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Model 763A Gage Pressure Transmitter
Section 4
Section 4—Maintenance
General Field and Periodic Maintenance
The electronic transmitter is basically maintenance-free and does not require a
routine preventative maintenance program other than periodic calibration checks.
!
WARNING: Except for replacement of O-rings, fasteners, and connector
assemblies, no
repair or component replacement on the Model 763A
is authorized. Unauthorized repairs void any
to
reports for design basis event performance.
WARNING: Do not tamper with the Bourdon tube inside the enclosure or
the delicate wires connected to it (Figure 3.4,
page 16
). Improper handling
can damage connections and cause the transmitter to be inoperable.
Periodic Calibration
Transmitter calibration is recommended at periodic intervals, determined
primarily by the usage of the transmitter, historical performance, the desired
accuracy of the output signal, or indications that the instrument may be out of
calibration.
A calibration should consist of at least nine checkpoints from minimum to full
scale calibrated pressure and back to minimum. For optimum results, the test
equipment should meet the requirements noted in Table 4.1.
Table 4.1—Calibration Equipment
Equipment
Requirements
Digital Multimeter
±0.05% precision (minimum)
Power Supply
15-55 Vdc, 60 mA minimum, regulation 3%, ripple 1%
Precision Load Resistor (if
voltage measurement of
output is made)
200 Ohm, ±0.05%, 1W (10-50 mA Transmitter)
500 Ohm, ±0.05%, 1W (4-20 mA Transmitter)
Pressure Source
To provide zero to full scale pressure (Accuracy: ±0.05%)
Milliamp Meter
To provide 0-50 mA minimum (Accuracy: ±0.05%)
To check for calibration accuracy, perform the following steps.
1. Shut down the transmitter as follows.
a. Remove electrical power from the transmitter loop.
b. Close the transmitter shut-off valves.
c. Close the main block valves at the process connections.
d. Open the transmitter drain valves and remove all pressure from the
unit.
2. Remove the calibration access plugs from the transmitter cover using a
socket or a wrench.
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