A SEMINAR REPORT O
ROLE OF SAFETY IN CHEMICAL PROCES INDUSTRIES For the partial fulfillment of the requirement for the degree of BACHELOR OF TECHNOLOGY IN CHEMICAL ENGINEERING Submitted By-
HIMANSHU SINGH Of 3rd Year, B.Tech. Chemical Engineering Department
Submitted ToEr. Dhananjay Singh And Durgesh Pratap
under the auspices of
Department of Chemical Engineering INSTITUTE OF ENGINEERING AND TECHNOLOGY,LUCKNOW, INDIA
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ACKNOWLEDGEMENT
We express our heartfelt gratitude to Mr Durgesh Pratap Singh for their expert guidance constant inspiration which made possible the compilation of the report. Indeed we consider ourselves fortunate to have worked under their supervision. He has inspired us at all stages and spared invaluable time for discussion, whenever we needed it. We also owe a depth of gratitude to Mr. Dhananjay Singh(Head of Chemical Engineering Department).His tremendous personal interest ,inspiration,encouraging support and sound advice went all the way in making this effort in suc cess. HIMANSHU SINGH B.TECH 3rd YEAR (CHEMICAL ENGINEERING)
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CONTENTS
1. Introduction…………………………………………………………………………. 2. The Nature of the Accident Process………………………………………………… 3. Inherent Safety……………………………………………………………………… 3.1 Inherent Safety techniques……………………………………………………… 4. Approach to occupational health and safety management in small and large chemical businesses……………………………………………………………….. 5. Relationship to Safety in Design…………………………………………………… 6. Safety Through Design in the Chemical Process Industry…………………………. 6.1 Inherently Safer Process Design……………………………………………. 6.2 The Layers of Protection…………………………………………………… 7. Approaches to Inherently Safer Design in the Chemical Industry…………………. 8. Conclusions…………………………………………………………………………. 9.
References…………………………………………………………………………..
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1. INTRODUCTION An industry in which the raw materials undergo chemical conversion during their processing into finished products, as well as (or instead of) the physical conversions common to industry in general; includes the traditional chemical petroleum, and petrochemical industries.
Major segments of our Chemical Processing include:
Inorganic and Organic Chemical Producers Producers of olefins, alcohols, ethylene and ethylene-based chemicals, polymerization, cyclical compounds, and solvents. Major companies engaged in the production of acids, compounds, and specialty chemicals
Industrial Gas Producers Manufacturers of hydrogen, nitrogen, oxygen, and other industrial gases
Agricultural Chemical Industry Bulk liquid and solid (granular, powder) agricultural product producers, including fertilizers, herbicides, pesticides, fungicides, and intermediates, such as urea, ammonia, nitric acid, and ammonium nitrate
Detergents and other Household Product Producers Manufacturers of soaps and detergents, cleaners, bleaches, disinfectants, and surface agents
Plastics, Rubbers, Fibers, and Resins Manufacturers The manufacturing of synthetic resins, plastics materials, nonvulcanizable elastomers, synthetic rubber by polymerization or copolymerization, cellulosic man-made fibers and the compounding of purchased plastics
Painting and Coating Producers Manufacturers of pigments, coatings, solvents, lacquers, enamels, stains, and varnishes for finishing
Producers of Other Chemicals Producers of explosives to inks, dyes, glues, lubricants, fire retardants, and chemicals
Alkalies and Chlorine
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Producers of caustic soda, soda ash (not produced at mines), chlorine (compressed or liquefied), carbonates (potassium and sodium)
2. The Nature of the Accident Process Chemical plant accidents follow typical patterns. It is important to study these patterns in order to anticipate the types of accidents that will occur. Fires are the most common, followed by explosion and toxic release. With respect to fatalities, the order reverses ,with toxic release having the greatest potential for fatalities.Economic loss is consistently high for accidents involving explosions. The most damaging type of explosion is an unconfined vapor cloud explosion, where a large cloud of volatile and flammable vapor is released and dispersed throughout the plant site followed by ignition and explosion of the cloud. An analysis of the largest chemical plant accidents is provided in Figure 1. As illustrated, vapor cloud explosions account for the largest percentage of these large losses .The ―other‖ category of Figure 1 includes losses resulting from floods and wind storms.Toxic release typically results in little damage to capital equipment. Personnel injuries ,employee losses, legal compensation, and cleanup liabilities can be si gnificant.
The Nature of the Accident Process Fires Others Explosions Vapour cloud explosions
Figure 1 : Types of loss for large hydrocarbon chemical plant accidents
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Figure 2 presents the causes of losses for the largest chemical accidents. By far the largest cause of loss in a chemical plant is due to mechanical failure.Failures of this type are usually due to a problem with maintenance. Pumps, valves, and control equipment will fail if not properly maintained. The second largest cause is operator error. For example, valves are not opened or closed in the proper sequence or reactants are not charged to a reactor in the correct order. Process upsets caused by, for example, power or cooling water failures account for 11% of the losses. Human error is frequently used to describe a cause of losses. Almost all accidents, except those caused by natural hazards, can be attributed to human error. For instance, mechanical failures could all be due to human error as a result of improper maintenance or inspection.
Accidents % 45 40 35 30 25 20 15 10 5 0
Figure 2: Causes of losses in the largest hydrocarbon-chemical plant accidents.
Most accidents follow a three-step sequence: • initiation (the event that starts the accident), • propagation (the event or events that maintain or expand the accident), and • termination (the event or events that stop the accident or diminish it in size)
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3.
Inherent Safety
An inherently safe plant relies on chemistry and physics to prevent accidents rather than on control systems, interlocks, redundancy, and special operating procedures to prevent accidents. Inherently safer plants are tolerant of errors and are often the most cost effective. A process that does not require complex safety interlocks and elaborate procedures is simpler, easier to operate, and more reliable. Smaller equipment, operated at less severe temperatures and pressures, has lower capital and operating costs. In general, the safety of a process relies on multiple layers of protection. The first layer of protection is the process design features. Subsequent layers include control systems, interlocks ,safety shutdown systems, protective systems, alarms, and emergency response plans. Inherent safety is a part of all layers of protection; however, it is especially directed toward process design features. The best approach to prevent accidents is to add process design features to prevent hazardous situations. The major approach to inherently safer process designs is divided into the following categories: • intensification • substitution • attenuation • limitation of effects • simplification /error tolerance
3.1 Inherent Safety Techniques
Type
Typical techniques
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Minimize
Change from large batch reactor to a smaller continuous reactor Reduce storage inventory of raw materials Improve control to reduce inventory of hazardous intermediate chemicals Reduce process hold-up
Substitute
Use mechanical pump seals vs. packing Use welded pipe vs. flanged Use solvents that are less toxic Use mechanical gauges vs. mercury Use chemicals with higher flash points, boiling points, and other less hazardous properties Use water as a heat transfer fluid instead of hot oil
Moderate
Use vacuum to reduce boiling point Reduce process temperatures and pressures Refrigerate storage vessels Dissolve hazardous material in safe solvent Operate at conditions where reactor runaway is not possible Place control rooms away from operations Separate pump rooms from other rooms Acoustically insulate noisy lines and equipment Barricade control rooms and tanks
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Simplify
Keep piping systems neat and visually easy to follow Design control panels that are easy to comprehend Design plants for easy and safe maintenance Pick equipment that requires less maintenance Pick equipment with low failure rates Add fire- and explosion-resistant barricades Separate systems and controls into blocks that are easy to comprehend and understand Label pipes for easy ―walking the line‖ Label vessels and controls to enhance understanding
4. Approach to occupational health and safety management in small and large chemical businesses a) Small business makes available to the public the basic information on its activities in the field of environmental protection and on work law relations – this is included in annual report; such obligation ensues from the Accounting Act. Annual report is compiled every year. b) Factual and full disclosure of information on corporate activities in the area of environmental protection and protection of working environment has become a matter of course for a large business. The main aim in this area is the maximal openness towards the employees and all other partners, such as the public, public media, public administration, non-governmental organizations and business partners. The main corporate targets in the area
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of environmental protection and occupational safety and health protection as well as the way of achieving them are presented by the business in regularly released Reports on Corporate Environmental Impacts. The reports are distributed in printed form and are also available to the public on corporate website. The business is a holder of RC logo and based on its participation in this programme it also meets all obligations in the area of disclosure of information. In addition, the basic information on corporate environmental approach and on work law relations is included in annual report. Annual report is placed on corporate website and is also available in the form of CD version. The business regularly organizes meetings with mayors of the municipalities in the region, where the participants are made acquainted with various activities not only in the area of environmental protection but also in the area of occupational safety and health protection. Up-to-date information is also made available to the public by means of corporate periodical. From the listed activities in the area of communication with the interested parties it is evident that the business goes above the framework of legal requirements. This means that it is aware of the importance of communication for improving credibility of the company and its attractiveness as employer. To address the interested parties, the business also chooses different communication tools. Such communication activity is also, beyond all doubt, a response to the requirements of the interested parties.
5. Relationship to Safety in Design Safety in Design can be based on either of the approaches described. Add-on safety features and layers of protection can be identified and incorporated during design. In fact, they should be incorporated into the process design — we should anticipate potential accidents during design and provide the appropriate protective systems, procedures, and devices, rather than discovering the need for these layers of protection later on as a result of accidents and near misses. However, the greatest potential for realizing an inherently safer process design is early in development. At this time, the designer still has considerable freedom in technology selection. For a chemical process, perhaps the greatest opportunities lie in the selection of the chemical synthesis route to be used,including the raw materials, solvents, chemical intermediates, reaction steps, and other physical and chemical operations to be used. See Figure 3 :
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Figure 3: Process Design
However, it is important to remember that it is never too late to consider inherently safer design options. In an existing plant, there will be different kinds of opportunities for modifications to improve inherent safety, but these opportunities can result in significant improvements. It may not be feasible to change the basic process chemistry and technology, but it may be possible to reduce inventory, simplify the plant, or otherwise make the plant more ―user friendly.‖ Significant improvements in the inherent safety of plants which have operated for many years have been reported.
6. Safety Through Design in the Chemical Process Industry 6.1 Inherently Safer Process Design
A chemical manufacturing process is described as inherently safer if it reduces or eliminates hazards associated with materials and operations used in the process, and this reduction or elimination is a permanent and inseparable part of the process technology. A hazard is
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defined as a physical or chemical characteristic that has the potential for causing harm to people. The key to this definition is that the hazard is intrinsic to the material, or to its conditions of storage or use. For example, chlorine is toxic by inhalation, gasoline is flammable, and steam at 600 psig contains significant potential energy. These hazards are basic properties of the materials and the conditions of usage, and cannot be changed. An inherently safer process reduces or eliminates the hazard by reducing the quantity of hazardous material or energy, or by completely eliminating the hazardous agent. A traditional approach to managing the risk associated with a chemical process is by providing layers of protection between the hazardous agent and the people, environment, or property which is potentially impacted. · Basic controls, alarms, and operator control · Critical alarms, operator control, and manual intervention · Automatic actions — emergency shutdown systems and safety interlock systems · Physical protection equipment such as pressure relief devices · Emergency response systems — for example, fire fighting
Figure 4: Inherent Safety
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6.2 The Layers of Protection
The layers of protection are intended to reduce risk by reducing either the likelihood of potential incidents resulting in an impact on people, the environment, or property, or by reducing the magnitude of the impact should an incident occur. The risk can be reduced to very low levels by providing a sufficient number of layers of protection, and by making each layer highly reliable (Figure 5). However, the basic process hazards remain, and there is always the potential — perhaps very small, but never zero — that all layers will fail simultaneously and the hazardous incident will occur. Furthermore, the layers of protection require significant expenditure of resources, both to design and build them initially, and to maintain their reliability throughout the life of the plant. Failure to adequately maintain the layers of protection may result in a significant increase in the process risk . The inherently safer design approach is to eliminate or reduce the hazard by changing the process itself, rather than by adding on additional safety devices and layers of protection. Ideally, hazards would be reduced to a level where no protective systems are required because the hazard is too small to be of concern. Even if this is not possible, an inherently safer process will allow the number of layers of protection to be reduced. The overall design is therefore more robust from a safety and environmental viewpoint, and is likely to be less expensive to build and operate because of the elimination of complex safety systems. The inherently safer design approach is to eliminate or reduce the hazard by changing the process itself, rather than by adding on additional safety devices and layers of protection. Ideally, hazards would be reduced to a level where no protective systems are required because the hazard is too small to be of concern. Even if this is not possible, an inherently safer process will allow the number of layers of protection to be reduced. The overall design is therefore more robust from a safety and environmental viewpoint, and is likely to be less expensive to build and operate because of the elimination of complex safety systems. See Figure 5 :
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Figure 5 : layers of protection
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7. Approaches to Inherently Safer Design in the Chemical Industry There are four basic strategies for implementing inherently safer chemical processes:
Minimize — Use smaller quantities of hazardous substances
Continuous reactors (stirred tanks, loop reactors,) in place of batch reactors
Reduced inventory of raw materials and in-process intermediates
Substitute — Replace a material with a less hazardous substance
Water based paints and coatings
Alternative chemistry using less hazardous materials
Less flammable or toxic solvents
Moderate — Use less hazardous conditions, a less hazardous form of a material, or
facilities which minimize the impact of a release of hazardous material or energy
Dilution
Refrigeration of volatile hazardous materials
Granular agricultural product formulations in place of powders
Simplify — Design facilities which eliminate unnecessary complexity and make operating
errors less likely, and which are forgiving of errors which are made
Develop fundamentally simpler technology with fewer reactions and processing operations
Eliminate unnecessary equipment (question need for each device or feature)
Remove unused or abandoned equipment
Human factors considerations in design.
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8. CONCLUSIONS
Since 1978 the industry has increasingly recognized the importance of the inherently safer design approach, and has extended the concept to include safety, health, and environmental (SHE) characteristics of chemical manufacturing processes. Inherent SHE represents a fundamentally different approach to Safety in Design. The objective becomes to eliminate or reduce hazards by changing the basic technology, rather than by adding safety devices and other layers of protection to a control hazards. While it is possible to reach a desired degree of safety using either approach, safety devices and layers of protection add significant cost to a chemical plant over its life cycle. Furthermore, the hazard is still present, and there is always the potential for an accident due to simultaneous failure of several layers of protection, or degradation of the layers of protection in the future. For many chemical processes, the inherent SHE approach to Safety in Design represents the most cost effective and robust approach. The chemical industry is beginning to develop tools to measure inherent SHE characteristics of processes. Measurement tools which can be quickly and easily used early in the life cycle of the process design are particularly important, because that is the time at which the designer has the greatest opportunity to change the basic process technology. A number of measurement tools have been developed in the past few years, and the applicability of several existing tools (for example, the Dow Indices) to the understanding of inherent SHE has been recognized. There is still a more work to do in this area, in calibrating tools which have been developed, improving them, and better understanding how they can be applied in the real world.
9. References 1. SAFETY IN THE CHEMICAL PROCESS INDUSTRIES, D. A. Crowl, C. DeFrain, . Wayne State University,Michigan Technological University. 2. www.epsc.org 3. Industrial Process Safety , Graham D. Creedy. 4. Safety Through Design inthe Chemical Process Industry: Inherently Safer Process Design Dennis C. Hendershot
