Thursday, 12 September 2013

Waratah - engine failure and methane gas.

There are two further theories I want to explore in today's post. The first relates to the possibility of total engine failure and potential outcome.The second looks at the remote possibility of the negative buoyancy effects of methane gas rising to the surface, from seabed deposits.

Starting with the power source of the Waratah, as per Lloyd's:


quadruple expansion engines with 8 cylinders of 23, 32 1/2, 46 1/2 & 67 inches diameter each pair; stroke 48 inches; 1,003 nominal horsepower;

5 single ended boilers; 20 corrugated furnaces; grate surface 376 sq. ft.; heating surface 14,967 sq. ft."

Speed: approximately 13 knots (25.0 km/h; 15.5 mph) service speed."

The steam engines operated through twin screws (propellers), which gives us two important clues.
Firstly, failure of one engine is possible, but both simultaneously, unlikely. Secondly, if there were mechanical steering problems, these two engines operating independently could be used to help keep the Waratah on a relatively even heading.

By this stage of steam engine construction the engines were mounted vertically, rather than horizontally which affords more protection.  The more 'exposed' vertical engines (vulnerable to damage) and parts were more efficient with lower maintenance costs than the horizontal alternative. The high pressure cylinders were aft and the low pressure cylinders forward.

From previous posts we can see that there are two potential causes for simultaneous engine failure. The first would have to have been a limited coal dust explosion within the engine room or surrounds. The explosion/s would have to have generated enough shock force to render vital component damage to the twin engines. However, the shock force would have to have been limited in terms of hull and bulkhead compromise.

A second possible source of simultaneous engine compromise could have been due to the explosion of a boiler. We have noted previously that the one boiler covering had a piece of smouldering coal requiring attention and which may have led to latent problems with the casing of that particular boiler. A boiler explosion could be highly destructive as in the case of the SS Sultana. But it is possible that the damage could have been limited to the immediate area of the engine room. Thus, the Waratah would have drifted at the mercy of the building storm. This in turn could have had two potential outcomes, the first being that she founded in the storm and the second, she drifted out into the southern ocean, beyond sight and discovery. There is a further possible cause for mechanical disablement. The rudder could have jammed into one of the screws (propellers) rendering the Waratah un-navigable.

Our second theory for today centres around the issue of methane in the seabed. Tests conducted in laboratory settings have shown that bubbles can sink floating objects. Methane deep in the sediments of the seabed is produced by the microbial reduction of CO2. This methane can escape and rise to the the surface of the sea in the form of bubbles.

Archimedes postulated that in order for an object to float, the density of the liquid has to be greater than the object. If the concentration of the bubbles reduces the density of the sea to less than  the floating object ie Waratah, she would fail to remain afloat and sink. Some argue that the the force of the currents of water the bubbles drag up with them is enough to maintain flotation. However, a further experiment showed that an object is likely to sink despite this counter force.‎

sea bubbles

trawler discovered drifting after the tsunami of 2010

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