Rising stem valves have stems that rise with the gate, providing a visual indication of whether the valve is open. There are two types of rising stem valves, one with a threaded nut and one with a threaded stem. Non-rising stem valves have gates that move up the stem, but no visual indication of their state.
A rising stem is a type of valve mechanism in which the valve stem rises together with the gate, disc or globe when opened. This gives a good visual indication of whether or not the valve is open because the raised stem is clearly visible. Rising stem valves may have handles or static wheels where the stem rises from the center of the handle or handles when opened or which lift with the stem.
Vertical acting valves typically have a gate or disc that obstructs the liquid flow path when closed. These gate valves are lifted vertically by a valve stem when the operating handle or wheel is turned. This opens up the flow channel of a valve and allows the unimpeded passage of liquid through the valve. There are two basic types of internal gate and stem used on this type of valve: non-rising stem and rising stem. Non-rising stem designs raise the gate around the stem and rising stem types feature a stem and gate that move up and down together.
Rising stem valve types are also divided into two different types. The first is a valve with a handle to which a threaded nut is attached. The valve stem is threaded with a similar thread and passes through the stem nut and down to the valve plug. As the valve wheel is turned, the stem is pulled through the center of the handle, thus pulling the gate up and opening the valve in the process. With this valve variant, the handle rotates but does not go up with the stem.
The second type of rising stem valve also features a threaded stem that passes through a matching thread in the valve bonnet. In this design, the handle is attached to the stem and when turned it rises with the stem as it rotates through the hood thread. Apart from this difference, the functioning of the two types is similar. One of the good features of both is that they give a good visual indication at a glance whether they are open or not.
Non-rising stem valves function similarly but have a gate with a threaded hole through which the similarly threaded stem passes. When the handle is turned, the gate moves up the stem opening the flow path. This type of valve gives no outward physical clues of its state and relies on a pointer or dial to indicate whether or not it is open.
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