The ultimate goal of the mine ventilation system is to deliver an adequate supply of
oxygen to the active working areas and to dilute, render harmless, and carry away flammable, explosive, noxious, and
harmful gases, and dust, smoke, and explosive fumes. This requires careful planning of the mine ventilation system.
Hundreds of years ago underground mines were ventilated by very crude methods. Early mines relied on
natural ventilation. This depended on the, mine openings having different elevations, or the use of air shafts sunk into
the workings some distance from the mine entrance.
By using the principle that warm air rises, the next improvement was the installation of an underground
furnace and a slack. This worked like the furnace and chimney in a house. The heated air would rise and cause fresh air to
be drawn into the mine. There were many hazards introduced by having a fire underground. Certain temperature and barometric
changes would cause the air to reverse. This forced smoke over the workers.
The penetration of coal mining to greater and greater depths, the constant expansion of the panels,
and the marked rise in installed electrical capacity have an ever-increasing effect on the underground climate. As the
mine climate steadily deteriorated, corresponding efforts were made to improve it. The method of climate improvement
is currently the most sensible and generally used is ventilation. Coal mines are ventilated almost exclusively by
electrically-driven up east main shaft fans. This is essential nowadays because the air quantity is subject to considerable
fluctuations due to temperature changes, shift changes, expansion of mine workings and other factors. In order to
compensate for these factors it is vital to be able to vary their volume or :he pressure of a fan installation. In the
most widely used axial fans this variation is achieved by blades, which can be hydraulically adjusted in service.
With radial fans adjustment of the air volume can be done only when the fan is stationary. The fan if
therefore adjusted to the varying air conditions by controlling the speed of the drive motor or by changing the pitch of
the fan blades. A modern installation commonly consists of two identical axial fans of horizontal design installed parallel
to each other and running at the same time. Two pillow-block bearings carry the two-stage fan rotor with blades that can be
adjusted on-line. Both the fan and the squirrel-cage motor are mounted on chassis that can travel on rails. All processes
including changeover of the travelling fan and motor sections must be automatic in the event of a fault. Normally the set
total air quantity is to be carried equally by both operating fans and kept constant.
1. All underground coal mines must be ventilated by mechanical ventilation equipment
(fans), and most underground non-coal mines are also ventilated by fans. A mine may have one fan or it may be ventilated
by multiple fans depending on its size and air requirements. These fans must supply enough air to completely ventilate the
mine. Air may be pushed into the mine by a blower (pressure) fan, or it may be pulled out of the mine by an exhaust fan.
Air enters through drifts (adits), slopes (inclined shafts), or shafts.
2. The range of main ventilation fans includes centrifugal, adjustable pitch axial and auto-variable
axial flow designs - all designed to the highest levels of efficiency and robustly constructed to the most exacting
standards. All fans are suitable for matching the changing duties encountered during the development of a mine. In the
case of centrifugal fans, by adding replaceable tails to the impeller blades; the blade pitch can be altered either
manually or automatically.
3. Surface ventilation fans are all designed to protect the working environment through the production
of low noise levels and silencers can be supplied to reduce further the sound levels emitted. Together with the optimum
efficiency and reliability, this results in an unsurpassed range of main ventilation fans for underground mining industry.
4. The problem is more difficult with auxiliary fans. They must meet a wide range of duties which may
change as the distance of a workface from the main drivage increases. New auxiliary fans of higher efficiencies than
hitherto known, with greater pressure reserves, lower noise levels and in different sizes were developed. It should be
noticed that maintenance was of paramount importance. Note should be taken as well of the extremely robust construction
with axial and radial stiffening to prevent damage underground.
There are numerous requirements for the installation and maintenance of main fans. Main fans at metal
and nonmetal mines classed as gassy (containing methane gas) must have the following fan features. Coal mine fans should
also have these features:
1. Installed on the surface.
2. Installed in fireproof housings and provided with fireproof air ducts.
3. Located in a manner to prevent possible explosive forces from destroying the fan.
4. Equipped with a pressure recording gauge
5. Equipped with devices which give an alarm if the fan slows down or stops. Main fans at gassy metal
and nonmetal mines must also be powered electrically and installed to permit prompt reversal of airflow.
There are other related regulations dealing with main fans. One requires action to remove persons from
a mine if the fan stops for a period of time, usually defined as 15 minutes. Coal mines are required to have a fan
stoppage plan, listing action to be taken when a fan stops.
Small fans which are located underground near the working places arc called auxiliary tans.
First blowers were introduced as early as 1923 to ventilate those places where air would not naturally
enter and speeded up great improvement in the ventilation of development ends. In the following years hundreds of
development ends were equipped with these blowers.
Auxiliary ventilation work was also performed by Duot Ventilation, which had fixed inlet guide vanes
and was driven by means of a compressed air turbine.
The next generation of fans was rather unusual with a 5 bladed screw type impeller and ten curved
discharge guide vanes, which were designed to set up a rotating motion of the air converging to a jet area about half the
impeller diameter beyond the guide vanes. These fan's could deliver about 1.18 m3/s through a 1525 m long duet.
Auxiliary fans are always used with a turbine attached to one side of the fan and extended to the face.
The turbine is mounted directly on the Circumference of the impeller resulting in a very compact unit. The first auxiliary
ventilation fans had motor housings, which rotated around a stationary shaft. The fan impeller was a patented design and
was bolted directly to the rotating motor housing. The overall efficiency of compressed air driven fans is far less than
that of electrically driven fans, and electrical ones have replaced most of these.
The first large fans were designed with a substantial safety factor to cater for the lack of tried and
tested design criteria. Strength calculations had to be performed by hand, sometimes with the aid of logarithm tables and
later the slide rule. Today computers are used to optimize the selection of fans forgiven duties, stress calculations,
selection of materials, bearings and improving fan design.
It is also usual practice to install electronic devices for monitoring vibrations and bearing
temperatures to anticipate fan failure and allow for timely repairs and the purchasing spares.
Part of the air from the main fan supply is either blown through the tubing to the face or pulled to
the end of tubing at the face and exhausted through the tubing and out the fan.
Auxiliary fans have certain advantages over conventional means of directing air to the face (line
brattice). Line brattice is often used to partition the entry so as to direct air to the face. Tubing requires less space
than line docs brattice and is generally less subject to damage by equipment. Tubing provides improved visibility for
equipment operators and better maneuverability for equipment.
These fans should be placed and operated in a way to prevent recirculation. Recirculation is the
repeated cycling of the same air through the fan. If the auxiliary fan moves more air than is available from the main fan
supply, recirculation will occur.
Modern axial fans widely employed in various branches of industry possess an unstable pressure
characteristic at the fan capacity below the optimum rating in the zone of the so-called surge. Type BM new axial fans
with meridional flow acceleration are free of all these disadvantages, which is ensured through the use of a special
stabilizing device located in the fan casing. The range of service capacities of the fans with the stabilizing device
increases greatly (practically twofold), while fan operation with unstable characteristics in the zone of surge and
increased vibration is completely ruled out. As a result, despite the minimum dimensions of the fans their effective
operation is ensured. The noise produced by the fan of the new type is 5-6 dB lower than that caused by the conventional
axial fans, at the same capacity and pressure. The advantages integrated in type BM fans have ensured the development of
a number of aerodynamic layouts and designs of the fans intended for mining industry The variety of aerodynamic
characteristics facilitates the selection of the most desirable fan modification to suit ventilation of mines. Ventilation
of blind underground workings in mines and tunnels is usually performed with the aid of newly developed flame-proof BM fans
which are built into vent pipes with a diameter of 400, 500, 600, 800 and 1200 mm. Fan capacity can be varied while the fan
is running by means of the guide vanes.
Booster Fans
Additional fans placed in an underground airway to supplement the main fans d called
booster fans. Rarely seen in coal mines, they are quite common in non-. mines. They should be placed and operated carefully
to prevent recirculation.
Источник: Mining transport and equipment// Методичний посібник для студентів 2,3 курсів факультету ФЕМА, магістрів та аспірантів. / Укладачи: ст.викл. Павлова Л.К., ст.викл. кафедри ГЗТіЛ Мельніков С.О., ас. Кушніренко О.М., ас. Гіровська І.В., ас. Алтухов А.В., студент групи СПУ-03 Корінь О.О. Донецьк: ДонНТУ 2005 - 161с.