3.13. Since the 1960s, the Free Expression Tunnel at North Carolina State Univer

Question

3.13. Since the 1960s, the Free Expression Tunnel at North Carolina State University has been the University's way to combat graffiti on campus. The tunnel is painted almost daily by various student groups to advertiseclub meetings, praise athletic accomplishments, and declare undying love. You and your engineering classmates decide to decorate the tunnel with chemical process flowcharts and key Adapted from a problem contributed by Paul Blowers of the University of Arizona. Copyright 2016 John Wiley & Sons 70 s and Process Variables equations found in your favorite text, so you purchase a can of spray paint. The label indicates that the can holds nine fluid ounces, which should cover an area of approximately 25 ft. (a) You measure the tunnel and find that it is roughly 8 feet wide, 12 feet high, and 148 feet long. Based on the stated coverage, how many cans of spray paint would it take to apply one coat to the walls and ceiling of the tunnel? in your engineering class, you want to take appropriate safety precautions while painting the tunnel. One useful source for this type of information is the Safety Data Sheet (SDS), a document used in industry to provide workers and emergency personnel with procedures for safely handling or working with a specified chemical. Other sources of information about hazardous substances can be found in handbooks,5 and some countries, including the United States, have laws that requireemployers to provide their employees with Safety Data Sheets. Besidescomposition information, the SDS contains information such as physical properties (melting point, boiling point, flash point, etc), other threats to health and safety, recommended protective equipment, and recommended procedures for storage, disposal, first aid, and spill handling. The SDS can typically be found online for most common substances. Search the web for "spray paint SDS" and find a representative SDS for a typical spray paint product. Based on the document you find, what are the top three hazards that you might encounter during your tunnel painting project? Suggest one safety precaution for each listed hazard

Explanation / Answer

(a) Principle:

Step 1: Calculate the total surface area of the ceiling and walls of the tunnel

Step 2: Knowing the area covered by one can of spray paint, calculate the number of cans required to paint the ceiling and walls of the tunnel

METHOD:

Step 1 :CalculatIion of the total surface area of the ceiling and walls of the tunnel

Area of the ceiling = length of the tunnel x its width = 148 ft x 8 ft = 1184 ft2

Area of one wall = length of the tunnel x its height = 148 ft x 12 ft = 1776 ft2

Area of TWO walls = 2 x 1776 ft2 = 3552 ft2

Total surface area of the ceiling and the two walls of the tunnel = 1184 ft2 + 3552 ft2 = 4736 ft2

Step 2: Calculation of the number of cans of the spray paint required to paint the ceiling and the 2 walls of the tunnel

Area covered by 1 can of the spray paint = 25 ft2

Number of cans required to paint 25 ft2 = 1

Therefore, the number of cans required to paint 4736 ft2 = 4736 ft2/ 25 ft2 = 189.44 = 190

The number of cans of spray paint reqired to to paint the ceiling and walls of the tunel = 190

(b) REPRESENTATIVE SAFETY DATA SHEET (SDS) FOR A TYPIAL SPRAY PAINT.

SAFETY DATA SHEET for LIQUITEX PROFESSIONAL SPRAY PAINT

HAZARDS :

HAZARD 1 :

HIGHLY FLAMMABLE

Vapours are heavier than air and may spread near ground to sources of ignition. Aerosol cans may explode in a fire

Specific Hazards

Aerosol containers can explode when heated, due to excessive pressure build up   

SAFETY PRECAUTIONS

Extinguishing Media

Use: Powder. Dry chemicals, sand, dolomite etc. Water spray, fog or mist

Advice for firefighters

Special Fire Fighting Procedures

Containers close to fire should be removed or cooled with water. Use water to keep fire exposed containers cool and disperse vapours.

HAZARD 2

INHALATION

Harmful by inhalation. In high concentrations, vapours are narcotic and may cause headache, fatigue, dizziness and nausea.

SAFETY PRECAUTIONS

Wear safety mask

HAZARD 3

SKIN CONTACT

Skin irritation is not anticipated when used normally. Repeated exposure may cause skin dryness or cracking.

Wear appropriate clothing to prevent any possibility of liquid contact and repeated or prolonged vapour contact

                                                                   

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