Chick cock
The plug valve is a valve with a mostly slightly conical , more rarely a cylindrical shut-off body ( throttle body ), the so-called plug.
Due to the pressure required for sealing and the larger contact surface with the plug valve, a greater torque may be required for actuation than with ball valves and other shut-off valves .
Plug valves are one of the oldest types of shut-off valves and are traditionally made entirely of brass . A truncated cone with a bore through which the liquid or gas flows is mounted in a seat. The plug valve is opened by swiveling the lever and thus turning the shut-off body (usually by 90 °). Chick taps are easy to manufacture. The sealing surface is the conical surface between the seat and the rotatable part. In the case of simple plug taps, tightness is guaranteed by precisely matching the cone to the shape of the housing and applying a sealant to the cone. Hot liquids or solvents can wash away the sealant, especially if they have a low viscosity or are under high pressure.
Chick taps are often used as a tap on beer or wine barrels, rain barrels and laboratory equipment made of glass.
term
In industry, the recess in the molded part in an injection mold is referred to as a mold cavity. The chick is in the nest, which is the name given to the movable shut-off part.
Design features
Chick and housing
In contrast to the ball valve, the shut-off body of the plug valve is designed in the shape of a truncated cone . Due to the conical shape, the plug can simply be pulled into the sealing seat so that it seals through the material pressure. The plug retaining screw must be retightened to compensate for wear and restore the seal. Soft brass is traditionally chosen as the material for the plug and housing, so that both parts wear out together and adapt to one another if there are deviations in shape.
In modern designs, there is usually a sealing bushing made of PTFE between the valve plug and the housing , which is chemical-resistant and can be used up to approx. 220 ° C. At higher temperatures, sealing bushings made of carbon fiber reinforced PTFE are used. The surface pressure between the plug and the housing can be reduced by bulges (pockets) on the inside of the housing. This reduces the actuation force.
Plug valves up to a nominal width of 125 mm are usually operated with a hand lever. In the case of larger nominal widths, worm gears are used for the drive, which also allow a motor drive (e.g. pneumatic, electric or hydraulic).
Special forms
Special forms of the plug valve allow, among other things, several flow paths.
Special plug taps are suitable as control valves. The control characteristic (linear or equal percentage change in the Kv value ) is determined by the shape of the plug hole.
properties
The function of the plug valve is similar to that of the ball valve . In contrast to this, however, a plug valve usually does not have any dead spaces, since the plug bze off the housing. is completely enclosed by the sealing sleeve. A plug valve is therefore also suitable when no part of the medium may remain in the valve. This applies to perishable liquids such as food as well as to some corrosive media. Solids contained in the medium can be deposited in the dead space and hinder the movement of the sealing body. Crystallization can also occur. In some contexts, certain types of plug valve are also referred to as rotary valves . (However, shut-off valves with a disc-shaped throttle body are usually referred to as rotary valves.)
Compared to other fittings, the plug valve has the following advantages :
- Almost dead space-free passage and complete flushing
- free passage without deflection of the flow; therefore, as in the ball valve to clean the pipeline by newts possible
- very small dimensions are possible
- adjustable
- less susceptible to wear than ball valves, as the sealing surfaces (in contrast to the sealing rings of conventional ball valves) do not have any edges that could be sheared off the edge of the plug
Disadvantages are:
- Plug taps with space-saving dimensions can have an increased flow resistance due to through bores that are too small or a constriction of the flow cross-section with a trapezoidal through opening
- Plug valves without gear reduction may require an increased operating torque, especially when they are new
For further advantages and disadvantages see also: Ball valve # Special features
Areas of application
The plug valve is used in particular to shut off liquid media, especially in the chemical (for example in plastics production) and food industries.
Patents
"Rooster with a cup-shaped chick" by Max Büttner around 1955.
Individual evidence
- ↑ GEMÜ glossary ( Memento of the original dated November 18, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 279 kB)
- ↑ Rotary valve / Kükenhahn , In: Schuf.de; accessed in June 2019
- ↑ Product overview & technical data sheets, Valves - Controllers - Drive Technology , Section 10, Page 01, Pre-Vent GmbH; accessed in June 2019
- ↑ Source: https://patents.google.com/patent/DE1194214B/de
