WHY USE A BALL VALVE VERSUS A GATE VALVE?

With so many different types of valves on the market today, it can be difficult to decide which valve is most suitable for your application. In this article, Yuanda explores the merits of ball valves versus gate valves.

 

Selecting the best valve can make or break your system. Ball valves and gate valves are both designed to restrict and control flow. Which gives better longevity and leak prevention though? Read on to find out.

 

WHAT IS THE MAIN DIFFERENCE BETWEEN BALL AND GATE VALVES?

Ball and gate valves essentially perform the same function. However, their structural qualities are markedly different. Ball valves have a stem and ball, which turn horizontally, and are commonly referred to as “rotational” valves. They are best suited to applications requiring on/off control without pressure drop.

 

Gate valves open by lifting a round or rectangular gate (or wedge) out of the path of the fluid. The sealing surfaces between the gate and seats are planar, so gate valves are often used when a straight-line flow of fluid and minimum restriction is needed.

 

HOW DOES A BALL VALVE WORK?

Ball valves are designed with a ball inside the valve. A ball valve is a form of quarter-turn valve which uses a hollow, perforated, and pivoting ball (called a “floating ball”) to control flow through it. It is open when the ball’s hole is in line with the flow and closed when it is pivoted 90-degrees by the valve handle. The handle lies flat in alignment with the flow when open, and is perpendicular to it when closed, making for easy visual confirmation of the valve’s status.

 

WHICH IS BETTER: BALL VALVES OR GATE VALVES?

Ball valves are durable, performing well after many cycles, and reliable, closing securely even after long periods of disuse. These qualities make them an excellent choice for shutoff applications, where they are often preferred to gates and globe valves. That said, they do lack fine control in throttling applications.

 

Although ball valves tend to cost slightly more than gate valves of comparable quality, the minimal saving is not worth the potential issues that are likely to follow. Moreover, ball valves seal much tighter – and are therefore much less prone to leaks – than gate valves because of their 100 percent shut-off characteristics. Ball valves offer greater longevity, and a lower rate of failure, and are easier to use than gate valves.

 

Advantages and Disadvantages

Due to the differences in operation and design between gate valves and ball valves, both have certain advantages and disadvantages. Depending on your application, one is usually better than the other. Check out our table below to learn the key differences between gate and ball valves.

	Ball valve	Gate valve
Shut off mechanism	Fast shut-off with only a quarter turn (90° turn) to close the valve.	Slow shut off as it requires more than a 360° turn to shut off the valve.
Water hammer	Fast opening and closing may cause water hammer.*	Slow opening and closing reduces the risk of water hammer.*
Visual detection	Open or closed state of valve can be visually detected with position of the handle.	Difficult to detect the open or closed state of valve.
Cost	Typically more expensive than a gate valve of the same specifications.	Typically cheaper than a ball valve of the same specifications.
Installation space	Requires more space than a gate valve to accommodate for quarter turn handle.	Requires relatively less installation space than a ball valve.
Size	Better suited for bore sizes below 2".	Better suited for bore sizes above 2".
Leakage	Provides tight seal even if used after a long period of time.	More prone to leaks than a ball valve.
Durability	Durable and less prone to damage	Valve stem can be prone to corrosion making the valve less durable.

If the flow is abruptly stopped by rapidly shutting off the valve, pressure builds up due to the momentum of the moving medium and this causes a short pressure surge. The pressure surge causes a noise which sounds like the pipes were struck by a hammer. A powerful water hammer can cause a rupture or leak in the system. 

 

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