Garry
Active Member
Posts: 45
|
Post by Garry on Aug 1, 2004 18:53:56 GMT
Can anyone please give some advice on the practialities of using automatic cylinder drain valves on piston valve locomotives. I have read that they should only be used on slide valves but I have been told of someone who uses them on piston valves. Are they good for getting rid of a lot of condensate? How do they work, it looks as if they would prevent the water escaping. Does anyone know of a site where I can get the dimensions needed for a 5" pacific loco, or do they have some themselves?
Garry
|
|
|
|
Post by alanstepney on Aug 4, 2004 2:30:21 GMT
I am not keen on automatic valves. They work OK 99% of the time, but it is that odd 1% that concerns me.
Manual valves only rely upon the driver, and it is your own fault if you forget to use them.
The same would apply irespective of the valve type.
They work the same as a safety valve, but set to blow at a few PSI above normal working pressure.
|
|
IP
Involved Member
Posts: 72
|
Post by IP on Aug 4, 2004 11:34:27 GMT
Gents,
I alaways thought that the automatic valves were a safety device to compliment manual valves, I also thought that the auto ones were fitted to the cylinder covers as well as the steam chest.
However I stand to be corrected but can't think why they can only be fitted to engines with slide valves .....or have the 12" / Ft lads been getting it wrong for the last 150 or so years.
Regards, IP
|
|
Garry
Active Member
Posts: 45
|
Post by Garry on Aug 4, 2004 12:02:43 GMT
Thanks for replies chaps but I am only going by the constuction sheet I was given (author William Van Brocklin) about the use for slide valves only. Also there is no mention of setting as it is a loose ball only in a large open chamber. These are to be used in place of the manual ones on the bottom of the cylinders with no mention of as well as others.
|
|
JohnP
Hi-poster
Posts: 186
|
Post by JohnP on Aug 5, 2004 12:33:39 GMT
I can't see the point of having an automatic drain valve in the steam chest of a loco fitted with piston valves. If the valves have any lap then there must be a point when the cylinder is not open to steam or exhaust. At the end of the exhaust part of the cycle there is a period of compression which would cause problems if there was a lot of condensate. This is not a problem with slide valves because thay can be lifted off the valve face by the excess pressure produced.
Rgards,
JohnP
|
|
|
|
Post by GeorgeRay on Aug 5, 2004 18:48:44 GMT
There isn't a lot of point in putting automatic TEXT cylinder drain valves on the steam chests of either type of valve because they are cylinder drain valves.  Seriously though are we talking about pressure relief valves or cylinder drain valves there is a difference. On full size the first is to ensure that where they are fitted the cylinder end covers will not pushed of if someone forgets to use the cylinder drain valves or if priming takes place. Three drain cocks were normally fitted to each cylinder, one each end of the cylinder and one to the steam chest to drain away any accumalation of water. They should normally be left open whenever a locomotive is left standing. |
|
|
|
Post by alanstepney on Aug 6, 2004 21:15:56 GMT
On models, automatic valves are sometimes used instead of the more usual manual one, to release condensate that is in the cylinder during the warming up period.
In theory, they work better than manual ones as they only release trapped water and dont allow steam to go to waste.
That is the theory.
If they work correctly every time, that is fine. However, sods law being what it is, they will jam open, or closed, at the worst possible moment.
As I said earlier, I prefer the manual ones.
|
|
Seriously though are we talking about pressure relief valves or cylinder drain valves there is a difference. On full size the first is to ensure that where they are fitted the cylinder end covers will not pushed of if someone forgets to use the cylinder drain valves or if priming takes place. Three drain cocks were normally fitted to each cylinder, one each end of the cylinder and one to the steam chest to drain away any accumalation of water. They should normally be left open whenever a locomotive is left standing.