Table 1. Risk Probability of Occurrence Determination
Thermal power plant is an electricity generation industry involving several operating systems using fossil fuel. Among the operating systems, Lignite Handling System contributes several unsafe acts and conditions that could interrupt the normal working of the plant. A risk assessment is an essential step in protecting the plant from such scenario. The intention of Hazard Identification and Risk Assessment is to identify the most potential hazards and to assess the identified hazards by calculating their frequencies and consequences, after which risk assessment matrix is developed to attain the risk level by means of risk severity. Subsequently, risk level is assigned to each identified hazard for determining the corrective actions to control or eliminate the hazard. In this paper, a HIRA is prepared for the Lignite Handling System of Thermal power plant, and suggested the possible control measures and preventive actions to minimize or eliminate the risk of future occurrence.
Electric power generation is being done through many sources in India. The major sources of electric energy in India are fossil fuels and water. The present contribution by different types of plants are
These plants are classified as under and depending upon their energy conversion. Power sector is one of the core industrial sectors which play a vital role in the overall economic growth of the country. The gap between energy demand and supply is very significant. Hence to meet the demand supply gap, apart from augmenting the capacity there is an immense need to improve the performance of the existing power generating units. Demand for electrical power is increasing at a rapid pace in our country.
The brown coal also called Lignite is the main fuel in the firing system to generate steam in the steam generator (Boilers). The other fuels such as light diesel oil, and furnace oil are also used in the firing system in the situations whenever required. The lignite which is required for continuous flame generation in the furnace, is taken from mines through the single conveyor system to Thermal Power Station storage yard. Transporting of lignite continuously as well as adequately is the biggest task.
Any failures in mining activities or any fluctuating power demand at the power station certainly affect the functions at both ends. So the system should be designed in such a way, which must have more than ordinary prominent features of coal mining whether from the technical or economic point of view. The reliable and efficient handling of lignite at various stages is a matter of prime concern to a power station. In the existing lignite handling system, various operational problems are experienced on many occasions like overloading, chute chocking under the utilization of mining conveyor capacity, increase in the idle running time of conveyors, time delay in bunker filling, increase in oil consumption due to delay in bunker filling, and also decrease in power generation due to critical bunker fuel conditions.
At the same time, during the entire process of generation it exposes a wide range of hazards. The hazards could be of physical, chemical, biological and environmental which may risk injury and cost human lives and property damage, which ultimately interrupt the production. Hazard Identification and Risk Evaluation is a methodological approach to preclude such instances.
This paper has been specifically taken up with a view to systematically identify and evaluate most of the forceable potential hazards related to the operation and maintenance of Lignite Handling System in Thermal power station and suggesting the possible corrective actions to control or minimize the risk.
The objectives of this study are to:
The Scope of the study is:
This study deals mainly with coal safety requirements within the cement industry which accounts for a small percentage of coal usage in pulverized coal firing systems. It also deals with the security requirements related to coal grinding, drying, blending, transporting and storing. Case histories investigated by the Mine Safety and Health Administration (MSHA) are going to be discussed, and proposals are going to be made for future fire and explosion prevention (Alameddin & Luzik, 1987).
Ahmad et al. (2016), Hazard Identification, Risk Assessment and Risk Control (HIRARC) Accidents at Power Plant: This paper highlights report on hazard identification, risk assessment and risk control applied in the coal-fired power plant located in Malaysia. It includes the methodological steps to identify the hazard, assess the risk level of the hazards, and apply or suggest the possible control measures and corrective actions to reduce or eliminate the risk.
Tixier et al. (2012), did a review of 62 risk analysis methodologies of industrial plants: In this paper, sixty-two methodologies are identified. Methodologies are separated into three phases (identification, evaluation and establishment of hierarchy). It also deals with the appliance fields and therefore the main limitations of those methodologies. This paper highlights the problems under consideration and all risks of plant and suggests that there is not just one general method to affect the problems of commercial risks.
Rathod et al. (2017), has presented a paper about Hazard Analysis and Risk Assessment in thermal power plant: This paper deals with various sorts of hazard analysis and finding a risk assessment in thermal power station. It discusses about the identification of various types of hazards in thermal power plant and determining what actions to take to eliminate or control identified hazards. The risk assessment identifies the areas of significant concerns which require extra preventive measures.
Barry (2002) explained in detail about Risk Informed Performance Based Industrial Fire Protection: The purpose of this paper is to provide an overview of fire risk-informed evaluation methods. Risk-informed fire protection evaluation is a risk-based decision support tool that evaluates fire and explosion consequence likelihood and includes an analysis of fire protection system’s performance reliability. The risk-informed evaluation framework provides the information needed to make informed fire protection decisions based on risk tolerance and cost-effectiveness.
Hazard Identification and risk assessment vary greatly across industries, ranging from simple assessment to complex quantitative analyses with extensive documentation. It ultimately avoids the tangible and intangible loss to the organization and enhances the safety standard of the plant. It comprises of consecutive steps such as hazard identification, consequence and frequency assessment, risk estimation based on the existing controls and recommendations to reduce those risks which are not under acceptable limits.
To be effective, the organization's procedures for hazard identification and risk assessment should appreciate the subsequent (Shrivastava & Patel, 2014).
It describes the system's mission, the system boundaries, and therefore the overall system architecture, including the most subsystems and their relationships. This description should provide a high-level overview of the system, suitable for managers that enhances the more technical description that follows.
Hazard identification should aim to determine proactively all sources, situations, or acts, arising from an organisation activity, with a potential for harm in terms of human injury or ill health.
Examples include,
Hazard identification should consider the different type of hazards in the workplace.
The following sources of information or input should be considered during the hazard identification process:
Hazard identification ought to consider all people approaching the working environment [e.g., customers, employee] and
Human factors like capabilities, behaviours and limitations need to be taken under consideration when evaluating the hazards and risk of processes, equipment and work environment.
In considering human factors, the organization's hazard identification process should consider the subsequent and their interactions:
Risk is the combination of the likelihood of an event of a hazardous event or exposure (s) and therefore the severity of injury or unhealthiness which will be caused by the event or exposure(s).
Risk assessment is the process of evaluating the risk(s) arising from the hazards, considering the adequacy of any existing controls and deciding whether the risk is acceptable.
Risk can be calculated by (Ahmad et al., 2016):
Risk (R) = Likelihood (L) x Consequence (C)
where,
(I) Likelihood determines the probability of event of the risk.
(ii) Consequence determines the severities associated with each hazardous effect for the identified scenarios. Inputs to risk assessment may include,
Risk assessment methodology (Tixier et al., 2002),
Risk Probability of occurrence determines the likelihood that an identified risk could occur. It uses a rating and value scale ranging from Highly unlikely (1) to very likely (4). Based on the likelihood of the occurrence, the following chart is discretionarily scaled 1 to 4, with 4 being the highest probability, as shown in Table 1.
Table 1. Risk Probability of Occurrence Determination
Risk consequence level determines the severity of the impact, or the extent of damage caused by the risk. Severity of consequences allocates a rating based on the effect of an identified risk to safety, resources, work execution, property etc. It uses a rating and value scale ranging from slightly harmful (1) to extremely harmful (4). Based on the magnitude of harm in terms of man days lost, the following chart is discretionarily scaled 1 to 4, with 4 being the highest severity as shown in Table 2.
Table 2. Risk Consequence Level Determination (Rathod et al., 2017)
Risk matrix defines the level of risk by considering the risk probability of occurrence or likelihood against the consequence severity. The results of such assessment help characterize risks as per the most serious and the less critical. In Table 3, we will perceive how high risk and low risk factors are shown in the matrices.
Table 3. Risk Matrix (Ahmad et al., 2016)
After the calculations are done, the quantified risk falls into these four risk levels; as shown in Table 4.
Table 4. Risk Level (Faizan et al., 2001)
These risk level zones make the after effect of a risk matrix more straightforward by giving out an obvious division about the future decisions that should be taken.
Having completed a risk assessment and having assessed existing controls, the organization ought to have the option to decide if existing controls are sufficient or need improving.
If new or improved controls are required, their choice ought to be determined by the guideline of the hierarchy of controls, i.e., the elimination of hazards where practicable followed successively of risk reduction with the adoption of Private Protective Equipment [PPE] as a final resort.
The following are examples of implementation of hierarchy of controls: (Standard & Standard, 2004)
The brown coal also called lignite is the main fuel in the firing system to generate steam in steam generator (Boilers), as shown in Figure 1. The lignite which is required for continuous flame generation is taken from mines and supplied to thermal power stations by means of conveyor systems. The conveyor system that takes the lignite from the mine conveyors to the storage bunkers (Receiving bunker) is known as external conveyor system. Transporting of lignite continuously as well as adequately is the biggest task. Each bunker has at least three alternate routes for receiving lignite uninterruptedly, even in the case of breakdown of one or two conveyors. The storage bunker has a shuttle conveyor to receive lignite. From the storage bunkers, blade feeders load the lignite to the conveyors taking it to the crusher house. The roller crushers crush the heavier lump size lignite into smaller size. The crushed lignite is taken by the conveyors to the boiler bunkers. Each boiler has several bunkers.
Figure 1. Lignite Handling System Flow Diagram
Risk Assessment of Lignite Handling System is shown in Table 5.
Table 5. Risk Assessment Table (Faizan et al., 2021)
Figure 2. Frequency of different Hazards in Lignite Handling System
In this study, it was found that very high risks are the most hazardous and unacceptable that need to be attended first, because the impact of those hazards are very dangerous; it may even be fatal. Then the other category risks are dealt according to its risk priority. On implementing and following the suggested control measures (Table 5), the unacceptable very high risk and intolerable high risk can be reduced to acceptable low risk. Hazard Identification and Risk Assessment study on a routine basis process can serve as a tool to reduce the occurrence of injury or disease in the lignite handling system of thermal power station.
In this paper it is observed that risk assessment is useful for finding the hazards in lignite handling system of the thermal power plant. Hazard analysis and risk assessment can be utilized to focus on the risks with the goal that the most hazardous circumstances are managed first and those very unlikely to happen can be thought about later. The risk level of the present and conceivable hazard of lignite handling system is evaluated, partitioning them into Acceptable, Tolerable, Unacceptable, and Intolerable risk level.
Based on the level of risk, possible corrective actions are also suggested to upgrade safety precautions and investigations. With this insight, the risk assessment should be practiced periodically so that the level of preparedness can be evaluated, and measures taken to enhance proficiencies through training and preparation of a more effective response to such occurrences.