200/202 Series Flowmeters and Controllers Instruction Manual
EAR99 Technology Subject to Restrictions Contained on the Cover Page
Page 21 of 27
3.
Maintenance
This section contains service and calibration information. Some portions of the instrument are delicate, so
please use extreme care when servicing the flow controller.
NOTICE:
It may prove more prudent in the long run to delegate the maintenance of Hastings flow
instruments to Hastings personnel with the appropriate equipment and training. Improper adjustments
to the flow instruments can result in inaccurate data, poor instrument function, and may lead to
sending the unit back for repair.
Authorized Maintenance
With proper care in installation and use, the flow controller will require little or no maintenance. If
maintenance does become necessary, most of the instrument can be cleaned or repaired in the field. Some
procedures may require recalibration. Do not attempt these procedures unless facilities are available. Entry
into the sensor or tampering with the printed circuit board will void the warranty. Do not perform repairs on
these assemblies while unit is still under warranty.
Troubleshooting
This section includes some of the more common issues that may arise when using a Hastings flow meter or
controller. Symptoms, causes, and recommended actions are grouped with each problem.
SYMPTOM:
Flow remains when 0.00 VDC is commanded or even when Override CLOSE function is enabled.
CAUSE:
Orifice out of adjustment or faulty op-amp
ACTION:
Check the valve voltage between pins 2 & 12 on the 15-pin D-connector for 15 Volt units and
Pins 5 & 8 on the DE-9 connector for 24 Volts. If the voltage is less than 3.00 VDC, then turn the orifice
slowly clockwise until flow stops.
NOTICE:
adjusting the orifice too quickly or two far can damage the valve seat and cause leak paths
that will not allow the controller to operate properly. Please adjust the orifice gently and with caution.
SYMPTOM:
Output of unit is proportional to flow but extremely small and not correctable by span pot.
CAUSE:
Sensor is not being heated.
ACTION:
Unplug the sensor connector (J4 for 15 V boards, J5 for 24 V boards) and check the following
resistances: The resistance between pins 2 & 3 of the sensor should be about
2.475 kΩ ±75 Ω
. The resistance
between pins 1 & 4 should be somewhere around 2 to 3
Ω
. The resistance between pin 2 or 3 and the base of
the sensor should be essentially infinite. If not, the heater wire is contacting the sensor base and the sensor
must be replaced. If the sensor passes the previous three tests, check the voltage output on pins 2 & 3 of the
sensor connector on the PCB. If it does not read approximately 22 to 23 VDC then replace the sensor heater
regulator (U1 on 15 V board, U2 on 24 Volt board).
SYMPTOM:
Sensor has proper resistance readings, but little or no output with flow.
CAUSE:
Plugged sensor.
ACTION:
Shut off gas supply and power supply. Remove cover and PC board from unit. Remove
sensor assembly and examine. If sensor has evidence of plugging, clean or replace as applicable
SYMPTOM:
Flow controller oscillates.
CAUSE:
Flow controller not adjusted for the dynamics of the flow system.
ACTION:
Check upstream and downstream pressures. The gas supply regulator should not have
excessive lockup when flow shuts off. Also ensure that there is not a large drop in pressure between the
regulator and the instrument due to line resistance. Oscillations can also be caused if a large flow
restriction is pneumatically close to the downstream end of the flow controller. The differential pressure
across the unit must be between 10-50 psig.
SYMPTOM:
Little or no flow, even with Valve Override OPEN enabled.