Emerson Bettis GVO-C Series Sil Safety Manual page 18

Section 8: Periodic Test and Maintenance Requirements
November 2017
Output Thrust
(Pressure in the cylinder)
Table 6.
Spring Cartridge
Spring
Spring Flange
Head/end flange / bolts
Spring Rod
Spring Container
O-Rings
Pneumatic Cylinder
Piston
Notes:
-
-
-
18
Failure mode detectable by the test:
Component
The ones listed above are the major failure modes of the main components
In case of manual procedure, the detectable failure modes are the same as per automatic
procedure. The test coverage is lower than the one for automatic mode, due to the human
factor
The manual procedure cannot be considered as diagnostic. The test can be considered as
"non-perfect Proof Test", and can be considered in the estimation of PFDAVG, while it is not
considered for the estimation of SFF
Case A: use of a Logic Solver:
1. Pressure transmitter
connected to the cylinder
chamber
2. Analog Input Module
included in the Logic Solver
3. Application SW function
(to compare the actual trend
with the one stored during
SAT)
Case B: use of a PST device:
1. Pressure transmitter
connected to the cylinder
chamber
2. PST device with integrate
SW function
Detectable failure modes
Automatic Procedure
Breakage
Weakened
Worn
Sticking
Breakage
Breakage
Unscrewing
Breakage
Total Breakage
Breakage => External leakage
Sticking
Periodic Test and Maintenance Requirements
SIL Safety Manual
SM-025-GVO Rev. 0
Skilled and trained personnel
(to check audible partial
sticking)
Manual Procedure
As per automatic procedure
As per automatic procedure