What is the difference between rising and non-rising stem gate valves?

Rising stem cast iron gate valve and concealed stem cast iron gate valve are two main structural types of gate valves. The core difference lies in the design and movement of the valve stem, which leads to different operating characteristics, applicable scenarios and maintenance requirements. The following is a detailed comparison between the two:

  1. Structure and working principle

     1.Rising Stem Gate Valve

 Stem design : The stem is exposed, the threaded part is located at the upper part of the stem (not in contact with the medium), and the stem moves up and down synchronously when the gate is raised or lowered.

 Movement mode : When the handwheel is turned, the valve stem nut (fixed on the valve cover or bracket) drives the valve stem to rotate and rise and fall vertically, and the gate moves accordingly.

 Visibility : The valve opening and closing status can be directly judged by observing the lifting height of the valve stem (such as the valve stem is fully raised for full open, and fully lowered for full close).

    2.Non-Rising Stem Gate Valve

Stem design : The stem is hidden in the valve body, with only the handwheel at the end exposed, and the thread is located at the bottom of the stem (in contact with the medium).

Movement mode : When the handwheel is turned, the valve stem rotates in place, and the gate is driven up and down through the internal thread, and the valve stem itself does not rise or fall.

Visibility : The open or closed state cannot be judged by the valve stem position, and it is necessary to rely on the number of handwheel rotations or external indicators.

2. Core Difference Comparison

3. Performance and Application Scenarios

 Advantages of rising stem cast iron gate valve

 Easy maintenance : the valve stem is exposed, and lubrication and replacement of seals do not require disassembly of the valve.

 Status visualization : Suitable for scenarios where valve status needs to be quickly confirmed (such as fire emergency).

 Wear resistance : The valve stem thread does not come into contact with the medium and has a longer service life.

Typical models : Z41T, Z41H (domestic standard), API 600 (international standard).

 Advantages of concealed stem cast iron gate valve

Space saving : low height, suitable for underground or trench installation.

Anti-pollution : The valve stem is hidden to reduce the interference of external dust on the transmission parts.

Economical : Usually cheaper than rising stem gate valve (simplified structure). 

Typical models : Z45T, Z45H, in compliance with GB/T 12234 standard.

4. Selection Suggestions

Scenarios where rising stem gate valves are preferred :

Pipeline systems that require frequent operation or maintenance (such as chemical plants, water treatment).

Scenarios that require high visibility of valve status (such as fire water supply and emergency shut-off).

The medium is clean, non-corrosive and there is ample installation space.

Scenarios where non-rising stem gate valves are preferred :

Space is limited (such as underground pipes, ship cabins).

The medium contains impurities (such as sewage, mud), but attention should be paid to regular maintenance of the internal threads.

Normally open/normally closed valves that do not require frequent operation for a long period of time.

V. Conclusion

Rising stem gate valve : The status is intuitively displayed through the exposed valve stem, which is convenient for maintenance and suitable for above-ground installation.

Non-rising stem gate valve : compact structure, concealed design is suitable for space-constrained or harsh environments, but maintenance is complex.

     Key selection criteria : installation space, medium characteristics, maintenance requirements and status visibility requirements.