Process Safety

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Table of Content

  1. Introduction
  2. Hazard in Process Industries
  3. Causes of Industrial Accidents
  4. Process Hazard Identification
  5. Risk Assessment

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1. Introduction

Process industries produce goods that improve the livelihood of mankind. Food and beverages, textile and garments, plastics and composites, drugs and pharmaceuticals are some examples of products delivered to the community from those dedicated industrial zones where darkness of the night evaporates away due to lights shimmering from flares burning unwanted combustibles, releasing heat along with smokes and water vapours – as a measure plant safety.

As the sector is well-developed, safety features available to enhance plant operations are many. Nevertheless, only a small portion of these are made compulsory by local legislation throughout the world, the bulk of them are considered among good practices. It is therefore important for managers and engineers alike to have safety in mind in running their respective process plant.

Safety is an issue that should never be taken lightly. Fire, explosion, toxic release and collapses of structures such as buildings and bridges had all taken too many lives and incurred tremendous amount of losses. Businesses, workers and environment have all been seriously affected. Some of these incidences have very long effects that spanned over many years. For example, Bhopal and Chernobyl incidents that happened in the 1980’s are still collecting tolls on various illness and environmental damages, if not fatality.

1.1 What is Process Safety?

Process safety differs from the traditional approach to accident prevention in a number of ways (Lees, Loss Prevention in the Process Industries, 2d ed., Butterworth-Heinemann, 1996, p. 1.8):

  • There is more concern with accidents that arise out of the technology.
  • There is more emphasis on foreseeing hazards and taking action before accidents occur.
  • There is more emphasis on a systematic rather than a trial-and-error approach, particularly on systematic methods of identifying hazards and of estimating the probability that they will occur, and their consequences.
  • There is concern with accidents that cause damage to plants and loss of profit but do not injure anyone, as well as those that do cause injury.
  • Traditional practices and standards are looked at more critically.

Process safety can be applied in any industry, but the term and the
approach have been particularly widely used in the process industries,
where it usually means the same as loss prevention.

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2.0 Hazard in Process Industries

In addition to typical hazards in any work place such as danger of falling objects, electricity and so forth and so on, there are three main additional hazards introduced by the chemical industries. These are Fire, Explosion and Toxic Release. In many instances, more than one of these hazards occur either simultaneously or in tandem of each other. For example, a fire may lead to explosion which subsequently causes more fire and toxic release. The effect can be devastating on the plant itself as well as surrounding communities and environment.

Click Here for Further Details on Hazards in Chemical Industries

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3.  Causes of Industrial Incidents

Industrial incidents happen due to two major factors :

1. Substandard Design (Unsafe Conditions)

2. Substandard Practice (unsafe Acts)

Of course there is always the third factor such as natural disasters, sabotage etc. Nevertheless, most previous incidents were the results of the two factors mentioned.

While substandard practices can be dealt with through proper safety management system that include safe operating procedures, training and retraining and motivating workers to increase the work place morale, substandard design must first be overcome. Decisions on design approaches and/or techniques/technology utilised should be taken carefully following proper hazard identification and Risk Assessment techniques.

Managing hazardous has received keen consideration by various parties. Despite not yet adopted as part of the local legislation here, standards adopted by other countries have been used as references for process safety management, particularly by the petrochemical as well as oil and gas sectors.

Click here to read more about Process Safety Management

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4.0 Process Hazard Analysis

Process Hazards Analysis (PHA) is the predictive identification of hazards, their cause & consequence and the qualitative estimation of likelihood and severity. Simply, PHA allows the employer to:

  • Determine locations of potential safety problems
  • Identify corrective measures to improve safety
  • Preplan emergency actions to be taken if safety controls fail

To be effective, a PHA team member should have reasonable amounts of the above ingredient, i.e., experience, skill and knowledge. Intuition is almost always useful and it is often the results of positive interactions between knowledge and experience. However, it can also hinder progress, especially when these “experienced members” went overboard with their opinions and not willing to consider other perspectives.

4.1 PHA and Process Safety Management (PSM)

PSM is now a standard practice with clear guidelines published to facilitate implementation. In United States, Occupational Safety and Health Administration (OSHA) has issued the Process Safety Management of Highly Hazardous Chemicals standard (29 CFR 1910.119), which contains requirements for the management of hazards associated with processes using highly hazardous chemicals. As part of the PSM requirements, process plants are required to carry out PHA to identify potential hazards and implement changes to increase safety standards.

4.2 Techniques Available

There are wide range of tools available. Some are qualitative, while others are quantitative or semi-quantitative.

4.2.1 Checklist

4.2.2 What If

4.2.3 HAZID

4.2.4  Hazard and Operability (HAZOP) Studies

The methodology used for the HAZOP study is well recognised throughout the process industry, and has been used extensively worldwide since the technique was first developed by ICI in the early 1970s. Hazop Studies consists of formal systematic and critical examination of the process and engineering intentions of the processes via the use of guide-words to explore abnormal modes of operation that can lead to undesirable condition. Methodical brainstorming and creative interaction of diverse disciplines, usually in a workshop format are used to identify potential hazards and operability problems. The aim of the study is to identify problems needing a solution, rather than to solve them.

Click Here For Further Details on HAZOP

4.2.5 LOPA

4.2.6 FMEA

4.2.7 FTA

4.2.8 ETA

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5. Assessing Risks Posed by Process Industries

Risk is defined as the likelihood of an adverse outcome. It is a combination of probability of occurrence and severity of the effect on events considered. These are then incorporated to formulate some index that will indicate the extent of risk involved. Mathematically, the index, conveniently termed as Risk, can be expressed by the following relationships:

Risk = Severity x Likelihood

Severity is the extent of damage incurred following the accident. It can be in the form of fatality, injury, material loss or environmental degradation. To estimate the severity on an incident, detailed mathematical models are often used. Many software are available in the market to facilitate the effort.

Severity is expressed as probability of fatality (0 to 1), or RM XXX Million of Losses incurred or some other measures depending on the nature of the assessment. Further information is available here.

Likelihood is the chance of an event to occur. It is estimated based on historical data on failure frequency of individual units or components. For example, there are failure data available for gasket failure, pipe rupture, pump switch failure etc. These data have been surveyed and collected over the years and published.

Risk is therefore expressed as Fatality per year, or RMXXX Million lost per year etc. There are several classes of risk assessments currently employed in the world. Some of these have been incorporated within safety legislation in Malaysia.

5.1 Qualitative Risk Assessment

Risk ranking is a common methodology for making risk based decisions without conducting quantitative risk analysis. The basis for risk ranking is the risk matrix that has both a consequence and frequency axis. The product of consequence and frequency provides a measure of risk. Each consequence /frequency pair on the risk matrix is assigned a risk ranking that includes risk levels that are tolerable and others that are intolerable. The intolerable risk levels may be further divided into higher and lower risks to prioritize mitigation actions.

Click here to read more on qualitative risk assessment.

5.2 Quantitative Risk Assessment

In simple terms, QRA involves five main components – Hazard Identification, Consequence Analysis, Frequency Analysis, Risk Estimation and Risk Mitigation. While some steps can be done in parallel, most are sequential. The outcome is the risk quantified and expressed as Individual or Societal Risks, which are evaluated against the accepted risk tolerability criteria. In Malaysia, as long as the location specific individual risks (LSIR) is less than one fatality in a million population per year (1 x 10-6) for residential population, the proposed installation can be considered tolerable (See guideline from Department of Environment). Nevertheless, assessment from societal risk is also very useful in evaluating the risks introduced to the community. For example the R2P2 document published by the UK HSE is recommended.

Based on the outcome of the assessment, mitigating measure are proposed. These include engineering and administrative controls that are to be observed during construction, installation and operation of the proposed facility.

Click Here to Read More on QRA

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