# Presentation: 708234

## Using Belt Air to Ventilate Active Working Areas

**Using Belt Air to Ventilate Active Working Areas**

## Federal Coal Mine Health and Safety Act of 1969

- Belt air could not be used to ventilate active works except for mines opened prior to the Act (Pre-Act Mines)

- Pre-Act mines could utilize belt air if needed with approval

**Notes:**
From House Committee Report :  Subsection (z) requires that in all mines entries used as intake and return airways should be separated from track and belt entries. The air in belt and track entries should have only the minimum velocity needed to supply oxygen in adequate concentrations to be safe for men and to keep such entries free from explosive gas in concentrations in excess of 1.0 percent. If an authorized representative of the Secretary finds, in presently operated mines, that entries other than the track or belt entries are in condition to be used as intake and return airways, the air velocities in belt or haulage entries should be limited to that needed to avoid oxygen deficiency and keep methane below 1.0 percent.

## Petitions for Modification

- First Petition Granted 1975
- 30 CFR § 75.326

- Approximately 90 Petitions granted from 1975 to 2003

- § 75.326 became § 75.350 in subsequent ventilation rulemaking

## Prior to Final Rule : Two ways to use belt air

- Petition for Modification

## Final  Belt Air Rule  April 2, 2004

- All granted petitions are superseded

- Any Pre-Act mines must also comply with final rule

## Ventilation of Belt Conveyor Entries

- DW Mitchell and CW Parisi, 1988

## Federal Coal Mine Health and Safety Act of 1969

- Act was based on information and technology available at the time
- Four research documents considered by Congress

## Mine Fires and Their Control

- Three Discussion Points :

- Electrical short-circuit protection required
- Abandoning trolley haulage
- Limiting air current in belt entry

- Only third was considered practical and implementable by Congress in 1969

## Float Dust Deposits in Return Airways in American Coal Mines

- Study showed float coal dust levels deposited in belt entries was seven times that of returns

- USBM IC 8150 (1963)

- 50 mine study

## Float Coal Hazard in Mines :       

- A Progress Report

- USBM RI 6581(1965)

- 50 mine study

- Higher velocities in return airways lowered concentration of float coal deposits
- Float coal not raised into suspension by air velocities from 50 to 550 fpm

## Fire Hazard of Conveyor Belts

- Rubber-based belting burned 10 to 30 times faster than other formulations (propagation)
- Flame spread was higher with air movement in belt entry than zero-flow
- Small fires were extinguished by automatic sprinklers

- USBM RI 7053(1967)

## Air Velocity

- Act limited air velocity and quantity to levels required to control methane gas and supply oxygen to men
- Intent in Act was to mitigate against fanning and propagating fire, contaminating mine entries prior to escape, and float coal dust

## Fire Detection Technology

- Heat activated point-type sensors (PTHS) were state of the art in 1969

*PTHS still accepted in 30 CFR for non-belt air mines*
*Belt Air Rule requires use of Atmospheric Monitoring (CO) System or Equivalent*

- AMS provides increased detection ability and earlier warning to miners

## CONCLUSIONS BY MITCHELL

- Provisions providing a greater level of protection to miners include:

- Allowing belt entries to be used to supplement ventilation at working faces
- Isolating belt entry from primary escapeway
- Permitting air velocities consistent with safe mining practices

## CONCLUSIONS BY MITCHELL

- Proposed warning and alarm levels of 10 and 15 ppm CO above ambient should be reconsidered

*Belt Air rule reduced levels to 5 and 10 ppm CO, and allow for further reductions based of USBM RI 9380*

- Concentration of CO is based on size of fire and airflow in the entry