2.0 The Difference Between OS&Y Gate Valves and NRS Gate Valves

Difference in Working Principle Between NRS Gate Valve and OS&Y Gate Valves

1. In a non-rising flange gate valve, the lifting screw only rotates without moving up or down, and the only part visible is a rod. Its nut is fixed on the valve disc, and the valve disc is lifted by rotating the screw, with no visible yoke. In a non-rising stem flange gate valve, the lifting screw is exposed, the nut is flush with the handwheel and is fixed (it neither rotates nor moves axially). The valve disc is lifted by rotating the screw, where the screw and valve disc only have relative rotational movement without relative axial displacement, and the appearance shows a yoke-type support.
2. The non-rising stem rotates internally and is not visible; the rising stem moves axially and is externally visible.
3. In a rising-stem gate valve, the handwheel is fixed to the stem, and both remain stationary during operation. The valve is actuated by rotating the stem about its axis, which raises or lowers the disc. In contrast, in a non-rising-stem gate valve, the handwheel rotates the stem, which engages with threads inside the valve body (or disc) to raise or lower the disc without vertical movement of the stem itself. In short, for a rising-stem design, the handwheel and stem do not ascend; the disc is lifted by the stem’s rotation. Conversely, for a non-rising-stem design, the handwheel and stem rise and fall together as the valve is operated.

Introduction of Gate Valves

Gate valves are one of the most widely used valves on the market. They are divided into two types: OS&Y gate valve and NRS gate valve. Below, we will explore their working principles, advantages, disadvantages, and differences in application:

OS&Y Gate Valve, common models include Z41X-10Q, Z41X-16Q, etc.

Working Principle: The gate is raised or lowered by rotating the stem. Since the stem and its threads are outside the valve body and fully visible, the disc’s position can be easily judged by the stem’s direction and location.

Advantages: The threaded stem is easy to lubricate and is protected from fluid corrosion.

Disadvantages: The valve requires more space for installation. The exposed stem is prone to corrosion and cannot be installed underground.

NRS Gate Valve, common models include Z45X-10Q，Z45X-16Q,etc.

Working Principle: This valve has its threaded transmission inside the body. The stem rotates (without moving up/down) to raise or lower the gate internally, giving the valve a low overall height.

Advantages: Its compact design and protected stem allow for use in tight, dusty spaces like ships and trenches.

Disadvantages: The gate position is not externally visible, and maintenance is less convenient.

Conclusion

Selecting the right gate valve depends on your environment. Use rising-stem gate valves in moist, corrosive locations like outdoors or underground. For indoor systems with space for maintenance, non-rising stem gate valves are better due to their easy disassembly and lubrication.

TWS can help. We offer professional valve selection services and a full range of fluid solutions—including butterfly valve, check valve, and air release valves—to meet all your needs. Inquire with us to find the perfect fit.