DEA
Engineering Company
Nutating
Micro Flowmeter
Mechanical Installation & Operating Considerations
Electronic Installation & Operating Considerations
Installation and Maintenance Instructions
TROUBLE SHOOTING
A. NO OUTPUT SIGNAL:
- Run the
Microflowmeter to at least 50% of its maximum rated flow range. In a
reasonably quiet environment [if this is impractical, apply the metal
end of a screw driver to the process housing and the handle to an ear],
if there is no audible hum from the meter, there is interference with
the moving parts. The Microflowmeter must be disassembled and cleaned
per the instructions on Page 5.
- If there is an audible hum with no signal, the electronics are not functioning properly. Make certain that the Microflowmeter is wired per the instructions and that power is "on". If there is still no signal, the Microflowmeter should be returned to the factory or other authorized repair facility since the electronic section is not field serviceable.
*In injection pump applications, the orifice may be plugged. If this is suspected, remove the orifice screw from the meter. Install it in a fitting suitable for high pressure back flushing. [The inside diameter of a 1/4" NPT schedule 40 pipe nipple can be tapped with an 1/8" NPT thread to accept the orifice screw for this purpose]. WARNING: In extreme circumstances, the resulting stream could be as sharp as a laser beam!
B. SIGNAL IS ERRATIC OR OBVIOUSLY INACCURATE:
- The bare
"Earth Ground" lead can act as an antenna in some environments. Make
certain that it is connected to both earth ground and electrical ground.
- Any entrapped
air or vapor within the nutating chamber can affect the travel of the
nutator which, in turn, will affect the accuracy of the Microflowmeter.
While the meter is running, turn it 180° vertically for a few minutes
[compression fittings are very helpful]. Return the meter to its normal
orientation. If the problem persists, repeat the process again.
- Microflowmeters
are positive displacement devices. They cannot differentiate between
liquid and gas displacement. If the process liquid is very volatile,
two phase flow may result which will appear to be liquid flow to the
meter. In such cases, higher process pressures should minimize or eliminate
this problem.
- For the
Microflowmeter to function properly, each piston of the nutator must
be in proximate contact with its respective chamber at all points of
travel. If the Microflowmeter is abused and the nutator is bent, this
will not be possible. Liquid will slip past the pistons without being
metered. This damage can be detected by setting the nutating assembly
as shown in POSITION 2 of Figure 1 [use a tooth pick or other soft device
to place the right piston flat on the bottom of the right chamber while
the nutator is in firm contact with the beam]. If the left and right
pistons do not make proximate contact at the same time, the nutator
is bent and should be replaced.
-
When using inductive devices such as relays, motors, or solenoids, care must be taken to avoid voltage transients which result when these devices are switched on and off. These transients can often be strong enough to interfere with [and even damage] system electronics. If the inductive devices are DC, a suppression diode should be placed across the coil as shown in Figure 4. With AC inductive devices, a type of transient suppression device called a Varistor [MOV] should be used. The power should be controlled by a solid state relay which switches at zero voltage. The power supply driving the inductive devices should not be used to drive the system electronics. The supply for the electronics should have an AC line filter either integral with the supply or as a separate module. It is strongly recommended that wires which control the inductive devices not be bundled over long distances with sensor signal wires, even if these wires are shielded.
FIGURE 4
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