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4-2
Section 4 Maintenance
Installation and Operation Manual
X-PR-SLA7800-PC-eng
Part Number: 541B047AAG
December, 2008
Model SLA7810 & SLA7820
This section contains suggestions to help diagnose pressure controller
related problems in the gas distribution system and answers commonly
asked questions.
A. System Checks
The Model SLA7810/SLA7820 is generally used as a component in gas
handling systems, which can be quite complex. This can make the task of
isolating a malfunction in the system a difficult one. An incorrectly
diagnosed malfunction can cause many hours of unnecessary down time.
If possible, make the following system checks before removing a
suspected defective pressure controller for bench troubleshooting or return
to the factory, especially if the system is new.
1. Verify a low resistance common connection and that the correct power
supply voltage and signals are reaching and leaving the controller (for
Analog I/O). The Break-out Board (P/N S-273-Z-649-AAA) will make
this job much easier.
2. Verify that the process gas connections have been correctly terminated
and leak checked.
3. If the pressure controller appears to be functioning but cannot achieve
setpoint, verify that sufficient inlet pressure and pressure drop are
available at the controller to provide the required flow.
4. Verify correct zero position and/or re-zero device.
a. Connect the power cable to the PC.
b. Allow the PC to warm-up for a minimum of 15 minutes.
c.
Close any inlet valves connected to PC.
d. Connect vacuum pump to PC outlet.
e. For upstream PC (SLA7820) give zero (0%) set point to device.
For downstream PC (SLA7810) give full scale (100%) set point to
device.
f.
Turn on the vacuum pump. When the pressure gauge reads less
than 1.0 mm Hg, press the zero button on the device.
g. Output process value should nominally read less than 10 mVdc
(0.2% full scale). If reading is greater than 10 mVdc
(0.2% full scale), consult factory.
B. Bench Testing
A basic bench test can be performed to isolate the cause of a problem or
to verify the proper operation of the pressure controller. This method can
be used if the full scale calibration pressure of the Pressure Controller is
greater than 14.7 psia (atmospheric).
1. Connect the Pressure controller to the appropriate power supply as
required for either Analog or DeviceNet.
2. Apply power to the pressure controller.
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