Chemical Engineering is defined as the branch of engineering which is involved in the application of physical science and mathematics to processing and converting raw materials and chemicals into more useful forms. The outputs and methods of these processes are not always safe and chemical hazards need to be overcome to make the working environment a satisfactorily hospitable for everyone that the process affects. This includes the general public and the environment as well as the workers involved. Chemical Engineers need to ensure that the safety measures which they devise regarding certain processes are adequate enough not to pose hazards and to meet the regulations of the law.
This term paper will outline some of the hazards which Chemical Engineers and other workers in the industry need to neutralise to ensure that the working environment is safe for those involved.
A hazard is defined as anything which could result in an accident. Such hazards include those caused by the release of noxious chemicals which can prove damaging to the health of people and the environment. Chemical hazards can be especially dangerous due to the toxic nature of the substances used in the industry.
Plant Safety
The health and safety of plant workers is a major concern to the chemical industry. Accidents which result in loss of life or injuries are especially damaging due to the high costs they inflict. Costs in retraining personnel, repairing equipment damaged in have huge costs, as well as the interruption in business that ensues after an accident.
The trends have shown that over the years fatalities have decreased but property costs have increased. This trend is due to the increased automated systems used in plants. These systems have increased complexity and productivity to older designs. In earlier designs the workers were more exposed to the chemical processes taking place in the plant, and were in turn exposed to more hazards. This however poses another problem because if workers are more isolated from a process, even if this greatly reduces health and safety hazards then if a malfunction occurs in the plant it is much more difficult to have experienced personnel available to fix a process problem. Due to this action compensation must be made in the case of higher property costs as opposed to loss of life and injury to workers.
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“As of the early 1990’s, annual worker fatalities ran about 9 per 100,000 employees; annual lost time disabling injuries ran about 4,000 per 100,000 employees. Property Losses increased fourfold from the 1970’s”. Safety assessments are now undergone on chemical plants to ensure that they adhere to safety levels proposed by regulation standards. Quantification of hazards such as overpressure potential and flammability were done by measurements of vapour pressure and of flash points and flammability limits.
The process designers need to make use of data that gives information pertaining to the hazards of a process such as information of reaction rates and the energies involved in exothermic reactions in which heat is given out, that of unstable chemicals, of temperature limits in which explosive decomposition can occur, rates of generation of gas and vapour and emergency fail-safes such as pressure releases for high pressure systems.
Citing Wikipedia, “Fault tree analysis (FTA) is a failure analysis in which an undesired state of a system is analyzed using Boolean logic to combine a series of lower-level events”. This is used to quantitatively combine the characteristics of human and component failure rates to obtain a safety assessment for that process.
Many changes arose in the 1980’s and 1990’s regarding safety requirements in the petrochemical and chemical industry. These were presented by industrial groups such as Chemical Manufacturers Association as and the American Petroleum Institute as consensus guidelines. The objective of these changes was to make sure that all members of these industries were designed, maintained and controlled in the safest way that would be economically viable. Kirk Othmer (1991-1998).
Hazard Analysis and Risk Assessment
Hazards associated with in facilities can be in the order of hundreds or thousands if the facility is large enough. These hazards occur as a result of factors such as the type of physical materials being used, the processes that are designed to make a product, the operating conditions and the design of a plant to name but a few. If hazards aren’t controlled a sequence of events can occur which will result in an accident. A hazard can result in an accident which is an unplanned sequence of events which can result in the loss of life, damage to the environment, damage to products and inventory and damage to equipment.
Risk involves probability and consequence of something undesirable occurring. It is impossible to completely define a risk without taking both of these components into consideration. For example a hazard could involve a large consequence but also could have a very low probability of causing an accident or vice versa. In both these cases it would be classed as a moderate risk.
The purpose of hazard analysis and risk assessment is therefore to characterise hazards, determine the probability of them occurring and then to consider and evaluate the consequences if an accident did occur. This procedure can be summed up by this flow chart in Figure 1.
Flow chart describing the full hazard analysis and risk assessment procedure
Fig. 1
Kirk Othmer (1991-1998)
Flow Chart Explanation
A committee is required to perform hazard analysis and risk assessment. Each member of the committee must have adequate experience to the chemical process that is being considered. The first step is to consider a detailed account of the process which describes it completely. This has to include the physical properties of the materials being used, instrument diagrams of processes, operating temperatures and pressures, materials for the construction of the equipment being used and any other detailed design specifications. The more detailed and updated this is, the more effective the analysis will be.
The next step involves identifying the hazards involved in the process. This is done by a certain number of established procedures. In this step it is not uncommon to find hundreds of hazards for complex processes.
The next step involves identifying all the scenarios which could result in the loss of control of the system, therefore resulting in an accident. This can be seen to be the most difficult step in the analysis. Most accidents occur due to improper accident scenario characterisation. Many complex chemical processes can have hundreds of different accident scenarios for each hazard but the most important part of this analysis is to pick the scenarios which are most dire but at the same time credible.
Risk assessment is the next part of the procedure. This involves determining accident probability and the consequences involved. This procedure is performed for all the accident scenarios that were identified in the last step. Statistical models used to represent failures are the method preferred for determining the probability of each accident. Source models are used to provide information about how material would be ejected from equipment, along with dispersion and explosion models, a good estimate can be made to the cost of the damage to the affected areas. Thus the consequence is now determined.
The final part of this procedure is to decide whether the risks involved are acceptable. If they are not then changes must be made and the process must be restarted to ensure that they are subsequently neutralised. If the risk is an acceptable one then the process can go ahead and be implemented.
Hazard analysis or risk assessment can be undergone at any time during the course of a process’ life. It is however, must more cost effective to perform this procedure at the initial stages where changes would be less costly to implement.
Process Safety Management
Several incidents which occurred in the late twentieth century indicated that there needed a significant improvement in the management of process hazards. There are three incidents that have produced the greatest legislative response. These incidents are as follows
The Flixborough disaster, U.K. 1st June 1974 in which a temporary bypass pipe ruptured causing 40 tonnes of cyclohexane to form a vapour cloud 100-200 metres in diameter. The cloud came in contact with an ignition source and exploded causing 1,800 buildings within a mile radius of the site were damaged. 28 dead. 89 serious injuries. Wikipedia, Flixborough Disaster (2010)
The Bhopal disaster, India. 3rd December 1984 in which a runaway reaction caused by water entering tank 610 containing 42 tonnes of methyl isocyanate vented to the surrounding areas forming a toxic cloud. ca. 3,000 dead. ca. 200,000 serious injuries. Wikipedia, Bhopal Disaster (2010)
Polyethylene Plant Explosion, Pasadena, Texas. 23rd October 1989 in which a valve failure caused a large amount of flammable gas to be released which subsequently exploded. 23 dead. 130-300 serious injury. (www.cholarisk.com/…/Philips%20PE%20Pasadona%20Explosion.ppt).
Standards and guidelines have been developed to ensure that these types of accidents do not occur again by improving management of process safety.
The Health and Safety at Work Act developed by the Health and Safety Executive (HSE) was devised following the Flixborough disaster this meant that the HSE would require that the type or quantity of chemical used or produced was to be registered and also the HSE submitted recommendations for maintenance functions plant design and methods for evaluating process hazards.
The Occupational Safety and Health Act devised by the Occupational Safety and Health Administration (OSHA) which was enacted in 1970 established standards for occupational hazards such as toxicity, equipment guarding and protection against falling, noise and electrical shock.
The New Jersey Toxic Catastrophe Prevention Act was developed after the Bhopal disaster and several other incidents such as that of Institute, West Virginia in 1985 and several chemical release incidents in New Jersey in 1986. This required for each of the 109 materials listed in regulations to be registered based on attainment of a material that can cause acute toxicity at a distance of 100m from a source of 1 hour release.
Kirk Othmer (1991-1998).
Safety and Hazard symbols
A hazard symbol is defined as a recognised symbol that is designed to warn about dangerous locations or materials.
NFPA 704- National Fire Protection Association
NFPA 704 or ‘the fire diamond’ is a standard maintained by the National Fire Protection Agency in the US. This standard is used by emergency personnel to easily and quickly identify the types of nearby hazards and to help determine what sort of equipment, precautions or procedures would need to be adhered to following an emergency response.
There are symbols attached to the fire diamond which each signify a particular type of hazard. They are colour coded. Red signifies a flammability hazard, blue signifies a health hazard, yellow signifies an instability or reactivity hazard and white signifies a specific hazard such as a material that reacts unusually with water such as sodium or certain alkali metals, a specific hazard can be anything from a biological hazard to a corrosive hazard.
Each of these hazards is ranked according to the level of risk they pose to personnel. It is ranked with 5 gradations, 4 being the highest and 0 being the lowest; this would pose no hazard at all. For each of the different types of hazards this high level of risk has a different definition. For a flammability hazard of 4 this would mean that the material has a flash point below that of room temperature and will burn readily at regular pressures and temperatures. Propane is an example of such a hazardous substance. For a health hazard of 4 this would signify that if one were exposed to the material for a short amount of time that it could cause death. An example of this would be hydrogen cyanide or phosphine. For an instability or reactivity hazard of 4 this would signify a substance that would be readily capable of detonation or decomposition at normal temperatures and pressure, such an example of this would be nitroglycerine. On the other end of the scale, a flammability hazard of 0 would be a substance that would not burn under any conditions such as water. A health hazard of 0 would be a substance that would pose no health hazard at all such as that of lanolin ointment. An instability/reactivity hazard of 0 would be a substance that is normally stable, even if it is exposed to fire, such as helium or any inert gas.
These are some examples of the fire diamonds for various substances
nfpa_diamond.png fire diamond for ethanol.jpg caffeine fire diamond.jpg
Fig 2.1 Nitroglycerine Fig 2.2 Ethanol Fig 2.3. Caffeine
Another method by which hazards can be averted is by specifying the types of precautions needed in handling potentially dangerous chemicals. The Hazardous Materials Identification Guide (HMIG) and Hazardous Materials Information System (HMIS) use a different system which signifies what type of protective equipment is needed when handling a certain chemical. This method is similar to the NFPA 704 (fire diamond). The differences lie in the white bar. In this system the white bar holds letters corresponding to different types of Personal Protective Equipment (PPE) which are needed. The letters used are A-K and X and mean the same for both the HMIG and HMIS. They are also augmented with pictures of what icons are pictures showing the types of PPE that would be needed.
HMIG.gif
Fig 2.4 (HMIG)
Safety Glasses
Safety Glasses, Gloves
Safety Glasses, Gloves, Apron
Face Shield, Gloves, Apron
Safety Glasses, Gloves, Dust Respirator
Safety Glasses, Gloves, Apron, Dust Respirator
Safety Glasses, Gloves, Vapour Respirator
Splash Goggles, Gloves, Apron Vapour Respirator
Safety Glasses, Gloves, Dust and Vapour Respirator
Splash Goggles, Gloves, Apron, Dust and Vapour Respirator
Air Line Hood or Mask, Gloves, Full suit, Boots
X- Ask Supervisor or Safety Specialist for handling instructions
Hazardous Materials Regulations
In an operation where chemicals are manufactured and distributed the role of packaging these chemicals safely is an important priority to the chemical industry. Careful consideration must be made to ensure that the packaging used provides adequate containment of any hazards that may be held in the packaging so as to ensure that it can be transported safely from the place of manufacture to where it is being used. Not only that, but the product must be packaged as to contain the product adequately to ensure that it does not become contaminated by the surroundings, to provide vital information about product identity, handling information and any potential hazards to shippers and users.
Due to environmental concerns packaging practises have undergone scrutiny by governments, regulatory agencies, consumer groups and environmentalists. It is becoming increasingly important that packaging is produced in a reasonable manner, is recycled when economically feasible and permitted by regulation, and is used in an efficient manner so as to ensure no wastage occurs where possible and to minimise usage of materials.
Most products can be stored and transported by most means of packaging; the choice of the type of packaging is taken usually by the manufacturer for economic or marketing reasons. For a chemical however the choice of packaging is mainly dictated by safety priorities and chemical compatibility factors. In this case, for physical distribution the cost of the packaging can be comparable to the manufacturing costs of the product and this in turn will have a knock-on effect for the cost of the product for the consumer.
Regulations regarding how a chemical product is packaged and shipped depend on whether the chemical is classified as hazardous or nonhazardous. Nonhazardous chemical substances are shipped and packaged subject to the rules of the carrier. The most common rules are those published in National Motor Freight Classification for trucks and Uniform Freight Classification for railroads. If items are not packaged according to the classification requirements then the carriers have a right to collect a surcharge and refuse paying handling or damage claims on such items. The regulations controlling packaging for hazardous materials are different. The primary document The Hazardous Materials Regulations (HMR) devised in the Code of Federal Regulations was changed in order to bring it to par with international rules and to “enhance safety through better classification and packaging”. The primary change was to replace specific containers with performance oriented packaging. This means that as long as a packaging system passes test requirements it can be used. Certification of a package is now the responsibility of the shipper. Tests on packaging must be approved by a test laboratory and in turn this laboratory must be approved by the Department of Transport (DOT).
Hazardous materials are regulated according to how they are classified. The HMR provides a table classifying the types of hazardous materials. There are 9 classes some with subdivisions.
HMR Classification
Class
Subdivision
Explosives
1.1 Mass Explosion Hazard
1.2 Projection Hazard; no mass explosion hazard
1.3 Fire hazard and minor projection or blast
1.4 No significant blast hazard
1.5 Very insensitive mass explosion hazard
1.6 Extremely insensitive detonating substances
Compressed Gases
2.1 Flammable Gas
2.2 Non-flammable Gas
2.3 Poison Gas
Flammable Liquids
Flammable Solids
4.1 Flammable Solid
4.2 Spontaneously Combustible
4.3 Dangerous When Wet
Oxidising Substances and Organic Peroxides
5.1 Oxidizer
5.2 Organic Peroxide
Poisonous and infectious Substances
6.1 Poisonous Substances
6.2 Infectious Substances
Radioactive Materials
Corrosives
Miscellaneous dangerous Substances
Fig 3. Kirk Othmer (1991-1998)
Packaging requirements for hazardous materials are determined by finding them listed in Hazardous Materials table of 49 CFR, section 172. From this the hazard class, packaging group, identification number, label requirements, packaging authorisations and special provisions can be ascertained from this. All types of designed packaging must be tested before approval. If approved, it must be marked with the UN packaging marking which specify any details pertaining to the packaged material such as the type of material, relative density of the material and maximum gross weight for which the packaging has been tested, the packaging group for which the package has been approved, whether the material is solid or under pressure, the state or country of origin, the year of manufacture and the testing facility. When the package is ready for shipment it must be labelled with the identification number and shipping name in the top left corner, the hazardous materials label in the centre of the panel, and the package marking in the bottom left corner. Shipping documents must also show the hazardous materials identification, the hazard class and an emergency telephone number. Improper packaging procedures including improper shipping documents, marking or handling can result in civil and/or criminal liabilities against the carrier, shipper or the packaging manufacturer.
Hazardous Pollutants
The chemical process industry is one of the most highly regulated industries in the world. It is regulated regarding areas of environmental protection, health and safety. Everything is affected by the chemical industry, the siting of a new location for a facility, the transportation of raw materials and finished products, working conditions for employees, packaging of finished materials and interactions with the community. The chemical industry also develops additional regulations alongside the regulatory agencies to ensure the proper protection of the community, the environment and the employees. For example, The Chemical Manufacturers Association (CMA) brought out the Responsible Care Initiative. This initiative, initially started in Canada, is a commitment on behalf of the chemical industry to continuously improve health, safety and environmental standards and to respond to public concerns. The initiative is implemented by 6 codes of management practices which cover Community Awareness and Emergency Response (CAER), Employee Health and Safety, Distribution, Process Safety, Pollution Prevention and Product Stewardship. More than 35 countries in the world have taken on responsible care and are developing their own means of implementation.
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Uniformity to environmental standards was attempted by the International Standard Organisation (ISO) by following up the ISO 9000 series of quality standards with the ISO 14000 environmental management standards. For example ISO 14001, Environmental Management Systems, is a statement of environmental policy which includes the commitment to comply with environmental legislation and a commitment to ensure continual improvement; it also ensures that environmental objectives within the plant are identified, management representatives that ensure that the companies plans are implemented and procedures that might detect any noncompliance to such standards by means of periodic environmental management system audits are carried out. Any company wishing to do business in the international market will need ISO 14001 certification.
Environmental Protection
Water
For a long time in the US water pollution control were taken on a basis of water quality standards for bodies of water such as streams, lakes and rivers, receiving bodies of water. There was no effective, national legal authority which limited the discharge of pollutants into bodies of water and was regulated more so on a state-by-state basis. In the late 1960’s the US revived the 1899 Refuse Act which prohibited discharging anything into navigable water unless certain permits were obtained. This provided a new control over discharges of materials by industry. Along with this, legislation from the Federal Water Pollution Control Act Amendments (FWPCA) was put forward with an objective “to restore and maintain the chemical, physical, and biological integrity of the nation’s waters.” Kirk Othmer (1991-1998). New water quality standards were introduced by means of stream use classification. This gave control to states to decide what they would use their water for. The EPA defined 4 categories.
Class A – Primary water contact recreation
Class B – Propagation of desirable aquatic life
Class C – Public water supplies prior to treatment and
Class D – Agricultural and industrial uses
After this, water quality criteria were to be developed. This means that for each designated water use there were going to be limits to the allowed concentration of pollutants. Limits of discharged effluent were controlled by means of regulating the unit weight of pollutant discharged per mass of product manufactured, rather than measuring the overall concentration of pollutant in a discharge stream. In this way chemical industries would be unable to dilute chemical pollutants to avoid surpassing concentration limits.
Air
2500 years ago lead pollution produced by silver smelters in Rome and Greece were a major cause of concern. Analysis of lake sediments has shown that this lead pollution has spread across the northern hemisphere. Air pollution caused in the modern working environment is usually due to burning of fossil fuels and as early as the 13th century this has been attributed to the burning of coal. The main cause for concern with coal burning was the unpleasant sulfurous odour released and the soot produced but the health effects caused by this has not been made clear until recently.
National Ambient Air Quality Standards
6 pollutants that cause major concern have been classed by the EPA under The Clean Air Act 1970. These are Sulfur Oxides (SOx), nitrogen oxides (NOx), lead, particulates i.e. (subdivisions of solid or liquid matter suspended in a gas), and photochemical oxidants (ozone).The EPA developed National Ambient Air Quality Standards (NAAQS) to combat levels of air pollution based on the level of highest concentration that would have no adverse effects on the environment or on human health. These standards are expressed by ground level concentrations where the concentrations of pollutants are measured at ground level in measurements of parts per million or micrograms per cubic metre.
Solid and hazardous waste
Implementation of laws concerning the control of pollution due to solid waste disposal was formulated much slower than for those were for water and air. The Resource Conservation and Recovery Act 1976 (RCRA) was the first act passed where newer substantial controls were authorised. The objective of the RCRA was to conserve public health, the environment and natural resources. It was implemented to ensure that practices regarding the production, storage, transportation and disposal of waste would minimise or completely eradicate the hazard to human health and the environment. The section of the RCRA that caused the most concern to the Chemical Industry was subtitle C. This was the hazardous waste management regulations. The objective of this was to monitor and regulate hazardous waste from the time of production to its disposal. Facilities which would work in the transportation, storage, treatment or generation of hazardous waste are covered by these regulations. The definition of a solid waste to the RCRA covers a broad category of substances including solids, semisolids or liquids or any contained gaseous materials. “A hazardous waste is a substance that must be either listed by the EPA or have a hazardous characteristic” Kirk Othmer (1991-1998). Certain types of solid wastes are excluded from the hazardous materials regulations specifically for the large volume by which they are produced or other reasons. These would include household wastes, fossil fuel combustion, exploration wastes and some agricultural and mining wastes. A solid waste is considered hazardous if it is listed in the EPA or has a specific characteristic hazard. There are four characteristics of hazardous wastes: reactivity, corrosivity, ignitability and toxicity. Toxicity refers to how leachable the waste is and the toxicity in the groundwater that would result using Toxicity Characteristic Leaching Procedure, an analytical method. Some examples of hazards included in TCLP are listed in the table below.
Maximum Concentration of Contaminants for Toxicity Characteristic
Contaminant
Regulatory Level (mg/L)
Arsenic
5.0
Benzene
0.5
Silver
5.0
Lead
5.0
Mercury
0.2
Chloroform
6.0
Chromium
5.0
Selenium
1.0
Fig 4. Kirk Othmer (1991-1998)
It is the responsibility of the producer of the substance to determine whether it is hazardous. They are required to hold records; label substances correctly, inform transporters and report to the EPA periodically. Groundwater and air quality are monitored for any facility that could potentially produce emissions. Any regulations concerning nonhazardous waste are controlled by the local and state authorities. Due to increased pressure on landfill sites these regulations are getting more stringent for nonhazardous solid waste. Better management of nonhazardous waste is encouraged through recycling, reduction and reuse.
Industrial Hygiene
Industrial hygiene is a profession devoted to anticipating, evaluating and recognising any environmental factors or stresses arising in the workplace which could cause impaired health and wellbeing, sickness, inefficiency and significant discomfort between workers and those of the local community. In the U.S., industrial hygienists are usually members of the American Industrial Hygiene Association (AIHA) or other groups such as the American Academy of Industrial Hygiene (AAIH). Industrial Hygienists work with other professions concerning health in the workplace such as safety engineers and occupational health nursing. All these groups work in implementing the laws regarding the regulation of health and safety in the workplace. The principal laws are the Occupational Safety and Health Act (OSHA) in the U.S. but similar laws are put into place all over the world which are proposed by International Organisations such as the International Labour Organisation (ILO) and the World Health Organisation (WHO).
Hazards arising from the workplace which industrial hygienists are interested in would include the following categories.
Chemical
Carcinogens, Reproductive Hazards, Acute Poisons, Irritants, Corrosives, Neurotoxins
Ergonomic
Repetitive Strain Injury (RSI), Back injury, Carpal Tunnel Syndrome, Human-Machine interaction
Physical
Noise, Cold, Heat, Ionising Radiation, Extremely Low Frequency Radiation (ELF), Ultraviolet Radiation, Laser Radiation, Infra Red Radiation
Industrial Hygienists must be able to detect what potential hazards might result from workplace materials, to evaluate hazards and determine how much risk is posed by it, and to recognise hazards as they occur. The best and cheapest way to approach workplace hazards is to anticipate them and if possible to completely prevent them from happening.
When a new chemical process is conceived an industrial hygienist must check the toxicology of the substance produced, either by animal testing or by human epidemiology. Some substances are self limiting, others are potent and carcinogenic but most chemicals lie somewhere in between. Wherever possible it is encouraged to abstain from using potentially dangerous chemicals. Also potentially damaging physical hazards which arise from certain processes such as excessive heat, noise or pressures must also be anticipated and avoided where possible. Usually industrial hygienists are capable in devising methods of using hazardous chemical substances safely.
To recognise potential hazards industrial hygienists must have an extensive knowledge of the kind of hazards that may occur in types of industry. Recognising hazards is done by looking for sources of harmful chemical or physical agents that would cause damage if exposed to workers.
Fugitive emissions are an example of an industrial hazard, and occur when there is a break in the barrier which provides containment for the chemical process. The main source of loss can be attributed to seal and flange leaks where material could escape. Even though the emissions can be incredibly small so that they are undetectable by a material balance, they can however build up in the work area which could lead to overexposure to harmful chemicals. Valve stem leaks are one example. These can worsen over time if not corrected. Pump seal leaks which are usually quite small can become large if there is total seal fail
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