Lecture 3 - Introduction to Chemical Process Safety PDF

Lecture 3 – Introduction to Chemical Process Safety Common Terms and Definitions Safety – the prevention of accidents through the use of appropriate technologies to identify the hazards of a chemical plant and eliminate them before an accident occurs. Hazard - a chemical or physical condition that...

Lecture 3 – Introduction to Chemical Process Safety Common Terms and Definitions Safety – the prevention of accidents through the use of appropriate technologies to identify the hazards of a chemical plant and eliminate them before an accident occurs. Hazard - a chemical or physical condition that has the potential to cause damage to people, property, or the environment. Risk - a measure of human injury, environmental damage, or economic loss in terms of both the incident likelihood and the magnitude of the loss or injury. Safety Program Accident and Loss Statistics Accident and loss statistics are important measures of the effectiveness of safety programs. These statistics are valuable for determining whether a process is safe or whether a safety procedure is working effectively. The common metrics used are: 1. OSHA incidence rate 2. Fatal Accident rate 3. Fatality rate or deaths per person per year OSHA (Occupational Safety and Health Administration) - Is responsible for ensuring that workers are provided with a safe working environment. Terms used by OSHA and Industry to Represent Work-Related Losses First Aid - Any one-time treatment and any follow-up visits for the purpose of observation of minor scratches, cuts, burns, splinters, and so forth that do not ordinarily require medical care. Incident Rate - Number of occupational injuries and/or illnesses or lost workdays per 100 full-time employees. Lost Workdays - Number of days (consecutive or not) after but not including the day of injury or illness during which the employee would have worked but could not do so. Medical treatment - Treatment administered by a physician or by registered professional personnel under the standing orders of a physician. Occupational injury - Any injury such as a cut, sprain, or burn that results from a work accident or from a single instantaneous exposure in the work environment. Terms used by OSHA and Industry to Represent Work-Related Losses Occupational Illness - Any abnormal condition or disorder, other than one resulting from an occupational injury, caused by exposure to environmental factors associated with employment. Recordable cases - Cases involving an occupational injury or occupational illness, including deaths. Recordable fatality cases - Injuries that result in death, regardless of the time between the injury and death or the length of the illness. Recordable nonfatal cases without lost workdays - Cases of occupational injury or illness that do not involve fatalities or lost workdays but do result in (1)transfer to another job or termination of employment or (2) medical treatment other than first aid or (3) diagnosis of occupational illness or (4) loss of consciousness or (5) restriction of work or motion. Recordable lost workday cases due to restricted duty - Injuries that result in the injured person not being able to perform their regular duties but being able to perform duties consistent with their normal work. Terms used by OSHA and Industry to Represent Work-Related Losses Recordable cases with days away from work - Injuries that result in the injured person not being able to return to work on their next regular workday. Recordable medical cases - Injuries that require treatment that must be administered by a physician or under the standing orders of a physician. The injured person is able to return to work and perform his or her regular duties. OSHA Incident Rate Lost workdays is number of days after but not including the day of injury or illness during which the employee would have worked but could not do so.  Fatal Accident Rate The FAR is used mostly by the British chemical industry. The FAR reports the number of fatalities based on 1000 employees working their entire lifetime. The employees are assumed to work a total of 50 years. Thus the FAR is based on 10^8 working hours.  Fatality Rate This system is independent of the number of hours actually worked and reports only the number of fatalities expected per person per year.  Sample Problem A refinery has 1,500 full time employees. Previous year (2022), this refinery has 38 reportable lost-time injuries with a resulting 274 lost workdays. Compute the OSHA incidence rate based on injuries and lost workdays. One employee (working hours) = 8 hrs/day * 5 days/week * 50 weeks/year One employee (working hours) = 2,000 hours/employee Total working hours of all employee = 1, 500 employee* 2,000 hours/employee Total working hours of all employee = 3,000,000 hours Sample Problem OSHA incidence rate (injuries) = (38 X 200,000)/3,000,000 OSHA incidence rate = 2.53 OSHA incidence rate (lost workdays) = (274 X 200,000)/3,000,000 OSHA incidence rate = 18.27  Sample Problem Ammonia plant employs 1,200 full time employees with resulting FAR of 5. How many industrial related deaths are expected every year. Period cover = 1 year = 2,000 hours/employee Total hours work of all employee = 1,200 employee * 2,000 hours/employee Total hours work of all employee = 2,400,000 hours Number of fatalities = (5*2,400,000)/100,000,000) Number of fatalities in a year = 0.12 deaths A death can be expected every 8.4 years  Sample Problem Airline company posted 4 deaths per 10,000,000 passenger miles. The average trip is 300 miles/passenger. Calculate the company’s fatality rate. Total number of passenger = (10,000,000 passenger miles)/(300 miles/passenger) Total number of passenger = 33,333 passenger Fatality Rate = 4/33,333 = 0.00012  Accident Pyramid Property damage and loss of production must also be considered in loss prevention. “No Damage” accidents are frequently called “near misses” and provide a good opportunity for companies to determine that a problem exists and to correct it before a more serious accident occurs. Acceptable Risk We cannot eliminate risk entirely. Every chemical process has a certain amount of risk associated with it. At some point in the design stage someone needs to decide if the risks are “acceptable.” Public Perception Types of loss for large hydrocarbon- chemical plant accidents Causes of losses in the largest hydrocarbon-chemical plant accidents Hardware associated with largest losses Accident three-step sequence 1. Initiation – the event that start the accident 2. Propagation – the event or events that maintain or expand the accident 3. Termination – stop or diminish the accident 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.