How to Identify Valve Open or Closed States Easily

Valves are indispensable core components of fluid control systems. They not only regulate the flow direction, pressure, and rate of fluids but also perform multiple critical functions such as connection, cutoff, diversion, and prevention of backflow in crucial moments. These complex tasks make valves essential in pipeline systems.

Today, we will explore how to determine the open or closed state of various common valves—ball valves, butterfly valves, globe valves, gate valves, check valves, and pressure-reducing valves.

Ball Valve Open/Closed State

Ball valves are straightforward and intuitive to assess:

• Open State: When the handle on top of the stem is parallel to the channel, the valve allows fluid flow.

• Closed State: When the handle is rotated 90° left or right, perpendicular to the channel, the valve blocks fluid flow.

It is important to note that while many plastic ball valves use T-shaped handles, they still follow the principles outlined above. The handle should align with the flow direction to indicate which side still has water when the valve is closed.

Butterfly Valve Open/Closed State

Butterfly valves operate similarly to ball valves but feature a different handle and locking mechanism.

This locking mechanism allows positioning between fully open and fully closed states to regulate flow.

Like ball valves, the handle should align with the flow direction in the pipeline.

Image source: iStock

Gate and Globe Valve Open/Closed State

Gate and globe valves with handwheels are slightly more complex to operate than ball or butterfly valves. They typically require manual rotation to determine the state.

• Open State: Rotate the handwheel counterclockwise until the valve is fully open, allowing free fluid flow.

• Closed State: Rotate the handwheel clockwise until it can no longer turn, ensuring the valve is fully closed.

Image source: iStock

Rising Stem vs. Non-Rising Stem Designs

Rising Stem Valves: The handwheel extends outward when open and retracts when closed, providing a visual cue for valve status.

Non-Rising Stem Valves: These require manual confirmation as their status cannot be visually determined.

Check Valve/Pressure-Reducing Valve Open/Closed State

Check valves and pressure-reducing valves differ from manually controlled valves in terms of open/closed state, as they are not entirely dependent on manual operation but are determined by fluid status or pressure.

Check Valve:

The primary function of a check valve is to prevent fluid backflow. Its open/closed state can be determined by observing the flow direction. The fluid should flow in the direction indicated on the valve body. The valve will automatically close when the fluid flows in reverse.

Pressure-Reducing Valve:

A pressure-reducing valve adjusts downstream pressure to maintain a stable output pressure. The open/closed state can be judged by measuring downstream pressure.

• Open State: The valve opens when the system pressure exceeds the set pressure, allowing fluid to flow and reduce pressure.

• Closed State: The valve closes when the system pressure falls below the set pressure, stopping fluid flow.

Using Pressure Gauges and Flow Meters for More Intuitive Judgments

Check Valve:

Install pressure gauges or flow meters on both sides of the check valve to detect pressure or flow changes, helping determine whether the valve is open.

• Open State: The flow meter shows flow, and the pressure gauge readings fall within the normal working range.

• Closed State: The flow meter shows no flow, and the pressure gauge indicates no flow or a pressure of zero.

Pressure-Reducing Valve:

Install a pressure gauge downstream of the pressure-reducing valve to directly check pressure values and determine whether the valve is functioning correctly.

• Open State: When downstream pressure is within the set range, the pressure-reducing valve is functioning normally.

• Closed State: If downstream pressure is too high or too low, it may indicate that the pressure-reducing valve is not properly open.

Image source: iStock

Key Points for Valve Operation

The correct operation of valves directly affects their lifespan and can even determine the safety of the entire system. Below are some important operational recommendations:

Avoid Excessive Force: Many operators tend to use levers or long wrenches to apply excessive force, which can lead to premature valve damage. Valve operation should be smooth and gentle to prevent overexertion.

Slightly Turn Back the Handwheel: For gate valves and globe valves, after fully opening or closing, turn the handwheel back 1/4 to 1/2 turn. This ensures better sealing and prevents overtightening, which could damage the valve.

Role of Bypass Valves: Large-diameter butterfly valves, gate valves, and globe valves are often equipped with bypass valves to reduce the torque required for operation. Before opening the main valve, open the bypass valve to balance the pressure between the inlet and outlet.

Prevent Blockage and Water Accumulation: Newly installed pipelines and equipment often contain debris such as dirt or welding slag. Manual valves left open may have debris stuck on the sealing surface. Use a slightly open position to allow high-speed flow to flush out debris before gently closing the valve.

Address Leakage Due to Cooling: After closing some manual valves, the temperature may drop, causing valve components to contract and creating small gaps in the sealing surface, leading to leaks. In such cases, the valve should be closed again after an appropriate interval.

Other Issues: If operation feels excessively difficult, analyze the cause. For example:

• If the packing is too tight, loosen it slightly.

• If the stem is misaligned, notify maintenance personnel for repairs.

• For valves in the closed state, thermal expansion of the closing element may make reopening difficult. In such cases, loosen the valve cover screws by half to one turn to relieve stress on the stem, then operate the handwheel.

Handling Special Situations

• High-Temperature Valves: When the temperature rises above 200°C, bolts may elongate due to heat, causing inadequate sealing. Perform "hot tightening" on the bolts, but avoid doing this while the valve is fully closed to prevent the stem from locking up and causing difficulties when reopening.

• Cold Weather Conditions (Below 0°C): For valves in steam or water systems that are temporarily idle, open the drain plug on the valve seat to remove condensate or accumulated water to prevent valve cracking due to freezing. For valves that cannot be drained or those used intermittently, ensure adequate insulation.

From ball valves to butterfly valves, gate valves, check valves, and pressure-reducing valves, each type has its unique methods for determining its open/closed state. Operational details significantly impact the lifespan of valves and the safety of the system. By mastering the methods for determining the state of various valves and applying proper operation techniques, you can ensure the stable operation of fluid systems and greatly extend equipment lifespan.

If you have any questions about valve selection, installation, or maintenance, please feel free to contact TFW Valve. As a professional valve manufacturer, we provide high-quality products and solutions to ensure the efficient and stable operation of your system.