Rising Stem Gate Valve VS Non-rising Stem Gate Valve

Gate valves are widely used in pipeline systems as a shut-off device. It can be divided into rising stem gate valves and non-rising stem gate valves, and what are the differences between these two types of gate valves?

• The stem of rising stem gate valves is exposed and can be seen, while the stem of non-rising stem gate valves is inside and is invisible from the outside. In other words, the lead screw on rising stem gate valve is visible while non-rising stem one is not.
• Difference between working principle. When the non-rising stem gate valve is opened or closed, the wheel and stem are connected together and relatively stationary. It is opened and closed by rotating the stem at a fixed point to drive the wedge up and down. However, for rising stem gate valves, the wedge is lifted or lowered by threaded drive between stem and wheel. In other words, wedge moves up and down together with stem and the wheel is always at the fixed point.
• The transmission thread of the non-rising stem gate valves is inside the valve body and the stem rotates in place during opening and closing, thus we cannot judge whether the valve is opened or closed. Contrarily, the transmission thread of the rising stem gate valve is visible and the position of wedge can be easily judged.
• The installation space of non-rising stem gate valve is relatively smaller while rising stem type requires larger installation space due to the large height when it is fully opened.
• Rising stem gate valve: The stem is outside the valve body, which is convenient for maintenance and lubrication. Non-rising stem gate valve: The stem is inside, which is difficult to maintain and lubricate. Stem is vulnerable to direct media erosion, thus damaging the valve. Rising stem gate valves are applied to a wider range of applications.

The advantages and disadvantages of rising stem gate valves:

• Small fluid resistance, sealing surface by less media erosion and scour
• Easy opening and closing
• Flow direction of media is not restricted.
• Short structure length, wide applications
• Erosion and abrasion easily occur between sealing surface, which is difficult for maintenance.
• Larger external dimension requires more space when opening.

The advantages and disadvantages of non-rising stem gate valves:

• The height of the valve is always the same, so installation space is small and this type is suitable for gate valves with large diameters or with limited installation space. Generally, it should be equipped with an open and close indicator to indicate the degree of opening and closing.
• The stem thread is unable to be lubricated and is directly eroded by media, which is easily to be damaged.