Program Handbook: PH92-V-6
Chapter 8
GUIDANCE FOR VENTILATION PLAN APPROVAL
IN MINES WHERE DIESEL-POWERED EQUIPMENT IS OPERATED
Individual Units of Diesel-powered Equipment
§75.325(f)requires that a minimum quantity of ventilating air be maintained where individual units of diesel-powered equipment are being operated. The minimum ventilating air quantities for individual units of equipment are not required to be specified in the ventilation plan. Paragraphs (f)(1) through (f)(3) indicate the locations where the minimum ventilating air quantity must be maintained.
Paragraph (f)(1) requires the minimum ventilating air quantity to be maintained in any working place where the equipment is being operated. It is anticipated that this quantity will be measured in the same required location as the quantity reaching the working face, described in §75.325(a)(2). This would necessitate making only one air quantity measurement to determine compliance with both §75.325(a)(1) and §75.325(f)(1). However, an air quantity measurement in the entry of the working place would also be acceptable.
Paragraph (f)(2) requires the minimum ventilating air quantity to be maintained at the section loading point during any shift when equipment of the type that can be used to perform work at the section loading point is on the working section. The location for this quantity is required by §75.371(ll) to be specified in the mine ventilation plan.
Paragraph (f)(3) requires the minimum ventilating air quantity to be maintained in the entry where the equipment is being operated outby the section loading point in areas of the mine developed on or after April 25, 1997. This quantity can be determined either within one crosscut of the diesel-powered machine or with the machine pulled into a crosscut.
Paragraph (f)(4) requires the minimum ventilating air quantity to be maintained in any air course with single or multiple entries where the equipment is being operated outby the section loading point in areas of the mine developed prior to April 25, 1997. This quantity can be determined either within one crosscut of the diesel-powered machine or with the machine pulled into a crosscut. However, air quantity measurement locations in a multiple entry air course should be made in each entry directly across from the previous entry's measurement location.
Paragraph (f)(5) allows the district manager to require minimum ventilating air quantities at other locations where individual units of diesel-powered equipment are being operated. Any such locations should be specified in the ventilation plan. The preamble to the final rule provides some examples of such locations, including underground repair shops, permanent fuel storage facilities, temporary fuel storage areas, or construction sites.
Multiple Units of Diesel-powered Equipment
When multiple units of diesel-powered equipment are on the working section, the minimum ventilating air quantity shall represent the sum of the nameplate ventilating air quantities of all of the diesel-powered equipment located on the working section, i.e., equipment located inby the loading point, excluding any equipment specifically exempted in the plan. The locations where the minimum air quantity must be maintained are stipulated in paragraph (g)(1) through (g)(3).
When multiple units of diesel-powered equipment are being operated in areas where mechanized mining equipment is being installed or removed, the minimum ventilating air quantity approved in the ventilation plan should represent the sum of the nameplate ventilating air quantities of all of the diesel-powered equipment located inby the mouth of the panel, excluding any equipment specifically exempted in the plan. This equipment should include all diesel-powered equipment used in the setup or removal process, such as shield haulers, scoops, pickups, etc. The location of the minimum air quantity would be specified in the intake entry or entries just outby the crosscut conducting the air into the face. Also, a monitoring point(s) may be set up under §70.1900(a)(4) to ensure that diesel-powered equipment is being adequately ventilated in the intake haulage entry.
Paragraph (d) should be used to address diesel-powered equipment that is actually on the removal or setup face, i.e., those pieces of equipment inby the last loading point or future loading point. The initial air quantity (before any exclusions) would be the sum of the nameplate ventilating air quantities on those pieces of equipment. The location where the minimum quantity must be maintained would be either in the crosscut conducting the air onto the face or at another appropriate inby location.
The diagram below provides examples of locations where minimum ventilating air quantities should be maintained for multiple units of diesel-powered equipment, and also indicates an example of a location for an air quality monitoring point required under §70.1900(a)(4). This would be in addition to the monitoring point required by §70.1900(a)(3).
| 75.325(d) |
- Quantity for equipment located inby former loading point |
75.325(g) |
- Quantity required to be maintained during removal of longwall equipment |
| 70.1900(a)(4) |
- Possible sampling location designated by the District Manager |
The following diesel-powered equipment may be excluded from the calculations of minimum ventilating air quantity under paragraph (g) for multiple units of diesel-powered equipment. All such exclusions must be approved by the district manager and specified in the ventilation plan:
- Self-propelled equipment meeting the requirements of §75.1908(b) (this would be “light-duty” equipment). Generally, light-duty equipment may be excluded from the calculation if the operator can substantiate that the duty cycle of such equipment will have a minimal impact on the nitrogen dioxide and carbon monoxide exposure of miners. An example where the equipment may not be excluded is a diesel-powered pick-up truck operated frequently in the intake haulage entry during a longwall set-up, transporting supplies and personnel. The use of this equipment is such that it would contribute significantly to the miners' total exposure to carbon monoxide and nitrogen dioxide during the shift. An example where exclusion may be appropriate is a diesel-powered mantrip which has a duty cycle that does not contribute significantly to the miners exposure because the mantrip is operated only to take the crew to and from the working section.
- Equipment that discharges its exhaust into intake air that is coursed directly into a return air course. Usually all such equipment would be excluded from the calculation.
- Equipment that discharges its exhaust directly into a return air course. Usually all such equipment would be excluded from the calculation.
- Other equipment having duty cycles such that the emissions would not significantly affect the exposure of miners. The length, duty cycle and type of operation of the equipment must be evaluated in making this determination. In some cases sampling may be needed to assess the effect of the equipment operation on the exposure of miners.
Approval of Reduced Minimum Ventilating Air Quantities under §75.325(i)
The minimum ventilating air quantity required under paragraph (g) is based upon the nameplate air quantities for the equipment engines. These nameplate quantities are determined by laboratory testing using MSHA test procedures, which are designed to approximate the duty cycles of the engines. The ventilation rates are based upon the exhaust contaminants measured at different engine speeds and loading factors. Because in-mine operation of multiple engines can vary depending on equipment loads and speeds, the regulations allow mine operators to request reductions in the required minimum ventilating air quantity for multiple units of equipment. It is important to note that the minimum ventilating air quantity for an individual unit of diesel-powered equipment cannot be reduced.
It is the mine operators responsibility to provide MSHA with data, such as results of on-shift, environmental, and personal sampling, to support any request for a reduced minimum ventilating air quantity. Such data may include a continuous and complete record of carbon monoxide, nitrogen dioxide, and the air quantities measured on the section. Data should be collected for all locations where the minimum air quantity is required to be maintained. Data logging instrumentation generally provides the most usable results. Computer-based mine wide monitoring systems could also provide valuable data. Data should indicate the time-weighted averages for the contaminants measured, peak contaminant concentrations, the associated measured air quantities, section production records, and the reduced minimum air quantity the company is requesting. The sampling period should be of a sufficient time to provide MSHA with enough data to make a valid determination.
To minimize possible concerns about the validity of the sampling data, MSHA should consider observing some portion of the mine operator's data gathering and sampling to assist in evaluating the request for reduced air quantities.
MSHA should review data to determine the potential effect of a reduction in ventilating air quantity by calculating the projected time-weighted average (TWA) concentrations for the contaminants. The following relationship can be used as a tool for making this determination:
| Q measured | ||
| TWA projected = | ------------------ | * TWA measured |
| Q requested |
The projected TWA must be less than the associated TLV for each contaminant for the reduced air quantity to be approved.
After calculating the projected TWA for the sampling data, the MSHA representative responsible for the data review can determine the potential for exceeding the 50 percent action level for sampling conducted as required under §70.1900. This can be calculated in the same manner as the projected TWA and is a method that can be used in determining if an increase in the action level requested by the mine operator is warranted:
| Q measured | ||
| PEAK projected = | ------------------ | * PEAK measured |
| Q requested |
When a reduction in the minimum ventilating air quantity has been approved and the reduction has been implemented, MSHA should confirm through sampling that the reduced air quantity is adequate to maintain compliance with the applicable TLV's.
Approval of Higher Action Levels under §75.325(j)
The mine operator may request that the action level specified in §70.1900(c) be raised. The increase in action level may be requested either separately or at the same time that a request for reduction in minimum ventilating air quantities is made.
It is the mine operator's responibility to provide MSHA with data, such as results of on-shift, environmental, and personal sampling, to support any request for an increased action level. Such data may include a continuous and complete record of carbon monoxide, nitrogen dioxide, and the air quantities measured on the section where the sampling is conducted. Data should be collected for all locations where the minimum air quantity is required to be maintained. Data logging instrumentation generally provides the most usable results. Computer-based mine wide monitoring systems may also provide valuable data.
Sampling in the area(s) or location(s) being evaluated, and/or personal sampling, should be conducted to demonstrate that an increased action level would continue to ensure that miners are not being overexposed to gaseous diesel exhaust contaminants. Gas sampling data submitted to MSHA should include the peak concentrations for each location and time-weighted averages for each occupation.
If full shift exposures for miners are appropriate, the results should be compared to the peak concentrations measured in the corresponding area(s) or location(s). If compliance with the TLV's is maintained at the same time that the gaseous contaminant levels in the return air course are greater than the 50 percent action level, the district manager may increase the action level.
Sampling should provide sufficient data representative of normal operating conditions. Duration should be appropriate depending on the circumstances at the mine. Data logging instrumentation will generally provide the most usable data for this analysis. MSHA should confirm through sampling that the increased action levels continue to provide protection to mine personnel.
Under §75.371(nn) the minimum ventilating air quantity for multiple units of equipment must be stipulated in the ventilation plan. This air quantity should be the sum of the nameplate air quantities of the units of diesel-powered equipment that are typically operated on the working section. However, if other units of diesel-powered equipment are being operated in addition to those that were used to calculate the air quantity stipulated in the ventilation plan, the minimum air quantity provided in locations stipulated in paragraph(g) must be the sum of the nameplate air quantities for all of the diesel-powered equipment, excluding exempted equipment, on the working section. This would result in a greater ventilating air quantity than the quantity stipulated in the ventilation plan.
MSHA inspectors, therefore, must measure the air quantity in the last open crosscut or other appropriate locations specified in §75.325, to determine if that air quantity is equal to or greater than the minimum air quantity stipulated in the ventilation plan. Inspectors must also identify the diesel-powered equipment on the working section and add up all of the equipment nameplate air quantities, excluding exempted equipment, to determine if the measured air quantity in the last open crosscut is equal to or greater than that summed minimum.
Corrective Action in Response to Sampling Results above the Action Level under §70.1900(c)
§70.1900(c) states that “Except as provided in §75.325(j) of this chapter, when sampling results indicate a concentration of CO and/or NO2 exceeding an action level of 50 percent of the threshold limit values(TLV™) adopted by the American Conference of Governmental Industrial Hygienists, the mine operator shall immediately take appropriate action to reduce the concentrations of CO and/or NO2 to below the applicable action level.”
Actions that an operator may take to reduce the concentrations below the applicable action level include the following:
- identification of the contaminant source, such as a poorly maintained diesel engine, and removing it from service;
- redistribution of the available ventilating air quantity;
- increasing the air quantity in the affected area; and
- reduction of the number of diesel-powered equipment in service.