Valve

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A valve is a device that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways.

Note

This article was written from a perspective of distilling and the use of 1/2" standard tubing. This article does not discuss other valve types as they are not practical for this application.

Characteristics

In distilling there are four main attributes we look at when comparing valves:

Start/stop: This is the amount of time it takes to turn fully on to fully off (and visa versus). When deciding why type of valve to use you should understand if you need to turn it on or off in a hurry.
Absolute Volume:Relative to the diameter of the pipe, how much does this valve restrict the flow of water when fully open.
Flow Control: How precisely will controlling the flow matter?
Solids: Can this handle solids or should it be used for pure liquids only.

Major types

Ball Valve

A ball valve is the most common type of valve that is used in distilling due to its low cost. It best used is in situations where the valve will be used fully open or closed like moving water or mash from one container or another. Ball valves offer inconsistent flow rates even when moved to the same position. Used for smaller diameter openings up to 2".

Start/stop: It is very easy to turn fully on to fully off.
Absolute Volume: Ball valves allow full flow of water for a given diameter of pipe.
Flow Control: Flow control is difficult with a ball valve.
Solids: It is able to pass solids like mash. At diameters less than 1" it may be difficult.

Gate Valve

A gate valve is less common. It offers some control over flow while still allowing full volume of fluid to pass. This valve is useful for situations that requires some control but not fine control. Control to a condenser would be a good use.

Start/stop: It is slower to turn fully on to fully off than a ball valve.
Absolute Volume: Gates valves allow full flow of water for a given diameter of pipe.
Flow Control: Flow control fairly easy but not precise.
Solids: Not recommended for solids.

Globe Valve

It offers precise control over flow, but it does not allow full volume of fluid to pass. Due to the limited flow of the 1/2" size it is not recommend for flow control to a condenser, but should serve well for a worm tub for a smaller still (5g or less). For larger diameters globe valves are better than gate valves. Globe valves are also more costly than Gate valves.

Start/stop: It is slower to turn fully on to fully off than a ball valve.
Absolute Volume: Globe valves do not allow free full flow for a given diameter of pipe.
Flow Control: Flow control easy and precise.
Solids: Not recommended for solids.

Needle Valve

Needle valves are used where precise flow control is needed. Needle valves are common in Liquid Management type stills.

Start/stop: It is very slow to fully turn on and off.
Absolute Volume: Needle valves reduce the available volume to pass.
Flow Control: Flow control is easy and precise.
Solids: Do not used with solids.

Butterfly Valve

The closing mechanism is a disk that rotates. Ok for solids like mash. Commonly used for larger diameters from 1" on up.

Start/stop: It is easy to fully turn on and off.
Absolute Volume: Allows full volume for diameter of pipe.
Flow Control: Flow control difficult.
Solids: It is able to pass solids like mash. At diameters less than 1" it may be difficult.

Relief Valve

A relief valve or pressure relief valve (PRV) is a type of safety valve used to control or limit the pressure in a system; pressure might otherwise build up and create a process upset, instrument or equipment failure, or fire. The pressure is relieved by allowing the pressurized fluid to flow from an auxiliary passage out of the system. In distilling we use pressure and vacuum relief valves. Both are normally set to a fixed PSI before they open, depending if they are used for the main boil kettle (5 psi)or in a steam jacket (15 psi or 1 bar).

Start/stop: Relief valves are set to a specific pressure. They remain closed until that pressure level is reached.
Absolute Volume: Not applicable, this is used for vapor/air pressure relief.
Flow Control: Not applicable
Solids: Not applicable



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