Process unit hazard factor

The first step is to calculate the Damage factor for the unit. The Damage factor depends on the value of the Material factor and the Process unit hazards factor (F3 in Figure 2). It is determined using Figure 8 in the Dow Guide. 

Process Unit Hazards Factor F, F,) F, Fire and Cxplollon tnclek (F, x MF - FdEJ ... 

The basis of the F El is a Material Factor (MF). The MF is then multiplied by a Unit Hazard Factor, F3, to determine the F El for the process unit. The Unit Hazard factor is the product of two factors which take account of the hazards inherent in the operation of the particular process unit the general and special process hazards, see Figure 9.2. 

The general process hazard factor (Ft) and special process hazard factor (F2) are multiplied together to produce a unit hazard factor (F3). The Dow F EI is computed by multiplying the unit hazard factor by the MF. Table 10-2 provides the degree of hazard based on the index value. 

The Unit Hazard Factor for process unit is the product of general and special process hazards. Penalties of general process hazards deal with different... 

The penalties comprising the unit hazard factor are calculated based on a single, specific instant in time during which the material represented by the MF is associated with the process unit in the most hazardous state of operation. Start up, general operation, and shut down are among the operational states that should be considered. 

Although both process units have a unit hazard factor (F3) of 4.0, the final measurement of their probable loss exposure must include the hazard of the material being processed or handled. 

If process unit B had a unit hazard factor of 2.7 instead of 4.0, the F EI would be the same as that of process unit A, 64. However, the damage factor for process unit B would be 0.64 (based on a material factor of 24), compared to a damage factor of 0.45 (based on a material factor of 16) for process unit A. 

D. Enclosed or indoor process units This factor accounts for the additional hazard where ventilation is restricted. 

The material factor MF for the process unit is taken of the most hazardous substance present, which lead to the analysis of the worst case that could actually occur. MF is a value, which denotes the intensity of energy release from the most hazardous material or mixture of materials present in significant quantity in the process. MF is obtained from the flammability and reactivity of the substances. The process is divided into units. The material factor is calculated for each unit separately. Dow (1987) has listed a number of chemical compounds and materials with their MF s. 

Include specific equipment identification, because omission can cause problems for readers in other process units or facilities who may have the same equipment and remain imaware of its hazards. Avoid downplaying human performance factors when drafting the report. There is a natural hesitancy to criticize or address normally encountered performance limitations or errors. Effects of fatigue from working excessive overtime are not always addressed in the written report. If these human performance factors are neglected, the error may be repeated. All facts of the incident must be considered relevant. 

As described in a highly referenced document (NRC, 1983), important components of this process include hazard identification, assessment of exposure and dose-response relationships, and characterization of the risk. Uncertainty factors are built into the risk assessment process to account for variations in individual susceptibility, extrapolation of data from studies in laboratory animals to humans (i.e. interspecies variation in toxicokinetics), and extrapolation from high-dose to low-dose exposures. In the case of the association between exposure to chemicals and drugs and autoimmunity or autoimmune diseases, much of the information needed to evaluate risk in the context of the traditional United States National Research Council paradigm is not available. The following represents a discussion of issues in chemical-induced autoimmunity relevant to the use of existing data and data needs in risk assessment. 

XYZ Chemical has similar operations consisting primarily of pesticide and herbicide manufacturing operations in the United States, Europe, Asia, and South America. Since the operations are similar, the prioritization process (illustrated in Table 3.4) consists of cataloging all chemicals in transit (in and out of their facilities), modes of transport, qnantities, and nnmber of annual shipments. Specifically, the prioritization process is a combination of the hazards- and consequence-based prioritization processes illnstrated in Figure 3.4. If this process were expanded to a likelihood- or risk-based process, then additional factors (e.g., the number of shipment, length of shipment) may have been included in the prioritization. With this data collected, the hazards of each chemical and the potential impacts are docnmented based on the chemical physical properties and quantities in transit. With all of the information collected, the following qualitative ranking is nsed to prioritize issnes for escalation and identification of countries and operations that will need to condnct more detailed risk analyses ... 

Hot oil heat exchange systems Since most hot oil (heat exchange) fluids will burn and are frequently used above their Hash points or boiling points, they represent an additional hazard in any process unit that uses them. A penalty factor between 0.25 and 1.15 is applied depending on quantity and temperature. 

The penalty factors applicable to the process unit considered are summed up resulting in the factor for general process hazards Fi and that for specific process hazards F2. The starting point is a base factor of 1 for both Fi and F2, which is the final word if no penalties have to be considered. A value of 0 is used for items, which are not applicable. 

The Chemical Safety Board (CSB) investigation report identified seven significant facility and operational factors that had contributed to the incident. One of those was siting support trailers for workers too close to the highly hazardous process unit. All fatalities occurred in and around the trailers. 

From these three hazards indicators (materials factor, general process hazards factor, and special process hazards factor), the Fire Explosion Index (FScEI) is calculated, 169 in the example. Table 24.6 shows the qualitative level of hazard for various values of the FScEI. Our example is in the severe hazard class. Although the F EI is useful in identifying process units where hazardous conditions exist, it does not estimate the damage that might result from such an event. 

Appropriate spacing of unit operations within a process and appropriate spacing of a process from other processes, from employees nonessential to day-to-day process operation, and from the public is inherently safer. A definition of appropriate spacing would assist in evaluating the process location alternatives. This definition may take the form of a table of distances as a function of the type of hazard, inventory quantity and other factors. 

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