Table G-4-Grinding and Abrasive Cutting-Off Wheels
Wheel diameter (inches) | Wheel width (inches) | Minimum exhaust volume (feet3/min.) |
To 9 | 11/2 | 220 |
Over 9 to 16 | 2 | 390 |
Over 16 to 19 | 3 | 500 |
Over 19 to 24 | 4 | 610 |
Over 24 to 30 | 5 | 880 |
Over 30 to 36 | 6 | 1,200 |
For any wheel wider than wheel diameters shown in Table G-4, increase the exhaust volume by the ratio of the new width to the width shown.
Example: If wheel width = 41/2 inches, then
4.5 ÷ 4 * 610 = 686 (rounded to 690).
Table G-5-Buffing and Polishing Wheels
Wheel diameter (inches) | Wheel width (inches) | Minimum exhaust volume (feet3/min.) |
To 9 | 2 | 300 |
Over 9 to 16 | 3 | 500 |
Over 16 to 19 | 4 | 610 |
Over 19 to 24 | 5 | 740 |
Over 24 to 30 | 6 | 1,040 |
Over 30 to 36 | 6 | 1,200 |
Table G-6-Horizontal Single-Spindle Disc Grinder
Disc diameter (inches) | Exhaust volume (ft.3/min.) |
Up to 12 | 220 |
Over 12 to 19 | 390 |
Over 19 to 30 | 610 |
Over 30 to 36 | 880 |
Table G-7-Horizontal Double-Spindle Disc Grinder
Disc diameter (inches) | Exhaust volume (ft.3/min.) |
Up to 19 | 610 |
Over 19 to 25 | 880 |
Over 25 to 30 | 1,200 |
Over 30 to 53 | 1,770 |
Over 53 to 72 | 6,280 |
Table G-8-Vertical Spindle Disc Grinder
Disc diameter (inches) | One-half or more of disc covered | Disc not covered | ||
Number1 | Exhaust foot3/min.) | Number1 | Exhaust foot3/min. | |
Up to 20 | 1 | 500 | 2 | 780 |
Over 20 to 30 | 2 | 780 | 2 | 1,480 |
Over 30 to 53 | 2 | 1,770 | 4 | 3,530 |
Over 53 to 72 | 2 | 3,140 | 5 | 6,010 |
1 Number of exhaust outlets around periphery of hood, or equal distribution provided by other means.
Table G-9-Grinding and Polishing Belts
Belts width (inches) | Exhaust volume (ft.3/min.) |
Up to 3 | 220 |
Over 3 to 5 | 300 |
Over 5 to 7 | 390 |
Over 7 to 9 | 500 |
Over 9 to 11 | 610 |
Over 11 to 13 | 740 |
Dia D. inches | Exhaust E | Volume Exhausted at 4,500 ft/min ft3/min | Note | ||
Min. | Max. | No Pipes | Dia. | ||
20 | 1 | 41/4 | 500 | When one-half or more of the disc can be hooded, use exhaust ducts as shown at the left. | |
Over 20 | 30 | 2 | 4 | 780 | |
Over 30 | 72 | 2 | 6 | 1,770 | |
Over 53 | 72 | 2 | 8 | 3,140 | |
20 | 2 | 4 | 780 | When no hood can be used over disc, use exhaust ducts as shown at left. | |
Over 20 | 20 | 2 | 4 | 780 | |
Over 30 | 30 | 2 | 51/2 | 1,480 | |
Over 53 | 53 | 4 | 6 | 3,530 | |
72 | 5 | 7 | 6,010 |
Entry loss = 1.0 slot velocity pressure + 0.5 branch velocity pressure.
Minimum slot velocity = 2,000 ft/min- 1/2-inch slot width.
Wheel dimension, inches | Exhaust outlet, inches E | Volume of air at 4,500 ft/min | ||
Diameter | Width, Max | |||
Min=d | Max=D | |||
9 | 11/2 | 3 | 220 | |
Over 9 | 16 | 2 | 4 | 390 |
Over 16 | 19 | 3 | 41/2 | 500 |
Over 19 | 24 | 4 | 5 | 610 |
Over 24 | 30 | 5 | 6 | 880 |
Over 30 | 36 | 6 | 7 | 1,200 |
Entry loss = 0.45 velocity pressure for tapered takeoff 0.65 velocity pressure for straight takeoff.
Standard Buffing and Polishing Hood
Wheel dimension, inches | Exhaust outlet, inches E | Volume of air at 4,500 ft/min | ||
Diameter | Width, Max | |||
Min=d | Max=D | |||
9 | 2 | 31/2 | 300 | |
Over 9 | 16 | 3 | 4 | 500 |
Over 16 | 19 | 4 | 5 | 610 |
Over 19 | 24 | 5 | 51/2 | 740 |
Over 24 | 30 | 6 | 61/2 | 1.040 |
Over 30 | 36 | 6 | 7 | 1.200 |
Entry loss = 0.15 velocity pressure for tapered takeoff; 0.65 velocity pressure for straight takeoff.
Dia D, inches | Exhaust E, dia. inches | Volume exhausted at 4,500 ft/min ft3/min | |
Min. | Max. | ||
12 | 3 | 220 | |
Over 12 | 19 | 4 | 390 |
Over 19 | 30 | 5 | 610 |
Over 30 | 36 | 6 | 880 |
NOTE: If grinding wheels are used for disc grinding purposes, hoods must conform to structural strength and materials as described in 9.1.
Entry loss = 0.45 velocity pressure for tapered takeoff.
Disc dia. inches | Exhaust E | Volume exhaust at 4,500 ft/min. ft3/min | Note | ||
Min. | Max. | No Pipes | Dia. | ||
19 | 1 | 5 | 610 | ||
Over 19 | 25 | 1 | 6 | 880 | When width "W" permits, exhaust ducts should be as near heaviest grinding as possible. |
Over 25 | 30 | 1 | 7 | 1,200 | |
Over 30 | 53 | 2 | 6 | 1,770 | |
Over 53 | 72 | 4 | 8 | 6,280 |
Entry loss = 0.45 velocity pressure for tapered takeoff.
Belt width W. Inches | Exhaust volume. ft.1/min |
Up to 3 | 220 |
3 to 5 | 300 |
5 to 7 | 390 |
7 to 9 | 500 |
9 to 11 | 610 |
11 to 13 | 740 |
Minimum duct velocity = 4,500 ft/min branch, 3,500 ft/min main.
Entry loss = 0.45 velocity pressure for tapered takeoff; 0.65 velocity pressure for straight takeoff.
Table G-10-Minimum Maintained Velocities Into Spray Booths
Operating conditions for objects completely inside booth | Crossdraft, f.p.m. | Airflow velocities, f.p.m. | |
Design | Range | ||
Electrostatic and automatic airless operation contained in booth without operator | Negligible | 50 large booth | 50-75 |
100 small booth | 75-125 | ||
Air-operated guns, manual or automatic | Up to 50 | 100 large booth | 75-125 |
150 small booth | 125-175 | ||
Air-operated guns, manual or automatic | Up to 100 | 150 large booth | 125-175 |
200 small booth | 150-250 |
NOTES:
(1) Attention is invited to the fact that the effectiveness of the spray booth is dependent upon the relationship of the depth of the booth to its height and width.
(2) Crossdrafts can be eliminated through proper design and such design should be sought. Crossdrafts in excess of 100fpm (feet per minute) should not be permitted.
(3) Excessive air pressures result in loss of both efficiency and material waste in addition to creating a backlash that may carry overspray and fumes into adjacent work areas.
(4) Booths should be designed with velocities shown in the column headed "Design." However, booths operating with velocities shown in the column headed "Range" are in compliance with this standard.
Example: To determine the lower explosive limits of the most common solvents used in spray finishing, see Table G-11. Column 1 gives the number of cubic feet of vapor per gallon of solvent and column 2 gives the lower explosive limit (LEL) in percentage by volume of air. Note that the quantity of solvent will be diminished by the quantity of solids and nonflammables contained in the finish.
To determine the volume of air in cubic feet necessary to dilute the vapor from 1 gallon of solvent to 25 percent of the lower explosive limit, apply the following formula:
Dilution volume required per gallon of solvent = 4 (100-LEL) (cubic feet of vapor per gallon) ÷ LEL
Using toluene as the solvent.
(1) LEL of toluene from Table G-11, column 2, is 1.4 percent.
(2) Cubic feet of vapor per gallon from Table G-11, column 1, is 30.4 cubic feet per gallon.
(3) Dilution volume required=
4 (100-1.4) 30.4 ÷ 1.4 = 8,564 cubic feet.
(4) To convert to cubic feet per minute of required ventilation, multiply the dilution volume required per gallon of solvent by the number of gallons of solvent evaporated per minute.
Table G-11-Lower Explosive Limit of Some Commonly Used Solvents
Solvent | Cubic feet per gallon of vapor of liquid at 70 °F. | Lower explosive limit in percent by volume of air at 70 °F |
Column 1 | Column 2 | |
Acetone | 44.0 | 2.6 |
Amyl Acetate (iso) | 21.6 | 1 1.0 |
Amyl Alcohol (n) | 29.6 | 1.2 |
Amyl Alcohol (iso) | 29.6 | 1.2 |
Benzene | 36.8 | 1 1.4 |
Butyl Acetate (n) | 24.8 | 1.7 |
Butyl Alcohol (n) | 35.2 | 1.4 |
Butyl Cellosolve | 24.8 | 1.1 |
Cellosolve | 33.6 | 1.8 |
Cellosolve Acetate | 23.2 | 1.7 |
Cyclohexanone | 31.2 | 1 1.1 |
1,1 Dichloroethylene | 42.4 | 5.9 |
1,2 Dichloroethylene | 42.4 | 9.7 |
Ethyl Acetate | 32.8 | 2.5 |
Ethyl Alcohol | 55.2 | 4.3 |
Ethyl Lactate | 28.0 | 1 1.5 |
Methyl Acetate | 40.0 | 3.1 |
Methyl Alcohol | 80.8 | 7.3 |
Methyl Cellosolve | 40.8 | 2.5 |
Methyl Ethyl Ketone | 36.0 | 1.8 |
Methyl n-Propyl Ketone | 30.4 | 1.5 |
Naphtha (VM&P) (76° Naphtha) | 22.4 | 0.9 |
Naphtha (100 °Flash) Safety Solvent-Stoddard Solvent | 23.2 | 1.0 |
Propyl Acetate (n) | 27.2 | 2.8 |
Propyl Acetate (iso) | 28.0 | 1.1 |
Propyl Alcohol (n) | 44.8 | 2.1 |
Propyl Alcohol (iso) | 44.0 | 2.0 |
Toluene | 30.4 | 1.4 |
Turpentine | 20.8 | 0.8 |
Xylene (o) | 26.4 | 1.0 |
1 At 212 °F.
29 C.F.R. §1910.94