Properties of water Is this chap correct?
Discussion
This concerns the Loco Flying Scotsman. Now whilst i know a little of the workings of Steam locomotives ( building a live steam 5in gauge one) This chaps comments confuse me
Watching a video of the loco pulling away recently with the cylinder cocks open, he commented 'amatuerish operation',as it appeared the cocks were open for possibly one or two revolutions.
and in his opinion is bad 'enginemanship'
Now i understood that these were opened to get rid of any water that may have accumulated in the cylinders and to stop the piston 'hydraulicing' and possibly causing damage to the connecting rod, and then closed to get the full use of the expansive property of steam under pressure to get the loco moving. The boiler is pressed at 220psi and has superheaters bringing the temp of the steam up to about 700F
Now i thought that,when the regulator is opened the steam is admitted into the cylinder at 220psi and at 700F, this would press on the piston and be expelled out the cocks and via the valve gear up the blastpipe. At the end of the pipe from the cocks the steam is released and like the spout of a kettle is an 'invisible' vapour until it starts to condense in the outside air. Now this guy states that
I suspect that the excessive use of the drain cocks is introducing water into the cylinders...
As the path of the steam is from boiler via cylinder, both under pressure to atmosphere how does it do what he says? as i would expect the steam temp to convert any excess water into steam for ejection, or does the superheated steam turn into water in the cylinder should the cocks be left open for too long, and if so how?
Hope the question and description doesnt look like too much gobbledegook!
Watching a video of the loco pulling away recently with the cylinder cocks open, he commented 'amatuerish operation',as it appeared the cocks were open for possibly one or two revolutions.
and in his opinion is bad 'enginemanship'
Now i understood that these were opened to get rid of any water that may have accumulated in the cylinders and to stop the piston 'hydraulicing' and possibly causing damage to the connecting rod, and then closed to get the full use of the expansive property of steam under pressure to get the loco moving. The boiler is pressed at 220psi and has superheaters bringing the temp of the steam up to about 700F
Now i thought that,when the regulator is opened the steam is admitted into the cylinder at 220psi and at 700F, this would press on the piston and be expelled out the cocks and via the valve gear up the blastpipe. At the end of the pipe from the cocks the steam is released and like the spout of a kettle is an 'invisible' vapour until it starts to condense in the outside air. Now this guy states that
I suspect that the excessive use of the drain cocks is introducing water into the cylinders...
As the path of the steam is from boiler via cylinder, both under pressure to atmosphere how does it do what he says? as i would expect the steam temp to convert any excess water into steam for ejection, or does the superheated steam turn into water in the cylinder should the cocks be left open for too long, and if so how?
Hope the question and description doesnt look like too much gobbledegook!
XM5ER said:
It sounds like he is typical know-it-all dimwit trying to sound clever.
It does sound that way; it would seem prudent to have the drains open for the first couple of revs after every start in case some water has condensed in the cylinders, with the added bonus of it appearing dramatic to have steam squirting everywhere. There isn't a danger of hydraulicing as the exhaust path is always open, but discharging water through the blast pipe will make an awful mess of the paintwork and the inside of the smoke box.Gassing Station | Science! | Top of Page | What's New | My Stuff