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Ballasting by gravity, by water ballst pumps & priming procedure

During ballast water or liquid cargo handling operations, always handle the valves and pumps with care so that there is no sudden change in the pressure or the flow rate of the liquid. On recently introduced larger sized vessels operation hitherto deemed routine, there is a higher possibility of water hammering and/or surging..



AA) Ballasting by gravity

Start the ballasting as per “Common Procedures”

BB) Ballasting by Water ballast pump (WBP)

  1. Ensure the Water ballast pump delivery valve is “Full shut”.
  2. Confirm the ballast suction line has positive pressure, fill up the line with sea water “Common Procedures”
    .
  3. Confirm that the ballast suction line is filled with sea water and “Priming” of the Water ballast pump is completed; by checking the WBP suction gauge pressure indication corresponds to the water head of the Ship’s draft and sea water comes out from the Air purge cock on the suction strainer of WBP.

    “Priming”

    “Priming” is defined as the process of filling up or the filled-up condition of pumps’ suction side with liquid, which is the most vital practice for any centrifugal pumps prior to start up. If the priming is insufficient, the pumps may take in vapor which brings about “Cavitation” and, furthermore, when the “Running Dry Condition” is continued it may result in the burn-out of the mechanical-seal of the pump.

  4. Simultaneously, line-up for relevant WBT(s) shall be done. WBP delivery valve should be opened slightly (about 10%) for some time to ensure safe condition of each part, and then proceed to set up “Normal running”.


Normal running

In many cases speed adjustment is not available for Electric driven WBP, so delivery pressure are controlled only by opening ratio of the delivery valve, When ballasting a WBT, WBP delivery pressure should be slightly higher than the corresponding maximum height for water head of the WBT from the WBP base line. For example, if the height of the WBT is 30M from the base line of the WBP, the delivery pressure of WBP should be slightly higher than 3 kg/cm2.
Above practice is not necessarily to be followed for De-ballasting through the overboard discharge valve above the sea water; free from any back pressure.

Finishing ballasting by gravity

As per Section “Common Procedures / Principle procedure to ‘Stop’ ballast handling by gravity” to close the valves, from the WBT suction filling line valve to the WBP sea chest valve in turn.

Finishing of ballasting using WBP

Procedures for tank-to-tank ballast water shifting

For adjusting ship’s list or other reasons, tank-to-tank ballast water shifting becomes necessary. In this case also, you should mind there is a possibility of “Surging” by an existence of Air Lump: When an Air lump exists in the ballast line between the “Supplying WBT” and the “Receiving WBT”, water flow from “Supplying WBT” rushes into the cavity (air lump), which may damage the downstream valve.
  1. Confirm that the ballast suction line is at positive pressure and then fill it up with sea water as per Section 1. “Common Procedures”.
  2. Close all ballast valves
  3. Open the “Supplying WBT” suction filling line valve slightly (about 10%-open).
  4. Open valves from Supplying WBT side toward Receiving WBT side in turn.
  5. After confirming the level in the “Receiving WBT” is rising, open the “Supplying WBT” suction filling line valve by 100%.


Note-Line-up for ballast operation by gravity
You should always choose the simple and shortest Line-up when shifting ballast water. If possible, the shifting shall be done between 2 tanks with the least difference of water-head to control water flow speed and to complete successful air purging.


Related guideline

  1. Ballast exchange procedure at sea


  2. Practical method for the control of transportation of harmful marine organisms


  3. Safety precautions during ballast operation


  4. Loading of high density cargo and water ballast distribution for bulk carriers


  5. Regulation of pumping system of bulk carriers


  6. Risk of partially filled ballast tanks


  7. Handling water ingress problems in bulk carrier, investigation and countermeasures

Reference publications

  1. MARPOL 73/78
  2. IMO Resolution A.774 (18) – “Guidelines for Preventing the Introduction of Unwanted Aquatic Organisms and Pathogens from Ship’s Ballast Water and Sediment Discharged”
  3. Ship’s “Procedure and Arrangements manual” (Approved by Class)
  4. Guide to Port Entry
  5. US NPDES Vessel General Permit Compliance Manual

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Operation of sea going bulk carriers involved numerous hazards . Careful planning and exercising due caution for all critical shipboard matters are important . This site is a quick reference to international shipping community with guidance and information on the loading and discharging of modern bulk carriers so as to remain within the limitations as specified by the classification society.
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