GE PanaFlow HT, User Manual

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PanaFlow HT User’s Manual 135
Appendix E. Special Applications
Appendix E. Special Applications
E.1 Pig Detection
When a pig passes through the pipeline, it will block the ultrasonic signals for a brief time. In previous products, this
might have resulted in a slight blip on the strip chart recorder or been completely missed, but the PanaFlow HT makes
flow measurements so fast that it will identify the pig in the line and signal a flow error. The expected result is an error
on the LCD, and the SIL Output will go to Fire Low or Fire High, depending on what the Dangerous Detected state is
set to. Once in that state, the flowmeter is designed to remain in that state until an Authorized User intervenes.
There is a simple method for clearing the error. The Authorized User goes into the Program Menu by entering a valid
SIL User password, then the Authorized User exits again without making any changes. This ensures the flowmeter that
an Authorized User is intervening, because the password checks out. This will clear the error.
If the Safety Engineer on site wishes to clear this type of error automatically, the DCS may be set up to do so. It is the
responsibility of the Safety Engineer at the customer site to ensure that this method is properly protected by a password
or other means in the DCS to avoid a risk of clearing errors unwisely.
What follows is the method for setting the DCS to clear a Dangerous Detected state in the flowmeter. The DCS would
issue the following commands over Modbus.
Note:
The SIL User password indicated in step 2 is unique to every flowmeter, so please insert your unique code
where the XXXX is stated.
1. Write “2” to SysReqLevel reg. 0x540 to program “SIL USER”
2. Write SIL User password “XXXX” to SysReq_Password reg. 0x542
3. Write “1” to SysReq_Command reg. 0x544 to execute “logging in”
4. Write “3” to SysReq_Command reg. 0x544; UPMU resets, takes about 1 sec to process reset.
Note:
The DCS will record a Fire Low or Fire High, followed by a return to normal flow measurement after a few
seconds. This may serve to indicate to the Operator when a pig passed through a particular measurement
point.
If there are any questions, please contact GE Service.