Table D-57.1-Grinding and Abrasive Cutting-Off Wheels
Wheel diameter, inches (cm) | Wheel width, inches (cm) | Minimum exhaust volume (feet3/min.) |
To 9 (22.86) | 11/2 (3.81) | 220 |
Over 9 to 16 (22.86 to 40.64) | 2 (5.08) | 390 |
Over 16 to 19 (40.64 to 48.26) | 3 (7.62) | 500 |
Over 19 to 24 (48.26 to 60.96) | 4 (10.16) | 610 |
Over 24 to 30 (60.96 to 76.2) | 5 (12.7) | 880 |
Over 30 to 36 (76.2 to 91.44) | 6 (15.24) | 1,200 |
For any wheel wider than wheel diameters shown in Table D-57.1, increase the exhaust volume by the ratio of the new width to the width shown.
Example: If wheel width = 41/2 inches (11.43 cm),
then 4.5 ÷ 4 * 610 = 686 (rounded to 690).
Table D-57.2-Buffing and Polishing Wheels
Wheel diameter, inches (cm) | Wheel width, inches cm) | Minimum exhaust volume (feet3/min.) |
To 9 (22.86) | 2 (5.08) | 300 |
Over 9 to 16 (22.86 to 40.64) | 3 (7.62) | 500 |
Over 16 to 19 (40.64 to 48.26) | 4 (10.16) | 610 |
Over 19 to 24 (48.26 to 60.96) | 5 (12.7) | 740 |
Over 24 to 30 (60.96 to 76.2) | 6 (15.24) | 1,040 |
Over 30 to 36 (76.2 to 91.44) | 6 (15.24) | 1,200 |
Table D-57.3-Horizontal Single-Spindle Disc Grinder
Disc diameter, inches (cm) | Exhaust volume (ft.3/min.) |
Up to 12 (30.48) | 220 |
Over 12 to 19 (30.48 to 48.26) | 390 |
Over 19 to 30 (48.26 to 76.2) | 610 |
Over 30 to 36 (76.2 to 91.44) | 880 |
Table D-57.4-Horizontal Double-Spindle Disc Grinder
Disc diameter, inches (cm) | Exhaust volume (ft.3/min.) |
Up to 19 (48.26) | 610 |
Over 19 to 25 (48.26 to 63.5) | 880 |
Over 25 to 30 (63.5 to 76.2) | 1,200 |
Over 30 to 53 (76.2 to 134.62) | 1,770 |
Over 53 to 72 (134.62 to 182.88) | 6,280 |
Table D-57.5-Vertical Spindle Disc Grinder
Disc diameter, inches (cm) | One-half or more of disc covered | Disc not covered | ||
Number1 | Exhaust foot3/min. | Number1 | Exhaust foot3/min. | |
Up to 20 (50.8) | 1 | 500 | 2 | 780 |
Over 20 to 30 (50.8 to 76.2) | 2 | 780 | 2 | 1,480 |
Over 30 to 53 (76.2 to 134.62) | 2 | 1,770 | 4 | 3,530 |
Over 53 to 72 (134.62 to 182.88) | 2 | 3,140 | 5 | 6,010 |
1 Number of exhaust outlets around periphery of hood, or equal distribution provided by other means.
Table D-57.6-Grinding and Polishing Belts
Belts width, inches (cm) | Exhaust volume (ft.3/min.) |
Up to 3 (7.62) | 220 |
Over 3 to 5 (7.62 to 12.7) | 300 |
Over 5 to 7 (12.7 to 17.78) | 390 |
Over 7 to 9 (17.78 to 22.86) | 500 |
Over 9 to 11 (22.86 to 27.94) | 610 |
Over 11 to 13 (27.94 to 33.02) | 740 |
FIGURE D-57.1-VERTICAL SPINDLE DISC GRINDER EXHAUST HOOD AND BRANCH PIPE CONNECTIONS
Dia. D inches (cm) | Exhaust E | Volume Exhausted at 4,500 ft/min ft3/min | Note | ||
Min. | Max. | No Pipes | Dia. | ||
20 (50.8) | 1 | 41/4 (10.795) | 500 | When one-half or more of the disc can be hooded, use exhaust ducts as shown at the left. | |
Over 20 (50.8) | 30 (76.2) | 2 | 4 (10.16) | 780 | |
Over 30 (76.2) | 72 (182.88) | 2 | 6 (15.24) | 1,770 | |
Over 53 (134.62) | 72 (182.88) | 2 | 8 (20.32) | 3,140 | |
20 (50.8) | 2 | 4 (10.16) | 780 | When no hood can be used over disc, use exhaust ducts as shown at left. | |
Over 20 (50.8) | 20 (50.8) | 2 | 4 (10.16) | 780 | |
Over 30 (76.2) | 30 (76.2) | 2 | 51/2 (13.97) | 1,480 | |
Over 53 (134.62) | 53 (134.62) | 4 | 6 (15.24) | 3,530 | |
72 (182.88) | 5 | 7 (17.78) | 6,010 |
Entry loss = 1.0 slot velocity pressure + 0.5 branch velocity pressure.
Minimum slot velocity = 2,000 ft/min- 1/2-inch (1.27 cm) slot width.
FIGURE D-57.2-STANDARD GRINDER HOOD
Wheel dimension, inches (centimeters) | Exhaust outlet, inches (centimeters) E | Volume of air at 4,500 ft/min | ||
Diameter | Width, Max | |||
Min= d | Max= D | |||
9 (22.86) | 11/2 (3.81) | 3 | 220 | |
Over 9 (22.86) | 16 (40.64) | 2 (5.08) | 4 | 390 |
Over 16 (40.64) | 19 (48.26) | 3 (7.62) | 41/2 | 500 |
Over 19 (48.26) | 24 (60.96) | 4 (10.16) | 5 | 610 |
Over 24 (60.96) | 30 (76.2) | 5 (12.7) | 6 | 880 |
Over 30 (76.2) | 36 (91.44) | 6 (15.24) | 7 | 1,200 |
Entry loss = 0.45 velocity pressure for tapered takeoff 0.65 velocity pressure for straight takeoff.
FIGURE D-57.3-A METHOD OF APPLYING AN EXHAUST ENCLOSURE TO SWING-FRAME GRINDERS
Note: Baffle to reduce front opening as much as possible
FIGURE D-57.4
Standard Buffing and Polishing Hood
Wheel dimension, inches (centimeters) | Exhaust outlet, inches E | Volume of air at 4,500 ft/min | ||
Diameter | Width, Max | |||
Min= d | Max= D | |||
9 (22.86) | 2 (5.08) | 31/2 (3.81) | 300 | |
Over 9 (22.86) | 16 (40.64) | 3 (5.08) | 4 | 500 |
Over 16 (40.64) | 19 (48.26) | 4 (11.43) | 5 | 610 |
Over 19 (48.26) | 24 (60.96) | 5 (12.7) | 51/2 | 740 |
Over 24 (60.96) | 30 (76.2) | 6 (15.24) | 61/2 | 1.040 |
Over 30 (76.2) | 36 (91.44) | 6 (15.24) | 7 | 1.200 |
Entry loss = 0.15 velocity pressure for tapered takeoff; 0.65 velocity pressure for straight takeoff.
FIGURE D-57.5-CRADLE POLISHING OR GRINDING ENCLOSURE
Entry loss = 0.45 velocity pressure for tapered takeoff
FIGURE D-57.6-HORIZONTAL SINGLE-SPINDLE DISC GRINDER EXHAUST HOOD AND BRANCH PIPE CONNECTIONS
Dia D, inches (centimeters) | Exhaust E, dia. inches (cm) | Volume exhausted at 4,500 ft/min ft3/min | |
Min. | Max. | ||
12 (30.48) | 3 (7.6) | 220 | |
Over 12 (30.48) | 19 (48.26) | 4 (10.16) | 390 |
Over 19 (48.26) | 30 (76.2) | 5 (12.7) | 610 |
Over 30 (76.2) | 36 (91.44) | 6 (15.24) | 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.
FIGURE D-57.7-HORIZONTAL DOUBLE-SPINDLE DISC GRINDER EXHAUST HOOD AND BRANCH PIPE CONNECTIONS
Disc dia. inches (centimeters) | Exhaust E | Volume exhaust at 4,500 ft/min. ft3/min | Note | ||
Min. | Max. | No Pipes | Dia. | ||
19 (48.26) | 1 | 5 | 610 | ||
Over 19 (48.26) | 25 (63.5) | 1 | 6 | 880 | When width "W" permits, exhaust ducts should be as near heaviest grinding as possible. |
Over 25 (63.5) | 30 (76.2) | 1 | 7 | 1,200 | |
Over 30 (76.2) | 53 (134.62) | 2 | 6 | 1,770 | |
Over 53 (134.62) | 72 (182.88) | 4 | 8 | 6,280 |
Entry loss = 0.45 velocity pressure for tapered takeoff.
FIGURE D-57.8-A TYPICAL HOOD FOR A BELT OPERATION
Entry loss = 0.45 velocity pressure for tapered takeoff
Belt width W. inches (centimeters) | Exhaust volume. ft.1/min |
Up to 3 (7.62) | 220 |
3 to 5 (7.62 to 12.7) | 300 |
5 to 7 (12.7 to 17.78) | 390 |
7 to 9 (17.78 to 22.86) | 500 |
9 to 11 (22.86 to 27.94) | 610 |
11 to 13 (27.94 to 33.02) | 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 D-57.7-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 D-57.8. 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 D-57.8, column 2, is 1.4 percent.
(2) Cubic feet of vapor per gallon from Table D-57.8, 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 D-57.8-Lower Explosive Limit of Some Commonly Used Solvents
Solvent | Cubic feet per gallon of vapor of liquid at 70 °F (21.11 °C). | Lower explosive limit in percent by volume of air at 70 °F (21.11 °C) |
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 (100 °C).
NOTE A:
(c1÷TLV1) + (c2÷TLV2) + (c3÷TLV3) + ; . . .(cN÷TLVN)1
Where:
c = Concentration measured at the operation in p.p.m.
Table D-57.9-Determination of Hazard Potential
Hazard potential | Toxicity group | ||
Gas or vapor (p.p.m.) | Mist (mg./m3) | Flash point in degrees F. (C.) | |
A | 0-10 | 0-0.1 | |
B | 11-100 | 0.11-1.0 | Under 100 (37.77) |
C | 101-500 | 1.1-10 | 100 200 (37.77-93.33) |
D | Over 500 | Over 10 | Over 200 (93.33) |
Table D-57.10-Determination of Rate of Gas, Vapor, or Mist Evolution1
Rate | Liquid temperature, °F. (C.) | Degrees below boiling point | Relative evaporation2 | Gassing3 |
1 | Over 200 (93.33) | 0-20 | Fast | High. |
2 | 150-200 (65.55-93.33) | 21-50 | Medium | Medium. |
3 | 94-149 (34.44-65) | 51-100 | Slow | Low. |
4 | Under 94 (34.44) | Over 100 | Nil | Nil. |
1 In certain classes of equipment, specifically vapor degreasers, an internal condenser or vapor level thermostat is used to prevent the vapor from leaving the tank during normal operation. In such cases, rate of vapor evolution from the tank into the workroom is not dependent upon the factors listed in the table, but rather upon abnormalities of operating procedure, such as carryout of vapors from excessively fast action, dragout of liquid by entrainment in parts, contamination of solvent by water and other materials, or improper heat balance. When operating procedure is excellent, effective rate of evolution may be taken as 4. When operating procedure is average, the effective rate of evolution may be taken as 3. When operation is poor, a rate of 2 or 1 is indicated, depending upon observed conditions.
2 Relative evaporation rate is determined according to the methods described by A. K. Doolittle in Industrial and Engineering Chemistry, vol. 27, p. 1169, (3) where time for 100-percent evaporation is as follows: Fast: 0-3 hours; Medium: 3-12 hours; Slow: 12-50 hours; Nil: more than 50 hours.
3 Gassing means the formation by chemical or electrochemical action of minute bubbles of gas under the surface of the liquid in the tank and is generally limited to aqueous solutions.
Table D-57.11-Control Velocities in Feet Per Minute (f.p.m.) for Undisturbed Locations
Class | Enclosing hood | Lateral exhaust1 | Canopy hood2 | ||
One open side | Two open sides | Three open sides | Four open sides | ||
B-1 and A-2 | 100 | 150 | 150 | Do not use | Do not use |
A-32, B-1, B-2, and C-1 | 75 | 100 | 100 | 125 | 175 |
A-3, C-2, and D-13 | 65 | 90 | 75 | 100 | 150 |
B-42, C-3, and D-23 | 50 | 75 | 50 | 75 | 125 |
A-4, C-4, D-33, and D-44 |
1 See Table D-57.12 for computation of ventilation rate.
2 Do not use canopy hood for Hazard Potential A processes.
3 Where complete control of hot water is desired, design as next highest class.
4 General room ventilation required.
Table D-57.12-Minimum Ventilation Rate in Cubic Feet of Air Per Minute Per Square Foot of Tank Area for Lateral Exhaust
Required minimum control velocity, f.p.m. (from Table D-57.11) | C.f.m. per sq. ft. to maintain required minimum velocities at following ratios (tank width (W)/tank length (L)).1 2 | ||||
0.0-0.09 | 0.1-0.24 | 0.25-0.49 | 0.5-0.99 | 1.0-2.0 | |
Hood along one side or two parallel sides of tank when one hood is against a wall or baffle.2 | |||||
Also for a manifold along tank centerline.3 | |||||
50 | 50 | 60 | 75 | 90 | 100 |
75 | 75 | 90 | 110 | 130 | 150 |
100 | 100 | 125 | 150 | 175 | 200 |
150 | 150 | 190 | 225 | 260 | 300 |
Hood along one side or two parallel sides of free standing tank not against wall or baffle. | |||||
50 | 75 | 90 | 100 | 110 | 125 |
75 | 110 | 130 | 150 | 170 | 190 |
100 | 150 | 175 | 200 | 225 | 250 |
150 | 225 | 260 | 300 | 340 | 375 |
1 It is not practicable to ventilate across the long dimension of a tank whose ratio W/L exceeds 2.0.
It is undesirable to do so when W/L exceeds 1.0. For circular tanks with lateral exhaust along up to 1/2 the circumference, use W/L = 1.0; for over one-half the circumference use W/L = 0.5.
2 Baffle is a vertical plate the same length as the tank, and with the top of the plate as high as the tank is wide. If the exhaust hood is on the side of a tank against a building wall or close to it, it is perfectly baffled.
3 Use W/2 as tank width in computing when manifold is along centerline, or when hoods are used on two parallel sides of a tank.
Tank Width (W) means the effective width over which the hood must pull air to operate (for example, where the hood face is set back from the edge of the tank, this set back must be added in measuring tank width). The surface area of tanks can frequently be reduced and better control obtained (particularly on conveyorized systems) by using covers extending from the upper edges of the slots toward the center of the tank.
29 C.F.R. §1926.57