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Harbors: Unloading Procedures

There are a number of procedures that must be followed to properly unload a vessel. These procedures are described below.




There are a number of procedures that must be followed to properly unload a vessel. These procedures are described below.




After the vessel is moored and all safety precautions are taken, the vessel must be grounded to the dock before cargo hoses are connected. To ground a vessel, take the following steps:


        Inspect the grounding system to verify continuity and testing according to applicable standards.

        Make sure the grounding switch is open.


        Make sure the grounding clamp on the ship grounding clamp is attached to a bare metal surface on the hull of the vessel. It may be necessary to sand a spot on the hull to make a good connection.

        Check the grounding system to see that there are no loose connections.


        Close the grounding switch.


Inspecting Vessel


The master of the vessel and the shore petroleum inspector must review the loading plan of the vessel for grades and amount of products carried. Also, they must review the layout of the cargo and the order in which products should be unloaded. Before unloading operations begin, the shore petroleum inspector must check the manifest and  DD Form 250-1 for serial numbers of valve seals. The inspector must verify that each seal is intact on isolation valves and sea suction valves. He must document reasons for missing or broken seals. Ullages, temperatures, and water soundings must be taken on each compartment by ship personnel and witnessed by shore personnel. These readings are recorded on  DA Form 3853-3. Great differences in compartment gages after loading and before discharging must be checked promptly. The vessel's master must explain these differences in a written statement attached to the ullage report.


Sampling and Testing Product


If the product aboard the vessel has been inspected on procurement by the government, unloading operations may begin after a type C test of an all-levels sample of product from each compartment shows no contamination. Multiple tank composite samples must then be sent to the laboratory for type B-1 tests. If the product aboard the vessel has not been inspected on procurement by the government, the laboratory must run a type A test on samples from the upper, middle, and lower portions of each tank or an all-levels composite sample from each tank before discharge. If no testing facilities are readily available, any product in question should be placed in isolated storage until laboratory tests confirm quality.


Connecting Cargo Hose


The steps for connecting the cargo hose to unload a vessel are the same as those used to connect it to load a vessel. See page 4-18 for these steps.


Connecting Loading Arms


The steps for connecting loading arms to unload a vessel are the same as those used to connect them to load a vessel. See page 4-19 for these steps.

Heating Cargoes


The cargo may need to be heated before it is unloaded. See the information on heating cargoes given on page 4-20.


Pumping Product


There are certain procedures that must be followed to unload product from vessel to shore. These procedures are as follows:


        Open the proper valves aboard the vessel so that product will flow from the correct tank to the dock manifold.

        Open the proper shore valves to permit flow to the proper shore tank.


        Start the pumps, and operate them at a slow speed. Closely watch the pumping pressure shown on the pressure gage. The gage is usually in the line near the dock manifold. If too much pressure builds up quickly, it means a valve is closed in the line. In this case, shut down the pumps at once. Do not start pumping again until the problem is corrected.


        Sometimes, shore pumps are used to boost product flow. When this happens, adjust the discharge rate of the vessel and the shore pumps after the pumps are started. This is done to prevent shore location pump fuel starvation and to decrease discharge time.


        Watch all hose and line connections for leaks. If leaks appear, stop the pumps immediately, and fix the leaks before starting again. A line walker should inspect the lines for leaks at least once every hour.


        Gage the shore tanks during the unloading operation only as directed in the orders. The JP-5 and JP-8 shore tanks should not be gaged during unloading operations.


        Carefully watch for changes in the tide and for slack or pull in the hose. Sudden movement of the vessel may cause damage to the hose and loss of product.


        In case of fire on the vessel or dock or near the shore line or tank farm area, stop the transfer operations immediately and close all the valves. If the tank farm is next to the port, disconnect the cargo hose and move the vessel a safe distance from shore.


        When an electrical storm is within a 3-mile radius of the transfer operation, stop transfer operations and close the valves on the vessel and dock. Coordinate on the weather before transfer operations are started. Maintain coordination during transfer operations if an electrical storm is probable. If there is no immediate hazard, the hose may be left connected. If there is an immediate hazard, the hose should be disconnected and drained and the main block valve on shore should be closed.


        When all the product has been pumped from one cargo tank, open the valves of the next tank carrying the same product and close the valves of the empty tank. Be careful not to pump water ashore. The pump should continue operating while tanks are being switched.


        Watch the draft of the vessel during the unloading operation to make sure the vessel maintains proper trim.


        When the shore tank nears capacity, open the valves leading to the next tank with the same product. Top off the first tank at a slower rate, and close the valves when the first tank is full.


        When the last of a series of vessel cargo tanks carrying the same product is almost empty, reduce the flow of product. When all product has been pumped from the last tank, stop all the pumps and close all line valves.


Performing Follow-Up Procedures

Certain follow-up procedures must be performed after a vessel is loaded. These procedures are as follows:


        The petroleum inspector or a representative checks to see that the tank compartments are empty. He then fills out a dry-tank certification on a  DD Form 250-1 or on the vessel's ullage report, or on both. The amount of any product that cannot be pumped ashore will be estimated. The estimate will be entered on the dry-tank certification.


        A representative of the US government does the final shore tank gaging. Sampling is witnessed by an officer or agent of the vessel or another authorized representative.


        The vessel's master may decide not to wait until after the product settles to gage the shore tanks. In this case, the estimated amount received, based on gages taken after unloading and before the end of the settling period, may be entered on  DD Form 250-1. A preliminary check should be made 30 minutes after receipt. Any two successive gages that agree are used as the correct gage.


        Fresh stocks of product should be allowed to settle for about two hours after they are added to shore tanks. After the product has settled, the final official gages are taken and the volume is corrected according to  DA Pamphlet 710-2-2. These readings are used for accountability and are noted on  DD Form 250-1.


        A composite sample, which is a mixture of upper, middle, and lower samples, is taken from each shore tank. The sample is tested according to  MIL-HDBK-200.


        Ballast water is pumped into the proper tanks if the vessel needs ballast to maintain trim during the voyage. Tanks must be clean before ballast is received, and only clean water should be pumped aboard.


        When all the tanks are empty and the ballast is loaded, all compartment hatches are closed and bolted down securely. All ullage sounding holes should be securely covered.


        All line valves should be closed. The cargo hose must be disconnected, and any remaining product must be drained from the hose. Spills are caught in drip pans placed beneath the hose connection. The hose should not be allowed to drain into the water or on the dock. If spills occur, they must be wiped up at once. The hose ends must be covered with blind flanges and gaskets. The hose is stored in a shelter or hose rack.


        The cargo hose must be disconnected, and the grounding switch must be opened. The bonding cable is then disconnected from the ship


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