What is ON/OFF Valve?

An ON/OFF Valve has two states of operation either open or close. It is identical in operation to an electric switch. In other words, the on/off valve is the fluid equivalent of an electrical switch. It either allows the fluid to pass or block through it. A tap to fill an overhead tank is the best example of an on-off valve. The tap has two modes of operation either fully open or fully closed.

These valves are often used for”

  1. Routing process fluid to different locations
  2. Starting and stopping batch processes
  3. Engaging automated safety functions.

What is ON/OFF Valve ?

The following valves come in the category of on/off valve.

  1. Ball Valve
  2. Butterfly Valve
  3. Gate valve
  4. Globe valve

These valves operate in two modes either fully open or fully closed. There is no intermittent stage of valve opening.

A large on/off valve does not hinder the fluid path during a fully open position.

on/off valve characteristics

All the on/off category valves have almost identical characteristics. Only the difference between various on/off valves is the difference of the rotating element. The ball valve has a spherical ball as its rotating element. But, the plug valve has a truncated cone as the rotary element.

The conical shape of a plug valve keeps the valve tightly closed in order to have exceptional sealing.

on/off valve sealing

The following pics show the cut-away ball valve (hand-actuated) in three different positions. It shows the inner workings of all ball valves.

What is ON/OFF Valve ?
Image Courtesy – Instrumentation tools

The left-hand image shows the valve in a closed position The valve prevents fluid to pass through it.

The right-hand image depicts the open position of the valve that allows the fluid to flow through it. In this condition, the bore axis is perpendicular to view. The middle image shows the valve in a partially open condition.

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