<A1. SAFETY INSTRUMENTED SYSTEMS INSTALLATION>
A1-2
IM 01R01B30-00E-E 8th edition November 01, 2019-00
All Rights Reserved. Copyright © 2003, Rota Yokogawa
A1.2.2 Diagnostic Response Time
In case of a fault the limit switches will go to their safe fail state immediately.
A1.2.3 Setup
A setup of the flowmeter is not required. Installation shall be done according to the manual.
A1.2.4 Proof Testing
The objective of proof testing is to detect failures within the flowmeter that are not detected by the diagnostics
of the flowmeter. Of main concern are undetected failures that prevent the safety instrumented function from
performing its intended function.
The frequency of the proof tests (or the proof test interval) is to be determined in the reliability calculations for
the safety instrumented functions for which the flowmeter is applied. The actual proof tests must be performed
more frequently than or as frequently as specified in the calculation in order to maintain required safety integrity
of the safety instrumented function.
The following tests need to be specifically executed when a proof test is performed. The results of the proof test
need to be documented and this documentation should be part of a plant safety management system. Failures
that are detected should be reported to Yokogawa.
Proof test for variable area flowmeter RAKD with inductive limit switches
:
When all the tests listed above are executed a proof test coverage of approximately 99 % of possible DU failures
in the variable area flowmeter RAKD can be claimed.
The following tools need to be available to perform proof testing:
•
Measurement instrument to verify output status of the limit switches
The person(s) performing the proof test of the Yokogawa RAKD variable area flowmeter should be trained in
SIS operations including bypass procedures, flowmeter maintenance and company management of change
procedures.
Step
Action
1
Take appropriate action to avoid a false trip
2
Inspect the device for any visible damage, corrosion or contamination.
3
Force the variable area flowmeter RAKD to reach a defined "MAX" threshold value and verify
that the inductive limit switch goes into the safe state.
Note: only applicable if RAKD is equipped with a "MAX" limit switch.
4
Force the variable area flowmeter RAKD to reach a defined "MIN" threshold value and verify
that the inductive limit switch goes into the safe state.
Note: only applicable if RAKD is equipped with a "MIN" limit switch.
5
Restore the loop to full operation
6
Restore normal operation