Steam & Excursion > Cylinder Cocks

Hi all...........

When a steam locomotive began moving after standing still for a while, the engineer opened the cylinder cocks to blow out water that had accumulated in the cylinder.

• Where in the cab would one find the control device for opening or closing the cylinder cocks?
• What would this device have been?  A lever?  A rod?  A valve handle like one would find on a garden hose?  Something else?

Thanks!
Tom
 

Tom_Greco Wrote:
-------------------------------------------------------
> Hi all...........
>
> When a steam locomotive began moving after
> standing still for a while, the engineer opened
> the cylinder cocks to blow out water that had
> accumulated in the cylinder.
>
>

• Where in the cab would one find the control
  > device for opening or closing the cylinder cocks?

At the Engineer's position.

• What would this device have been?  A lever? 
  > A rod?  A valve handle like one would find on a
  > garden hose?  Something else?

Depending on the age of the locomotive, i.e. very, VERY old locomotives had a mechanical lever and rod/rods arrangement to open & close the cylinder cocks. Later locomotives could have either compressed air operated cylinder cocks (the Engineer would have a small lever within his reach to provide compressed air to open the cylinder cocks), or steam operated cylinder cocks (the Engineer would have a round handled steam supply valve to open and close the cylinder cocks).

• > Thanks!
  > Tom

Can't really speak for other roads, but Frisco was partial to Viloco steam operated cylinder cocks. In front of the engineer is a regular valve where you close it to operate them and open it to provide steam pressure to close them.  Allegedly, if they were full of water and you started the train with them closed, they were spring loaded and the water would force them open to relieve the pressure and stop hydraulic damage.
They worked great on 1522.
 

Slight correction:

Steam closed cylinder cocks
use a dual diameter, Steam closed
Plug-valve to close the smaller
water drain.

The plug has the smaller water plug
closed by a slightly larger diameter
Steam piston to close the water-plug.

So, yes, they are held closed by
Steam pressure. If there is water
under pressure. The steam-closed
Valve is forced open by water pressure, from the moving piston

So, steam-operated cylinder cocks
Are kept closed by steam pressure
, and open when forced open by
Water pressure from a piston while moving.

Since they are Steam closed,
I prefer steam closed cylinder
cocks, to air-operated cocks.

W.

Posted from iPhone



Edited 1 time(s). Last edit at 04/02/25 18:27 by wcamp1472.

Welcome back Wes.

Operationally, it matters not whether they are mechanically, pneumatic, or steam operated - they are used the same way. However, if an engineer fails to open mechanical cylinder cocks when they should be, somethings more likely to break.

That considered, slide valves engines are not likely to be damaged, as the excess back pressure will harmlessly unseat the valves, releasing the water into the underside of the valve chamber into the exhaust port and up the stack. This will then rain down black droplets of sooty water onto anything or anyone within about 100 feet, or so, of the engine. Bad thing to do at a station.

It's good practice to crack the throttle a tiny bit a few minutes before departure to warm the cylinders, exhaust standpipe, and smoke box appliances,and to reduce condensation starting from a station stop.

-LD

wcamp1472 Wrote:
---------------------

> So, steam-operated cylinder cocks
> Are kept closed by steam pressure,
> and open when forced open by
> Water pressure from a piston while moving.

So water in the cylinder gets safely out even if the engineer fails to open the cocks? Did most RRs use that kind of cock?

timz Wrote:
-------------------------------------------------------
> wcamp1472 Wrote:
> ---------------------
>
> > So, steam-operated cylinder cocks
> > Are kept closed by steam pressure,
> > and open when forced open by
> > Water pressure from a piston while moving.
>
> So water in the cylinder gets safely out even if
> the engineer fails to open the cocks?

Yes, since the hydraulic pressure of the compressed water would over-come the boiler pressure steam supply to the cocks, thus opening the cock and expelling the liquid.

Did most RRs
> use that kind of cock?

Have no idea. I know that the SP and UP used the steam type, while the NKP used the air pressure type.

Most small locomotives that one finds running today use the old fashioned lever operated cylinder cocks.

HotWater Wrote:
-------------------------------------------------------
>
> Yes, since the hydraulic pressure of the
> compressed water would over-come the boiler
> pressure steam supply to the cocks, thus opening
> the cock and expelling the liquid.
>
I have seen that stated many times, but have always wondered how well it works.  Realizing that the hydraulic pressure wouldn't even begin to spike until hydraulic lock is actually starting, can the excess water be expelled fast enough to avoid breaking something?  I guess it depends on how close to top-dead-center the piston is and how fast it is moving when it hits the water.

Have you ever witnessed such an event?  I wouldn't ask a hogger to confess to such a thing, but as a fireman, you might have seen or heard it.

Interesting point. How does hydraulic lock work, anyway? Can the whole space between piston and cylinder head get full of water? For that matter, isn't the admission valve always open as the piston nears end of stroke?

Once, I have experienced the relief of steam  cylinder cocks.

It was 2102  on a Benson fan trip fan out of  Norristown, Pa.
On the right side we were going past a steel mill, when the engineer 
widened on the throttle...... on the fireman's side.
we were doing a little over 30 mph, and the engineer 
wanted to accelerate ...

He opened the throttle, increasing pressure in the cylinder .....
At the cylinder's lower pressure steam was in the gaseous state, with 
a 'light throttle' , when he added higher pressure boiler steam
it condensed the cylinder's gas state of water to the liquid 
state in one side of a piston :  A single, loud, sudden  burst 
of steam mad a 'report', like a rifle-shot....and vapor cloud soon 
evaporated...

Only once.... high temperature water popped out.

​W.

Re timz, above...

 

Wes,

We've experienced such "pops" from the cylinder cocks on 4449, 844, and 3985, all of which are equipped with the steam operated type of cylinder cocks. After stating with the cocks open, even after progressing some distance and the cocks are then closed, they might "pop" loudly. The Engineer then re-opens them in order to continue cleaning the moisture.