1. (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.

2. (b) Hood and Branch Duct Performance Requirements.

   1. (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. (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 (Inches)

      Wheel Width (Inches)

      Minimum Exhaust Volume (Cubic Feet/Min.)

      To 9

      1 ½

      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 ½ inches. Minimum Exhaust Volume = 4.5/4 x 610 = 686 (rounded to 690).

      TABLE V-2

      BUFFING, POLISHING, AND SCRATCH-BRUSH WHEELS

      Wheel Diameter (Inches)

      Wheel Width (Inches)

      Minimum Exhaust Volume (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 (Inches)

      Minimum Exhaust Volume (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

      Note: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 (Inches)

      Exhaust Volume (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. (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.

3. (c) Hood Design.

   1. (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. (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. (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. (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. (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. (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. (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. (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.

4. (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 SPINDLE DISC GRINDER EXHAUST HOOD AND BRANCH PIPE CONNECTIONS

   

   FIGURE V-2 STANDARD GRINDER HOOD

   

   FIGURE V-3 A METHOD OF APPLYING AN EXHAUST ENCLOSURE TO SWING-FRAME GRINDERS

   Note: Baffle to reduce front opening as much as possible.

   

   FIGURE V-4 STANDARD BUFFING AND POLISHING HOOD

   

   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

   

   

   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

   

   FIGURE V-8 A TYPICAL HOOD FOR A BELT OPERATION

   

   Belt Width W, inches

   Exhaust Volume, ft³/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 cited and Reference: 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).

4. Change without regulatory effect providing more legible illustrations for Figures V-1, V-2, V-3, V-4, V-5, V-6, V-7 and V-8 filed 3-2-2009 pursuant to section 100, title 1, California Code of Regulations (Register 2009, No. 10).