Badger Meter Hydrometer - Manual (Page 3)

Section I
Paragraphs 1-1 to 1-10
SECTION I
USE AND MAINTENANCE
1-1. PURPOSE.
1-2. The Series 12 flowmeter is an instrument for the accurate
and continuous measurement of the rate of flow for liquids
and gases at nominal pressures.
1-3. MODELS.
1-4. The Series 12 flowmeter is available in three basic
models; Model 124, Model 129 and Model 120. (Refer to
Flowmeter Model Conversion Key, Page 9). Each model is
available as a single stage or multi-stage flowmeter. Each
stage consists of a matched tube and float with a calibrated
scale and necessary mounting connections. A multi-stage
flowmeter consists of two or more matched tubes and floats,
normally of the same model together with scales and mounting
connections, assembled into a steel shell.
1-5. Bypass valves are required for most multi-stage
flowmeters to bypass the lower stages when operating in the
higher flow ranges, thus maintaining a normal pressure drop
over the entire flow range.
NOTE
On a maximum stage standard flowmeter of
any model, the pressure drop through the
flowmeter will not exceed 6 psig, except for
flowmeters with bypass orifice sections
where the pressure drop is approximately 8
psig.
1-6. VARIATIONS WITHIN MODELS.
1-7. Multi-stage flowmeters usually consist of tubes of the
basic model as in paragraph 1-4, but to meet certain
requirements, some multi-stage flowmeters have been
produced with intermixed size 40, 90, 100 and 140 tubes.
Other requirements have resulted in incorporating size 60
tubes intermixed with one or more of the standard Series 12.
To correctly identify any tube refer to the number etched near
the top of the tube. This number consists of the flowmeter
serial number, tube size, and model number. For example,
12001-47 indicates flowmeter serial number 12001-47 and
tube size seven in the Model 124-300 group.
1-8. Other variations within models are:
a. Fluorescent backlighting for each and
convenience in reading flow.
b. Orifice valve and calibrated auxiliary bypass
orifice to increase the capacity of a particular
flowmeter.
1-9. DESCRIPTION.
1-10. In multi-stage flowmeters the top of each glass tube is
connected with the bottom of the next larger tube by a
copper tube at the rear of the shell. This provides a
continuous passage from inlet at the lower end of the
first tube to the outlet at the top of the last tube (see fig.
3). Each tube is fitted with a metal float which
positions itself in the tube according to the rate of flow.
Since the pressure drop across the float is constant
throughout the range of any particular tube, any change
in rate of flow will result in a relocation of the float to a
position where the annulus area is such as to maintain
this constant pressure drop across the float. Since the
tube is of an expanded taper, an increase in flow will
result in a rise in the float position and inversely a
decrease in flow will result in a lowering of the float
position. When the maximum capacity of a tube is
approached, the increased rate of flow affects the float
in the next tube. This sequence is continued through all
tubes until one of the floats comes to rest within the
limits of its scale at which point the rate of flow is read.
Tubes are calibrated and scales are engine divided to
read in pounds per hour, gallons per minute or other
units to fit specific requirements.
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