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How to prevent water hammer and surging during routine ballast operations at sea ?

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..

Common Procedures

AA. For offsetting “Negative pressures” in relevant pipelines to prevent the “Water Hammer Effect ”
Confirm the pressure in the ballast line is “Positive” by the suction gauge on Water Ballast Pump (hereinafter “WBP”) or Water Ballast Eductor (hereinafter “WBED”).

If the line pressure is “Negative”, the following is required to avoid a” Water Hammer” which may be caused by the negative pressure at the initial stage of ballasting : make the line pressure positive prior to ballasting by slightly opening (10% / crack open) the suction valve of the empty ballast tank or the overboard discharge valve which is above the water line.

Note on the in-line-pressure judgment. When the ship’s trim is more than usual and the water remains in the line as well, there is a possibility that the suction gauge does not indicate the negative pressure. The remaining water in the ballast line near the pump may cause the gauge to indicate positive pressure, though the other end of line is under extreme negative pressure.

BB. Procedure for leading water in the lines / Filling up water in WB suction pipes

: Prior to start of ballasting, the relevant lines should be filled up with sea water to prevent the acceleration of the water flow in the ballast suction line. Confirming above (1), open the Water Ballast Pump sea-chest valve 10 % (Slight open) to lead seawater into the line. Moreover, stop operation of the valve until: i) The Water Ballast Pump suction gauge indication corresponds to the water head of the Ship’s draft and indicates a stable reading. ii) Confirm sea water comes out from the Air purge cock on the suction strainer of WBP.

Letting in the water to WBP through sea chest valve:

CC. Prevention of “Surging” / the existence of “Air lump in the line”

When the process AA. and BB. are complet the ballast suction line is filled up with sea water and it is confirmed is at a positive pressure, the “Water Hammer” possibility is quite low, it is the time to proceed Line-up for ballasting on a full scale.

In the meantime, countermeasures for preventing “Surging” possibly triggered by “Air lump” in the line shall be carried out. The line-up should be done observing following basic practices.

  1. Priming the ballast suction line with sea water, ensure successful air purging.
  2. To avoid accelerating water flow in the ballast suction line, start the ballasting operation from the closest tank to the WB sea chest valve, and the de-ballasting from the closest tank to WBP (or WB overboard discharging valve).
  3. To ease the impact of “Surging” by extraction of “Air lump” in the ballast suction line, gentle gravity shall be used for checking water-heads.
  4. Principle procedure to “Stop” the ballast operation by gravity When sustaining Ballasting, De-ballasting or Shifting ballast water internally by gravity, close from the furthermost valve to upstream water source one by one (i.e. from the lowest water-head to higher water-head) so as not to detain enormous volume of air in the ballast suction line,.

Preventing “Liquid block” in suction lines

On a ballast voyage of bulk carriers, when suction lines are filled with water, the suction-filling valve of one of the Water Ballast Tanks shall always be open as a precaution against “Liquid block”; so that the pressure inside ballast line does become negative.

*“Liquid block” is the boosting of internal pressure by liquid volume expansion in closed pipe space due to temperature rise. Sometime, excessive “Liquid block” results in damages to the valve seat ring or other, thus care should be taken to avoid a liquid block in any pipe.

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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