U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health TRAPED

MENT OF HEALTH & HUMAN SERVICES . USA

Using Propeller Fans To Improve Ventilation

in Large-Entry Stone Mines

Objective

To improve the air quality in large-opening stone

mines by developing better ventilation techniques,

including appropriate fan selection in conjunction with

air-coursing methods.

Background

Stone mines are the most common underground largeentry mines in the United States. Data from the Mine

Safety and Health Administration (MSHA) for the year

2000 indicate that there were 162 active nonmetal

underground mines in the United States, of which 117

were stone mines. Many underground stone mines are

drift mines developed from previous quarry operations.

Typically, these room-and-pillar mines have entries that

are 20 ft or higher and at least 40 ft wide. These large

dimensions lead to a very small ventilating pressure loss,

even when significant air quantities move through the

mine. This is especially true of drift mine operations

where ventilating pressure losses of <0.25 in w.g. are

common. Underground stone mines with shafts that are

<200 ft deep typically have ventilating pressure losses

that are <2 in w.g. The pressure losses through these

mines are much lower than those of a typical coal mine

or deep metal/nonmetal mine. Therefore, the ventilation

techniques and principles are quite different. In addition,

because of new MSHA regulations that limit the

concentration of diesel particulate matter, these mines

may need to greatly increase their ventilation airflow.

Therefore, large-opening mines need a fan that can move

large air quantities and operate at low static pressures.

There are three fan types for mine ventilation:

centrifugal, axial vane, and propeller. Centrifugal fans

are uncommon in underground stone mines as they are

often associated with mines requiring the

highest of ventilation pressures. Axial vane fans are

widely used in all types of mining operations. They are

the most common fan type currently found in underground large-opening stone mines. However, they

typically do not operate at low static pressures with high

efficiency. Propeller fans are currently uncommon in

underground stone mines. They are designed for low

static pressures and large air quantities at higher efficiency. This fan type best suits the ventilation needs in

large-opening stone mines—they produce large air

quantities at low pressure losses. Mines with air shafts

<100 ft long and at least 12 ft in diameter have fairly low

mine static pressures and may also benefit from

propeller fans.

Results

Research on propeller fans in underground drift stone

mines has shown that significant ventilation improvements can be achieved. In large-entry mines that do not

have any high resistance-sections (shafts >100 ft long or

shaft diameters <12 ft), propeller fans can greatly

increase the total system airflow. Propeller fans can be

used as either main mine fans or as freestanding auxiliary

(jet) fans. NIOSH researchers have documented the

Technology News

Milestones in Mining Safety and Health Technology

SAFER HEALTHIER PEOPLE

No. 499 December 2002
Figure 1.–Two propeller fans installed in an underground stone mine.

performance of two recently installed propeller fans in a

working limestone mine (figure 1). Together the fans

exhausted 750,000 cfm at a rated hp of 200. These fans

replaced an axial vane main mine fan that produced

300,000 cfm at a rated hp of 250. The use of the

propeller fans more than doubled the air quantity while

operating at 50 hp less than the original main mine fan

system. In addition, the new fans, when used with

effective air-coursing methods such as stoppings, reduced

or eliminated recirculation near the face areas. This is

because propeller fans are more efficient at lower

pressures and can produce large air quantities at lower

horsepower requirements than axial vane fans.

For More Information

For more information on the use of propeller fans,

contact Roy H. Grau III or Susan B. Robertson, NIOSH

Pittsburgh ResearchLaboratory, Cochrans Mill Rd., P.O.

Box 18070, Pittsburgh, PA15236-0070, phone: (412)

386-6562 or (412) 386-6720, respectively; e-mail:

RGrau@cdc.gov or SBRobertson@cdc.gov,

respectively.

To receive additional information about occupational

safety and health problems, call 1-800-35-NIOSH (1-

800-356-4674), or visit the NIOSH Web site at

www.cdc.gov/niosh

Mention of any company name or product does not

constitute endorsement by the National Institute for

Occupational Safety and Health.