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Slide valve: Difference between revisions
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The '''slide valve''' is a rectilinear valve used to control the admission of steam into, and emission of exhaust from, the cylinder of a steam engine. | |||
The '''slide valve''' is a | |||
==Use== | ==Use== | ||
In the 19th century, most steam locomotives used slide valves to control the flow of steam into and out of the [[ | In the 19th century, most steam locomotives used slide valves to control the flow of steam into and out of the [[cylinder]]s. In the 20th century, slide valves were gradually superseded by [[piston valves]], particularly in engines using superheated steam. There were two reasons for this: | ||
* With piston valves, the steam passages can be made shorter. This reduces resistance to the flow of steam and improves efficiency. | * With piston valves, the steam passages can be made shorter. This reduces resistance to the flow of steam and improves efficiency. | ||
* It is difficult to | * It is difficult to lubricate slide valves adequately in the presence of superheated steam. | ||
== Murdoch's D slide valve == | == Murdoch's D slide valve == | ||
The '''D slide valve''', or more specifically '''Long D slide valve''', is a form of slide valve, invented by [[William Murdoch]] and patented in 1799. It is named after the hollow central D-sectioned piston. | The '''D slide valve''', or more specifically '''Long D slide valve''', is a form of slide valve, invented by [[William Murdoch]] and patented in 1799. It is named after the hollow central D-sectioned piston. | ||
This valve worked by "connecting the upper and lower valves so as to be worked by one rod or spindle, and in making the stem or tube which connects them hollow, so as to serve for an induction pipe to the upper end of the cylinder." This allowed two valves to do the work of four. | This valve worked by "connecting the upper and lower valves so as to be worked by one rod or spindle, and in making the stem or tube which connects them hollow, so as to serve for an induction pipe to the upper end of the cylinder." This allowed two valves to do the work of four. | ||
The above description (referring to upper and lower valves) clearly relates to an engine with a vertical cylinder, such as a | The above description (referring to upper and lower valves) clearly relates to an engine with a vertical cylinder, such as a beam engine. Where the cylinders are horizontal, as in a steam locomotive, the valves would be side-by-side. | ||
==Balanced slide valve== | ==Balanced slide valve== | ||
The balanced slide valve was invented by the | The balanced slide valve was invented by the Scottish engineer Alexander Allan. It was not much used in the UK but, at one time, had great popularity in the USA. It gave some of the advantages of a piston valve to a slide valve by relieving the pressure on the back of the valve, thus reducing friction and wear. | ||
==See also== | ==See also== | ||
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==External links== | ==External links== | ||
* [http://oldenginehouse.users.btopenworld.com/slide.htm The Slide Valve] | * [http://oldenginehouse.users.btopenworld.com/slide.htm The Slide Valve] | ||
[[Category:Engine valves]] | [[Category:Engine valves]] | ||
[[Category:Engines]] | [[Category:Engines]] | ||
[[Category:Engine technology]] | [[Category:Engine technology]] | ||
Latest revision as of 04:44, 2 March 2010
The slide valve is a rectilinear valve used to control the admission of steam into, and emission of exhaust from, the cylinder of a steam engine.
Use
In the 19th century, most steam locomotives used slide valves to control the flow of steam into and out of the cylinders. In the 20th century, slide valves were gradually superseded by piston valves, particularly in engines using superheated steam. There were two reasons for this:
- With piston valves, the steam passages can be made shorter. This reduces resistance to the flow of steam and improves efficiency.
- It is difficult to lubricate slide valves adequately in the presence of superheated steam.
Murdoch's D slide valve
The D slide valve, or more specifically Long D slide valve, is a form of slide valve, invented by William Murdoch and patented in 1799. It is named after the hollow central D-sectioned piston.
This valve worked by "connecting the upper and lower valves so as to be worked by one rod or spindle, and in making the stem or tube which connects them hollow, so as to serve for an induction pipe to the upper end of the cylinder." This allowed two valves to do the work of four.
The above description (referring to upper and lower valves) clearly relates to an engine with a vertical cylinder, such as a beam engine. Where the cylinders are horizontal, as in a steam locomotive, the valves would be side-by-side.
Balanced slide valve
The balanced slide valve was invented by the Scottish engineer Alexander Allan. It was not much used in the UK but, at one time, had great popularity in the USA. It gave some of the advantages of a piston valve to a slide valve by relieving the pressure on the back of the valve, thus reducing friction and wear.
