Hazard Identification and Management in Oil & Gas Industry
Any industry plays a major role in world’s economy. Such as Oil & Gas, Petrochemical, Chemical and manufacturing facilities.Huge investments are made to keep the upkeep of the facilities in order as well as to increase the production capacity, even marginally.
Any accident like blowout, oil spill, operational problems etc shall cause heavy economical loss to the industry which might include loss of equipment, assets and human life.
Several techniques are available to identify and assess these hazards
- Hazard and Operability study (HAZOP)
- Failure Mode and Effective Analysis (FMEA)
- Quantitative Risk Assessment (QRA)
- Event Tree Analysis (ETA)
- Fault Tree Analysis (FTA)
Let’s start with HAZOP
Hazop is applicable at four stages of operation
1. Drawing Board (Design Stage, such as FEED)
2. Construction Stage
3. During Process Modification ( Such as PCR or MOC)
4. After Accident Occurs (Accident Investigation Report)
HAZOP STUDY- AN OVERVIEW
Hazard and Operability (HAZOP) Study is a structured and systematic evaluation of a planned and/or existing operation to identify and evaluate potential hazards in design and operation. This study is carried out by a team of engineers from different disciplines. The team looks at each section of a plant or system or operation (node), considers potential deviations from intended operation and analyses their consequences against any existing safeguards. Impact of identified hazards on safety, asset and environment are assessed.
HAZOP is a guideword driven brainstorming technique. Team members contribute based on their collective experience and lessons learnt from past projects.
HAZOP study records the identified hazards without proposing any solution, unless a solution is obvious. Proposed solutions may include additional safeguards or operational procedures as necessary. The study record serves as a guide to determine the Health, Safety and Environment (HSE) issues to be resolved during the project.
OBJECTIVES
The objectives of the HAZOP study are:
- Identify and evaluate potential hazards and risks associated with process facilities
- Identify operability and maintenance issues
- Understand these hazards / issues and determine their potential consequences
- Determine (design and procedural) safeguards or risk reduction measures incorporated in the design and evaluate their adequacy and
- Recommend additional safeguards or operational procedures as necessary
These steps will lead to a better design of the facility to mitigate the potential hazards identified.
DOCUMENTS REQUIRED
Following are the documents required,
- Project and Facility Description
- Facility Layout Drawings
- Material Selection Studies
- Process and Utility Flow Diagrams
- Piping & Instrumentation Diagrams
- Cause & Effect Matrix
- Electrical Single Line Diagram
- Hazardous Area Classification Drawings
- Hazardous Chemicals and inventories. Their Material Safety Data sheets
- Company Guidelines, Operating and HSE/ Safety Philosophies
- Safety and Environmental Studies — undertaken or proposed to be conducted
HAZOP METHODOLOGY
NODE DEFINITION
The HAZOP study progresses through the plant node by node. The selection of the node sizes and the route through the plant is made before the study by the facilitator. The node should be described in terms of:
- Brief description of the node
- Typical operating and design conditions
STANDARD GUIDE WORDS
Guide words are simple words or phrases used to qualify or quantify the intention and associated parameters in order to suggest deviations.
· No, Low, More, Reverse, misdirected
TYPICAL PARAMETERS/ELEMENTS
· Flow, Pressure, Temperature, Level
· Composition, Concentration, Sediments
· Fouling, Air or Moisture Ingress
· Separation
· Measure, Control, Sequence in batch operations e.g pigging
· Operate, Start-up, Shutdown, Maintain, Services, Signal, Communication
· Sampling
· Corrosion
DEVIATIONS
Deviations are departures from the design intent of the process. The combination of parameters and guide words in sequence will identify all the deviations (no flow, more temperature etc.). There may be significant overlap between the deviations considered (eg. no flow may have the same effect as more pressure). These will be identified and excluded during the team discussion.
Not all guide words can be combined to all parameters to get a meaningful deviation. Usually the following combinations are employed.
CAUSES
The team will brainstorm to find all the potential causes of the deviation. All potential causes should be identified and discussed as the consequences and actions may be different.
The three major categories of causes in decreasing probability are: -
- Human error
- Equipment failure
- External events
CONSEQUENCES
The potential consequences for each deviation are discussed and assessed within the limits of the information available and the expertise of the team. There may be several consequences involving escalation to other pieces of equipment
Having identified the credible causes of the Deviation, discussion should move on to analyze and assess the significant of the consequences. This may be done by ranking the Consequences in terms of Likelihood and Severity to determine Risk. Risk Ranking should not take into consideration any safeguards.
RISK RANKING
A Risk is the amount of harm that can be expected to occur during a given time period due to specific harm event (e.g., an accident).
Statistically, the level of risk can be calculated as the product of the probability that harm occurs (e.g., that an accident happens) multiplied by the severity of that harm (i.e., the average amount of harm or more conservatively the maximum credible amount of harm).
Example of a 7x7 Risk matrix used for Hazop Study
STEP BY STEP APPROACH
Hazop study is conducted in a systematic way with following step by step approach.
1. Select a system. Explain its general intent in terms of design and operation
2. Select a node (small area of focus) in the selected system. Usually a vessel and its piping or a pump and its piping. Explain its general intent in terms of design and operation
3. Apply the first operating parameter, such a Flow or Pressure. Apply to the parameter a guide word or possible deviation, such as No to develop a deviation e.g. No Flow
4. For the deviation look at possible causes and consequences; their hazards, existing safeguards. Recommend additional protection as necessary.
5. Repeat for all guide words applicable for the selected parameter
6. Repeat for all parameters.
7. Node complete. Repeat for all nodes in the system
8. System complete. Repeat for all systems in the plant
RECORDING
PHA-Pro 6.0 worksheets are normally used to capture HAZOP team discussion and findings. There are other similar software in the market.
VENUE AND TIMING
The HAZOP meeting is held in a conference or meeting hall on a pre-decided mutually convenient date.
STUDY TEAM
Typical disciplines represented are Projects, Safety or HSE, Process, Instrumentation, Mechanical, and Operations. Other disciplines are invited as and when needed.
HAZOP APPROACH
The HAZOP study usually is started with an overview of process facilities and plant layout. This helps the team members to become familiar with the facility. A brief introduction will be given on systems with high pressure, high temperature, low temperature and hazardous chemicals.
The facility is segregated into nodes, as detailed in HAZOP worksheets. Nodes are the sections in the plant enabling the team to stay focused.
For each node — potential hazards were identified in a systematic way, using a Guideword and Parameter. Each hazard and possible causes or initiating events were discussed and recorded in the HAZOP worksheet. Then the team discusses potential impact for each cause or event and reviewed available safeguards — as a result of standard design practices or company requirements. Where it is deemed necessary, the team suggests additional protection or changes to philosophy or calls for additional studies to be performed. All these points are captured in the HAZOP worksheet and projected on an overhead screen for all participants to review and concur before closing out the session.
The HAZOP team raises ’n’ of recommendations out of ’n’ nodes studied during the meeting. Recommendations are prepared for the HAZOP study.
The HAZOP details and findings are presented in HAZOP worksheets.
RECOMMENDATIONS APPROACH
The recommendations (action items) identified during the HAZOP Study are included in the HAZOP Report and later tracked to closure. The objective of the HAZOP session was to raise hazards, operability or integrity issues, not to solve any problems. Therefore, the recommendations generated have been worded in a general manner using words like ‘Consider’, ‘Ensure’ and ‘Other action verbs’; see below for detailed description. It should be noted that the responses to the HAZOP recommendations should provide a clear audit trail including the reasons for taking or not taking action. Guidelines for responding to HAZOP Study recommendations are as follows:
“…Ensure…” Ensure is generally used as a reminder to include a particular point in documents, such as P&ID, Operating, Control & Shutdown Philosophy and Cause and Effects, etc., which may not have been ready at the time of the HAZOP. Where the document is issued prior to HAZOP closeout the response should include a note of precisely what has been done. If the document will not be issued until after HAZOP close-out, then the response should indicate how the point will be transmitted for future implementation.
“…Review…” Review is used where the HAZOP team believes that some action may be necessary, but there is some uncertainty as to precisely what is required, or whether action is reasonably practicable, or may have other unacceptable consequences. The response should outline the options considered and the conclusions reached, including justification for the action (including no action) taken.
“…Other action verbs…” Recommendations starting with other action verbs are mandatory actions that shall be implemented by respective party for each recommendation.
To be continued…