SI157001_RPT - Gasoline Overfill Protection SIS IMMEAS-SIS1 - Layers of Protection Analysis

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Simon Storage Ltd – Immingham East Terminal
Gasoline Import – Layers of Protection Analysis
P & I Design Ltd DOCUMENT NO: SI057001_RPT
2 Reed Street, Thornaby, UK, TS17 7AF ISSUE: G DATE: 29.06.12
Tel: + 44 (0)1642 617444 PAGE 25 OF 34
Fax: + 44 (0)1642 616447
Initiating Event 2
Cause Description Notes No of
events/year
2 Whilst
importing
from a ship,
overfill of
Gasoline Tank
with correct
line up due to
the capacity of
the tank being
less than
expected.
Surveyor performs manual dip prior to the start
of each import operation. 18 Ship Imports per
year. Probability that the manual dip is
incorrect and under-dipped by a metre or more.
(This is the amount considered between normal
fill alert and overfill where the dip reading
could lead to a problem) 9.69x 10-3 based on
HEART Data. (See Appendix 2). Probability
based on historical group site data, for operator
making error over 10 years = 1.35 x 10-4 (See
Appendix 3). Conservative probability of
operator error assumed = 0.1. (Total
Frequency: 18 x .01 /yr). This is conservative
as here it has assumed the worst case scenario
where the quantity being charged is in excess
of the available ullage.
1.8 x 10-1
AND I.E. Modifier 1 Cross Check: Operator / Stock clerk confirm
dip figure with book-stock figures prior to
import. (Using Software) Book-stock is
updated from receipts (from imports) and
exports. The cross check also compares the Bill
of lading against physical dip/ullage.
Probability that incorrect ullage is not picked
up by checks and corrected = 0.065 based on
HEART Data (See Appendix 2). Probability
based on historical group site date, for operator
making error over 10 years = 6.74 x 10-5 (See
Appendix 3)
Conservative probability assumed = 0.1
0.1
Overall Frequency of Initiating Event :
(1.8 x 10-1) x (1 x 10-1)
= 1.8 x 10 -2 per year