LF364001_MNL - Overfill Protection SIS Design Manual

Local Fuel – Shoreham Oil Terminal

Safety Requirement Specification

P & I Design Ltd

DOCUMENT NO: LF364005_RPT

2 Reed Street, Thornaby, UK, TS17 7AF

ISSUE:C DATE: 14.08.15

Tel: + 44 (0)1642 617444

PAGE 5 OF 19

Fax: + 44 (0)1642 616447

2.2

Overview of System

This document has been prepared based on the requirement for a SIL 2 rated system for

Gasoline storage with a Risk Reduction Factor of 200 (Mid-range SIL2).

The purpose of the SIL 2 SIF protection layer is to prevent an overfill and overflow of a gasoline

storage tank (Tanks 1 & 3) leading to a release of product capable of being ignited and possibly

causing a vapour cloud explosion.

This is achieved by use of an independent, to the normal tank level measurement, level switch.

A logic solver provides monitoring of this level and on reaching a predefined value will initiate

the closure of the gasoline pipeline valve independent of the process control.

The original design for the Safety Instrumented System included the shutting down of the

gasoline pipeline valve in the event of a high level in any of tanks 1, 2, 3 or 4. This facility will

be maintained even though tanks 2 & 4 will now be used to store Marine Gas Oil, which is

imported through a different pipeline The tanks have been physically disconnected from the

Gasoline Pipeline. As tanks 2 & 4 have not been removed from the SIS, these tanks will be

tested and maintained as though they are. There will not be simultaneous import of Gasoline

and Marine Gas Oil.

The remaining distillate tanks will also have an independent, to the normal tank level

measurement, level switch. A logic solver provides monitoring of this level and on reaching a

predefined value will initiate an annunciator.

Within the installation, there will be the facility for future tank side valves to be installed on

the gasoline and distillate tanks. See section 4.3

The terminal has an individual SIS panel with logic to operate the Safety Instrumented

Functions associated with all storage tanks. The logic panel is located in a safe area in the

switchroom.