Why are there so many different types of control valves? Because there are hundreds of unique applications for them across multiple industries—from metals and mining to food and beverage. With a range of designs for specific uses and conditions, engineers can optimize their process systems with different control valves to improve quality, reduce costs, and cut fugitive emissions.
It is possible to buy custom control valves, precisely engineered to the requirements of your individual process system. But, if you’re new to control valves, it’s helpful to get a grasp of the basics before you dive into the specification process. So, we’ve created a “Control Valves 101” blog series to deliver the knowledge you need.
Below we’ll explore the basic types of control valves that are available, from their common applications to design elements.
Globe control valves
Globe control valves are also known as linear motion or rising stem valves, which makes sense when you see how they move! It’s one of the most commonly used control valves in the process industry because it’s a rugged all-rounder that can be configured and adapted to a huge breadth of applications.
Common industries/applications
Globe control valves can be used anywhere you have to modulate a flow. You’ll find them applied everywhere, from power generation to wastewater treatment.
Advantages
- Versatile design that can be modified in a variety of ways for different applications.
- Reduced spare parts inventories because the same parts can be applied across the process system.
- Maintenance is made easier with top-entry.
- Withstands a wide range of pressures and temperatures.
- Flow characteristic is built into the trim, allowing more accuracy in flow control.
Disadvantages
- Design is larger and heavier than the rotary control valve.
- Thrust required for linear action limits its size.
Design elements
The design elements of a globe control valve are:
- Globe body
- Plug and stem
- Seat ring
- Retainer or cage
- Actuator and stem
- Bonnet
V-notch/segmented ball control valves
A conventional ball control valve uses a hollow, pivoting ball that controls the flow of a medium as it passes through the flow passage. A similar mechanism is used in a v-notch or segmented ball control valve, but the ball has a contoured, v-notch segment carved out.
They excel at completely shutting off flow and they also have good rangeability. This means they can precisely and accurately control a wide range of process conditions.
Common industries/applications
Due to their rangeability and shutoff capability, v-notch/segmented ball control valves are helpful across a wide range of industries where you need precise control of flow rates.
This is particularly true where throttle control with high accuracy and reliability is needed. This includes pulp and paper and metals and mining process systems, where the V-notch/segmented ball control valve’s shearing action facilitates shut-off of fibrous and slurry media.
Advantages
- High capacity and high turndown/rangeability, meaning they can handle high and low flows.
- Designed to be non-clogging, which means they prevent or minimize the accumulation of debris.
- Effective shearing action against fibrous or slurry media such as pulp or biological waste.
- Smaller and more lightweight than globe control valves.
- Larger flow coefficient (Cv) size-for-size, meaning it is more efficient at regulating flow rate.
- Lower torque requirement, which means small actuators are needed to automate them.
Disadvantages
- Only capable of handling relatively low pressure drops.
- Cannot control flow as precisely as a globe control valve.
Design elements
The design elements of a V-notch / segmented ball control valve are:
- Body (which is flanged or flangeless)
- Drive shaft
- V-notch or segmented ball
- Seat ring
- Post or shaft
- Bearings
Eccentric plug rotary control valves
Also known as a rotary globe valve, the eccentric plug rotary control valve has a plug-shaped, flow-restricting component that follows a non-circular (or eccentric) path.
To control flow, the plug works together with a seat ring, which acts as a seal. The plug doesn’t make contact with the seat until it turns within a few degrees of its shutoff position. The plug then rotates (cams) and aligns with the seat ring, forming a seal and stopping flow.
Common industries/applications
The precision, durability and capacity of eccentric plug rotary control valves mean they’re particularly good at maintaining pressure under harsh service conditions. As such, they work well in industries such as food and beverage manufacturing and oil and gas processing.
Advantages
- Frictionless, cammed sealing offers benefits such as reduced wear-and-tear, tight shut-off and lower energy requirements.
- High capacity, meaning they can handle large flow rates.
- Designed to be non-clogging, which means they prevent or minimize the accumulation of debris.
- Smaller and more lightweight than globe control valves.
- Larger flow coefficient (Cv) size-for-size, meaning it is more efficient at regulating flow rate.
Disadvantages
- Only capable of handling relatively low pressure drops.
- Cannot control flow as precisely as a globe control valve.
Design elements
The design elements of an eccentric plug rotary control valve are:
- Body (which is flanged or flangeless)
- Drive shaft
- Eccentric plug
- Seat ring
- Post or shaft
- Bearings
Throttling ball valves
When a ball valve is used as a throttling control device, you would ideally configure it with a reduced port (bore) mechanism. A port (or bore) is a cylindrical flow passage through the center of the ball. When the ball is in a fully open position, the medium passes through the cylindrical flow passage. When the ball is in a fully closed position, the medium cannot pass through.
The port of a full port ball valve equals the pipeline diameter and presents little or no restriction to flow to allow for pigging. Pigging is the process used to clean, inspect and maintain pipelines.
The port of a reduced port ball valve is smaller than the pipe to absorb a small amount of pressure drop.
Common industries/applications
Throttling ball valves are durable and have excellent shutoff. But, they don’t offer the same level of precision flow control as v-notch/segmented ball control valves or eccentric plug rotary control valves. So, it’s ideal for applications where durability is paramount and precise flow rate is less sensitive, such as chemical and petrochemical processing.
Advantages
- Capable of handling high pressures with their proven, Three-Piece Trunnion Mounted Bodies.
- Bonnet extensions are available for high temperature and cryogenic services.
- High capacity, meaning they can handle large flow rates.
- Designed to be non-clogging, which means they prevent or minimize the accumulation of debris.
Disadvantages
- Only capable of handling relatively low pressure drops.
- Cannot control flow as precisely as a globe control valve.
Design elements
The design elements of a throttling ball valve are:
- Body (which is always flanged)
- Drive shaft
- Ball
- Seat ring
- Trunnion post or shaft
- Bearings
High performance/double offset butterfly valves
Butterfly valves control flow rate with a rotating disc. For butterfly control valves in throttling control applications, one type of valve is now the industry standard—high performance butterfly valves (HPBVs).
Also known as double offset valves, they’re notable for having straight-through flow paths and their ability to facilitate solids and viscous media.
Common industries/applications
Any industry that needs constant and large flow rates to be managed will employ HPBVs. This includes process systems where solids or slurries need to be transported over long distances in large-diameter pipes, such as power generation from coal or mining.
Advantages
- Lower cost.
- Suitable for use in large diameter pipes.
- Works well for constant process loads, which means that the process conditions stay relatively stable over time.
- Very high capacity, meaning they can handle the largest flow rates.
- Designed to be non-clogging, which means they prevent or minimize the accumulation of debris.
Disadvantages
- Only capable of handling relatively low pressure drops.
- Intended only for general service applications that don’t require precise throttling.
Design elements
The design elements of a high performance/double offset butterfly valve are:
- Body (including the lug and wafer)
- Drive shaft
- Eccentric disk
- Seat
- Post
- Bearings
Choosing the right type of control valve
Even with this handy guide to the basic types of control valves, it can still be time-consuming to figure out exactly what you need for your critical processes.
Luckily, the Trimteck team is on hand to help. We also offer two quote pathways to make the process of buying custom control valves feel simple. Either share your specs with one of our Applications Engineers or use our AccuValve™ software to gather that information for you. Start your quote today in just a few clicks.
