From ventilation Book

1. Ventilation
control
Syed M.Haris
13pwmin0688

2. Control devices in a ventilation system
Three Elements
A Pressure Source or Fan
Connected mine airways
Control devices : stoppings, doors, airlocks, regulators and air crossings
Auxiliary fan: for coursing the air to the heading faces (with brattice cloth, ducts)
Booster fan: If a high resistance district is getting insufficient air

3. Typical elements of a mine ventilation system

4. Stoppings:
In developing a mine, connections made between intakes and returns.
When theses are no longer required for access or ventilation,
they should be blocked by stoppings to prevent short-circuiting of the airflow.
A stopping may be of permanent or temporary in nature
Temporary: made of brattice cloth, plastic cloth with wire netting reinforcement
can be hung as curtains or nailed onto a frame work
Permanent: For long term control,
between main intake and main return

5. Stoppings can be constructed from brick with lime or cement, concrete blocks or
fireproofed timber blocks.
Prefabricated steel stoppings may also be employed.
Stoppings should be well keyed into the roof, floor and sides, particularly if the strata are
weak or in coal mines liable to spontaneous combustion.
Every stopping between the main return air way shall be constructed of masonry or brickwork,Every stopping between the main return air way shall be constructed of masonry or brickwork,
of at least 25cm in thickness .of at least 25cm in thickness .

6. Doors
Doors are employed when a gallery has to be kept
available for haulage and/or traveling and at the
same time airflow through the gallery has to be
prevented.
Doors are commonly made of mild steel sheets,
strengthened with steel flats or angle irons,
and may be of the single leaf double leaf type set
in a steel frame with hinges.
In the past, doors made of wooden boards
set in wooden door frames, (often with
a regulator fitted at the centre) were commonly
Used but these were prone to greater air leakage
in normal operation and posed risk of damage
at the time of a mine fire.

7. Airlock doors
Ventilation doors located between main intakes and
returns are usually built as a set of two or more to form
an airlock.
This prevents short-circuiting when one door is opened
for passage of vehicles or personnel.
The distance between doors should be capable of
accommodating the longest train of vehicles required to
pass through the airlock.
For higher pressure differentials, multiple doors also
allow the pressure break to be shared between doors.
With two doors in series, at least one door can always be kept shut when tubs or men are
to pass through the other one.
In important locations, such as near the pit bottom, usually a set of three or four doors
are provided, one of which is arranged to open in the opposite direction to the others so
that at least that door remains shut when air current is reversed in the mine in case of an
emergency.

8. a door fitted with one or more adjustable orifices.
Its purpose is to reduce the airflow to a desired
value in a given airway or section of the mine.
The most elementary is a rectangular orifice cut
in the door and partially closed by a sliding panel.
The airflow may be modified by adjusting the
position of the sliding panel manually.
Passive regulators may be actuated by motors,
either to facilitate their manual adjustment or to
react automatically to monitored changes in the
quantity or quality of any given airflow.
Regulators

9. Where intake and return air have to cross each other, an air crossing is needed.
Usually made as an overcast, :
Roof is ripped over one of the galleries, two chambers constructed and one of the air
currents, usually the return is made to go via the top chamber.
Steps may be provided on both sides to help persons travelling in the return road to climb up
to and down from the top chamber.
Air crossings
Poor construction of overcast
Excellent construction for overcast
Undercast: the floor-dug up to make the two chambers, and one of the air currents, usually t
the return, is made to flow through the lower chamber.

10. In mines working thick or contiguous seams, crossing of intake and return air currents may be
effected through natural air crossings provided by galleries in different horizons in the same
seam or in contiguous seams.
Undercast- Not preferred as it may give rise to the
problem of water accumulation in the lower
gallery.
An air crossing should be strong, leak proof and
have a large cross section with small aerodynamic
resistance.
Inexpensive but efficient overcastIf an air crossing is weak, it may give way during
an emergency such as an explosion and may cause
short-circuit of air.
The partition and walls of the every air-crossing shall be at leastThe partition and walls of the every air-crossing shall be at least 25cm thick25cm thick ifif
constructed ofconstructed of masonary or of concrete not properly reinforcedmasonary or of concrete not properly reinforced,,
and at leastand at least 15 cm in thickness15 cm in thickness if constructed of properlyif constructed of properly rein forced concreterein forced concrete..

11. Used for ventilation of blind headings
Line Brattice, commonly made out of treated jute cloth is used to course the air current from
the nearest junction to the working face in a heading.
(treated to make it fire and rot resistant, cheapest and most favoured material)
Brattice cloth is nailed on to timber supports placed at 1 to 1.5 m intervals along the heading
at ¼ to 1/3 width distance from one of the sides.
The heading is thus longitudinally partitioned into two airways of dissimilar c.s. permitting
easy travel of man and machinery thru the large sized ones.
As brattice cloth made of jute though cheap, tends to be leaky.
Some countries have replaced it with plastic sheeting, plastic reinforced with nylon or
polyster and combinations of plastic coatings/laminations on jute.
Line Brattice or Brattice partition
Auxiliary Ventilation

12. Auxiliary Ventilation
Line brattices used for auxiliary ventilation.
Brattice cloth, in general, leak heavily at the gaps in the
roof and sometimes in the floor.
Hence, brattices are restricted to only short lengths of
headings and should be kept extended right up to the
face to give adequate quantity of air at the face.
Brattices increase the effective resistance of the
heading by doubling the length of the airway and
reducing the cross sectional area.
The alternative to the use of brattice cloth is auxiliary
ventilation through ducts.

13. Thank you