Valves play a critical role in marine and industrial systems by controlling the flow of fluids, gases, and slurries through pipelines. For businesses involved in shipbuilding, petrochemical plants, water treatment, and other industrial applications, choosing the right type of valve can significantly impact safety, efficiency, and maintenance costs.

At Aik Soon Hardware Pte Ltd, a trusted marine and industrial valve stockist and distributor based in Singapore, we often get asked about the difference between rising stem and non-rising stem valves—two commonly used gate valve configurations. In this article, we’ll explain what each type is, explore their pros and cons, and help you decide when to use one over the other.

What Are Rising Stem Valves?

A rising stem valve, also known as an OS&Y (Outside Screw and Yoke) valve, features a stem that moves up and down as the valve is opened or closed. The threaded portion of the stem is located outside the valve body, allowing the stem to rise visibly when the valve is opened and descend when it’s closed.

Key Features:

• The stem is attached to the gate and moves vertically.

• The threads are outside the fluid flow path.

• The position of the stem indicates the valve’s open/closed status.

What Are Non-Rising Stem Valves?

A non-rising stem valve has a stem that rotates in place without moving vertically. The gate inside the valve moves up or down by the rotation of the stem, but the stem itself stays at a constant height.

Key Features:

• The stem stays stationary in height while turning.

• The threads are located inside the valve body, exposed to the flow medium.

• The valve’s open/closed status is not visually apparent from the outside.

Pros and Cons of Rising Stem Valves

✅ Advantages:

• Visual Position Indicator: Easy to see whether the valve is open or closed.

• Thread Protection: External threads are not in contact with the fluid, reducing corrosion risk.

• Ease of Maintenance: Easier to inspect and lubricate stem threads.

❌ Disadvantages:

• Space Requirement: Needs vertical space above the valve for stem movement.

• Exposure: The rising stem can be exposed to environmental elements, which may require protection in outdoor applications.

Pros and Cons of Non-Rising Stem Valves

✅ Advantages:

• Space-Saving Design: Ideal for confined installations where vertical space is limited.

• Compact Size: The overall valve size remains constant, simplifying installation in tight spaces.

❌ Disadvantages:

• No Visual Indicator: Operators cannot see valve position without additional indicators.

• Thread Exposure: Internal threads are in contact with fluid, increasing the risk of corrosion and wear.

• Harder Maintenance: More difficult to inspect or repair without disassembling the valve.

When to Use Rising Stem vs Non-Rising Stem Valves

Conclusion

Understanding the difference between rising stem and non-rising stem valves is essential for selecting the right component for your system. Rising stem valves provide excellent visibility and thread protection, making them ideal for outdoor and industrial setups. Non-rising stem valves, on the other hand, are compact and suitable for tight or enclosed spaces like marine engine rooms.

At Aik Soon Hardware Pte Ltd, we supply a wide range of high-quality marine and industrial valves to suit various applications. Whether you're retrofitting an existing system or building a new one, our experienced team can help you choose the right valve for optimal performance and durability.

Contact us today to learn more about our inventory or to get a quote tailored to your project requirements.