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(a) General. Every establishment performing dry grinding, dry polishing, or buffing shall provide suitable hoods or enclosures that are connected to exhaust systems which are run continuously during operations.
EXCEPTION: When the concentration at the operator's breathing zone of any airborne contaminant generated by such an operation is below the applicable limit prescribed in Section 5155 or any other section of Title 8.
(b) Hood and Branch Duct Performance Requirements.
(1) Hoods connected to exhaust systems shall be used, and such hoods shall be designed, located, and placed so that the dust or dirt particles shall fall or be projected into the hoods in the direction of the air flow. No wheels, discs, straps, or belts shall be operated in such manner and in such direction as to cause the dust and dirt particles to be thrown into the operator's breathing zone.
(2) Wheels and belts shall have not less than the minimum exhaust volumes shown in the following tables:
TABLE V-1.
GRINDING AND ABRASIVE CUTTING-OFF WHEELS.
Wheel Diameter Wheel Width Minimum Exhaust Volume
(Inches) (Inches) (Cubic Feet/Min.)
To 9 1 1/2 220
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 1200
NOTE: For any wheel wider than that shown, increase the table exhaust volume by the ratio of the actual width to the table width. Example: For wheel width = 4 1/2 inches. Minimum Exhaust Volume = 4.5/4 x 610 = 686 (rounded to 690).
TABLE V-2
BUFFING, POLISHING, AND SCRATCH-BRUSH WHEELS
Wheel Diameter Wheel Width Minimum Exhaust
(Inches) (Inches) (Cubic Feet/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 1040
Over 30 to 36 6 1200
TABLE V-3
HORIZONTAL SPINDLE DISC GRINDER
Wheel Diameter Minimum Exhaust Volume
(Inches) (Cubic Feet/Min.)
Single Spindle Double Spindle
Up to 12 220 610
Over 12 to 19 390 610
Over 19 to 25 610 880
Over 25 to 30 610 1200
Over 30 to 53 880 1770
Over 53 to 72 880 6280
TABLE V-4
VERTICAL SPINDLE DISC GRINDER
Disc Diameter One-half or More of Disc Covered Disc not Covered
(Inches) Exhaust Volume Exhaust Volume
Number1 (Cubic Feet/Min.) Number1 (Cubic Feet/Min.)
Up to 20 1 500 2 780
Over 20 to 30 2 780 2 1480
Over 30 to 53 2 1770 4 3530
Over 53 to 72 2 3140 5 6010
1 Number of exhaust outlets around periphery of hood, or equal distribution provided by other means.
TABLE V-5
GRINDING AND POLISHING BELTS
Belts Width Exhaust Volume
(Inches) (Cubic Feet/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
(3) Cradles requiring partial enclosures to house the complete operation shall be ventilated sufficiently such that a minimum air velocity of 150 feet per minute shall be maintained over the entire opening of the enclosure.
(c) Hood Design.
(1) Vertical-spindle disc grinders shall be encircled with a hood so constructed that the heavy dust is drawn off a surface of the disc and the lighter dust exhausted through a continuous slot at the top of the hood as shown in Figure V-1.
(2) Exhaust hoods for floor stands, pedestals, and bench grinders shall be designed as effective as Figure V-2. The adjustable tongue shown in the Figure shall be kept in working order and shall be adjusted within one-fourth inch of the wheel periphery at all times.
(3) Swing-frame grinders shall be exhausted in the same manner as provided for cradles, and shall be provided with exhaust booths as indicated in Figure V-3.
(4) Hoods for polishing and buffing and scratch-brush wheels shall be constructed to conform as closely to Figure V-4 as the nature of the work will permit.
(5) Cradle grinding and polishing operations shall be performed within a partial enclosure similar to Figure V-5. The operator shall be positioned outside the working face of the opening of the enclosure. Cradle enclosures shall be ventilated sufficiently such that a minimum air velocity of 150 feet per minute shall be maintained over the entire opening of the enclosure.
(6) Hoods for horizontal single-spindle disc grinders shall be constructed to conform as closely as possible to the hood shown in Figure V-6.
(7) Horizontal double-spindle disc grinders shall have a hood encircling the wheels and grinding chamber similar to that illustrated in Figure V-7. The openings for passing the work into the grinding chamber should be kept as small as possible, but must never be less than twice the area of the branch outlets.
(8) Grinding and polishing belt hoods shall be constructed as close to the operation as possible. The hood should extend almost to the belt, and 1-inch wide openings should be provided on either side. Figure V-8 shows a typical hood for a belt operation.
(d) Portable Operations.
Portable grinding, polishing, and buffing operations, whenever the nature of the work permits, shall be conducted within a partial enclosure over which an average face air velocity of not less than 200 feet per minute shall be maintained, or a low volume, high velocity local exhaust hood attachment shall be used. (Title 24, T8-5152)
Figure V-1 - VERTICAL SPINDAL DISC GRINDER EXHAUST HOOD AND BRANCH PIPE CONNECTIONS
_____________________________________________________________________
| | |
Dia. D inches (cm) | Exhaust E | Volume |
____________________________|__________________| Exhausted | Note
| | | | at 4,500 |
Min. | Max. | No | | ft/min |
| | Pipes | Dia. | ft(3)/min |
_________________|__________|_______|__________|___________|_________
| | | | |
.................| 20 | 1 | 4 1/4 | 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 | 5 1/2 | 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/mn - 1./2 inch slot width.
Figure V-2 - STANDARD GRINDER HOOD
Wheel dimension, inches | |
______________________________________| Exhaust | Volume
| | outlet, | of air
Diameter | | inches | at
_______________________| Width, Max | E | 4,500
| | | | ft/min
Min= d | Max= D | | |
__________|____________|______________|_______________|________
| | | |
| 9 | 1 1/2 | 3 | 220
Over 9 ...| 16 | 2 | 4 | 390
Over 16 ..| 19 | 3 | 4 1/2 | 500
Over 19 ..| 24 | 4 | 5 | 610
Over 24 ..| 30 | 5 | 6 | 880
Over 30 ..| 36 | 6 | 7 | 1,200
__________|____________|______________|_______________|____
FIGURE V-3
A METHOD OF APPLYING AN EXHAUST
ENCLOSURE TO SWING-FRAME GRINDERS
FIGURE V-4
STANDARD BUFFING AND POLISHING HOOD
_____________________________________________________________________
| |
Wheel dimension, inches | |
_____________________________________________| Exhaust | Volume
| | outlet, | of air
Diameter | | inches | at
______________________________| Width, Max | E | 4,500
| | | | ft/min
Min= d | Max= D | | |
_________________|____________|______________|_______________|________
| | | |
| 9 | 2 | 3 1/2 | 300
Over 9 ..........| 16 | 3 | 4 | 500
Over 16 .........| 19 | 4 | 5 | 610
Over 19 .........| 24 | 5 | 5 1/2 | 740
Over 24 .........| 30 | 6 | 6 1/2 | 1,040
Over 30 .........| 36 | 6 | 7 | 1,200
_________________|____________|______________|_______________|______
FIGURE V-5
CRADLE POLISHING OR GRINDING ENCLOSURE
Entry Loss = 0.45 velocity pressure for tapered takeoff
FIGURE V-6
HORIZONTAL SINGLE-SPINDLE DISC GRINDER
EXHAUST HOOD AND BRANCH PIPE CONNECTIONS
______________________________________________________________
| |
Dia D inches | Exhaust E | Volume
_____________________________________| dia. | exhausted
| | inches | at 4,500
Min. | Max. | | ft/min
| | | ft(3)/min
_____________________|_______________|___________|_____________
| | |
| 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.
FIGURE V-7
HORIZONTAL DOUBLE-SPINDLE DISC GRINDER
EXHAUST HOOD AND BRANCH PIPE CONNECTIONS
_____________________________________________________________________
| | |
Disc dia.inches | | Volume |
| Exhaust E | exhausted |
____________________________|__________________| at | Note
| | | | 4,500 |
Min. | Max. | No | | ft/min. |
| | Pipes | Dia. | ft(3)/min |
_________________|__________|_______|__________|___________|_________
| | | | |
| 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.
FIGURE V-8
A TYPICAL HOOD FOR A BELT OPERATION
________________________________________________________
|
| Exhaust Volume
Belt width W. inches (centimeters) | 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.
NOTE: Authority and reference cited: Section 142.3, Labor Code.
HISTORY
1. New section filed 7-18-75; effective thirtieth day thereafter (Register 75, No. 29).
2. Amendment filed 7-16-76; effective thirtieth day thereafter (Register 76, No. 29).
3. Amendment of subsection (a) filed 4-27-79; effective thirtieth day thereafter (Register 79, No. 17).
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