The Ultimate Guide to Choosing Ball Screw Gate Valves

Gate valves are used to completely stop or start the flow of fluid through a pipeline by lifting or lowering a solid, rectangular gate. These valves consist of a valve body, seat, disc, spindle, gland and actuator.

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Gate valves are not used to regulate flow — they are designed to be fully open or fully closed. These valves are slower than quarter-turn valves (like ball valves) because they require more than a 360° turn to change the position of the gate, whereas a ball valve requires only a 90° turn to cycle from open to closed or vice-versa. Because of this, gate valves may not be the best choice for applications that require frequent operation or fast cycle times. Gate valves are most commonly controlled by a manual handwheel, but electric and pneumatic actuation options are also available.

While a solid rectangular gate controls the flow of media through a gate valve, a ball valve relies on a pivoting ball to control the flow of liquid or gas. The ball has a bore (or hole) in it that the media passes through, and its position indicates whether the valve is open or closed.

Ball valves can be designed with multiple openings, also known as ports. Two-way ball valves have two ports and are used for basic on/off control. There are also multi-port valves that are used in applications that need to divert media in different directions or that may require more than one source of media.

Since ball valves only require a 90° turn to control the position of the ball, they are a faster option for on/off control than gate valves. Ball valves are available with manual or automated actuation.

As we mentioned, ball valves operate by rotating a ball 90° while gate valves are controlled by moving a gate up or down. Because of their design, ball valves can perform an almost immediate shutoff, whereas gate valves are not able to act as quickly. This makes ball valves a better choice for applications where fast cycle speed is desired.

The 90° operation of ball valves makes them faster to cycle, both manually and with an actuator. This is a benefit in most instances but can potentially cause water hammer in high-pressure applications. If the pressure is high enough, the pipe could weaken or even break, which is why users of manual ball valves should turn the levers slowly to avoid water hammer.

Applications & Use Cases

Gate Valve Uses Ball Valve Uses Shutoff and isolation service for:

• Wastewater Plants
• Power Plants
• Mining
• Process Plants
• Large Water Supply Lines

Gate valves are commonly found in older home plumbing systems.

On/off control for specialized industries including:

• Oil & Gas
• Food & Beverage Equipment
• Automotive
• Vehicle Wash Systems
• Power Processing
• Pharmaceutical
• Chemical Admixtures & Treatment
• Irrigation & Water Treatment Equipment
• Manufacturing Facilities

Ball valves are also found in newer home plumbing systems.

Cost

In the gate valve vs. ball valve debate, cost is a major differentiating factor. Up front, gate valves are less expensive than ball valves, but they can be more susceptible to corrosion which means they will need repairs and replacement more frequently. Ball valves have a higher initial cost, but they are the better choice for longevity since they are more durable and highly effective at forming tight seals.

Maintenance

As we just discussed, gate valves are, in general, less durable than ball valves. In moderate or high cycle applications, gate valves will require routine maintenance or replacement. Most ball valves are designed to be maintenance-free and should be replaced rather than repaired. Three-piece ball valves, however, are designed so that the valve seats and seals can be easily replaced without removing the valve from service. This is why 3-piece ball valves are often used in high cycle or high pressure applications where valve seal failure is likely to occur more quickly. However, 3-piece ball valves typically come with a higher up-front cost than the more popular 1-piece or 2-piece body constructions.

Ultimately, the choice between a gate valve and a ball valve will depend on the application. Gate valves are best suited for applications that require infrequent operation and small installation space. Ball valves are ideal for applications that require fast cycle times, multiple ports, reliable, tight seals and/or frequent operation.

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Here is a recap of what we’ve covered in this article to further assist your decision:

Type of Media

Ball valves create a reliable, tight seal, so they can be used with both liquids and gases. Gate valves are better suited for thick liquids (like oil) since they are more prone to leaking.

Space

Ball valves are smaller than gate valves, but they require more space for operation. A manual ball valve requires a lever that can turn 90° but a manual gate valve can operate with a small handwheel. Some ball valves are available with small form factor handle options, such as wing or round-style handles. These handles work well with smaller pipe sizes but often do not provide enough leverage for larger ball valves.

Application

Gate valves are recommended for liquid media applications that require infrequent operation. Ball valves are used across a variety of industries that require active, quick control of the flow of media.

Ports

Unlike ball valves, gate valves are not widely available in multi-port configurations. If your application requires a multi-port flow pattern, a ball valve may be the right choice.

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Gemini Valve designs, manufactures and distributes performance-engineered ball valves, including custom products. If you have questions about whether a ball valve or gate valve is right for your application, contact us here for more information or to speak with a specialist.

How to choose a better gate valve? Part 1 of this guide covered using standards compliance, materials selection, high-quality processing, and design value as indicators of valve quality and ultimately of the gate valve’s long term performance. The final part of this guide expands on those principles as they relate to the spindle and the seals of the gate valve, then delivers a brief summary of all the checks outlined in this guide so far. With this you can quickly assess whether a gate valve will continue to operate long after installation, or will fail prematurely, leading to costly repair work.

The spindle, also known as the stem, is the core element for gate valve actuation. Inspecting this component for quality before installation can save you in the long term, because if its threaded surface is damaged, which commonly occurs from corrosion, the spindle can abrade the wedge nut, typically made of softer brass material, making the valve harder to operate. The seals around the spindle and bonnet can also be checked to ensure they will not prematurely fail in service, resulting in water leakage.
 

Tip 1: Adequate number of seals

• There should be a minimum of 4 seals here, with 2 between the spindle and the spindle bearing or O-ring carrier and another 2 between the carrier and the bonnet. There should also be a wiper ring on top of the bonnet to avoid the ingress of dirt and other foreign material.
   
• The thickness of the seals must be 3 mm or greater, as thin O-ring seals have less sealing area and will wear out faster.
   

Tip 2: Easy maintenance

• Confirm that the O-rings or other spindle seals can be replaced while the pipeline is in service. Although not needed very often, this can prevent service interruptions and reduce maintenance costs.
   

Tip 3: Corrosion protection of the threads

• Verify that the bonnet gasket interlaces with the bolts. A gasket that does not do this will allow corrosion of the threads in the valve body.

Tip 4: Spindle bearing and/or O-ring carrier are reliably fixed in the bonnet

• Threaded connections are the most prone to damage and/or leakage and should be avoided in favor of a bayonet or double bayonet style connection. The double bayonet connection is the best, as it prevents unwanted unturning of the assembly that could result in the possibility of leakage and also spreads the load on the bonnet coating over a larger area.
   
• For the bayonet style connection, ensure the internal surfaces of the bonnet are completely coated to prevent corrosion.

The following expert spindle checks require additional testing which may or may not be provided by the manufacturer:
 

Tip 6: Spindle material

• Confirm that the spindle material of the gate valve matches what is claimed by the manufacturer. This can be done using a spectrometer, which provides a break-down of a material’s chemical composition.
   
• Based on the chemical composition, you can then calculate or look up the pitting resistance equivalent number (PREN), a reliable indicator for through-wall corrosion resistance. As a general rule, if you are unsure about the corrosivity of the water and/or the soil around your valve, you should choose a spindle material with a PREN value of 25 or greater.

The spindles of Hawle E3 gate valves are cold-rolled, also on the shaft, thereby achieving extremely smooth surfaces. This preserves the wedge nut as well as the spindle sealing O-rings.

By following the recommendations listed throughout Part 1 and Part 2 of this guide, you can be confident that your next gate valve will perform better, last longer, and have a lower lifecycle cost than a lower-quality alternative. The Hawle E3 gate valve meets or exceeds all the best practices explored by this guide. Following the below-summarized inspection points will help you to select a top-quality valve that you can depend on:

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Only high-quality materials

• Are made of top-quality GJS400-15 ductile iron
• Use lead-free materials
• Use a spindle made of 1. duplex stainless steel, which has a chromium content of 21.5% for extremely high corrosion resistance and reliable long-term strength