MKS P9B, Инструкция по эксплуатации, Страница: 88 / 112

Chapter Seven: Maintenance Flow Zero Adjustment
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
Via the protocol Zero Service.
 For DeviceNet – Refer to “MKS P9 Devicenet Profile Document”.
 For RS485 – Refer to “MKS Document, Command Specification, P9 RS485 Interface”.
Flow Zero Adjustment Procedure
1) Assure that the MFC is setup in the exact process conditions:
a)
Verify that the MFC is installed in the final equipment and orientation (base up, base down, vertical
flow up, etc.)
b) Verify that the MFC is powered at operating temperature for at least 30 minutes.
If the MFC will be subjected to elevated ambient temperature conditions, verify that these temperatures have
been achieved and stable for at least 30 minutes before continuing.
2)
Verify that the pressure drop across the MFC is reduced to zero. Depending on the gas panel
configuration, this may be done by one of the following procedures.
a)
System has upstream and downstream positive shut off valves
i)
Close the upstream valve.
ii)
Close the downstream valve.
iii)
Open the MFC’s control valve.
iv)
Allow pressure across MFC to equilibrate as flow output approaches zero and stabilizes.
v)
Close the MFC’s control valve.
vi)
Wait one minute and adjust the zero using one of the methods specified for the device I/O type.
b)
For systems with downstream valve only
- Zero the MFC at typical operating inlet pressure.
i)
Close the downstream valve.
ii)
Open the MFC’s control valve.
iii)
Allow pressure to equilibrate across the MFC as flow output approaches zero and stabilizes.
iv)
Close the MFC’s control valve.
v)
Wait one minute and adjust zero using one of the methods specified for the device I/O type.
c) For systems with upstream valve only -
MFC may be re-zeroed with downstream line under
vacuum or atmosphere.
i)
Close the upstream valve.
ii)
Open the MFC’s control valve.
iii)
The MFC may be evacuated to vacuum or exposed to atmosphere on downstream side. For either
case, the downstream pressure must be kept constant to insure there is no pressure drop across
MFC.
iv)
Allow pressure to equilibrate across MFC as flow output approaches zero and stabilizes.
v)
Close the MFC’s control valve.
vi)
Wait one minute and adjust zero using one of the methods specified for the device I/O type.