Issue/Rev. 0.2 (7/00)
Page 9
Troubleshooting
1.
The 24 volt power supply to the 7300 must be
good, steady, and ripple free. Half wave rectifier
sources normally are not acceptable, producing
unreadable displays.
2.
If the RTD (Resistance Temperature Device) that
measures the fluid temperature should “short” or
“open” the 7300 will continue to operate, but will lose
its temperature compensating ability. The RTD
is located at the bottom of the hollow stud that comes
up into the condulet from the probe. The stud is the
3/8” threaded rod onto which you attach the probe
clip wire from the electronic assembly. To remove
the RTD, you first remove the electronic assembly
and then pull the RTD out by the cable going into
the hollow stud. The RTD is coated with a white
heat transmitting grease. Wipe the grease off and
transfer it onto the new RTD before installing it.
3.
If the water cut reading drifts, but the shakeouts
show the cut to be constant, check the temperature
and probe readings from the LED display. Stop the
fluid flow through the probe to see if the reading
stabilizes. If it does, then the problem is flow related,
and could be caused by any of the following:
a.
If the temperature is varying, and you are on
manual TC, you may need to:
(1) Go to the two cut method and let the 7300
calculate it’s own temperature compensa-
tion factor.
(2) Change the manual TC number. The 600
number is a TC that normally is good for
most oils, but may not be for yours. If the
indicated water cut goes up with an in
crease in temperature, the manual TC
number is too high and should be reduced.
Since all oils vary in their reaction to tem-
perature changes, it is not possible to say
how much reduction in TC is needed.
Some experimenting may be required.
Conversely, if the indicated cut goes down
with a temperature increase, you need to
increase the TC value.
b.
If the probe value is varying, look for:
(1) An increase in the API gravity of the oil.
This will cause the value to go down. Con-
versely, a decrease in API gravity will
cause the reading to increase. This is not
a linear function, and varies from oil to oil,
but generally is consistent.
(2) A variation in the amount of solution gas
in the oil.
(a) NEVER mount a probe down stream
of the dump valve when moni-
toring oil from a pressure vessel as
solution gas will break out as the fluid
goes from the higher vessel pressure
to the lower pressure downstream of
the valve. An increase in gas will make
the reading become smaller. Also,
since the size and volume of the gas
bubbles is constantly changing with
flow, the probe value can be very un-
stable as it attempts to follow the fluc-
tuating gas content.
(b) A change in pressure on the oil as
the divert value switches from “good”
to “bad” oil on a LACT. Switching to
a higher pressure bad oil line can make
the 7300 read higher. Switching to a
lower pressure can make it read lower.
For good operation, the pressure must
be kept constant to keep the solution
gas bubble size constant. Please note
that air eliminators will vent slugs of
gas, but not solution gas.
(3) A change in chemicals, of either volume,
type or supplier. Remember that the probe
looks at/checks everything that flows
through it including chemicals, stuffing box
rubbers, oil, water, minerals, etc. Chang-
ing chemical conditions normally cause
the greatest trouble as it is easy to forget
that they can affect the Dk of the stream
and, hence, affect the readings. Normally
an increase in chemical will cause the read
ings to increase. However, just changing
types and/or suppliers usually will require
a recalibration after the system has stabi-
lized.
(4) Other things that can cause troubles are:
(a) Having loose fitting on the suction side
of the pump that is pumping the fluid
through the monitor probe. The pump
will suck in air causing the oil to act as
if it had gas in it.
(b) Mounting the probe directly on the
pump discharge. This will/may be ok
as long as the pump has plenty of suc-
tion head, is not over speeding, has
the proper impeller, etc. But the pos-
sibility for trouble always exists.
(c) Mounting the probe directly to a static
mixer. A static mixer functions by mix-
ing (as violently as possible) the fluid
going through it. The fluid exiting the
mixer is normally still full of bubbles
and will cause erratic readings. If the
mixer has been installed backwards,
the results are disastrous.
(5) Probe Problems
All internal “wetted” parts of the probe are
either teflon or coated by a baked on ep-
oxy. Normally a probe will give many years
of service without any problems. How
ever, chemicals added to the process
stream often will cause a conductive film
to coat over the teflon insulators and the
