Superheated Steam Water Tube Boilers
Facilities Engineering Jobs - Jobs with Boilers - High Pressure Boilers - Stationary Engineer - Low Pressure Steam - Plant Engineers ry -
Work on Ships - Yachts - Tugboats - Cruise Ships
Marine boilers, such as those in the photo above, were once the heart of many
engine rooms. Boilers generated the steam that drove turbines. Boiler jobs aboard
ships are becoming less common, but they are still common on shore. Follow this
link to learn about a Boiler Plant Equipment Mechanic Job. Aboard a ship, lighting off
a boiler used to be a laborious process. And it would take hours to gradually raise
temperature and pressure in a manner that didn't cause thermal strains on
superheater and water tube elements.
With the high reliability of today's diesel engines, steam has been phased out of
modern ships. There are no air-preheaters, boiler feed pumps, forced draft fans, or
feed water heaters to worry about. Everything is simpler on a large marine diesel.   
The USNS Comfort (T-AH-20), at right and above, is one of two Mercy-class hospital ships
owned by the U.S. Navy. The unarmed vessel is crewed by government civilian mariners and
medical professionals. It is part of the US Military Sealift Command fleet. The vessel is 694' long,
106' wide, and draws 33' of water. Her deep draft reveals her origins as a tanker that was
converted into a hospital ship. She displaces 69,360 tons and makes 17.5 knots, powered by a
steam plant that includes the boilers. (Source USMSC)  
A Babcock & Wilcox sinuous header water tube boiler is pictured below. These
unites were used on Victory Ships. Unlike the gentle saturated steam boilers used
on Liberty Ships (which employed triple expansion steam engines), this hot water
kettle generated superheated steam (see the superheater sections in the drawing -
Courtesy of U.S. Maritime Service Training Manual.
What is Superheated Steam?
Superheated steam means the
steam is reheated after it comes off
the first pass of the boiler tubes.
Unlike Liberty Ships, Victory Ships
used steam turbines. Saturated
steam is "wet" in that it contains
droplets of moisture (which is good
for reciprocating steam engines
because it lubricates the piston and
cylinder surfaces, but disastrous for
high pressure steam turbines
spinning at 3,000 rpm). For turbines,
your steam needs to be "dry", which
is achieved through the superheating
process. The two types of steam
were also different in the danger they
posed to a wiper or oiler making
engine room rounds. A low pressure
saturated steam leak from a pipe
could badly scald a wiper with its
heat and pressure. On the other
hand, a blast of superheated steam
at high pressure could cut a man in
two. Anyone who worked on a turbine
ship treated superheated steam with
great respect.