Задвижка против шарового крана: Какой тип клапана лучше?

Industrial valves are crucial for controlling the flow of liquids, gases, slurries or fluidized solids in a wide range of applications. However, with so many options to choose from, selecting the right valve can be challenging.

Two of the most common types of industrial valves are gate valves and ball valves. At first glance, both valves seem very similar – they are used to start, stop and regulate flow. But there are some important differences in how they are designed, their advantages and best use cases.

So should you use a gate valve or ball valve? Here’s a complete guide to help you decide.

How Gate Valves And Ball Valves Work

Let’s start by taking a quick look under the hood to understand how gate valves and ball valves actually work.

Задвижки

As the name suggests, Задвижки use a flat “gate” to control the flow. This gate moves perpendicularly to the flow path to start, stop or throttle the flow.

Here are the key components of a gate valve:

• Тело: Houses the gate and other components
• Капот: Covers the stem and gland packing
• Gate: The plate that blocks or allows flow
• Корень: Connects the gate to the handwheel
• Seat: Gate seal surface when valve is closed
• Packing: Prevents leakage around the stem

To open the valve, you turn the handwheel to lift the gate off the seat. When fully open, the gate no longer obstructs the flow path through the valve body.

Closing it involves lowering the gate back onto the seat to create a tight seal and stop the flow. The valve can also be partially opened to throttle flow if required.

Шаровые краны

In a шаровой клапан, a rotating ball with a bore is used to control flow instead of a gate. As you rotate the ball 90 degrees, the bore lines up with the valve body to allow flow. Rotating it 90 degrees again seals off the flow by placing the ball perpendicular to the flow path.

Ball valves consist of:

• Тело: Houses the ball and stem
• Мяч: Rotating component with a bore
• Сиденья: Ball seal surface when valve is closed
• Корень: Connects ball to handle for operation
• Packing: Prevents leaks between body and stem

Ball Valve vs Gate Valve: Key Differences

Now that you understand what’s inside a gate valve and ball valve, let’s discuss some of the main differences when comparing the two types of valves.

Операция

One of the biggest differences is in how you operate them.

Шаровые краны only need a 90 degree turn to either completely open or close the valve. This 1/4 turn operation makes them very quick to operate.

Задвижки, on the other hand, require you to turn the handwheel multiple 360 degree turns to raise or lower the gate. So they take more time and effort to operate vs ball valves.

Sealing Ability

Both valves provide excellent shut-off when closed. But шаровые краны tend to form slightly better seals as there are fewer gaps for leaks in the design.

This makes them well suited for applications that require minimal fluid leakage when inactive for long periods. For example, buried pipelines handling volatile liquids like crude oil or gases.

Gate valves still seal very well, but may allow small leaks if kept closed for months at a time.

Pressure Ratings

In most cases, you’ll find that Задвижки have higher pressure ratings than ball valves of the same size and material.

Gate valves are typically rated for pressures like 200 psi, 300 psi or even 600 psi for high pressure models.

Ball valves usually max out at around 800 psi for standard models. You can get specialty ball valves that handle pressures up to 1500 psi, but these cost more.

So if you need a valve that can handle really high pressures, a gate valve is generally the better pick.

Flow Control Ability

Both valve types allow you to completely stop flow. But what about regulating the flow?

Шаровые краны excel at quickly starting and completely stopping flow. You can also use them for throttling flow, but only to a certain extent.

Fully open or closed is best for ball valves. Partial openings can damage the ball or seats over time in throttling applications.

Задвижки, on the other hand, are well suited for accurately regulating flow. You can precisely control flow rate by lifting the gate slightly off the seat.

Gate valves also tend to have less erosion issues vs ball valves when used for flow throttling.

Расходы

If cost is a major factor in your project, Задвижки are generally the more economical choice.

Simple gate valves are inexpensive, ranging from $50 to $250 depending on size and material. The pricing remains relatively low even for specialty high pressure or cryogenic models.

Шаровые краны almost always carry a higher price tag. For example, a standard 2” ball valve may cost around $100. That jumps to $250 or more for a high pressure version made of stainless steel or alloy material.

So if your application doesn’t require other capabilities unique to ball valves, gate valves help keep valve budgets under control.

Applications Best Suited For Each Valve

Now that you know the main differences between these two common valve types, let’s discuss which applications they are best suited for.

When To Use A Gate Valve

Here are a few examples of applications where a gate valve makes the most sense:

• Water Networks: Gate valves are extremely common in municipal water distribution systems to start and stop flows. Their slower operation prevents water hammer issues.
• Steam Systems: Used to isolate steam lines as the gate valve body remains cooler compared to other designs.
• Wastewater Lines: The organic material and solids won’t damage the gate as easily as a ball valve.
• High Pressure Applications: Gate valves have excellent seals even at high pressures around 1500+ psi.
• Cryogenic Services: Special “cryogenic” gate valves remain operable even at extremely low fluid temperatures.
• Large Pipe Sizes: Gate valves are available in very large diameters to accommodate huge pipelines.

Essentially, you’ll want to select a gate valve when handling water, steam or other fluids at high pressures, in large diameter pipes or cryogenic conditions.

When To Use A Ball Valve

Here are some examples where a ball valve is usually the better option:

• Fuel Gas Systems: Ball valves virtually eliminate leakage issues when used in natural gas and liquid petroleum pipelines.
• Chemical Processing Lines: The ball surface resists corrosion from chemicals. Ball valves also prevent contamination buildup issues.
• HVAC Systems: Quick 1⁄4 turn operation allows rapidly starting and stopping flows as needed in heating/cooling systems.
• Compressed Air Circuits: Ball valves maintain tight seals even with frequent cycling in high pressure compressed air lines.
• Hydraulic Power Applications: The low pressure drop of ball valves is important for efficiency in fluid power transfer systems.

In summary, you’ll want to use ball valves for quickly starting, stopping or changing direction of gases, hazardous chemicals, and liquids at high cycling frequencies.

Frequently Asked Questions

Here are answers to some common questions about ball valves vs gate valves:

Are ball valves better than gate valves?

There is no definitive “better” option. Ball valves are preferable over gate valves in some applications due to quicker operation, lower contamination risks or better sealing.

But gate valves have advantages like higher pressure ratings, throttling ability and lower cost that make them a superior choice in other applications.

You need to compare the capabilities of each valve against your application requirements to decide which is the better fit.

Can you use a gate valve to replace a ball valve?

It is possible to substitute a gate valve for a ball valve in some situations. For example, lower pressure gas or liquid lines where cycle speed isn’t critical.

However, you may experience flow performance issues if the piping system was designed for a ball valve. It’s best to consult an engineer to ensure seamless interchangeability before attempting to swap valve types.

What is the difference between a gate valve and a ball valve?

The main differences are that gate valves use a gate and screw system to control flow, while ball valves use a rotating ball with a bore. Gate valves require multiple turns to operate vs the quick 1⁄4 turn action of ball valves.

Gate valves also handle higher pressures and allow throttling flow control better. Ball valves typically form tighter seals and have a lower chance of leakage over time.

Why are ball valves better than gate valves?

Ball valves excel in applications needing quick, frequent on/off operation thanks to the 90 degree rotation design. They allow flow in either direction and have low contamination risks. Ball valves also tend to maintain a tight seal over many cycles.

These advantages make them preferable for gas pipelines, chemical lines, hydraulics and other cyclic or bi-directional flow systems.

Why are gate valves used instead of ball valves?

Gate valves have higher pressure ratings and sophisticated throttling control ability compared to ball valves. This makes them well suited for steam, water and other liquid or gas flows that:

• Need to handle very high pressures up to 2000+ psi
• Require precise flow regulation
• Have large diameter pipe sizes
• Risk contamination from a ball valve bore

Заключение

Deciding between a gate valve vs ball valve depends greatly on the specifications and operating conditions of your particular application.

Gate valves are the economical option for handling high pressure fluids, cryogenic temperatures or caustic materials. Their throttling ability also allows smoother flow control.

Ball valves excel when you need to start, stop or change direction of flow frequently. Their tight seals prevent leaks even after long inactive periods.

Now that you understand the pros and cons of ball valves and gate valves, you can make an informed decision on which is better for your specific needs. Utilize the application examples and FAQs in this guide to pick the right valve type for any industrial piping system.