by William Lafferty » August 7, 2015, 3:14 pm
William, when Cleveland-Cliffs repowered the Frontenac, William G. Mather and Pontiac, each boat was fitted with one large boiler. Do you happen to know why Cliffs did that?
All three were repowered with De Laval cross compound geared steam turbines, 5500-shp, or well over twice their original horsepower, although it is a bit misleading to compare the indicated hp of a reciprocating engine with the shaft hp of a turbine. Anyway, the original three Scotch boilers of each of the trio (the
Mather had water tube Scotch boilers) would have been, I imagine, insufficient to generate enough steam at the pressure required to supply a turbine of that size, especially of the De Laval design. All three conversions used super-heated steam: The boilers of the
Frontenac, for example, operated at 180 psi, very typical for boiler installations of that type back in the day; with the new boiler, the super heated safety valve cutoff was set at 483 psi. The original boilers of the
Mather had a working pressure of 250 psi. The boilers of the
Frontenac and
Pontiac gained around 40% in heating surface area with the conversion; the
Mather's gain, with its water tube boilers, was negligible. Two other factors would have been that the original boilers were coal-fired, so replace rather than convert to oil makes sense under the circumstances, and I'm pretty sure De Laval and Babcock & Wilcox marketed these products together as a proven unit. The use of a single boiler for a turbine was a little unusual it seems. I think all the later Canadian steam turbine lakers had two, many built by B & W, as well as the
Ryerson,
Armco, etc. This may have been since these were repowerings and not specifically-designed installations for newbuilds, but I don't know.
[quote]William, when Cleveland-Cliffs repowered the Frontenac, William G. Mather and Pontiac, each boat was fitted with one large boiler. Do you happen to know why Cliffs did that?[/quote]
All three were repowered with De Laval cross compound geared steam turbines, 5500-shp, or well over twice their original horsepower, although it is a bit misleading to compare the indicated hp of a reciprocating engine with the shaft hp of a turbine. Anyway, the original three Scotch boilers of each of the trio (the [i]Mather[/i] had water tube Scotch boilers) would have been, I imagine, insufficient to generate enough steam at the pressure required to supply a turbine of that size, especially of the De Laval design. All three conversions used super-heated steam: The boilers of the [i]Frontenac[/i], for example, operated at 180 psi, very typical for boiler installations of that type back in the day; with the new boiler, the super heated safety valve cutoff was set at 483 psi. The original boilers of the [i]Mather[/i] had a working pressure of 250 psi. The boilers of the [i]Frontenac[/i] and [i]Pontiac[/i] gained around 40% in heating surface area with the conversion; the [i]Mather[/i]'s gain, with its water tube boilers, was negligible. Two other factors would have been that the original boilers were coal-fired, so replace rather than convert to oil makes sense under the circumstances, and I'm pretty sure De Laval and Babcock & Wilcox marketed these products together as a proven unit. The use of a single boiler for a turbine was a little unusual it seems. I think all the later Canadian steam turbine lakers had two, many built by B & W, as well as the [i]Ryerson[/i], [i]Armco[/i], etc. This may have been since these were repowerings and not specifically-designed installations for newbuilds, but I don't know.