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Before cargo discharge can begin, the appropriate cargo valves must be opened so that the cargo will flow to the pumps and from the pumps ashore. Careful attention to the proper setting of the valves is required, as the following case studies indicate.

Case studies
A 90,000 DWT crude oil tanker began discharging cargo at a Trieste terminal shortly after midnight. At 0300 oil was discovered on the sea surface and pumping was stopped. The source of the oil was traced to one loose sea valve and one loose line valve in the pumproom. Several tons of oil had escaped, contaminating the harbour, nearby beaches, yachts and small fishing craft. A bond of USD 170,000 was required to be posted to permit the vessel to depart. Final costs of USD 540,000 were paid.
A 120,000 DWT crude oil tanker began discharging crude oil at Quebec in the morning and discovered oil on the nearby sea surface 24 hours later. Oil leakage was traced to a valve in the pumproom not being properly closed. The vessel owner's P&I Club posted a letter of undertaking to permit the release of the vessel. Clean up costs and fines totalling USD 275,000 were paid.

Case analyses
Overboard discharge valves are frequently the cause of pollution incidents and claims against tankers. To minimise the chances of leakage while discharging, they should be subjected to a routine proof test programme to provide early indication of defects. (See section 2.18.1)
When the ship's valves are being set for discharge, the overboard discharge valves in the pumproom should be checked with a valve wrench to see that they are firmly seated. It is obvious that in the cases above, neither of these tests were applied. The result of this neglect was a cost to owners and their liability insurers of more than USD 800,000!

5.17.1 Valve setting programme
Cargo valves will normally be set for the discharging operation while the transfer hoses/arms are being connected. The setting of valves should be done according to a written plan. Each valve to be opened should be identified by a unique identity number or other code. When the cargo system has been set for discharging, the ship's manifold valve at the transfer arm/hose connection should be the only valve closed against cargo flow.

5.17.2 Valve setting procedure
The basic rule for setting cargo valves is that 'any valve not required for the discharging operation must be closed'. The easiest way to ensure this condition is to first close all cargo valves in the ship, then systematically open only those valves to be used for the first step of the discharging operation. This is easily done from an automated tanker's CCR, but more difficult on tankers where manual valves are still used.
The valve setting orders should be used as a checklist. The completed checklist should be signed by the officer in charge of setting the valves.

5.17.3 Valves and valve position indicators
Each cargo watch officer must understand the types of valves used in the cargo system, their correct method of operation, their modes of failure and indications of possible failure.
The cargo officers and pumpmen must fully understand the functioning of the ship's valve position indicators and the modes of failure of the indicators. This is particularly important on automated vessels with CCR operation. Wherever possible, critical valves should be examined visually to ensure that they are in the position indicated by the remote indicator in the CCR. Any valve which shows an ambiguous position signal when operated from the CCR should be considered suspect and not used until it can be examined. It may be necessary to disable the remote function of the valve and operated it locally by hand until necessary repairs can be made. When a valve actuator is disabled a notation on the CCR valve control board, on the CCR status board and in the cargo orders is required.

5.17.4 Independent check
An independent check of the valve alignment must be performed to discover any one-man-errors in the cargo system discharging alignment. After the valves have been set, their positions should be verified by an officer who did not participate in the initial valve setting. Once again, the valve alignment orders should be used as a checklist and the completed audit signed by the verifying officer. Particular care should be taken to check that all drain valves, bypass valves and crossover valves are closed unless indicated to be open.

5.17.5 Pumproom check
The case studies indicate the importance of verifying that the pumproom valves are properly set. Checking that the overboard valves are tightly seated is essential to avoiding accidental overboard leakage while discharging cargo. The closed overboard valves must be sealed and the seal numbers recorded in the log prior to beginning discharge. The independent petroleum inspector should request to see the sealed overboard valves in the pumproom. If he does not, ask him to witness the fact that the valves are sealed and to record the seal numbers and time in his report.
Verify that the cargo pump bypass valves are closed, that the bilges are clear of oil and that no immediate repairs are needed. No repairs to pumproom equipment should be undertaken while discharging. Any necessary repairs should be completed before the pumps are started.

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