For any piping system, valves play a pivotal role in controlling and regulating the flow and pressure of different contents such as liquid, gas or oil. When there is talk about valves, it is impossible to not mention globe valves. There are various applications of globe valves but one wonders why they are so much important and what makes them so effective? We will find that out but first, let’s get to know about them.
What is a Globe Valve?
It is a linear motion valve that is specifically designed to start, stop, and regulate the flow in a pipeline. It comprises of a stationary ring seat and a movable disk-type element. The direction of the flow can be handled with the help of a globe valve. An internal baffle is used to separate the spherical body shaped globe valve into two halves. It is also commonly known as a throttle valve.
A globe valve consists of 6 important parts:
- Body: It is the structure of the valve that contains most of the pressure.
- Bonnet: The valve body is provided leak-proof closure with the help of a bonnet.
- Disc (disk) or Plug: It is connected to the stem which is either screwed down or up for the purpose of throttling the flow.
- Stem: It plays a role of a connector between the inside of the valve and the actuator.
- Cage: It is present inside the body of the valve and surrounds the plug.
- Seat: A replaceable, uniform and stable shut off the surface is provided the seat ring.
How They Work
There is an important device in a globe valve that is called baffle. The purpose of the device is to regulate fluid flow. It consists of two parts: a ring-shaped seat and a flat plug. Fluid flow is completely stopped whenever plug fits into the seat. Depending on how much fluid flow you want, you can easily open or close the baffle to acquire the desired result. All in all, globe valves are used to control flow, pressure drop etc.
Types of Globe Valves
There are three body designs of globe valves that are most commonly used. They are:
- Tee Pattern Globe Valves
They have higher pressure drop and lowermost coefficient of flow. They are most commonly used in bypass lines and most importantly near a control valve because of their severe throttling services. They can be used where throttling is only required and pressure drop is not a big problem.
- Angle Pattern Globe Valves
These types of globe valves do not require using one extra weld or an elbow for the purpose of turning the flow directions. Since these valves can handle the slugging effect of pulsating flow, they are most commonly used in applications where there are periods of pulsating flow.
- Wye Pattern Globe Valves
Among other globe valves, Wye pattern glove valves are known for offering the minimum resistance to flow. For a startup or seasonal operations, it is mostly recommended to use them for throttling purposes. They do not show signs of severe corrosion even when they are cracked open for a long time.
Advantages of a Globe Valve
- Its capability of a good shut-off makes it quite likable
- The structure is simple and easy to operate
- There is no need for high maintenance
- As compared to a gate valve, there are shorter strokes
- Modest to good throttling proficiency
- Comes in three types that offer different capabilities
- It can be used as a stop-check valve when the disc is not attached to the stem
- It offers a most dependable form of seating
Disadvantages of a Globe Valve
- As compared to a gate valve, it has a higher pressure drop
- A larger actuator or greater force is needed to seat the valve
- The shutoff flow is over the seat and throttling flow is under the seat
- It requires a large opening and closing power
- The regulation performance can be poor
Applications of Globe Valves
- When there are major considerations such as safety and leak tightness, they are preferably used for low-point drains and high-point vents
- They are used in fuel oil systems
- Cooling water systems due to their flow regulating properties
- Feed water or chemical feed systems
- Extraction drain and condenser air extraction systems
- Turbine lube oil systems
- Turbine drains and seals
- Hot and chill water coils
The Bottom Line
For decades, globe valves were used extensively for various applications and they were also deemed as the industry standard in control valves. They are still preferably used in applications that do not require a constant flow of fluid. Needless to say, these throttle valves are still playing an important role in many fields.