Guide to Valve Handwheel Operation

In industrial production, valves play a crucial role in precisely controlling the flow of fluids. Whether they are pneumatic, electric, hydraulic, or manual valves, the handwheel (or handle) is an indispensable device. In case of sudden situations such as failures of valve actuation mechanisms, the handwheel can help us manually open or close the valve to ensure the smooth progress of the production process. Therefore, mastering the correct operation method of the valve handwheel not only ensures the normal operation of equipment but also effectively prolongs the service life of the valve, providing strong support for the stable production of enterprises.

Before operating the valve handwheel, we must first determine the current state of the valve. Valves typically have two basic states: closed and open. By observing the position of the handwheel or the indication marks on the valve, we can determine which state the valve is in. Generally, clockwise rotation of the handwheel closes the valve, while counterclockwise rotation opens it. However, some special valves may have opposite opening and closing directions. Therefore, before operation, we must carefully check the opening and closing marks on the valve to ensure the accuracy of the operation direction.

After understanding the necessary inspections before valve handwheel operation, we need to delve into the correct operation techniques. These techniques are the foundation for ensuring the safe and efficient operation of the valve and are key to extending its service life.

The sealing performance of a valve is critical to its normal operation. To achieve a good seal, the contact area between the valve core and the seat is often made of elastic rubber material. When opening the valve, we must pay special attention to the smoothness of the force applied. Excessive force can not only damage the sealing surface of the valve but also cause damage to the handwheel itself. Therefore, during operation, we should apply force slowly and evenly to allow the valve to open or close smoothly.

Valve handwheels are designed based on the physical strength of an average person. For handwheels with a diameter less than 320 mm, one person can operate it. However, if the handwheel diameter is greater than or equal to 320 mm, it is permissible for two people to operate together or to use tools such as levers to open and close the valve. However, it is particularly important to note that diaphragm valves and non-metallic valves must not be operated with tools such as levers. These valves are made of relatively fragile materials, and using levers may cause irreparable damage to the valve, thereby shortening its service life.

Gate Valves and Globe Valves: When closing or opening these valves to their limit positions, we should rotate the handwheel back by 1/4 to 1/2 turn. This is to ensure better engagement of the threads and prevent over-tightening, which could damage the valve. Additionally, gate valves and globe valves should not be used as throttling valves, as this can lead to erosion of the valve plate and sealing surface, causing vibration and leakage, and ultimately damaging the valve.

Valves with Bypass Valves: For valves such as butterfly valves, gate valves, and globe valves that have bypass valves, the bypass valve should be opened first when initiating the opening process. This balances the pressure difference between the inlet and outlet, reducing the torque required to open the valve and facilitating smoother operation. When closing the valve, the sequence is reversed: the bypass valve should be closed first, followed by the gradual closure of the main valve.

Steam Valves: Before opening a steam valve, the pipeline must be preheated, and any condensate in the pipe should be drained. During the opening process, it is crucial to operate slowly to avoid water hammer, which can damage the valve and other equipment.

Ball Valves, Butterfly Valves, and Plug Valves: When opening or closing these valves, if the groove on the top of the valve stem is parallel to the passage, the valve is in the fully open position. If the valve stem is rotated 90 degrees to the left or right, making the groove perpendicular to the passage, the valve is in the fully closed position. Some ball valves, butterfly valves, and plug valves indicate an open position when the handle is parallel to the passage and a closed position when it is perpendicular. Operation of three-way and four-way valves should follow the markings for opening, closing, and directional changes, and the movable handle should be removed after operation.

Manual valves are widely used in industrial fields such as petrochemical plants. When operating manual valves, the following points should be noted.

The opening direction of valves generally follows the principle that counterclockwise rotation indicates the valve is open, while clockwise rotation indicates it is closed. Therefore, when operating valves, it is essential to be accurate with the direction to avoid damage to the valve or improper functioning due to incorrect direction.

Valve handles and handwheels are designed for manual operation. Under normal circumstances, manual rotation of the valve is sufficient for opening and closing operations. The use of levers or wrenches is generally not allowed, as this can lead to excessive force and damage to the sealing surface and other components.

When closing or opening gate valves and globe valves to their limit positions, it is necessary to rotate the handwheel back by 1/4 to 1/2 turn. This ensures better engagement of the threads and prevents over-tightening, which could damage the valve components.

Large-diameter gate valves, globe valves, and butterfly valves may have bypass valves. The primary function of the bypass valve is to balance the pressure on both sides of the valve, reducing the force required to open it. Therefore, when opening the valve, the bypass valve should be opened first, followed by the gradual opening of the main valve. When closing the valve, the bypass valve should be closed first, followed by the gradual closure of the main valve.

Some valves may experience slight leakage at the sealing surface after closing due to contraction of the valve components as the temperature drops. In such cases, it is advisable to slightly retighten the valve after closure to ensure proper sealing.

After mastering the correct operation methods for valve handwheels, it is also important to be aware of common incorrect practices. These mistakes can not only reduce the service life of the valve but also lead to equipment failure and even safety accidents.

Some operators are accustomed to using levers and long wrenches to operate manual valves, believing that greater closing force is always better. However, this is a misconception. Experience has shown that, except for impact-type handwheels, over-forceful operation of valves can easily damage the handwheel, handle, scratch the valve stem, and damage the sealing surface. Therefore, it is important to avoid this incorrect practice and follow the design requirements for valve operation.

If a handwheel or handle is damaged or lost, it should be promptly replaced with the correct part. Using a pipe wrench as a substitute is not advisable, as its size and shape may not match the handwheel or handle, potentially causing damage to the valve during operation.

Different types of valves have different operational requirements. For example, diaphragm valves and non-metallic valves must not be operated with levers or long wrenches, and excessive or forceful closing of the valve is also prohibited. Ignoring these special requirements can lead to premature valve failure and even safety accidents.

Inspection and maintenance after valve operation are critical to ensuring the long-term stable operation of the valve and are important measures for extending its service life. Therefore, this step should not be overlooked. Attention to every detail is necessary to ensure that the valve is always in its best working condition.

After operating the valve, it is essential to check its sealing performance to ensure that the valve is in good working condition. If leakage is detected, the cause should be promptly identified and addressed.

Operators should establish a dedicated log or record book to document the operation of various valves in detail. This is particularly important for critical valves, high-temperature and high-pressure valves, and special valves, including their actuation mechanisms. Information such as faults, troubleshooting methods, and replaced parts should be recorded. These records are valuable not only for the operators but also for maintenance personnel and manufacturers, serving as important references. By maintaining a detailed log, responsibilities can be clarified, management can be strengthened, and issues can be identified and resolved in a timely manner to ensure the normal operation of the valve.

High-Temperature Valves: When the temperature rises above 200℃, bolts can elongate due to heat, leading to poor sealing of the valve. In such cases, “hot tightening” of the bolts is necessary. However, hot tightening should not be performed when the valve is fully closed to avoid valve stem binding, which could make future opening difficult.

Low-Temperature Valves: During seasons with temperatures below 0℃, for valves that are not in use and have stopped steam or water flow, it is important to open the valve seat plug to drain condensate and accumulated water to prevent the valve from freezing and cracking. For valves that cannot be drained or those that operate intermittently, insulation measures should be taken.

Adjustment of Packing Gland: The packing gland should not be tightened excessively. It should be adjusted to allow for smooth operation of the valve stem. The belief that a tighter packing gland is always better is incorrect, as it can accelerate stem wear and increase operating torque. Under unprotected conditions, it is not advisable to replace or add packing under pressure.

The correct operation of valve handwheels is vital for the service life of the valve and the normal operation of equipment. By conducting thorough inspections before operation, mastering the correct operation techniques, avoiding common mistakes, and performing careful inspection and maintenance after operation, we can effectively extend the service life of the valve, improve the efficiency and safety of equipment operation. It is hoped that every operator will pay attention to the operating standards of valve handwheels and apply this knowledge to practical work, contributing to the stable production of enterprises and the long-term stable operation of equipment.