SCOPE

This policy outlines the requirements for abrasive, polishing and buffing operations.  The following charts illustrate the recommended exhaust volumes.

General Exhaust Systems

1. Exhaust systems for grinding, polishing, and buffing operations should be designed in accordance with American Standard Fundamentals Governing the Design and Operation of Local Exhaust Systems, Z9.2-1960.
2. Exhaust systems for grinding, polishing, and buffing operations shall be tested in the manner described in American Standard Fundamentals Governing the Design and Operation of Local Exhaust Systems, Z9.2-1960.
3. All exhaust systems shall be provided with suitable dust collectors.
4. When dust leaks are noted, repairs shall be made as soon as possible.
5. The static pressure drop at the exhaust ducts leading from the equipment shall be checked when the installation is completed and periodically thereafter to assure continued satisfactory operation. Whenever an appreciable change in the pressure drop indicates a partial blockage, the system shall be cleaned and returned to normal operating condition.

Grinding, Polishing, and Buffing Operations

1. Organic-bonded wheels, the thickness of which is not more than one forty-eighth of their diameter for those up to, and including, 20 inches in diameter, and not more than one-sixtieth of their diameter for those larger than 20 inches in diameter, used for a multitude of operations variously known as cutting, cutting off, grooving, slotting, coping, and jointing, and the like. The wheels may be "solid" consisting of organic-bonded abrasive material throughout, "steel centered" consisting of a steel disc with a rim of organic-bonded material molded around the periphery, or of the "inserted tooth" type consisting of a steel disc with organic-bonded abrasive teeth or inserts mechanically secured around the periphery.
2. Wherever dry grinding, dry polishing or buffing is performed, and employee exposure, without regard to the use of respirators, exceeds the permissible exposure limits prescribed in 1910.1000 or other sections of this part, a local exhaust ventilation system shall be provided and used to maintain employee exposures within the prescribed limits.
3. 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.

Tables     

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-1 with a recommended minimum duct velocity of 4,500 feet per minute in the branch and 3,500 feet per minute in the main.  

           TABLE G-1 - GRINDING AND ABRASIVE CUTTING-OFF WHEELS

      ________________________________________________________________

         Wheel diameter   | Wheel width (inches)       |    Minimum exhaust

                    (inches)   |                                           | 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

       _____________    |____________________   |____________________________

Note: For any wheel wider than wheel diameters shown in Table G-1, 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).

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-2.

                     TABLE G-2 - BUFFING AND POLISHING WHEELS 

   _______________________________________________________________

                Wheel diameter        |     Wheel width        |     Minimum exhaust

                          (inches)          |        (inches)            |     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

              _________________  |  _____                    |_____________             

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-3.

                 TABLE G-3 - HORIZONTAL SINGLE-SPINDLE DISC GRINDER

           _____________________________________________________________

                                                                     |     Exhaust volume

                     Disc diameter (inches)             |     (ft. (3)/min.)

           __________________________      |_______________________________    

                 Up to 12...........................  |           220

                 Over 12 to 19....................  |           390

                 Over 19 to 30....................  |           610

                 Over 30 to 36....................  |           880

            __________________________     |_______________________________

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-4.

                     TABLE G-4 - HORIZONTAL DOUBLE-SPINDLE DISC GRINDER

          _______________________________________________________________

                                                                              |        Exhaust volume

                 Disc diameter (inches)                          |        (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

           ____________________________           |____________________________

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-5.

                             TABLE G-5 - VERTICAL SPINDLE DISC GRINDER

           ______________________________________________________________

                                                |   One-half or more         |   Disc not covered

                     Disc                     |   of disc covered            |________________________

                 diameter                  |_________________    | Number  | Exhaust

                  (inches)                  | Number  |  Exhaust        |     (1)      | foot (3)/min

                                                |     (1)      | 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.