Noise Source Identification Project Draglines, Shovels & Air Arc Cutting Team Members Richard Gates, Assistant District Manager - District 9 Bob Cornett.

Noise Source Identification Project

Draglines, Shovels & Air Arc Cutting

Team Members

Richard Gates, Assistant District Manager - District 9

Bob Cornett

Michael S. Horbatko

Michael L. Lynham

Robert Smith

Peter Saint

Noise Source Identification Project

Draglines

Background Information

MSHA has conducted noise surveys on over 220 operators/oilers. Although the sound pressure levels ranged from 96 dBA to 112 dBA, only 12.5% had exposures above the PEL.

Noise Source Identification Project

DraglinesOilers are required to perform various tasks in the dragline house.

The time required to perform these tasks varies from day to day. It ranges from 30 minutes to greater than 2 hours.

Major Noise Sources

Dragline HouseThe major noise sources connected with dragline houses are:

• House Fans

• Motor Generating Sets

• Wall Fans

• Motor Cooling Fans

• Swing, drag, hoist and propel motors

Noise Source Identification Project

Potential Noise Controls

A meeting pertaining to “Achieving MSHA Noise Standards on Draglines” was held in December, 2000 at Milwaukee, WI. The meeting was sponsored by Bucyrus International. It was attended by MSHA/NOISH, mine operators, dragline manufacturers, and noise abatement consultants.

The purpose of the meeting was to share:

1. Information what steps have been taken to comply with MSHA’s noise standard.

2. Information on current noise control methods and,

3. Strategies on achieving compliance with MSHA’s noise standards.

Noise Source Identification Project

Potential Noise Controls

Silencers

Vibration Isolation

Fan Blade Damping (coating)

Change of Fan RPM

Automatic Fan Control

Isolation/Barrier

Noise Source Identification Project

Potential Noise Controls Current Developments

Currently, the most effective means of controlling exposure to noise is to use administrative controls to limit the amount of time spent in the dragline machine house.

Remote monitoring using cameras can be used to reduce the time necessary for dragline operators/oilers in the dragline house.

P & H Mining Company is developing methods for quieting motor cooling fans in the machine house of their shovels.

Noise Source Identification Project

Air Arc Cutting

Background

Air arc cutting is used to cut dragline or shovel buckets to remove defective parts or to gouge out cracks found in the frames of draglines or buckets. A copperclad, carbon rod is used to create an arc that generates enough heat to melt the metal. Compressed air is used to remove the molten metal from the cut. The noise is generated when the air disturbs the magnetic field created by the arc which results in a loud crackling sound. The sound pressure level ranges from 108 to 120 dBA.

A welder’s personal noise exposure depends on the amount of time spend gouging during their work shift. The highest dose obtained during this study was 483 percent for 10 hour shift.

Air Arc Cutting - 3/8" Rod - Shop Work Bench

0.0

20.0

40.0

60.0

80.0

100.0

120.0

31.5 63 125 250 500 1000 2000 4000 8000

Frequency (Hz)

So

un

d P

res

su

re in

dB

100 Psi, 240 Amps 100Psi, 360 Amps

240 Amps - 110 dBA Average

360 Amps - 116 dBA Average

Air Arcing (1/4" rod, 1/4" Plate) @ 180 Amps on Work benchALCOA - Sandow Mine

0.0

20.0

40.0

60.0

80.0

100.0

120.0

One Third Octive Band Frequency (HZ)

So

un

d P

ress

ure

Lev

el i

n d

B

Blue - Air Pressure of 110 psi (Avg. 115dBA)Red - Air Pressure of 80 psi (Avg. 112.6dBA)

Sound Pressure Levels of Various Gouging Rods & Plasma Cutting

Parameters

3/8”X-Egron

Rod

3/8”Copperclad

Rod

1/4”Copperclad

Rod

1/4”Certanium

Rod

3/8”Cronatron

Rod

PlasmaTorch with

Gouging Tip

Amperage 700 700 400-600 700 600 200Air

Pressure(psi)

90 90 125 90 100 50

LAVG indBA

115.5 112.3 108.4 103.0 100.9 102.2

* EstimatedExposure

Time in min

14.0 21.8 37.4 79.2 105.9 88.4

* The estimated exposure times would result in a dose of 100 percent.Welders Comments:The Certanium and Cronatron gouging rods are slow and do not move the molten metal aseffectively as the copperclad gouging rods. They feel it would take longer to do the samejob using the Certanium and Cronatron rods thus gaining no advantage in lowering theirnoise exposure.

It is difficult to follow a small crack with the plasma tool due to the size and shape of thecutting head.

Air Arc Technical Noise Study

The Sabine Mining Company

July 11, 2001

Table 1 List of Materials Gouged or Cut

Station Thickness MaterialA 3-inches Mild Steel, Gouging a crackB 3 - inches 12 % Magnesium Steel (Hoist Chain)C ½ - inch Chromium Carbide Overlay PlateD 3/8 - inch Aluminum Flat BarE 1 ½ - inch 87 % Magnesium / Bronze BushingF 1 ½ - inch Chromium Carbide 4 – inch Wide Flat BarG 1 - inch thick by 36 -inch

diameter8 % Magnesium / Bronze Thrust Washer

H 12 - inch diameter 4340 Stock Pinion GearI 3 - inch inside diameter Tapered Roller BearingJ 2 1/4 - inch diameter Wire RopeK Two , 1 - inch plates @ 90

degreesMild Steel Welded at 90 degrees

Table 2

Summary of Q-300 Noise Dosimeter ReadingsProduct/Method

ParametersTime *

(min:sec)LAVG 2

(PEL)dBA

DOSE (PEL)Percent % at *

PDOSE (PEL) % at 8-Hrs

Electra Rod3/16 inch dia375 amps

23:49 86.6 3.10 62.28

Hypertherm-Plasma80 amps55 psi air pressure

22:42 94.5 8.79 185.66

Magnum Rod.3/4 inch rod60 psi air

29:18 85.6 3.33 54.55

Cronatron3/16 inch rod420 amps

22:08 86.4 2.82 60.94

Certanium1/4 inch440 amps

19:09 88.6 3.26 81.71

Petrogen20 psi gas60psi oxygen

20:48 92.9 6.48 149.54

Arc Air3/8 inch rod600 amps120 psi air

23:45 108.8 66.968 1353.30

* Based on Duration of Time Each Product was Tested

List of Products and Manufacturers

Electra Rod - Rockmount Research & Alloys, Inc.

Hypertherm - Plasma - Hypertherm, Inc.

Magnum Rod - Magnum Manufacturing, Inc.

Cronatron Rod - Cronatron Welding System, Inc.

Certanium Rod - CT Engineering

Petrogen - Petrogen International , LTD.

Carbon Air Arching

Noise Source Identification Project

Air Arc CuttingRecommendations (Gouging Alternatives)

• Based on the data collected, there are alternative methods of performing carbon air arc cutting that will reduce related noise exposures. The information obtained from this study should assist mine operators in choosing products for air arc cutting activities that generate less noise, thereby reducing the noise exposure of miners performing these tasks.

Noise Source Identification Project

Air Arc CuttingRecommendations (Bucket Maintenance)

• Reduce maintenance that may result in the need for air arc cutting on dragline and shovel buckets

• Changing bucket teeth

• Improved blasting techniques

• Minimize backdragging

Noise Source Identification Project

Air Arc CuttingRecommendations (Work Practices)

• Discourage side-by-side air arcing

• Limit amount of time air arcing