To know about Non-rising Stem gate valves, we need to understand at first about gate valves. Gate valves are linear-motion valves operated manually which have circular or vertical rectangular discs which can slide across the opening for stopping the fluid flow which acts like the – “Gate”. Based on the stem, there are two types of gate valves – a) Rising Stem Gate Valves with Outside Screw and b) Non-Rising Stem Gate Valves. Choose the particular gate valve as per applications. Get in touch with a top supplier of such gate valves. Keep reading this post to explore more about non-rising stem gate valves.
What are Gate valves and their functions?
Gate valves consist of circular or rectangular discs which allow for ceasing the fluid flow. Gate valves are used especially for isolation purposes, completely closed or open. These valves are not ideal for throttling services as high-velocity flow may cause the open disc (partially) to vibrate & chatter. It can lead to disc erosion. Gate valves consist of a seat, valve body, gland, and spindle along with a wheel to operate the valves. These valves need little space and can hardly obstruct the fluid flow when the gate is completely opened.
What is the construction of gate valves?
Common gate valves are actuated through threaded stems which connect an actuator (like a motor or handwheel) to the gate. These are characterized as either rising or non-rising stem gate valves, relying on which stem end is threaded. Rising stems are rigid and fixed to the gate, it rises and lowers together when the gate valve gets into operation, offering a clear visual indication of the gate valve’s position. When we talk about non-rising Stem gate valves, these are rotated with/ fixed to an actuator. They are intertwined/ threaded with the gate. These valves do have pointers threaded into the stem that indicates the position of the valve as the motion of the gate is latent inside the valve. NRS gate valves are used where vertical space is limited. Gate valves are generally constructed of cast carbon steel, ductile iron, cast iron, stainless steel, gunmetal, alloy steel etc.
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What are non-rising stem gate valves?
Non-rising stem gate valves refer to the outside stem. These types of valves are also known as blind stem wedge gate valves or rotary stem gate valves. In non-rising stem gate valves, the stem turns to close and open the gate but this stem does not move either up or down. When the stem is turned, it moves out or into the NRS valve and that moves the gate to close/ open the valve. These valves contain a handwheel which moves together with the stem and there is neither lowering nor rising of the stem in these valves. The stem remains in contact with the particular flow medium. One of the best advantages of using NRS valves – they take up very less space and you can install an open-close indicator for indicating an open-close degree.
What are the major differences between non-rising stem gate valves and rising stem gate valves?
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As per structural differences
As mentioned earlier, there is a structural difference between both rising stem gate valves and non-rising stem gate valves. While talking about the rising stem gate valves, their structure is that the stem nut present is on the bracket/bonnet. When you close or open the gate, the stem nut is rotated for realizing the raising of the stem. Now let us come to non-rising stem gate valves.The structure of them is – the stem nut is located in the body of the NRS valve and remains in contact with a specific medium when you open or close the gate.
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Variance in the transmission method
The transmission method of rising stem gate valves is – the handwheel steers the nut for rotating in place. The stem gets raised linearly and lowered. In the case of non-rising stem gate valves, the handwheel steers the stem for rotation.
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Space of installation
The rising stem gate valves need a large space for installation. In NRS gate valves, you will not need excess space at the time of installation.
Conclusion
We hope you have liked reading this post on NRS gate valves. So, in non-rising stem gate valves, the stem turns to close or open the gate though the stem present does not move upwards or downwards while turning. Non-rising stem gate valves are used in various applications like potable water transmission, water and wastewater treatment plants etc. Contact a trusted supplier of NRS gate valves.
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