Michigan Administrative Code › Department - Labor and Economic Opportunity › MIOSHA › General Industry and Construction Safety and Occupational Health Standards › Occupational Health Standards › Part 525 - GRINDING, POLISHING, AND BUFFING OPERATIONS › Section R. 325.52504 - Hood and branch pipe requirements

Current through Vol. 24-12, July 15, 2024
Rule 4.
(1) An
					 employer shall ensure that hoods connected to exhaust systems be used, and
					 hoods shall be designed, located, and placed so that dust or dirt particles
					 shall fall or be projected into the hoods in the direction of the airflow.
					 Wheels, discs, straps or belts shall not 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)
					 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 specified 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 in Figure G-1. If any wheel is wider than
					 wheel diameters shown in Table G-4, then the exhaust volume shall be increased
					 by the ratio of the new width to the width shown.
Example: If wheel width = 4 1/2 inches, then 4.5 / 4 x
						610 = 686 (rounded to 690).
Table G-4 Grinding and Abrasive Cutting-off
						Wheels
Wheel Diameter (inches)
Wheel Width (inches)
Minimum Exhaust Volume
								  (feet3/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
(3) 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
					 specified in Table G-5.
Table G-5
Buffing and Polishing Wheels
Wheel Diameter (inches)
Wheel Width (inches)
Minimum Exhaust Volume
								  (feet3/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
(4) 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 specified in Table G-6.
Table G-6
Horizontal Single-Spindle Disc
						Grinder
Disc Diameter (inches)
Exhaust Volume
								  (feet3/min.)
Up to 12
220
Over 12 to 19
390
Over 19 to 30
610
Over 30 to 36
880
(5) Grinding wheels or discs for horizontal
					 double-spindle disc grinders shall have a hood enclosing the grinding chamber.
					 The hood shall be connected to 1 or more branch pipes having exhaust volumes as
					 specified in Table G-7.
Table G-7
Horizontal Double-Spindle Disc
						Grinder
Disc Diameter (inches)
Exhaust Volume
								  (feet3/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
(6) 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 1 or more branch
					 pipes having exhaust volumes as specified in Table G-8.
Table G-8
Vertical Spindle Disc Grinder
Disc Diameter (inches)
One-half or more of disc covered
Disc not covered
Number1
Exhaust (ft.3/min)
Number1
Exhaust (ft.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
1 Number of exhaust outlets around periphery of hood, or
						equal distribution provided by other means.
(7) 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 specified in
					 Table G-9.
Table G-9
Grinding and Polishing Belts
Belts Width (inches)
Exhaust Volume (feet 
								  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
(8) Cradles and swing-frame grinders. If
					 cradles are used for handling the parts to be ground, polished, or buffed,
					 requiring large partial enclosures to house the complete operation, then a
					 minimum average air velocity of 150 feet per minute shall be maintained over
					 the entire opening of the enclosure. Swing-frame grinders shall be exhausted in
					 the same manner as provided for cradles. (See Fig. G-3).
(9) If the work is outside the hood, then air
					 volumes shall be increased as shown in American Standard Fundamentals Governing
					 the Design and Operation of Local Exhaust Systems, Z9.2-1960 (section 4,
					 exhaust hoods). ANSI Z9.2-1960 is adopted by reference in this rule. Printed
					 copies of ANSI Z9.2-1960 are available from Global Engineering Documents, 15
					 Inverness Way East, Englewood, Colorado 80112, telephone number 1-800-854-7179,
					 website: www.global.ihs.com [File Link Not Available], at a cost as of the time
					 of adoption of these rules of $27.00 or is available for inspection at the
					 Michigan Department of Consumer and Industry Services, Standards Division, 7150
					 Harris Drive, P.O. Box 30643, Lansing, Michigan 48909.