal, systematic examination of a processing plant in order to identify hazards, failures and operability problems, and assess the consequences from such mal-operation.

HAZOP will generates a list of identified problems, usually with some suggestions for improvement of the system. It will  improves safety, reliability and quality by making people more aware of potential problems. It also will help to sort out loopholes and inconsistencies

in procedures and force plant personnel to get their instructions up to date.

Basic philosophy of HAZOP; if a process operates within its intended design philosophy then undesired hazardous events should not occur. The objective of a HAZOP is mainly to identify how process deviations can be prevented or mitigated to minimize process hazards.

Basic Ideas of HAZOP are to stimulate the imagination of a review team, including designers and operators, in a systematic way so that they can identify potential hazards in a design; AND to let the mind go free in a controlled fashion in order to consider all the possible ways that

process and operational failures can occur.

Outcomes of HAZOP; to recommend necessary changes to a system to meet company risk guidelines, AND to recommend procedures or changes for eliminating or reducing the probability of operating deviations.

HAZOP used as an application at the correct stage in a project means that problems are identified and can be rectified during detailed design. It will provide a considerable amount of useful material for inclusion in the plant operating instructions.

HAZOP Terminology; (1) Design intent - the way in which the plant is intended to operate. (2) Deviation - any perceived deviations in operation from the design intent. Cause - the causes of the perceived deviations. (3) Consequence - the consequences of the perceived deviations. (4) Safeguards - existing provisions to mitigate the likelihood or consequences of the perceived deviations and to inform operators of their occurrence, (5) Actions - the recommendations or requests for information made by the study team in order to improve the safety and/or operability of the plant. (6) Guide words - simple words used to qualify the intent and hence discover deviations. (7) Parameters - basic process requirements such as 'flow', 'temperature', 'pres-sure' and so on.

HAZOP COMPONENTS are Team, Procedure and Guide words. HAZOP Team normally comprises between four and eight members,  each of whom can provide knowledge and experience appropriate to the project to be studied. The team needs to be small enough to be efficient and allow each member to make a contribution, whilst containing sufficient skills and experience to cover the area of study comprehensively.

Two types of person are required in a Hazop team: those with detailed technical knowledge of the process; AND those with knowledge and experience of the HAZOP technique and the ability to chair and report upon technical meetings.

typical member of a Hazop team are chairman or team leader, secretary, process design engineer, control engineer, operations specialist and project engineer. Other specialists may be consulted or be available for specific points.

Chairman or team leader is selected for his or her ability to effectively lead the study. He/she should have sufficient seniority to give the study recommendations the proper level of authority and has a knowledge and experience of the Hazop technique.

Secretary should have a technical appreciation of the project and be familiar with the HAZOP technique. The technical members are usually part of the project design team.

Hazop PROCEDURE

1. Begin with a detailed flow sheet. Break the flow sheet into a number of process units.  eg the reactor area might be one unit, and the storage tank another. Select a unit for study.

2. Choose a study node (vessel, line, operating instruction).

3. Describe the design intent of the study node. eg example, vessel V-I is designed to store the benzene feedstock and provide it on demand to the reactor.

4. Pick a process parameter( flow, level, temperature, pressure, concentration, pH, viscosity, power, Inert and etc.

5. Apply a guide word to the process parameter to suggest possible deviations.(NO, MORE, LESS, REVERSE and etc)

6. If the deviation is applicable, determine possible causes and note any protective systems.

7. Evaluate the consequences of the deviation (if any).

8. Recommend action: what, by whom, by when.

9. Record all information.

10. Repeat steps 5 through 9 until all applicable guide words have been applied to the chosen process parameter.

11. Repeat steps 4 through 10 until all applicable process parameters have been considered for the given study node.

12. Repeat steps 2 through 11 until all study nodes have been considered for the given

section and proceed to the next section on the flow sheet.

 

 

 

HIRARC: FMEA

FMEA is an acronym that stands for Failure Modes and Effects Analysis. It can identifies the potential failure of a system and its effects, assesses the failures to determine actions that would eliminate the chance of occurrence and documents the potential failures.

It’s oriented towards equipment rather than process. Particularly suited for mechanical and electrical systems. FMEA systematically in identifies the consequences of component failure on that system and to  determines the significance of each failure mode with regard to the system's performance. It will improve the safety, Quality and Reliability.

The purpose of this Hazard Identification system are to identify single equipment of system failure modes and the potential effects or consequences of the failure modes on the system or plant, AND to generate recommendation for increasing equipment or system reliability, thus improving process safety.

Resource requirements to do this system are;(1) Technical drawing of the equipment / system,(2) Knowledge of equipment function and failure modes,(3) Personnel with knowledge of system /plant function and responses to failure equipment failure AND (4) Personnel with knowledge of FMEA methodology and analysis.

It also can be define as the extent of the system to be analyzed. It usually performed in relatively small steps. It requires analysts / personnel with a knowledge of the system. It will show the functional relationships of the parts of the system and their performance requirements.

Level of Analysis are based on the functional structure of a system and the failure modes are expressed as failure to perform a particular subsystem function. Primary function is that for which the subsystem was provided and secondary function is one which is merely a consequence of the subsystem's presence.

It will be use to analyze Failure modes of  premature operation, failure to operate when required, intermittent operation, failure to cease operation when required, loss of output or failure during operation, degraded output and etc. It will looks at the likely causes and the effects on both the components and the system, consideration is given to the relative importance of the effects and the sequence AND safeguards against such failures and methods of detecting them are then examined.

Reporting of FMEA are to identify the most significant failures in terms of their effects on the overall system, decide whether or not the existing safeguards and detection devices are adequate AND more detailed analysis on the ‘weak link’. There are no standard reporting format; typically covers  The unit/system, Failure mode, Consequence of failure, Symptoms, safeguards and Corrective action.

 

FMEA CRITICALITY ANALYSIS (FMEACA)

Criticality is defined in the same way as risk – that is, a combination of the severity of an effect and the probability or expected frequency. It is the simplest approach that requires a form of ranking or quantification in effect / consequence AND frequency.

Effects are normally ranked into one of the following categories; (1) loss of mission due to inability of equipment to perform,(2) economic loss due to lack of output or function, (3) damage to plant or third party property, (4) injury to operating personnel or the public, (5) death to operating personnel or the public and/or significant damage to the environment.

Quantification of frequency depends on the data available and may again be a simple ranking, such as one depending on failure probability during the operating time interval, for example; extremely unlikely, remote, Occasional, reasonably frequent AND frequent.

Alternative ranking for effect (reverse order or severity), For Example; (1) catastrophic - may cause death or total system loss,(2) critical- may cause severe injury or damage,(3) major - may cause some injury or damage AND (4) minor - requires unscheduled maintenance.

Corrective Action And Follow-up are (1) reduce probability that the cause of failure will result in the failure mode,(2) reduce severity of failure by redesign or add protection redundancy AND (3) increase probability of detection.