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Examples

Review for first exam

- Be able to define accident and loss statistics (OSHA Incident rate, FAR, Fatality rate) and be able to calculate FAR and Fatality rates
- List the various responses of humans to toxic exposure and whether they are reversible.

- Be able to explain the difference between ED, TD and LD.
- Be able to determine the predicted response to various exposures using probit analysis.
- Be able to calculate Threshold Limit Values (TLV) and time weighted TLV’s.

- Be able to estimate the vaporization rate of a liquid and the expected ambient concentration.
- Be able to calculate the flow rate of liquids through a) a hole with constant back pressure; b) a hole in a tank; and c) through a broken pipe.

- Be able to calculate the flow rate of vapors/gases through a hole, adiabatic flow through a pipe and isothermal flow through a pipe.
- Be able to calculate the rate of release for a flashing and boiling liquid

- A gasoline filling station has an underground gasoline storage tank with a volume of 5000 gallons. The tank has a 1.0 inch diameter vent. The tank must be filled every week with 4000 gallons of gasoline through an 8 inch diameter opening from a tank truck. The tank is never emptied completely. It takes one hour to fill the tank from the truck.
- Vapor Pressure @77°F=4.6 psia, Approximate molecular weight=94
- What is the gasoline concentration in ppm assuming an effective ventilation rate for outside exposures of 3000 ft3/min during the filling operation?

- Cppm during filling (modified 3.24)

- Eq. 3.18

Assume ½ of fill pipe “open” for evaporation Afill~0.175ft2

- Assume worst case conditions
- Φ=1 Splash Filling
- k=0.1 Poor Mixing
- Vapors escape through ½ of 8” hole during filling
- Qv =3000 ft3/min
- P=atmospheric=14.7 psia
- Psat=4.6 psia

- Cppm=9474 ppm
- If no evaporation through fill pipe 9302 ppm
- If neglect evaporation entirely 9297ppm

- A gasoline filling station has an underground gasoline storage tank with a volume of 5000 gallons. The tank has a 1.0 inch diameter vent. The tank must be filled every week with 4000 gallons of gasoline through an 8 inch diameter opening from a tank truck. The tank is never emptied completely. It takes one hour to fill the tank from the truck.
- Vapor Pressure @77°F=4.6 psia, Approximate molecular weight=94
- What is the gasoline concentration in ppm assuming that the tank is vented with an effective ventilation rate of 3000 ft3/min when the tank is not being filled?

- Modified Eq 3.14
Assume no gasoline in venting air and ideal gas

- Eq. simplifies for evaporation through 1” vent
- Cppm = 5.4 ppm

- A gasoline filling station has an underground gasoline storage tank with a volume of 5000 gallons. The tank has a 1.0 inch diameter vent. The tank must be filled every week with 4000 gallons of gasoline through an 8 inch diameter opening from a tank truck. The tank is never emptied completely. It takes one hour to fill the tank from the truck.
- TLV for gasoline is 300 ppm
- What is the time weighted average exposure for a worker on a 10 hour shift during which the tank is filled?
- What is the time weighted average exposure for a worker on a 10 hour shift during which the tank is not filled?

- Determine the average time-weighted concentration, CTWA, of hydrogen sulfide in ppm that would be estimated to cause 10% fatalities if exposed for 15 minutes.
- How many times greater is this compared to the TLVTWA, i.e., what is the Safety Factor?

- TLVTWA = 10 ppm (Table 2.8)
- From Handout in class
- C in ppm, t in min
- For H2S
- a=-11.5
- b=1.0
- n=1.9

- From Table 2.4
10% corresponds to Y=3.72

Some algebra

- More Algebra

- More algebra

The concentration that would kill 10% of the people is nearly twice the threshold limit value