Chapter 3
Flow Rates and Pressure Measurements
3.1 Introduction
In the previous chapter, an overview of environmental conditions in mining was
offered from the viewpoint of occupational health. In this chapter, that summary is
fleshed out by considering measurement and control of the main physical variables
in a ventilation system. In general, these variables are pressures, airflow speeds
and, indirectly, flow rates. These measurements, which are crucial in guaranteeing
an airflow for miners and for the equipment used, are among the main inputs for
mathematical models of ventilation. This section covers the main techniques and
devices used in determining them.
3.2 Measurement of Static Pressure
The instruments most commonly used in measuring air pressure are mercury barometers
1 and aneroid barometers. The first of these (Fig. 3.1a) comprises a tube filled
with mercury with a closed top in which a vacum is made and an open bottom that
is immersed in a vessel containing this metal. The rises and falls in the level of
mercury inside the tube indicate increasing and decreasing air pressure. In aneroid
barometers (Fig. 3.1b), measurements are based on the expansion and contraction
of a flexible-walled cylinder in which a partial vacuum has been produced. These
movements are amplified by means of a mechanical linkage and finally are indicated
on a dial.
Barometers can indicate obstructions at points along the airflow circuit. Hence,
an increase in circuit resistance usually implies a growth in static pressure if the air
speed remains constant.
1 The European Commission restricts the use of measuring devices containing mercury under
Commission Regulation (EU) No 847/2012.
© The Editor(s) (if applicable) and The Author(s), under exclusive license
to Springer Nature Switzerland AG 2020
C. Sierra, Mine Ventilation, https://doi.org/10.1007/978-3-030-49803-0_3
65
Flow Rates and Pressure Measurements
3.1 Introduction
In the previous chapter, an overview of environmental conditions in mining was
offered from the viewpoint of occupational health. In this chapter, that summary is
fleshed out by considering measurement and control of the main physical variables
in a ventilation system. In general, these variables are pressures, airflow speeds
and, indirectly, flow rates. These measurements, which are crucial in guaranteeing
an airflow for miners and for the equipment used, are among the main inputs for
mathematical models of ventilation. This section covers the main techniques and
devices used in determining them.
3.2 Measurement of Static Pressure
The instruments most commonly used in measuring air pressure are mercury barometers
1 and aneroid barometers. The first of these (Fig. 3.1a) comprises a tube filled
with mercury with a closed top in which a vacum is made and an open bottom that
is immersed in a vessel containing this metal. The rises and falls in the level of
mercury inside the tube indicate increasing and decreasing air pressure. In aneroid
barometers (Fig. 3.1b), measurements are based on the expansion and contraction
of a flexible-walled cylinder in which a partial vacuum has been produced. These
movements are amplified by means of a mechanical linkage and finally are indicated
on a dial.
Barometers can indicate obstructions at points along the airflow circuit. Hence,
an increase in circuit resistance usually implies a growth in static pressure if the air
speed remains constant.
1 The European Commission restricts the use of measuring devices containing mercury under
Commission Regulation (EU) No 847/2012.
© The Editor(s) (if applicable) and The Author(s), under exclusive license
to Springer Nature Switzerland AG 2020
C. Sierra, Mine Ventilation, https://doi.org/10.1007/978-3-030-49803-0_3
65