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| Valves https://www.rypn.org/forums/viewtopic.php?f=1&t=6035 |
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| Author: | Seth Jackson [ Wed Jun 11, 2003 11:40 pm ] |
| Post subject: | Valves |
When were piston valves first introduced and what is their advantage(performance, maintenance) over slide valves? Thanks. Seth Wilmington & Western RR sethajackson@hotmail.com |
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| Author: | Tom Gears [ Thu Jun 12, 2003 9:08 am ] |
| Post subject: | Re: Valves |
Seth, I think piston vavles were introduced around the turn of the century. The big advantage is that the steam is balanced over the entire valve making them were more evenly and last longer. Also they would also tend to expand more evenly when they heat up because of the shape, this would make them wear more evenly. I am sure they were probably easier to fabricate and install as well. There is more to it than that but I don't have my books here in front of me right now. I am more of a boiler guy but I think I hit some of the major points. Tommy |
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| Author: | Bill Conklin [ Thu Jun 12, 2003 9:43 am ] |
| Post subject: | Re: Valves |
I believe that piston valves also have greater volumetric efficiency...will flow more- better- faster when combined with advances in port design. Bill staybolt@bellsouth.net |
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| Author: | Roger Mitchell [ Thu Jun 12, 2003 10:22 am ] |
| Post subject: | Re: Valves |
2 things that mandated the use of spool or piston valves were higher steam pressures and the use of superheated steam. D or slide valves did not take well to either. Roger Mitchell Master Mechanic Fort Collins Municipal Railway n0mcr@netzero.net |
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| Author: | Jack Anderson [ Sat Jun 14, 2003 3:58 pm ] |
| Post subject: | Re: Valves |
Many locomotives were converted to superheat and retro-fitted piston valves to the slide valve engines with bolted on conversions. Another advantage is that piston valves generally kept the live steam between the rings, in the spool area, with the exhaust steam directed to the ends of the valve, thereby easing the job of valve rod packing, which had only to seal exhaust pressure. This is referred to as "inside admission". Lima tried to keep their superheated engines slide valve, but their West Coast competitor Willamette quickly realized that only piston valves would work with 200 psi superheated steam. It took a few years, but Lima finally conceded to this fact when they developed their Pacific Coast Shays. Our 1928 70-ton Climax is superheated and has piston valves, but it is "outside admission" (the live steam is at the ends of the piston valve)so they could still use the slide-valve designed valve gear and steam piping to the valve chest. steamrr@mashell.com |
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