SIGTTO Guidelines for the Alleviation of Excessive Surge Pressures on ESD for Liquefied Gas Transfer Systems

Published: July 2017

This publication provides advice at every level of liquefied gas carrier operation. It encourages a mutual understanding of safe transfer procedures between designers, engineers and operators of both liquefied gas carriers and terminal loading and unloading systems. Readers are also made aware of the factors contributing to surge pressure hazards and the benefits of a linked ship/shore ESD system in mitigating these.

Table of Contents

1. Introduction and Scope

2. Surge

2.1 What is Surge?

2.2 Liquefied Gas Cargo Transfer Systems

2.3 Secondary Surges

2.4 Line Pack Effect

3. Surge Hazards and Risk Management

3.1 Hazards and Risk Management

3.2 Risk Assessment

3.3 Bowtie

3.4 Bowtie Hazards

3.5 Causal Factors

3.6 Barriers

3.7 Surge Bowtie

4. Recommendations and Guidelines

4.1 Principal Design Recommendations

4.2 Principal Operational Recommendations

Annexes

Surge Technical Background

Surge Pressures in a Typical Loading System

Surge Pressures in a Typical Unloading System

Valves

Design Approach to Alleviate Surge Pressures

Surge Pressure Relief