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See also rotary feeder

airflow of rotary valve in two positions

A rotary valve is a type of valve in which the rotation of a passage or passages in a transverse plug regulates the flow of liquid or gas through the attached pipes. The common stopcock is the simplest form of rotary valve. Rotary valves have been applied in numerous applications, including:

• Changing the pitch of brass instruments.

• Controlling the steam and exhaust ports of steam engines, most notably in the Corliss engine.

• Periodically reversing the flow of air and fuel across the open hearth furnace.

In the context of brass instruments, rotary valves are usually found on French horns, and sometimes on other brasses; many European classical trumpet players tend to favor rotary valves, as do some tuba players. American trumpets, however, are almost always equipped with piston valves. Rotary valved instruments use a specific oiling method that involves a needle-thin tube that dispenses oil within the rotors.

For much of the 19th century many professional musicians preferred rotary valve instruments as being more reliable and having faster action, but as improved designs of piston valve instruments were mass produced from the late 19th century on the rotary valve has become much less common. A reason why they have become less common is that the rotary valve makes slurs in music sound a little more uneven and staccato, as opposed to the piston valve, which makes them sound more smooth and natural.

In the industry, a rotary valve (which can also be called Airlock) is often used to enter or extract material from two chamber with different pressure level.

• Valve
• Airlock

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