Examples Review for first exam. Learning Objectives for 1 st Exam Be able to define accident and loss statistics (OSHA Incident rate, FAR, Fatality rate)

Examples

Review for first exam

Learning Objectives for 1st 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

In Class Homework Team Problem 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?

In Class Homework Team ProblemSolution to Part A

Cppm during filling (modified 3.24)

6

,

10satppm L

v out L

P TC Q KA

kQ PT

3 340008.913 min60min 7.48L

gal hr ft ftQhr gal


Eq. 3.18 1/ 3

00

MK K

M

1

3180.83

94cmK s

. 60sec0.478

2.54 12 . min

in ftcmK s cm in

0.942 minftK


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

220.00545

4 12vent

ftA ft

228

0.3494 12fill

ftA ft


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

3

2 2 6

3

(4.6 ) 1.08.913 0.942 0.175 0.00545 10min min

0.1 3000 14.7min

ppm

psia ft ftC ft ftft psia



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?

In Class Homework Team ProblemSolution for Part B

Modified Eq 3.14

Assume no gasoline in venting air and ideal gas

,

max,

satin out

in v outout in L

v out

T P MKAPC Q

T P RTC

kQ

In Class Homework Team ProblemSolution for Part B

Eq. simplifies for evaporation through 1” vent

Cppm = 5.4 ppm

6

2 6

3

10

4.6 1.00.942 0.00545 10min

0.1 3000 (14.7 )min

sat

ppmv

ppm

PC KA

kQ P

psia ftC ftft psia



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?

In Class Homework Team ProblemSolution for Part C & D

1 9474 (9 ) 5.4

8

1190 300

10 5.4

8

6.8 300

TWA

TWA

TWA

TWA

hr ppm hr ppmTLV

hr

TLV ppm ppm

hr ppmTLV

hr

TLV ppm ppm

In Class Homework Team Problem

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?

In Class Homework Team ProblemSolution for Problem 2

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

lnn

Y a b V

V C t


From Table 2.4

10% corresponds to Y=3.72

Some algebra

ln( )

Y a

b

Y aV

b

V e


More Algebra

ln ln

lnln

n

n

V C t

VC

tV

n Ct

VtCn


More algebra ln

ln

exp

Vt

n

Y a

b

C e

et

Cn


3.72 11.15ln exp /15

1.0exp

1.9

602

ppm

ppm

C

C ppm


602 15min 60min8

18.8

18.81.9

10

TWA

TWA

TWA

TWA

hrppmC

hrC ppm

C

TLV

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

Documents

Examples Review for first exam. Learning Objectives for 1 st Exam Be able to define accident and loss statistics (OSHA Incident rate, FAR, Fatality rate)