Failure Mode And Effect Analysis (FMEA)

FAILURE MODE AND EFFECT ANALYSIS (FMEA)

            This is an analytic technique, which explores the effects of failures or malfunctions of individual components in a system – i.e., “if this part fails, in this manner, what will be the result?”. First the system under the consideration must be defines, so that system boundaries are established. Thereafter the essential questions are:

1. How can each component / part fail?
2. What might cause these modes of failure?
3. What could the effects be if the failures did occur?
4. How serious are these failure modes?
5. How is each failure mode detected?

An example FMEA worksheet:

Component / part	Potential failure mode	Potential effects of failure	Severity	Potential causes of failure	How will failure be detected	Action to control risk
Bulb	Filament break	No illumination	/	Voltage too high	Human visual	Regulate voltage
Bulb	implosion	Etc.,

NOTE: There are many software's available for FEMA, the format of one differs to another.

The level of risk determined by Risk Matrix

Or         RISK = PROBABILITY OF FAILURE X SEVERITY CATEGORY

Where severity may be categorized thus:

Category	Degree	Description
I	Minor	Functional failure of part of machine or process – No potential injury
II	Critical	Failure will probably occur without major damage to system or serious injury
III	Major	Major damage to system another potential serious injury to personnel
IV	Catastrophic	Failure causes complete system loss and / or potential or fatal injury

And probability may be categorized thus:

Level	Probability	Individual Failure Mode
A	Frequent	Likely to occur frequently.
B	Probable	Likely to occur several times in the life of an item.
C	Occasional	Likely to occur sometime in the life of an item.
D	Remote	Unlikely to occur but possible.
E	Improbable	So unlikely that occurrence may not be experienced.

Application:

                     A practical application of the FEMA technique would involve the completion of a worksheet in which the failure modes of individual components, such as relays and switches, are identified, evaluated and risk priority codes identifies. A summary sheet can then be prepared in which failure modes are listed in declining order or risk priority codes. The summary should also list the corrective measures required to reduce the frequency of failure or to mitigate the consequences. Corrective actions could include changes in design, procedures organizational arrangements e.g. the additional of redundant features and detection methods or a change in maintenance policy may be suggested.

                   FMEA can be used for single point failures but can be extended to cover concurrent failure modes. It can be a costly and time consuming process but once completed and documented it is available for future reviews and as a basis for other risk assessment techniques such as Fault Tree Analysis and Event Tree Analysis.

What if Analysis

“WHATIF” HAZARD ANALYSIS

                   “What–If” Hazard Analysis is a structured brainstorming method of determining what things can go wrong and judging the likelihood and severity of those situations occurring. The answers to these questions form the basis for making judgments regarding the acceptability of those risks and determining a recommended course of action for those risks judged to be unacceptable.

                   Assembling an experienced, knowledgeable team is probably the single most important element in conducting a successful “WhatIf” analysis. Individuals experienced in the design, operation, and servicing of similar equipment or facilities are essential. Their knowledge of design standards, regulatory codes, past and potential operational errors as well as maintenance difficulties brings a practical reality to the review. Team members may include the P.I., Laboratory Manager, RM&S representative(s), and representatives with specific skills, as needed (maintenance rep., compressed gas rep., manufacturer rep. etc.).

                The next most important step is gathering the needed information. The operation or process must be understood by the review team. If these documents are not available, the first recommendation for the review team becomes clear. Develop the supporting documentation! Effective reviews cannot be conducted without updated reliable documentation. An experienced team can provide an overview analysis, but not without proper documentation. 

“WhatIf” questions can be formulated around human errors, process upsets, and equipment failures.

The questions could address any of the following situations:

• Failure to follow procedures or procedures followed incorrectly
• Procedures incorrect or latest procedures not used
• Operator inattentive or operator not trained
• Procedures modified due to upset
• Process conditions upsets
• Equipment failure
• Instrumentation miscalibrated
• Debugging errors
• Utility failures such as power, steam, gas
• External influences such as weather, vandalism, fire
• Combination of events such as multiple equipment failures

             To minimize the chances that potential problems are not overlooked, moving to recommendations is held until all of the potential hazards are identified.

           The review team then makes judgments regarding the likelihood (e.g., unlikely, possible, quite possible) and severity (e.g., minor, serious, very serious) of the “WhatIf” answers. If the risk indicated by those judgments is unacceptable then a recommendation is made by the team for further action. The completed analysis is then summarized and prioritized, and responsibilities are assigned.

Hazard and Operability study (HAZOP)

Hazard and Operability study (HAZOP)

          A Hazard and Operability (HAZOP) study is a structured and systematic examination of a planned or existing process or operation in order to identify and evaluate problems that may represent risks to personnel or equipment, or prevent efficient operation.

       The HAZOP Technique was developed to Chemical process systems, other types of systems, complex operations and software systems.

A HAZOP study is a qualitative technique and is carried out by multi-disciplinary team (HAZOP) during a set of meetings.

The HAZOP study should preferably be carried out as early in the design phase as possible - to have influence on the design. On the other hand; to carry out a HAZOP we need a rather complete design. As a compromise, the HAZOP is usually carried out as a final check when the detailed design has been completed. A HAZOP study may also be conducted on an existing facility to identify modifications that should be implemented to reduce risk and operability problems. 

  HAZOP Team & Meetings

HAZOP Team Leader:

Responsibilities:

•  Define the scope for the analysis
•  Select HAZOP team members
•  Plan and prepare the study
•  Chair the HAZOP meetings

1.  Trigger the discussion using guide-words and parameters
2.  Follow up progress according to schedule/agenda
3.  Ensure completeness of the analysis

The team leader should be independent (i.e., no responsibility for the process and/or the performance of operations).

HAZOP Participant:

• Be active! Everybody’s contribution is important
• Be to the point. Avoid endless discussion of details
• Be critical in a positive way - not negative, but constructive
• Be responsible. He who knows should let the others know

HAZOP Meeting:

Proposed agenda:

1. Introduction and presentation of participants

2. Overall presentation of the system/operation to be analyzed

3. Description of the HAZOP approach

4. Presentation of the first node or logical part of the operation

5. Analyze the first node/part using the guide-words and parameters

6. Continue presentation and analysis (steps 4 and 5)

7. Coarse summary of findings

Focus should be on potential hazards as well as potential operational problems

HAZOP Recording:

The findings are recorded during the meeting(s) using a HAZOP work-sheet, either by filling in paper copies, or by using a computer connected to a projector (recommended). The HAZOP work-sheets may be different depending on the scope of the study - generally the following entries (columns) are

included:

1. Ref. no.

2. Guide-word

3. Deviation

4. Possible causes

5. Consequences

6. Safeguards

7. Actions required (or, recommendations)

8. Actions allocated to (follow-up responsibility)

Process HAZOP

As a basis for the HAZOP study the following information should be available:

1. Process flow diagrams
2. Piping and instrumentation diagrams (P&IDs)
3. Layout diagrams
4. Material safety data sheets
5. Provisional operating instructions
6. Heat and material balances
7. Equipment data sheets Start-up and emergency shut-down procedures

HAZOP Procedure:

1. Divide the system into sections (i.e., reactor, storage)

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

3. Describe the design intent

4. Select a process parameter

5. Apply a guide-word

6. Determine cause(s)

7. Evaluate consequences/problems

8. Recommend action: What? When? Who?

9. Record information

10. Repeat procedure (from step 2)

Modes of operation:

The following modes of plant operation should be considered for

each node:

1. Normal operation
2. Reduced throughput operation
3. Routine start-up
4. Routine shutdown
5. Emergency shutdown
6. Commissioning
7. Special operating modes

Worksheet entries:

Node

A node is a specific location in the process in which (the deviations of) the design/process intent are evaluated. Examples might be: separators, heat exchangers, scrubbers, pumps, compressors, and interconnecting pipes with

equipment.

Design Intent

The design intent is a description of how the process is expected to behave at the node; this is qualitatively described as an activity (e.g., feed, reaction, sedimentation) and/or quantitatively in the process parameters, like temperature, flow rate, pressure, composition, etc.

Deviation

A deviation is a way in which the process conditions may depart from their design/process intent.

Process Parameters:

Process parameters may generally be classified into the following

groups:

• Physical parameters related to input medium properties
• Physical parameters related to input medium conditions
• Physical parameters related to system dynamics
• Non-physical tangible parameters related to batch type processes
• Parameters related to system operations

These parameters are not necessarily used in conjunction with guide-words:

1. Instrumentation
2. Relief
3. Start-up / shutdown
4. Maintenance
5. Safety / contingency
6. Sampling

HAZOP PROCEDURE

A procedure HAZOP is an examination of an existing or planned operation (work) procedure to identify hazards and causes for operational problems, quality problems, and delays.

• Can be applied to all sequences of operations
• Focus on both human errors and failures of technical systems
• Best suited for detailed assessments, but can also be used for coarse preliminary assessments
• Flexible approach with respect to use of guide-words

Procedure:

1. Breakdown of operation (work) procedure to suitable steps
2. Define intention of each step
3. Establish boundary conditions 
   else as 
   conventional Process HAZOP
4. Apply guide-words to intention and boundary conditions for 
   each step.

Guide words

Guide words	Meaning
No (not, none)	None of the design intent is achieved
More(more of, higher)	Quantitative increase in a parameter
Less (lessof, lower)	Quantitative decrease in a parameter
As well as(more than)	An additional activity occurs
Part of	Only some of the design intention is achieved
Reverse	Logical opposite of the design intention occurs
Other than(other)	Complete substitution - another activity takes place

Reporting:

Report Contents:

Summary

1. Introduction

2. System definition and delimitation

3. Documents (on which the analysis is based)

4. Methodology

5. Team members

6. HAZOP results

– Reporting principles

– Classification of recordings

– Main results

Appendix 1: HAZOP work-sheets

Appendix 2: P&IDs (marked)

Review Meetings:

Review meetings should be arranged to monitor completion of

agreed actions that have been recorded. The review meeting 

should involve the whole HAZOP team. A summary of actions 

should be noted and classified as:

• Action is complete
• Action is in progress
• Action is incomplete, awaiting further information

HAZOP Results:

• Improvement of system or operations

             – Reduced risk and better contingency
             – More efficient operations

• Improvement of procedures

             – Logical order
             – Completeness

• General awareness among involved parties
• Team

Advantages:

• Systematic examination
• Multidisciplinary study
• Utilizes operational experience
• Covers safety as well as operational aspects
• Solutions to the problems identified may be indicated
• Considers operational procedures
• Covers human errors
• Study led by independent person
• Results are recorded

Pitfalls and Objections:

• Time consuming
• Focusing too much on solutions
• Team members allowed to divert into endless discussions of details
• A few of the team members dominate the discussion
• “This is my design/procedure”

           – Defending a design/procedure
           – HAZOP is not an audit

• “No problem”
• “Wasted time”

Standards & Guidelines

1. IEC 61882. “Hazard and operability studies (HAZOP studies)

– Application guide”. International Electrotechnical Commission, Geneva.

2. Crawley, F., M. Preston, and B. Tyler: “HAZOP: Guide to best practice. Guidelines to best practice for the process and chemical industries”. European Process Safety Centre and Institution of Chemical Engineers, 2000

3.Kyriakdis, I.: “HAZOP - Comprehensive Guide to HAZOP in CSIRO”, CSIRO Minerals, National Safety Council of Australia, 2003

Risk Analysis

Risk Analysis

       Everyone in the engineering profession is familiar with Murphy's Law, "If anything can go wrong, it will.". The extended version which states, "If a series of events can go wrong, it will do so in the worst possible sequence". 

Risk analysis is a sort of Murphy's Law review in which events are analyzed to see the destructive nature that they might produce. Risk analysis is a term that is applied to a number of analytic techniques used to evaluate the level of hazardous occurrences. Technically, risk analysis is a tool by which the probability and consequences of accidental events are evaluated for hazard implications. These techniques can be either qualitative or quantitative.

Risk analysis can be broken down into four main steps:
(1) Identify accident occurrences.
(2) Estimate the frequency of the occurrences.
(3) Determine the consequences of each occurrence.
(4) Develop risk estimates associated with the frequency and consequence.

Risk Identification and Evaluation

  The basic methodology adopted for the formal risk evaluation in the petroleum and related industries, both for existing facilities and new projects, normally contain the following steps:

1. Definition of the Facility - A general description of the facility is identified. Input and outputs to the facility are noted, production, manning, basic process control system (BPCS), ESD, fire protection philosophy, assumptions, hazardous material compositions, etc.
2. Identification of Hazards - A listing of the processes and storage of combustible materials and the process chemistry that can precipitate an incident.
3. Development of Accidental Events - Identified scenarios that can cause an accident to occur.
4. Frequency Analysis - An examination of the probabilities or possibilities of and accident to occur.
5. Consequence Modeling - A description of the possible incidents that can occur.
6. Impact Assessment - The development of the severity of the incident in terms of injuries, damage, environmental impact, business interruption and public reaction.
7. Summation of Risk - The combination of severity and probability estimates an incident to occur.
8. Effect of Safety Measures An evaluation of the mitigation effects of layers of protective systems of different integrity, on the effects or prevention of an incident.
9. Review Against Risk Acceptance Criteria - The comparison of an incident risk which is supplemented by the selected safety measures to achieve the requirements for company safety levels.

During the process hazards identification and definition phase of a project design, a basic process control system (BPCS) strategy is normally developed in conjunction with heat and material balances for the process.

Both qualitative and quantitative evaluation techniques may be used to consider the risk associated with a facility. The level and magnitude of these reviews should be commensurate with the risk that the facility represents.

Qualitative Assessment

Qualitative assessment are studies base on the generic experience of personnel and do not involve mathematical estimations. Overall these reviews are essentially checklist reviews in which questions or process parameters are used to prompt discussions of the process design and operations and possible accident scenarios.

 Some of the examples are HAZOP, What if reviews, Preliminary hazard analysis (PHA), etc. 

Quantitative Assessment

Quantitative reviews are mathematical estimations that rely upon historical evidence or estimates of failures to predict the occurrence of an event. These reviews are sometimes referred to as a Quantitative Risk Assessment (QRA).

Some of the examples are Event tree analysis, Fault tree analysis, Failure mode effect analysis.

There are other studies according to hazards present at the time of process like leak estimation, combustible vapor dispersion, fire water reliability, etc.,

Note: In glossary some terms are given for readers reference.


Glossary

Checklist or Worksheet - A standardized listing which identifies common protection features required for typical facilities is compared against the facility design and operation. Risks are expressed by the omission of safety systems or system features.

Preliminary Hazard Analysis (PHA) - Each hazard is identified with potiential causes and effects. Recommendations or known protective measures are listed.

What-If Reviews - A safety study which by which “What-If’ investigative questions (brainstorming approach) are asked by an experienced team of a hydrocarbon system or components under examination. Risks are normally expressed in a qualitative numerical series (e.g., 1 to 5).

HAZOP - A formal systematic critical safety study where deviations of design intent of each component are formulated and analyzed from a standardized list. Risks are typically expressed in a qualitative numerical series (e.g., 1 to 5) relative to one another. 

Relative Ranking Techniques (DOW and MOND Hazard Indices) - This method assigns relative penalties and awards points for hazards and protection measures respectively in a checklist accounting form. The penalties and award points are combined into an index which is an indication of the relative ranking of the plant risk.

Event Trees (ET) - A mathematical logic model that mathematically and graphically portrays the combination of events and circumstances in an accident sequence, expressed in an annual estimation.

Fault Trees (FT) - A mathematical logic model that mathematically and graphically portrays the combination of failures that can lead to a specific main failure or accident of interest, expressed in an annual estimation.

Failure Modes and Effects Analysis (FMEA) - A systematic, tabular method of evaluating the causes and effects of known types of component failures, expressed in an annual estimation.

Leak Estimation - A mathematical model of the probability and amount of potential hydrocarbon releases that may occur from selected processes or locations.

Depressurization and Blowdown Capabilities - A mathematical calculation of the system sizing and amount of time needed to obtain gas depressurization or liquid blowdown according to the company’s philosophy of plant protection and industry standards (i.e., API RP 521).

Combustible Vapor Dispersion (CVD) - A mathematical estimation of the probability, location, and distance a release of combustible vapors will exist until dilution will naturally reduce the concentration to below the LEL or no longer considered ignitable (typically defined as 50% of the LEL).

Explosion Overpressure - A mathematical estimation of the amount of explosive overpressure that may be expected from an incident. It is portrayed as overpressure radii from the point of initiation until the overpressure magnitudes are of no concern, i.e., less than 0.02 bar (3.0 psio). Evaluations perforned for enclosed areas will also estimate the amount of overpressure venting capability available.

Survivability of Safety Systems - An estimation of the ability for safety systems to maintain integrity from the effects of explosions and fires. (Safety systems may include ESD (Electrostatic discharge), depressurization, fire protection - active and passive, communication, emergency power, evacuation mechanism, etc.).

Firewater Reliability - A mathematical model of the ability of the firewater system to provide firewater upon demand as required by the design of the system without a component failure, e.g., a Mean Time Between Failure (MTBF) analysis.

Fire and Smoke Models - A mathematical estimation model depicting the duration and extent of heat, flame and smoke that may be generated from the ignition of a hydrocarbon release. The results of these estimates are compared against protection mechanisms (e.g., firewater, fireproofing, etc.) afforded to the subject area to determine adequacy.

Emergency Evacuation Modeling - A study of the mechanisms, locations and time estimates to complete an effective removal of all personnel from an immediately endangered location or facility.

Fatality Accident Rates (FAR) or Potential Loss of Life (PLL) - A mathematical estimation of the level of fatalities that may occur at a location or facility due to the nature of work being performed and protection measures provided, may be calculated at an annual rate or for the life of the project.

Human Reliability Analysis (HRA) or Human Error Analysis - A reliability analysis that estimates the potential for human errors to occur due to the work environment, human-machine interfaces, and required operational tasks.