2
Issue/Rev. 0.6 (2/06)
Introduction
The INVALCO Turbine Flowmeter is a device used to measure the volumetric flow of a fluid. The flowmeter consists of
the body, a multiblade rotor (usually 6 to 10 blades depending on size), bearings and supports for the rotor. As a fluid
passes through the flowmeter the rotor spins. The speed of the rotor is directly proportional to the fluid velocity or flow
rate.
As the rotor spins, the balde tips pass through a magnetic field generated by permanent magnets in a pickup coil
mounted in close proximity to the rotor but separated from it and the process fluid by the wall of the flowmeter body.
Each time a blade passes the magnet, it generates a small alternating current in the pickup coil. (See Figure 7) The
pickup coil is attached to the pickup by two terminals or wires.
Each rotor blade passing through the magnetic pickup flux lines produce one alternating current cycle. Depending on
the flowmeter size, a certain number of pulses are produced for each volumetric unit of liquid passing through the turbine
flowmeter. This is known as the “K-Factor” of the turbine flowmeter. The variation of this factor over the specified flow
range is the Linearity or accuracy of the flowmeter.
Note: Meter should be installed with ten diameters of straight pipe the same size as turbine meter bore
up and 5 straight pipe diameters downstream of meter.
Note: If valve is to be used, it must be downstream from the meter. This is necessary not only to keep the line
full for accuracy in batching applications, but to prevent damage caused by striking an empty meter with a
high velocity stream.
Control valves should always be located downstream from the flowmeter. If a line is empty and a valve is opened, the
high velocity fluid stricking the flowmeter can cause severe damage. Air eliminators should be used in cases where
gases are flowing in the process stream. Air in the liquid will cause the flowmeter rotor to spin at a different rate than the
liquid giving incorrect readings.
Spools should be installed in the flowmeter position during start up to prevent damage to the flowmeter from solids
(welding slag, rust, scale, etc.) in the process liquid.
Note: Sleeved bearings used in INVALCO flowmeters are lubricated with the process fluid. Never spin
the flowmeter at high speeds with air. Always confirm that the flow line contains fluid at start up.
The life of the flowmeter can be extended by using a mesh filter in the flow line. Table I shows the recommended filter for
various sizes of flowmeters.
Mechanical Installation
Turbine Flowmeters are affected by upstream and downstream piping configurations. Upstream piping has a
pronounced effect on flowmeter performance making it necessary to have ten (10) straight pipe diameters up-
stream of the turbine flowmeter and five (5) pipe diameters downstream of the turbine flowmeter. Flowmeters
should be installed with the arrow marked on the body pointing in the direction of flow.
Table 1
Turbine Flowmeter Size
Mesh Size Opening Size
1/2”
3/4”
1”
1-1/2”
2”
40
40
40
18
14
0.015
0.015
0.015
0.0386
0.051
Figure 1
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