Types of ventilation systems with special reference to U, W and Z air routes and bleeder ventilation.

1. TYPES OF VENTILATION SYSTEMS WITH SPECIAL REFERENCE
TO U, W AND Z AIR ROUTES AND BLEEDER VENTILATION.
SUBJECT: MINE ENVIRONMENT PLANNING
GUIDED BY: SUBMITTED BY:
PROF. N.C KARMAKAR ARAB RAJ (19152007)
NARENDRA SINGH BANJARE
(19152019)
SHIBASOUMYA GHOSH (19152026)
IIT (BHU), VARANASI

2. CONTENTS:-
 GENERAL PRINCIPLES
TYPES OF VENTILATION SYSTEMS
 CENTRAL VENTILATION SYSTEM
BOUNDARY VENTILATION
 U VENTILATION SYSTEM
 W VENTILATION SYSTEM
Z VENTILATION SYSTEM
 BLEEDER VENTILATION
 REFERENCES

3. GENERAL PRINCIPLES: Figure depicts the essential elements of a
ventilation system in an underground mine or other subsurface facility.
Fig:- Typical elements of a main ventilation system

4. Contd…
Fresh air enters the system through one or more downcast shafts, drifts (slopes, adits),
or other connections to surface.
 The air flows along intake airways to the working areas or places where the majority of
pollutants are added to the air. (These include dust, toxic or flammable gases, heat,
humidity, and radiation).
The contaminated air passes back through the system along return airways.
The intake and return airways are often referred to simply as intakes and returns
respectively.
The return air eventually passes back to the surface via one or more upcast shafts, or
through inclined or level drifts.

5. TYPES OF VENTILATION SYSTEMS:-
Depending on the relative position of intake and return airways, ventilation
systems in mines can be broadly divided into the following:-
a) Boundary or Unidirectional
b) Central or Bi-Directional
c) U
d) W
e) Z

6. CENTRAL OR BI-DIRECTIONAL VENTILATION SYSTEM:-
 The system is commonly adopted in in-the seam of coal mines where both
intake and return shaft are located close by at the centre of the property.
 Intake and return air from any district travel in opposite directions through
parallel roadways usually separated by stopping erected in the cross-section
between them.
 Also return air from a district has to cross the intake in order to join the
main return.

7. Advantages of central ventilation system:-
 The deposit can be worked after short development leading to a quicker start
of production.
 Long development headings are not necessary and hence there is no
associated problem of their ventilation.
 Central pits cause less loss of minerals in shaft pillars.
 Sinking of deep pits close together economizes the cost of sinking as certain
common facilities can be shared by the pit.

8. Dis-advantage of central ventilation system:-
 Central ventilation system allows a substantial leakage because of the
number of stopping and air crossing used so that volumetric efficiency
is only 40-50% with this system.

9. Figure:- Room and pillar development with line brattices to regulate airflow in conveyor belt entry:
(a) bi-directional system; (b) uni-directional system.

10. BOUNDARY VENTILATION SYSTEM:-
In boundary ventilation system, the air flows in Uni-directional from the
intake to the return through the workings.

11.  It is commonly adopted in metal mines, where the intake and return shafts
are located at the strike boundaries of the mine.
 It is the most efficient system necessitating the least use of ventilation
control devices and thus resulting in a high volumetric efficiency of
ventilation (70-80%).

12. Figure:- Boundary Ventilation

13. Advantages of boundary ventilation:-
 It necessitates the minimum use of ventilation control devices.
 This apart from saving the capital invested on them as well as the cost of
their operation and maintenance, reduces leakage and result in a high
volumetric efficiency.
 Different sections of the mine can be independently ventilated by separate
fans.
 There is greater safety because of larger number of outlets to the surface.

14. Disadvantages of the boundary ventilation system:-
 Separate fan installations increase the cost of their operation,
supervision and maintenance.

15. “U” Ventilation system:-
"U Ventilation" where intake air comes in the main-gate and returns in the
tailgate; there is no connection to any airways behind the face line. If a longwall
advancing face is ever used, this is the only means of ventilation available.

16. Figure:- “U” Ventilation System

17. “W” Ventilation system:-
“W Ventilation” is adopted in longwall double unit face where air enters from
both the tailgates and leaves from the common main-gate for each longwall
panel.

18. “Z” Ventilation System:-
"Z or Y Ventilation" where both main and tailgates carry intake air and all
the return air is carried to main returns behind the face.

19. Figure:- “Z” Ventilation System

20.  For U ventilation, the air flow across the face itself is from main to tail (in
the opposite direction to the coal flow and sometimes referred to as
"antitropal" ventilation).
 For Z ventilation the flow is from tail to main (or "homotropal").

21. Bleeder Ventilation:-
Special air courses developed and maintained as part of the mine ventilation
system and designed to continuously move air-methane mixtures emitted by
the gob or at the active face away from the active workings and into mine-
return air courses.

22. Contd..
 In a bleeder design, fresh air is provided from the main entries as shown in Figure (next
slide).
 The intake air then splits in three directions, towards the face, returns with the
conveyer belt and in-by the face to the bleeder fan.
 The face air goes in two directions, in-by the face, deep into the mine, where it is
exhausted to the surface by the fan via the bleeder shaft and tailgate return.
 Air from bleeder entries enters the gob to dilute the methane below the explosive limit
and exhaust the methane to the surface.

23. Figure:- Bleeder ventilation plan

24. Bleederless Design:-
 Bleederless designs are used for longwall systems in other countries with
different regulations.
 The progressively sealed gob design must include methods to control
spontaneous combustion and accumulations of methane–air mixtures in the
worked out areas.
 The U type ventilation (bleederless), as illustrated in Figure (next slide), is
used for progressively sealed gobs.

25. Figure:- U-System of Bleederless Ventilation

26. Figure:- Progressively sealed Y ventilation system

27. References:-
 https://www.slideshare.net/ANILKUMARKUDIRE/types-of-ventilation-systems-in-
mines-central-boundary-u-w-z
 http://ethesis.nitrkl.ac.in/7180/1/Underground_Sethi_2015.pdf
 http://web.mst.edu/~tien/218/lab8-systems.pdf
 https://mountainscholar.org/bitstream/handle/11124/170036/Saki_mines_0052E_
10926.pdf
 https://www.mvsengineering.com/files/Subsurface-Book/MVS-
SVE_Chapter04.pdf