Friday, 21 July 2017

ENTRAIN WATER.

If a coal bunker fire required flooding of that particular bunker to gain control of flames and smoke, a factor called water entraining comes into play. In effect the amount of coal would absorb or retain about 30% of the total coal weight, preventing this component of water from being ejected by bilge pumps. 

Let us create a hypothetical scenario: Waratah's starboard side lower deck alongside casing - 137.5 tons is on fire. Water is being played onto this coal and the bunker flooded. This weight could be increased by 41.25 tons to 178.75 tons by entrained water, creating a list to starboard. Furthermore the bilge pumps are being choked by the coal dust saturation of the free water to be eliminated. This further increases the list to starboard - free water effect. With each degree of list, this would reduce the starboard freeboard by at least 6 inches. Waratah would roughly have had a starting point freeboard aft of 9.5 ft.. Theoretically the ship would have been compromised by a list of only 19 degrees. In order to avoid a list to this fatal extent, Captain Ilbery might have elected to lighten Waratah, increasing freeboard, by discharging water from ballast tanks 1 (129 tons) and / or 8 (222 tons) and keep flooding the affected bunker; or allow the fire to burn out of control, spreading to other bunkers and holds. The result of the former action could worsen the situation considerably by reducing GM, increasing top heaviness factor, and further exacerbating the list with free water within the partially emptied tank/s. An example of this is the Clan Gordon which heeled completely over during such an operation to trim the stern. If lead concentrates and carcasses shifted, well it would all be over in minutes.

If Waratah was attempting to return to Durban due to coal bunker fire that was gaining the upper hand, it must have been a terrifying time with excruciating decisions to be made. 





Rena, 20 degrees list - all over for Waratah.

Apprentice Sydney Lamont of the Clan MacIntyre claimed that Waratah was heeling like a yacht when she overhauled them. His claim flew in the face of his officers and captain who maintained that Waratah was upright and steaming strongly. If Lamont's untruthful account had been true, it would have all been over for the Waratah by 9.30 am, 27 July, 1909!!


Thayer, G. David. First to Die: The Tragic Loss of the SS Vestris (Kindle Locations 253-255). Rapidsoft Press ®, jointly with Our American Stories ® LLC. Kindle Edition.

2 comments:

Stuart Flood said...

Another good case of a lot of weight high up causing a fatal list is the troop transport Lafayette (the French line's Normandie). She was being converted into a troop ship after the states entered the war and seized her. A lot of water was pumped into her upper decks to fight a fire which caused her to become top heavy and roll over in her New York berth.

andrew van rensburg said...

It seems, Stuart, that one couldn't win in many cases of a fire on board. Thank you for the example of the Lafayette!