A-17
Model 199 Differential Pressure Unit (DPU)
Section 3
General Startup Practice Considerations
Observe the following practices when starting up an instrument.
1. Always start with the block valves closed.
2. Perform a zero check on the instrument as follows.
IMPORTANT: For gas service, it is recommended that zero check be performed with
both block valves closed. If the gas flow is pulsating, there may be a
standing wave effect in the process line which can displace the indicator
and appear as a zero error.
a. Open the bypass valve(s), then open one shutoff valve. This proce-
dure equalizes the pressure between both sides of the instrument.
The instrument should indicate zero.
b. If the instrument does not indicate zero, check for gas or liquid en-
trapment in the lines or in the DPU (depending on the orientation of
the piping layout and service).
c. If necessary, adjust the pen or pointer by turning the zero adjust on
the instrument.
3. Check the manifold and piping for leaks as follows.
a. Open the bypass valve(s), then open one shutoff valve to pressurize
the instrument.
b. Close the shutoff valve and the bypass valve.
c. Any leakage will be indicated by pen or pointer movement, up or
down scale.
IMPORTANT: Be careful not to subject the DPU to unnecessary shock or overrange
pressure during operations.
Содержание BARTON 289A
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