Both ball valves and plug valves play an integral role in the modern plumbing and piping industry. In this guide, we shall compare some key attributes of these plumbing systems.
From valve design, symbol, and working principle to applications – you will find all the information about these valves right here.
What is a Ball Valve?
This rotational motion valve with a quarter-turn employs a spherical closure (the ball) with a hole running through it in the middle.
Turning the handle 90 degrees in one direction aligns the hole with the pipeline and allows fluid to flow; turning it opposite prevents it.
What is a Plug Valve?
A Plug valve is a quarter-turn valve that regulates the fluid flow using a cylindrical or tapered plug with a hole.
Turning the valve causes the plug to align perfectly with the pipeline or misalign, which enables or hinders flow.
Comparing Ball Valve to Plug Valve
Valve Symbol
Ball Valve
There is a diagonal line illustrates where the ball is inside the valve. Other critical aspects include:
- Position Indication
It tells whether a valve is open or closed by looking at the circle with the diagonal line.
- Direction of flow
A ball valve’s sign often includes an arrow pointing toward the direction of the flow.
Plug Valve
- Basic Representation
The form of a plug valve resembles a tapered cylinder or cone with a line running through it.
- Position Indication
The direction of the line within the symbol denotes the position of the plug, much like the ball valve does.
A valve is open when the line is parallel to the flow direction.
- Flow Direction
A plug valve sign may also include an arrow to denote the direction.
Function
Ball Valve
Design and Operation:
As the name suggests, a plug valve is a spherical or round device with a hole within its structure. It is through this hole that fluid flows.
Closing the ball causes it to rotate 90 degrees, which places the hole perpendicular to the flow and completely blocks it.
Quick On/Off Control:
Ball valves can shut off quickly and consistently.
A rapid 90-degree movement of the handle or actuator can swiftly switch them from open to fully closed.
Low Pressure Drop:
Ball valves have little flow resistance when completely opened, causing a low-pressure drop across the valve.
Limited Control for Throttling:
Ball valves have limited control for throttling since they are not for fine flow control or throttling.
Ball valves might become worn out and have a shorter lifespan if you try to open them.
Plug Valve
Design and Use:
With a hole or route through it, a plug valve utilizes a cylindrical or tapered plug.
The plug’s hole lines up with the flow route when open, enabling fluid to pass through. The plug rotates when it is closed, stopping the flow.
Throttling Capability:
Plug valves provide the capacity to precisely control flow rates, making them useful for situations where throttling is necessary.
To precisely control flow, position in a variety of ways.
Sealing Mechanism:
For you to operate a plug valve, a cylindrical or tapered plug must fit into a corresponding seat.
It creates a tight seal and lowers the risk of leaking.
Advantages
Ball Valve
There are many reasons why you can consider ball valve for your applications;
- Quick On/Off control
- Low-pressure drop in a fluid system
- Most valves have compact designs hence durable
Plug Valve
There are many reasons to consider plug valves for your applications;
- Offers an accurate flow control mechanism
- They are suitable for both high-pressure and temperature applications
- These valves offer a tight shut-off
- Valves are easy to maintain
Limitations
Ball Valve
- Limited Throttling Ability
Ball valves are not ideal for applications that call for precise control of flow rates due to their limited throttling capacity.
Ball valves might suffer from higher wear and shorter service lives if you try to open them partially.
- Potential Cavitation Risk
Ball valves may be prone to cavitation in high-pressure situations with abrupt variations in flow velocity. Cavitation can harm the valve and downstream components.
- Not Recommended for Slurry or Viscous Media
High viscosity or abrasive fluids may be tricky for ball valves to manage because the ball design might cause blockage and erosion.
- Risk of Seat Damage
A ball valve’s seat may be vulnerable to abrasive media or high-velocity flow damage based on the material and design of the valve.
- Limited Size Variety
Ball valves come in various sizes, yet making large balls can be more difficult and expensive.
Plug Valve
- Higher Torque Requirement
Plug valves need greater torque to function in bigger diameters or high-pressure applications.
They have an impact on the actuator and driving system selection.
- Slower Opening/Closing Time
Plug valves may operate more slowly than ball valves since the plug must rotate more than once to open or close the valve.
- Potential for Wear in High-Velocity Flow
High-velocity applications wear out the plug and the inside of the valve more quickly due to the spinning movement of the plug.
- Limited to Moderate Pressure Ratings
Plug valves handle a variety of pressures, but they may need to be appropriate for situations involving very high pressures that may call for specialist valves.
- Complex Internal Mechanism
A plug valve’s internal mechanisms may be more complicated than a ball valve, which might increase production costs and maintenance needs.
Design and Structure (Compare Various Parts)
| Ball Valve | Plug Valve |
| Body Usually, metals like cast iron, brass, or stainless steel make up the ball valve’s body. It offers a solid framework and housing for the other valve parts. | Body A plug valve’s body is cylindrical or tapered and comprises alloy metals, cast iron, or stainless steel. |
| Ball It is a spherical closure element with a hole running through the middle. By lining up the hole with the flow route or obstructing it, the ball rotates to regulate the fluid flow. | Plug A hole or route runs through the plug that is a cylindrical or tapered closing piece. It rotates to align the hole with the flow channel or block it, controlling the flow. |
| Stem It attaches the ball to a handle or actuator. Steam transfers the handle’s rotating motion to the ball, enabling a valve to open or close. | Stem The stem joins the handle or actuator to the plug. It transfers the rotating motion to the plug, enabling the valve to open or close. |
| Seats Ball valves have two seats, typically made of soft materials like PTFE (Teflon), which provide a seal when the valve is closed. | Seats One or two seats, composed of PTFE or metal, are in plug valves. |
| Seals and O-rings Prevent leakage around the stem and other potential points in the valve assembly.
| Seals and O-rings Plug valves feature seals and O-rings, similar to ball valves, which stop leaks at the stem and other potential leak locations. |
| Handle or Actuator This is the part of the valve manually connected to an automated system. It controls the movement of the ball within the valve. | Actuator or handle Plug valves provide two control options: a handle for human operation or an actuator for automatic operation. |
| End Connections Ball valves can have various end connections, including flanged, threaded, or welded ones. The valve may be linked to a pipeline system thanks to these connections. | End Connections For integration into diverse pipeline systems, plug valves can have a variety of end connectors, such as threaded, flanged, or welded. |
Working Principle
Ball Valve:
- Closure Element
The main element of a ball valve is the ball, which is a spherical closure element with the hole (bore) punched through the middle of this ball.
- Rotational Movement
A stem is attached to the ball inside the valve body. The ball spins together with the stem whenever the stem is turned (often by moving a handle or actuator).
- Flow Control
The ball’s rotation causes the bore to line up with the flow channel, allowing fluid to pass through.
A 90-degree rotation places the bore perpendicular to the flow, obstructing it.
- On/Off Control
Ball valves work incredibly well for rapid on/off control.
They offer a tight seal when fully closed and permit a complete flow when fully open.
Plug Valve:
- Closure Element
A cylindrical or tapered plug with a hole is a seal element in a plug valve.
- Rotational Movement
The plug is attached to a stem, much like a ball valve.
The stem’s rotation causes the valve body’s internal plug to spin.
- Flow Control
Fluid passes through when the stopper is in line with the flow channel.
Rotating the stopper causes it to block the flow.
- Precise Flow Control
Plug valves are well-known for their superb throttling abilities. The valve can be opened or closed partially to fine-tune flow rates.
- Strong Shut Off
Plug valves minimize leaking by offering a dependable and fast shut-off when fully closed.
Application
Ball Valve
High-Pressure Systems:
Ball valves are appropriate for high-pressure applications, such as petrochemical plants, power production facilities, and oil and gas processing facilities.
Low Viscosity Liquids and Gases:
These fluids, such as water, air, natural gas, and other non-viscous media, are suitable for handling because of their low viscosity.
Corrosive Environments:
In areas with corrosion, including in chemical processing facilities, employ ball valves made with corrosion-resistant materials like stainless steel or specific alloys.
Hydraulic Systems:
They frequently employ hydraulic systems to regulate the flow of hydraulic fluid in machinery and equipment.
Plug valve
Accurate Flow Control:
They are perfect for applications requiring precise flow rate control, such as those in chemical processing, refineries, and pharmaceutical manufacturing, plug valves.
Viscous or Abrasive Media:
They are suitable for handling fluids with greater viscosities and abrasive or slurry-like material. Because of this, they are prime in sectors including mining, pulp and paper manufacturing, and wastewater treatment.
Environments with High Temperatures and Pressures:
Plug valves are effective in processes requiring High Temperatures and Pressures, making them useful for oil and gas production, refining, and power generation.
Conclusion
The ability to precisely regulate flow makes plug valves ideal for applications that involve viscous or abrasive material, whereas ball valves excel in conditions requiring rapid shut-off.
More resources:
Plug Valve – Source: Wikipedia
Brass Ball Valve – Source: DR
Ball Valve – Source: IQS Directory
