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Immingham East Terminal – Gasoline Overfill Protection
Safety Instrument System
P & I Design Ltd
DOCUMENT NO: SI277001_RPT
2 Reed Street, Thornaby, UK, TS17 7AF
ISSUE:
F
DATE: 31.10.14
Tel: + 44 (0)1642 617444
PAGE 19 OF 29
Fax: + 44 (0)1642 616447
www.pidesign.co.uk7.2.3
Final Element Subsystem
The final element sub-system comprises an electrically operated, spring return solenoid valve
and a air operated spring return pneumatic actuator mounted onto a 90° ball valve. Failure
mode is that the valve will close on loss of electric or pneumatic signal. The solenoid is EExd
certified.
The tanks may contain gasoline at atmospheric conditions. The materials of construction of
the valve is carbon steel with 316L stainless steel ball, on which the stored product has no
chemical effect. The range of specific gravities for the materials to be stored in the tanks is
from 0.798 to 1.2.
The system is a 1oo1 configuration and currently the valve is not utilised as part of the BPCS.
7.2.3.1 Solenoid Valves
The solenoid valves utilised are manufactured by Seitz certified to AK-7/SIL 4.
For a 1oo1 configuration, from the attached calculation (Section 7.2.3.6) it can be seen that a
typical value for the PFD, with a proof test interval of 365 days and a MTTR of 72 hours, for
a seitz CP 0632….oH solenoid valve is 1.02 x 10
-6
. The safe fail fraction for the solenoid
valve is 99%
This value provides a safety integrity level of > SIL 2.
The valve components have been proven to have a very high reliability. However a concern
of failure is the requirement of a clean, water free Air supply to ensure no freezing or debris
enters the valve, and as such it is recommended to install individual filters with automatic
drains to the solenoid valve.
7.2.3.2 Actuated Import Valves
The valves are fitted with open and closed limit switches and the logic solver checks that the
valves have completely closed following each operation prior to system reset.
The valves utilised are standard, full bore ball valves manufactured to internationally
recognised standards. Valves from different manufacturers have been used reliably for many
years at the terminal. The valves supplied for this SIS are trunnion ball valve type. As this
valve is to be utilised in a SIS it has been specified with an oversize actuator to ensure
effective closing.
The actuator is fitted with a vent restrictor for slow closing, this is important, as if the valve
slammed shut, the consequences to the import line and ship could be considerable. It must be
ensured that the slow closing restrictor is protected against un-authorised adjustment,
resulting in the valve being unable to vent and therefore not closing.
The speed of closing the valve is to be set such that following operation of the high level SIF,
the product entering the tank, during the closing time, cannot overspill.