Page 194 - International safety guide for oil tankers and terminals

INTERNATIONAL SAFETY GUIDE FOR OIL TANKERS AND TERMINALS

If the flow is to be diverted from one tank to another, either the valve on
the second tank should be opened before the valve on the first tank is
---ใช้เพื่อการศึกษาเท่านั้น---
closed, or pumping should be stopped while the change is being made.
Valves that control liquid flow should be closed slowly. The time taken for
power operated valves to move from open to closed, and from closed to
They are more likely to be severe where long pipelines and high flowชย์นาวี
open, should be checked regularly at their normal operating
temperatures.

11.1.4 Pressure Surges

The incorrect operation of pumps and valves can produce pressure
surges in a pipeline system.

These surges may be sufficiently severe to damage the pipeline, hoses or
metal arms. One of the most vulnerable parts of the system is the
งานห้องสมุด ศูนย์ฝกพาณิ
ship-to-shore connection. Pressure surges are produced upstream of a
closing valve and may become excessive if the valve is closed too quickly.

rates are involved.

Where the risk of pressure surges exists, information should be
exchanged and written agreement reached between the ship and the
terminal concerning the control of flow rates, the rate of valve closure,
and pump speeds. This should include the closure period of remotely
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controlled and automatic shutdown valves. The agreement should be
included in the operational plan. (Generation of pressure surges in
pipelines is discussed in more detail in Section 16.8.)

11.1.5 Butterfly and Non-Return (Check) Valves
Butterfly and pinned back non-return valves in ship and shore cargo
systems have been known to slam shut when cargo is flowing through
them at high rates, thereby setting up very large surge pressures which
can cause line, hose or metal arm failures and even structural damage to
jetties. These failures are usually due to the valve disc not being
completely parallel to, or fully withdrawn from, the flow when in the open
position. This can create a closing force that may shear either the valve
spindle, in the case of butterfly valves, or the hold open pin, in the case of
pinned back non-return valves. It is therefore important to check that all
such valves are fully open when they are passing cargo or ballast.

11.1.6 Loading Procedures

11.1.6.1 General
The responsibility for safe cargo handling operations is shared
between the ship and the terminal and rests jointly with the Master
and the Terminal Representative. The manner in which the
responsibility is shared should therefore be agreed between them
so as to ensure that all aspects of the operations are covered.

11.1.6.2 Joint Agreement on Readiness to Load
Before starting to load cargo, the Responsible Officer and the
Terminal Representative should formally agree that both the
tanker and the terminal are ready to do so safely.

160 © ICS/OCIMF/IAPH 2006