Liquid Controls MS Meters - Manual (Page 4)

4
How LC Meters Work
Liquid Controls MS-Series meters are positive
displacement flowmeters. They are designed for liquid
measurement in both custody transfer and process
control applications. Because of their simple design, they
are easy to maintain, and can easily be adapted to a
variety of systems.
The meter element (1) is designed with three cylindrical
bores (2). A Blocking rotor (3) and two Displacement
rotors (4,5) turn in a synchronized relationship within the
bores. The three rotors are supported by bearing plates
(6,7). The ends of the rotors protrude through the bearing
plates. Blocking rotor gear (8) is placed on the end of
the blocking rotor (3). Displacement rotor gears (9,10)
are placed on the ends of the displacement rotors (4,5).
These gears create the synchronized timed relationship
between the three rotors.
As fluid moves through the meter element, the rotor
assembly turns. The liquid is segmented into uniform
sections by the turning rotors. Fluid displacement
happens simultaneously. As fluid enters, another portion
of the fluid is being partitioned and measured. At the
same time, the fluid ahead of it is being displaced out of
the meter and into the discharge line. Since the volume
of the bores is known, and the same amount of fluid
passes through the meter during each revolution of the
blocking rotor, the exact volume of liquid that has passed
through the meter can be determined.
This true rotary motion is transmitted through either the
pulse output device (POD) to the encoder, or the face
gear and drive shaft to the counter/register. True rotary
motion output means consistent accuracy since the
register indication is in precise agreement with the actual
volume throughput at any given instant.
At any position in the cycle, the meter body, the blocking
rotor, and at least one of the displacement rotors form a
continuous capillary seal between the un-metered
upstream product and the metered downstream product.
Capillary seals mean no metal-to-metal contact within
the metering element. This means no wear. No wear
means no increase in slippage, and no increase in
slippage means no deterioration in accuracy.
Throughout the metering element, the mating surfaces
are either flat surfaces or cylindrical faces and sections
that are accurately machined. These relatively simple
machining operations, plus the fact that there is no
oscillating or reciprocating motion within the device,
permit extremely close and consistent tolerances within
the LC meter.
The product flowing through the meter exerts a dynamic
force that is at right angles to the faces of the
displacement rotors. The meter is designed so that the
rotor shafts are always in a horizontal plane. These two
facts result in no axial thrust. Therefore, with no need
for thrust washers or thrust bearings, the rotors
automatically seek the center of the stream between the
two bearing plates eliminating wear between the ends of
the rotors and the bearing plates.
Liquid Controls meters are made of a variety of materials
to suit a variety of products. Because of our no-wear
design, capillary seals, and unique rotary metering, LC
meters provide unequalled accuracy, long operating life,
and unusual dependability.