Figure 1-21.Fuel oil pump.
such as flowmeters and draft gauges, increases safety and
promotes efficiency. All of these instruments may be
either indicating or recording.
A Utilitiesman must be able to identify the different
types of monitoring instruments and understand their
operation and use. Meters used to measure quantities are
divided into two general types:
1. Those indicating rate, such as flowmeters
2. Those indicating the total, such as scales
Many devices are designed to measure and indicate
the pressure of steam flow. One of these devices is
shown in figure 1-23. This meter uses a weighted
inverted bell (called a Ledoux bell) sealed with mercury.
The bell moves up and down as the rate of flow changes.
The movement is transmitted to a pen that records the
STEAM AND AIR FLOWMETERS
A combustion air and steam flowmeter is shown in
figure 1-24. This meter is used as a guide in controlling
the relationship between air required and air actually
supplied to burn the fuel. The rate of steam generation is
used as a measure of air necessary to burn the required
amount of fuel. The flow of gases through the boiler
setting is used as a measure of air supplied.
The essential parts of the meter are two airflow bells
supported from knife-edges on a beam, which is
supported by other knife-edges, and a mercury displacer
assembly supported by a knife-edge on the beam. The
bottoms of the bells are sealed with oil, and the spaces
under the bells are connected to two points of the boiler
A draft gauge is a form of pressure gauge. In boiler
practice, the term draft usually refers to the pressure
difference producing the flow. Drafts are pressures
below atmospheric pressure. They are measured in
inches of water. A draft gauge is essential to boiler
operation. Its use increases the safety of operation.
A simple type of draft gauge is the U-tube gauge.
The source of draft is connected to one leg of the U and
the other end is left open. The difference between the
levels of the liquid in the two legs is a measure of the
draft. Water is generally used in this type of gauge. Take