HPCL CPM 3-PCP 5-Risk Anaylsis & Hazop Studies- PPT.pptx

Persons closer to the cloud but not within it will be

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Persons closer to the cloud, but not within it, will be able to take action to protect themselves (e.g., moving farther away as the flames approach, or seeking shelter inside structures or behind solid objects).

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Heat Flux - Probit In the event of a continuous torch fire during the release of flammable gas or gas/aerosol, or a pool fire, the thermal radiation levels necessary to cause fatal injuries to the public must be defined as a function of exposure time. This is typically accomplished through the use of probit equations, which are based on experimental dose-response data
Heat Flux - Probit Pr = a + b ·ln ( t · Kn ) -where: Pr = probit -K = intensity of the hazard -t = time of exposure to the hazard -a , b , and n = constants

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Probit The product ( t · Kn ) is often referred to as the “dose factor .” According to probit equations, all combinations of intensity Kn and time t that result in equal dose factors also result in equal values for the probit Pr and therefore produce equal expected fatality rates for the exposed population. Work sponsored by the U.S. Coast Guard [Tsao and Perry, 1979] developed the following probit relationship between exposure time and incident heat flux.
Probit Equation Pr = −36.378 + 2.56·ln ( t · I 4/3 ) -where: - t = exposure time, sec -I = effective thermal radiation intensity, kW/m2

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- Hazard Distances – Storage Tanks On Fire As per IP Code, thermally protected facilities and storage tanks can withstand a thermal radiation of 32 KW/M 2 while unprotected tanks and process facilities can withstand only up to 8 KW/M 2 . Normal persons can withstand an intensity of 1.5 KW/M 2 for a long duration. A radiation intensity of 4.5 KW/M 2 can cause 1st degree burn if a man is exposed for more than 20 seconds.
Pump Mechanical Seal Failure Pump Mechanical Seal Failure The frequency of failure for mechanical seal of centrifugal pumps specially handling light hydrocarbons is quite high and poses risk due to fire and explosion. Failure of seals releases considerable quantity of hydrocarbons into atmosphere and creates a hazardous zone. Present thinking is to adopt double mechanical seal especially for light hydrocarbon services. This helps in reducing their frequency of hydrocarbon releases to atmosphere but still contribute to a great extent to the overall risk of the plant. However, the type of seal, single or double, does not affect their releases rate or the hazard distances. Hazard distances have been calculated for the pump mechanical seal failure

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Pump Mechanical Seal Failure The above table shows that the hazard distance of 1st degree burn i.e. 4.5 KW/m 2 may extend up to a distance of 42 meters
UNIT-16 Risk Computation & Characterisation

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**Vulnerability Zone
**Risk Contour

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Generic- Quantitative Consequences
Societal Risk and F-N Curves

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Societal Risk and F-N Curves Societal Risk Criteria Societal risk (SR) is the relationship between the frequency and the number of people suffering from a specified level of harm in a given population from the realisation of specified hazards, Institution of Chemical Engineers 1992.
• Fall '19
• Safety engineering, fault tree, Hazards

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