Review Article ACCIDENT PREVENTION BY USING HAZOP STUDY AND WORK PERMIT SYSTEM IN BOILER Karthika. S Address for Correspondence M.E -Industrial Safety Engineering, Department of Mechanical Engineering, K.S.R College of Engineering, Tiruchengode, INDIA ABSTRACT Even though accidents can never be eliminated completely, employers can prevent many of the injuries and fatalities that occur each year. Hazop study provide a safe system of work during inspection, maintenance operation especially in boilers, through that work permit system formed to prevent the accident. When, in a workplace, a hazard has been identified and the risk to health assessed, an appropriate prevention or control strategy is required. The fact that preparatory work is more important than the work itself. Many times people get killed inside tanks and other confined spaces because of misunderstandings like entering without permission to do some job or merely put their head inside to inspect the inside. Through HAZOP study and work permit, accident can be prevented. KEYWORDS Accident prevention, hazard, accident control, HAZOP study, work permit 1. INTRODUCTION 1.1. HAZARD AND OPERABILITY STUDY: A hazard and operability study (HAZOP) is a structured and systematic examination of a planned or existing process or operation in order to identify and evaluate problems that may represent risks to personnel or equipment, or prevent efficient operation. The HAZOP technique was initially developed to analyze chemical process systems, but has later been extended to other types of systems and also to complex operations such as boiler operation and to record the deviation and consequence. A HAZOP is a qualitative technique based on guidewords and is carried out by a multi-disciplinary team (HAZOP team) during a set of meetings. BOILER: A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exist the boiler for use in various processes or heating application. The pressure vessel in a boiler is usually made of steel or alloy steel. The source as heat for boiler is combustion of any as several fuels, such as wood, coal, oil, natural gas, electric stream boiler use a resistance or immersion type heating elements. Boilers and unfired pressure vessels have many potential hazards in common that must be controlled by safety devices and safe work practices. Boilers are closed vessels in which water is heated by fuel combustion or heat from other sources. Workers should make sure that all these elements work properly and are operated only under safe conditions. USAGE HAZOP is best suited for assessing hazards in facilities, equipment, and processes and is capable of assessing systems from multiple perspectives: 1. Design Assessing system design capability to meet user specifications and safety standards Identifying weaknesses in systems 2. Physical and operational environments Assessing environment to ensure system is appropriately situated, supported, serviced, contained, etc. 3. Operational and procedural controls Assessing engineered controls (ex: automation), sequences of operations, procedural controls (ex: human interactions) etc. Assessing different operational modes startup, standby, normal operation, steady & unsteady states, normal shutdown, emergency shutdown, etc. STEAM SYSTEM Heat Recovery from Continuous Boiler Skimmers Boiler Exhaust Heat Recovery with Condensing Economizer Initiate a Steam Trap Program Reduce Boiler Pressure A flow chart giving HAZOP procedure is given below 1) THE BASIC CONCEPT Essentially the Hazops procedure involves taking a full description of a process and systematically questioning every part of it to establish how deviations from the design intent can arise. Once identified, an assessment is made as to whether such deviations and their consequences can have a negative effect upon the safe and efficient operation of the plant. If considered necessary, action is then taken to remedy the situation. This critical analysis is applied in a structured way by the Hazop team, and it relies upon them releasing their imagination in an effort to discover credible causes of deviations. In practice, many of the causes will be fairly obvious, such as pump failure causing a
loss of circulation in the cooling water facility mentioned below. However, the great advantage of the technique is that it encourages the team to consider other less obvious ways in which a deviation may occur, however unlikely they may seem at first consideration. In this way the study becomes much more than a mechanistic check-list type of review. The result is that there is a good chance that potential failures and problems will be identified that had not previously been experienced in the type of plant being studied. WORK PERMIT SYSTEM The human element of the system has one of the biggest potentials for either causing or preventing an accident. Safe job performance by operating, maintenance personnel and contractors has a tremendous positive impact on safety. Work Permit Work permit to be raised by the concerned before commencing the job. Check list to be verified by the Safety Concerned in charge to sign in the permit. Permit to be cleared by Safety For any electrical related job line clear permit to be raised. Concerned Electrical person to isolate the power supply and clear the permit. One line clear log to be maintained by Electrical. After work completion permit to be closed. For any Confined space work, Vessel Entry Permit should be obtained. PURPOSE The purpose of this standard is to describe procedures and guidelines on work permit system to carry out jobs of inspection, testing, maintenance, alternation, repair, upkeepment and construction in safest possible manner. The implementation of this system will help in bring down the risks at work sites to acceptable level, thereby reducing possibility of any accident, fire, explosion, property damage and adverse effect on environment. WORKS REQUIRE PERMIT Normally all maintenance, repair, construction work shall be carried out with a proper work permit. Jobs where work permit is required include but not limited to followings: Major and minor maintenance work Inspection Construction Alteration Any hot work (including use of normal battery driven equipment in operating areas) Entry into confined space Excavation Vehicle entry into process areas Work at height Handling of materials using mechanized means in operating areas Erection and dismantling of scaffold Radiography GENERAL PRINCIPLES The following aspects should be considered with respect to Permit to Work Systems: Human factors; Management of the work permit systems; Poorly skilled work force; Unconscious and conscious incompetence; Objectives of the work permit system; Types of work permits required; and Contents of the work permits. The following issues may contribute towards a major accident or hazard: Failing of the site safety management system; Failure to recognize a hazard before and during maintenance; Failure to comply with the work permit system in hazardous environments; and Communication failure during the use of a work permits system. Major hazards Major hazards arise while working Wrong type of work permit used; Wrong information about work required on the work permit; Failure to recognize the hazards where work is carried out (e.g. flammable substances); Introduction of ignition source in controlled flameproof area (e.g. welding, non sparkproof tools, non-intrinsically safe equipment used in intrinsically safe zones); Terms of work permit not adhered to (e.g. failure to isolate plant and/or drain lines of hazardous substances); Failure to hand-over plant in safe condition on completion of work/cancelling of work permit; Unauthorized staff performing work permit functions; Poor management of the work permit system; and Insufficient monitoring of the work permit system. OCCUPATIONAL HEALTH AND SAFETY Facility-specific occupational health and safety hazards should be identified based on job safety analysis or comprehensive hazard or risk assessment using established methodologies such as a hazard identification study [HAZID], hazard and operability study [HAZOP], or a scenario-based risk assessment [QRA]. The most significant occupational health and safety hazards occur during the operational phase of a coal processing facility and primarily include the following: Process Safety Oxygen-Enriched Gas Releases Oxygen-Deficient Atmospheres Inhalation hazards Fire and explosions Process Safety: Process safety programs should be implemented due to industry-specific characteristics, including complex chemical reactions, use of hazardous materials (e.g., toxic, reactive, flammable or explosive compounds), and multistep reactions. Process safety management includes physical testing hazard analysis preventive maintenance, employee training, and emergency planning. Oxygen-Enriched Gas Releases: Prevention and control measures to reduce on-site and off-site exposure to oxygen-enriched atmospheres include installation of an automatic
Emergency Shutdown System that can detect and warn of the uncontrolled release of oxygen, implementing hot work permits, good housekeeping practices to reduce combustible materials, and fire prevention and control equipment. Oxygen-Deficient Atmosphere: The potential releases and accumulation of nitrogen gas into work areas can result in asphyxiating conditions. Prevention and control measures to reduce risks of asphyxiation include nitrogen venting systems, emergency shutdown systems, and confined space entry programs. Chemical exposure in coal processing facilities is primarily related to inhalation of coal dust, coal tar pitch volatiles, carbon monoxide, and other vapors such as methanol and ammonia. Workers exposed to coal dust may develop lung damage and pulmonary fibrosis. Exposure to carbon monoxide results in formation of carboxyhemoglobin (COHb), which inhibits the oxygen-carrying ability of the red blood cells. Mild exposure symptoms may include headache, dizziness, decreased vigilance, decreased hand-eye coordination, weakness, confusion, disorientation, lethargy, nausea, and visual disturbances. Greater or prolonged exposure can cause unconsciousness and death. Protection measures include worker training, work permit systems, use of personal protective equipment (PPE), and toxic gas detection systems with alarms. Coal Storage and Preparation: Coal is susceptible to spontaneous combustion, most commonly due to oxidation of pyrite or other sulphidic contaminants in coal. Coal preparation operations also present a fire and explosion hazard due to the generation of coal dust, which may ignite depending on its concentration in air and presence of ignition sources. Coal dust therefore represents a significant explosion hazard in coal storage and handling facilities where coal dust clouds may be generated in enclosed spaces. Dust clouds also may be present wherever loose coal dust accumulates, such as on structural ledges. Recommended techniques to prevent and control combustion and explosion hazards in enclosed coal storage include the following: 1. Storing coal piles so as to prevent or minimize the likelihood of combustion, including: Compacting coal piles to reduce the amount of air within the pile, Minimizing coal storage times, Avoiding placement of coal piles above heat sources such as steam lines or manholes, Constructing coal storage structures with non-combustible materials, Designing coal storage structures to minimize the surface areas on which coal dust can settle and providing dust removal systems, and Continuous monitoring for hot spots (ignited coal) using temperature detection systems. When a hot spot is detected, the ignited coal should be removed. Access should be provided for firefighting; 2. Eliminating the presence of potential sources of ignition, and providing appropriate equipment grounding to minimize static electricity hazards. All machinery and electrical equipment inside the enclosed coal storage area or structure should be approved for use in hazardous locations and provided with spark-proof motors; 3. All electrical circuits should be designed for automatic, remote shutdown; and 4. Installation of an adequate lateral ventilation system in enclosed storage areas to reduce concentrations of methane, carbon monoxide, and volatile products from coal oxidation by air, and to deal with smoke in the event of a fire. The project will of a great help to operation and maintenance personnel for keeping boiler& turbine and their auxiliaries under safe conditions. This will not only keep the equipment safe but will also help in safety of human beings. HAZARD IDENTIFICATION IN BOILER Pitting Erosion Vibration Rupture Corrosion fatigue Thermal fatigue Over temperature Maintenance damage Material flaws Welding flaws The following table gives an overview of commonly used guide word - parameter pairs and common interpretations of them. Boiler explosion A boiler explosion is a catastrophic failure of a boiler. As seen today, boiler explosions are of two kinds. One kind is a failure of the pressure parts of the steam and water sides. There can be many different causes, such as failure of the safety valve, corrosion of critical parts of the boiler, or low water level. Corrosion along the edges of lap joints was a common cause of early boiler explosions. Causes of boiler explosions "The principal causes of explosions, in fact the only causes are deficiency of strength in the shell or other parts of the boilers, over-pressure and over-heating. Deficiency of strength in steam boilers may be due to original defects, bad workmanship, and deterioration from use or mismanagement." "Cause.-Boiler explosions are always due to the fact that some part of the boiler is, for some reason, too weak to withstand the pressure to which it is subjected. This may be due to one of two causes: Either the boiler is not strong enough to safely carry
its proper working pressure, or else the pressure has been allowed to rise above the usual point by the sticking of the safety valves or some similar cause". safe condition & act once in six months. Corrective actions to be suggested Action plan to be prepared with responsibility and target date All concerned to be communicated and to be followed up Progress to be reviewed during safety committee meeting Accident reporting, investigation and remedial action: Getting first information of the accident and to inform DGM(SHE) Investigation of the accident to find out the root cause and suggesting remedial action to avoid re occurrence. Follow the suggested remedial action for compliance. Assisting HR to send the report to Factory Inspectorate. Getting the man days lost from HR Conducting safety Audit & taking corrective action Safety audit to be conducted to find out un
CONCLUSION This project focuses on a preventing the accident in boiler by using HAZOP study and also through work permit system during maintenance operation and periodic inspection, in that hazards will identified and minimized. Study is carried out by visiting various work process in dairy industry and work permit checklist for each and every individual work is prepared by analysing the type of work, nature of work, PPE s needed, precaution measure for that work and hazardous present in work through HAZOP study. REFERENCE 1. A.R. Qureshi, The role of hazard and operability study in risk analysis of major hazard plan t, Journal of Loss Prevention in the Process Industries, Volume 1, Issue 2, Pages 104-109, April 1988, 2. Diana M. Ceballos, MS, PhD,Scott E. Brueck, MS, CIH, Confined Space Program Recommendations for Dairy Plant Inspectors Nationwide Health Hazard Evaluation Report,HETA 2010-0175-3144,November 2011. 3. Jouko Suokas, The role of safety analysis in accident prevention, Accident Analysis and Prevention, Volume 20, Issue 1, Pages 67-85, February 1988. 4. Liu Yinga, Hua Zhijiaa, Lei Lianbaob, Motivation Mechanism of Accident Prevention in Coal Mine, Procedia Engineering, Vol 43, Pages 174 179, 2012. 5. Michael Booth, John D. Butler, A new approach to permit to work systems offshore, Volume, Pages 309 326,November 1992. 6. Mary Lynn Garcia, Entry Control, Design and Evaluation of Physical Protection Systems (Second Edition), Pages 187 217, 2008. 7. Paul A. Erickson, Confined space entry and hot work, Practical Guide to Occupational Health and Safety, Pages 100 116, 1996. 8. R.E. Iliffe, P.W.H. Chung and T.A. Kletz, More effective permit-to-work systems, Trans IChemE, Vol 77, Part B, March 1999. 9. S. Matsuoka, M. Muraki, Implementation of Transaction Processing Technology in Permit-to-Work Systems, Volume 80, Issue 4, Pages 204 210, July 2002. 10. Trevor Kletz, Entry to Vessels, Case Histories of Process Plant Disasters and How They Could Have Been Avoided, Pages 207 219, 2009. 11. Trevor Kletz, Entry into Confined Spaces, Case Histories of Process Plant Disasters and How They Could Have Been Avoided, Pages 375 389, 2009.