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1910.94(b)(3)(i)
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.
1910.94(b)(3)(iii)
Scratch-brush wheels and all buffing and polishing wheels mounted on floor stands, pedestals, benches, or special-purpose machines shall have not less than the minimum exhaust volume shown in Table G-5.

TABLE G-5 - BUFFING AND POLISHING WHEELS
Wheel diameter
(inches)
Wheel width
(inches)
Minimum exhaust
volume (feet (3) /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
1910.94(b)(3)(iv)
Grinding wheels or discs for horizontal single-spindle disc grinders shall be hooded to collect the dust or dirt generated by the grinding operation and the hoods shall be connected to branch pipes having exhaust volumes as shown in Table G-6.

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
1910.94(b)(3)(ix)
Where the work is outside the hood, air volumes must be increased as shown in American Standard Fundamentals Governing the Design and Operation of Local Exhaust Systems, Z9.2-1960 (section 4, exhaust hoods).
1910.94(b)(3)(v)
Grinding wheels or discs for horizontal double-spindle disc grinders shall have a hood enclosing the grinding chamber and the hood shall be connected to one or more branch pipes having exhaust volumes as shown in Table G-7.

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
1910.94(b)(3)(vi)
Grinding wheels or discs for vertical single-spindle disc grinders shall be encircled with hoods to remove the dust generated in the operation. The hoods shall be connected to one or more branch pipes having exhaust volumes as shown in Table G-8.

TABLE G-8 - VERTICAL SPINDLE DISC GRINDER
Disc
diameter
(inches)
One-half or more
of disc covered
Disc not covered
Number
(1)
Exhaust
foot (3)/min
Number
(1)
Exhaust
foot (3) /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

Footnote(1) Number of exhaust outlets around periphery of hood, or equal distribution provided by other means.
1910.94(b)(3)(vii)
Grinding and polishing belts shall be provided with hoods to remove dust and dirt generated in the operations and the hoods shall be connected to branch pipes having exhaust volumes as shown in Table G-9.

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
1910.94(b)(3)(viii)
Cradles and swing-frame grinders. Where cradles are used for handling the parts to be ground, polished, or buffed, requiring large partial enclosures to house the complete operation, a minimum average air velocity of 150 feet per minute shall be maintained over the entire opening of the enclosure. Swing-frame grinders shall also be exhausted in the same manner as provided for cradles. (See fig. G-3)

FIGURE G-3 A METHOD OF APPLYING AN EXHAUST ENCLOSURE TO SWING-FRAME GRINDERS
Note: Baffle to reduce front opening as much as possible.
1910.94(b)(3)(ii)
Grinding wheels on floor stands, pedestals, benches, and special-purpose grinding machines and abrasive cutting-off wheels shall have not less than the minimum exhaust volumes shown in Table G-4 with a recommended minimum duct velocity of 4,500 feet per minute in the branch and 3,500 feet per minute in the main. The entry losses from all hoods except the vertical-spindle disc grinder hood, shall equal 0.65 velocity pressure for a straight takeoff and 0.45 velocity pressure for a tapered takeoff. The entry loss for the vertical-spindle disc grinder hood is shown in figure G-1 (following 1910.94(b)).

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 = 4 1/2 inches, then
          4.5 divided by 4 X 610 = 686 (rounded to 690).

FIGURE G-1 VERTICAL SPINDLE DISC GRINDER EXHAUST HOOD AND BRANCH PIPE CONNECTIONS

Figure G-1 -- Vertical Spindle Disc Grinder Exhaust Hood
      and Branch Pipe Connections
Dia. D inches (cm) Exhaust E Volume
Exhausted
at 4,500
ft/min
ft (3)/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
72
4
5
6
7
3,530
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.


TABLE G-4 - GRINDING AND ABRASIVE CUTTING-OFF WHEELS
Wheel diameter
(inches)
Wheel width (inches) Minimum exhaust
volume (feet (3)/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 1,200

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