04-07-2019, 06:56 PM
(04-07-2019, 08:54 AM)peter scott Wrote: En route the locomotive takes on water and also periodically blows out water from its cylinders.
What do you mean by 'periodically', Peter?
When a locomotive comes to a standstill, the cylinders start to cool down and any remaining steam condenses. When steam is readmitted to start the loco again, some of this will also condense as it comes into contact with the cooler (or even cold) cylinders and pistons.
This causes a problem as, whilst steam can be compressed, water cannot so that, when the piston reaches the end of the cylinder, a hydraulic explosion is possible. I've seen a cylinder to which this has happened with the end completely blown off. It was on a Southern Region Merchant Navy which was immediately withdrawn when the incident happened. (It was subsequently bought for possible restoration because it was in particularly good mechanical condition because of its premature scrapping.)
What had happened is that the footplate crew had either failed to open the drain cocks or shut them again before the cylinders were hot enough when pulling away after a station stop.
Opening the cocks and flushing out the cylinders, then leaving them open until the correct working temperature is reached is a rigidly observed routine whenever the loco (re)starts but I wouldn't expect to see it at any other time except, possibly, if the loco had been coasting downhill for a reasonable length of time, which obviously wouldn't be the case here!
