DSK wrote:



A stop-and-lock on a turbine plant takes a bit less skill, since all you
have to do is shut of steam on the ahead throttle and crack open the
astern throttle, then slowly open it further. Less things to break, too.

You would not disengage the main gearbox? Do you think the main turbine
gets spun backwards by the reversing turbine? Two other common methods
are CPP and clutches with reversing gears (the clutches are particularly
interesting from an engineering aspect).

Cheers

A stop-and-lock on a turbine plant takes a bit less skill, since all
you have to do is shut of steam on the ahead throttle and crack open
the astern throttle, then slowly open it further. Less things to
break, too.

Nav wrote:
You would not disengage the main gearbox?

How?

... Do you think the main turbine
gets spun backwards by the reversing turbine?

In most turbine powered ships, yes. The propulsion plant is a locked train.


... Two other common methods
are CPP and clutches with reversing gears (the clutches are particularly
interesting from an engineering aspect).

For what kind of plants? AFAIK clutches are quite rare on steam powered
ships. Diesels, yes... provided they aren't using variable pitch props.

DSK

Nav wrote:


DSK wrote:



A stop-and-lock on a turbine plant takes a bit less skill, since all
you have to do is shut of steam on the ahead throttle and crack open
the astern throttle, then slowly open it further. Less things to
break, too.


You would not disengage the main gearbox? Do you think the main turbine
gets spun backwards by the reversing turbine? Two other common methods
are CPP and clutches with reversing gears (the clutches are particularly
interesting from an engineering aspect).

Cheers

In my experience, with pure steam turbine plants, if you are at "sea
speeds", to stop the HP turbine you first have to pull out the extra
nozzles, then shut down the steam, then open the "guarding valve", and
when the shaft has stopped or nearly so, you can start cracking steam to
the LP turbine .... not the quickest of procedures.
There are no clutches or methods to disengage the main gearbox
(reduction gears).
For direct drive diesel (majority of ships nowadays) there are no
clutches or reversing gears.

otn

otnmbrd wrote:

In my experience, with pure steam turbine plants, if you are at "sea
speeds", to stop the HP turbine you first have to pull out the extra
nozzles, then shut down the steam, then open the "guarding valve", and
when the shaft has stopped or nearly so, you can start cracking steam to
the LP turbine .... not the quickest of procedures.
There are no clutches or methods to disengage the main gearbox
(reduction gears).

Steamboats have not used manually controlled nozzles for many years. The
modern turbine throttle valve uses a lifting beam to sequentially lift a
set of nozzle valves in the steam chest. A hydraulic cylinder lifts the
beam under control of the console throttle lever or wheel in maneuvering
mode or an electronic speed control when at sea speed.

The guardian valve may be operated remotely at the console and may be
selected to open when the throttle is moved astern. The engine does not
have to be stopped before opening the astern throttle and crash stops
are routinely performed after majopr maintenance or shipyard work on the
control system.

Rick

Rick wrote:
otnmbrd wrote:

In my experience, with pure steam turbine plants, if you are at "sea
speeds", to stop the HP turbine you first have to pull out the extra
nozzles, then shut down the steam, then open the "guarding valve", and
when the shaft has stopped or nearly so, you can start cracking steam
to the LP turbine .... not the quickest of procedures.
There are no clutches or methods to disengage the main gearbox
(reduction gears).


Steamboats have not used manually controlled nozzles for many years. The
modern turbine throttle valve uses a lifting beam to sequentially lift a
set of nozzle valves in the steam chest. A hydraulic cylinder lifts the
beam under control of the console throttle lever or wheel in maneuvering
mode or an electronic speed control when at sea speed.

The guardian valve may be operated remotely at the console and may be
selected to open when the throttle is moved astern. The engine does not
have to be stopped before opening the astern throttle and crash stops
are routinely performed after majopr maintenance or shipyard work on the
control system.

Rick

ROFL Shows ya how far back MY steam experience was !!! Waddahey, I'm a
deckie, I ain't even s'posed to know how to get down into the pit.

otn