A valve handwheel is a common type of valve actuator. This means it is used to regulate the opening and closing of a valve manually. There are different types of valve handwheels, and you should understand how they work before you decide to buy one. In this article, we will go into details of different types of valve handwheels, including their designs and specifications, so you'll know what to look out for during your purchase.
In this article we will take a closer look at:
1. Types of Valve Handwheels
> Handwheels Fixed to Stem
> Hammer Handwheels
2. Gate Valve Handwheels
3. Handwheels Standards
4. Handwheel Related Products
> Position Indicators
Valve handwheels fixed to stems provide a mechanical advantage. However, in high temperatures, these types of handwheels fixed are susceptible to thermal binding. When you shut off a valve while it is hot and allow it to cool, it can get stuck, making it impossible for you to reopen the valve. This is an apt description of thermal binding.
A hammer handwheel comprises a primary wheel, lug, and secondary wheel attached to a threaded stem. This attachment allows you to shut the valve tightly for closure. Based on the design, the primary wheel moves through a portion of its turn freely and then hits against the lug on its secondary wheel.
Depending on the design of the valve, you may need to fit in manually-operated gears around the bonnet for additional mechanical advantage. This is especially useful for large valves that can only be operated by two people simultaneously.
The gears provide a more mechanical advantage, giving two individuals the strength and leverage to a single person. Portable air motors reduce the valve's operating time.
Gate valves have a rectangular gate or wedge attached to the path of a flowing fluid. These valves are named as they are because they can stop or allow the flow of fluid ultimately. A gate valve has a threaded stem connecting the handwheel or actuator to the stem of the gate.
Gate valves are used in fully-closed or fully open positions. It would be best if you didn't use them in partially open conditions as it makes it difficult for you to regulate pressure effectively. One reason for this is the fluid's flow rate isn't directly proportional to how wide open the valve is. A gate valve consists of a valve body, seat and disc, a spindle, gland, and a wheel for operating the valve.
Plug disk gate valves, expanding gate valves, parallel gate valves, ball valves, butterfly valves, and wedge gate valves are some of the most common types you'd find in a mechanical tools supply store, whether online or offline. Handwheels for gate valves are made of cast steel, carbon steel, cast iron, stainless steel, and aluminum. They also come in different dimensions and sizes.
Most knife gate valves have handwheels through 24 inches (DN 600). You'll need a low torque bearing handwheel assembly for heavy-duty equipment, consisting of a heavy-duty Fabri-Valve yoke assembly fitted with a roller bearing stem nut.
Another thing to note here is rim-pull which is the amount of force you need to exert on the handwheel to open or close the valve. Typically, rim-pull remains within reasonable limits, but this is not always the case. It may exceed these limits depending on a combination of factors like the valve's service conditions and packing drag. Another common cause of this is when the pressure drops across the valve.
If the rim-pull exceeds reasonable limits, you can use bevel gear operators to regulate the force. Here's a simple chart to help you choose a handwheel for your valve.
Valve handwheels are designed for installation on the yoke of globe valves. As you operate the handwheel, take extra care not to add friction to the actuator. Also, use link mechanisms for handwheels on rotary valves so that control of the valve position is not lost when the handwheel is engaged. Handwheels with gears are connected to pinion shafts to allow one person to operate them.
Valve position indicators (VPIs) use mechanical counters to convert the valve's open and closed positions to electronic signals. With this, you are sure to send out accurate valve signals to your control room and avoid any form of injuries plus damage.
You can install VPIs on new and existing valves, even when they are under pressure. These indicators are handy in explosion-proof areas, and the best part about them is, you don't have to bother about regular maintenance. VPIs provide second safety by detecting valve position independent of the actuator.
A VPI consists of a range of sensors and switches fixed into a protective housing of stainless steel. The body of the VPI and other coupling materials are made from stainless steel 316. It also has a custom-made coupling attached to the valve.
In this article, we've highlighted the most important things you should know about valve handwheels to help you make the best purchasing decision.
At Reid Supply, we provide high-quality valve handwheels in different designs. Beyond valve handwheels and other handwheels, we also stock various machine handles such as crank handles, revolving handles, iron handwheels, and plastic handwheels. Along with positioning indicators and other industrial hardware.
Visit our website today to browse through our catalog and find the right fit for your machinery.
If you have any questions just call us at 1(800) 253-0421 or send an email to firstname.lastname@example.org.