What are ball valves?
A ball valve is a precise shut-off valve that controls the flow of liquids or gases in pipelines by a 90° rotation of a drilled ball within the housing. This design allows for quick and reliable shut-off, making the ball valve particularly suitable for use with critical media such as flammable or toxic substances.
Properties of Ball Valves
Ball valves consist of the housing, the name-giving (shut-off) ball, a shaft with bearings and seals, the ball seal, and the hand lever for operation. The shut-off ball is provided with a cylindrical bore and either allows or blocks the passage with a 90° rotation. Therefore, ball valves can be easily and very quickly opened or closed.
Ball valves are used in pipelines for transporting liquids or gases such as water, oil, natural gas, compressed air, etc.
Since they completely shut off the flow, they are also preferred for critical, flammable, or toxic media.
Due to their design, ball valves are not suitable for flow regulation.
Ball valve, one-piece,
reduced passage, soft-sealed
Ball valves come in a variety of designs and can be distinguished by the following characteristics:
Size of the ball hole
They are classified into two variants according to the size of their ball hole, with full or reduced bore
Ball valve, full passage
Full passage
Full passage means that the ball bore has the same inner diameter as the pipeline. The flow losses are extremely low in this case.
Ball valves with full passage are piggable, meaning that the pipeline or the system can be maintained with a special cleaning or inspection device (pig).
Reduced Diameter
In a reduced diameter, the ball bore is smaller than the internal diameter of the pipeline, which can lead to significant flow losses. Therefore, they are specifically used in pipelines where the flow velocity of the medium is to be increased (jet effect).
Ball valve, reduced passage
Ball storage
Ball valve,
ball floating
Floating bearing
Most ball valves are used with a ball supported in a floating manner. In this case, the ball is held in position by the sealing rings arranged on both sides. This simple principle allows for cost-effective manufacturing. However, this type of support is not suitable for high pressures.
Pin bearing
More elaborate in manufacturing is the version with guided ball. Here, pins are attached to two opposite sides of the ball, which are supported in the housing. Due to this pin bearing, only one sealing ring is required. Furthermore, these ball valves can also be used at higher working pressures.
Ball valve,
Ball with pin bearing
Type of ball sealing
Ball valve, soft sealing
Soft-sealing
The “classic” ball valve is soft-sealing and, due to its versatility, is still the most commonly used today. The (ball) sealing rings are made of a plastic, mostly PTFE. The PTFE sealing rings are suitable for most liquids and gases and can be used up to a temperature of +200 °C, depending on the additive, even up to +260 °C.
Soft-sealing ball valves are not suitable for solid-containing media or higher working temperatures.
Metallic sealing
In applications with conveyed solids or at higher working temperatures, metallic ball seals are used. The sealing rings are made of stainless steel or other high-alloy steels, some of which are additionally hardened. Metallic sealing ball valves are suitable for working temperatures of up to approx. +650 °C.
Ball valve, metal sealing,
full passage, plug-supported,
access from above
Connection Types
Ball valves are mainly supplied with the following connection types:
- On both sides with internal or external thread
- One side with internal thread – the other side with external thread
- On both sides with welding ends
- On both sides with flanges
- Compact ball valve for clamping between two flanges
Both sides internal thread / female thread
Both sides external thread
Compact design
Both-sided welding ends
Flanges on both sides
Housing Design
With regard to the housing, the following design types are common
One-piece ball valve
The housing consists of only one component, the passage is reduced, and only an internal thread is possible as connection type.
Ball valve, one-piece housing
Ball valve, two-part housing
2-piece ball valve
Two housing parts are screwed together, design with full or reduced passage, all types of connections are possible.
3-part ball valve
The ball valve consists of three parts (inlet side – middle section – outlet side). This design is particularly maintenance-friendly, as the middle section can be easily removed to either replace it completely or to only replace individual sealing components such as ball and body sealing rings or spindle seals.
Another advantage is that the middle section, including the ball and sealing system, can be combined independently with all types of connections. For example, one side can be equipped with a flange connection while the other side can have a threaded connection or welding ends.
Ball valve, three-piece body
Three-way or Four-way Ball Valve
With full or reduced passage, flange or threaded connection. Instead of a through hole, the ball is provided with an L- or T-shaped hole. This allows for different switching options for distributing to one or two outlets or for mixing the flow medium.
3-way ball valve
Possible switching positions of a 3-way ball valve,
with T or L bore
Actuation Types
Like all shut-off valves, ball valves can also be operated in various ways
- Lever:
The operation is manual through a 90° rotational movement of the lever.
One-piece ball valves with reduced passage are often actuated with a wing handle.
- Electric drive:
The operation is carried out by an electric swivel drive; swivel drives are available for all voltages as well as for direct current, alternating current, or three-phase current.
- Pneumatic- and Hydraulic drives:
These drives are actuated by compressed air (pneumatic) or by oil (hydraulic). Here, a distinction is made between double-acting and single-acting drives.
-
Double-acting drive:
Opening and closing occurs by supplying compressed air or oil. -
Single-acting drive:
Air pressure or oil pressure opens - the drive closes by spring force;
the reverse function is also possible: spring force opens - air/oil closes
Advantages and Disadvantages of Ball Valves
The main advantages of ball valves are as follows:
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Due to their design, ball valves are quite compact.
-
Opening and closing occurs very quickly with a 90° turn.
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Ball valves with full passage can be cleaned.
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Ball valves are absolutely tight-sealing, depending on the design and material, even at high temperatures and pressures.
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With full passage, very high flow rates are possible, high Kvs value, and only slight pressure losses.
These disadvantages contrast with the advantages:
The sealing surfaces of the ball valves can wear out quickly.
At high pressures or large nominal sizes, the shaft must be supported with a pin, leading to higher manufacturing costs.
Ball valves are not suitable for flow regulation.
In the pipeline system, pressure surges can occur due to the rapid closing of a ball valve.
In standard ball valves, the operating medium touches the so-called dead space of the ball valve.
Due to the design, the medium intrudes into the area between the body and the ball in a partially open position, which is referred to as dead space. In the closed state, it is then trapped there, and the medium has no way to expand during temperature fluctuations. This can lead to damage to the sealing system, the ball, and ultimately to operational disruptions.
Dead zones in the ball valve
By means of an elaborate processing, a ball valve can be executed almost "dead space free".
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