A globe valve is a kind of valve that is used to control flow in a pipeline. It consists of a movable plug or disc element where a stationary ring seat in a generally spherical body. Globe valves are closing down valves. They exhibit linear motion in which the closure member moves squarely on and off the seat.
The design of a globe valve necessitates two types of changes in the flow direction. This results in resistance in liquid lines and objectionable pressure drop. Globe valves are installed with a special purpose. They ensure the flow is up through the seat ring and it is against the bottom of the disc. The result prevents dirt and debris from accumulating above the disc.
Here is a quick guide on how you can choose the right globe valve for different industrial applications:
1. The Main Application Standard
This is the first and one of the most important factors. You must keep this factor in mind when choosing a globe valve. There are two primary standards available in the valves market. One is ASME (USA) and the other is EN (Europe).
You will use one of the above standards depending on where the plant or facility exists. This important information can easily be found in the technical specifications of an application.
In ASME standards, you will likely find the indication of pressure class in terms of # (lbs.) and “ (inches) when it comes to the size. Meanwhile, the pressure class is usually indicated in PN. The size is indicated in DN as well as in EN standards.
Keeping in mind, this is not the only case for the variety of valves available in the market.
Even though you might see an indication that the globe valve has PN 100 and DN 400. It is not necessary that the valve is in accordance with EN standards. Many valves have mixed standards in today’s world. It is always recommended to check twice and clear the standards with the manufacturer of ball valve china. Click here for more info.
2. Body Materials
The materials which are used in the main components of your globe valve may greatly vary. This usually depends on the properties of the process media. The engineer who is responsible for specifying the valve must ensure that the materials are compatible with the process media. This includes gas, steam, fluid, and so on.
Don’t forget about the working conditions. This is because they play a vital role in the valve’s material selection. For example, while stainless steel is a long-lasting material, it is not at all suitable in a salty working environment. In this case, aluminum bronze is a better choice.
3. Pressure Class of the Valve
In most cases, the pressure class of a valve is already supplied by the piping system’s pressure class. Well, if the case is the opposite, the pressure class will be determined by combining the main body materials along with the pressure and temperature.
In order to determine the proper pressure class for your globe valve, it is important to first define the piping system’s design temperature plus the pressure. Be careful not to choose the pressure class which is based on the system’s operating conditions. This is because when a system’s “worst case scenario” hits, your favorite globe valve may not be able to withstand the hit.
4. Size of the Globe Valve
A globe valve is typically installed in a pipeline where the size is already specified. If this is the case, it is simple. The main reason is the size of the globe valve that will be comparable to the size of the pipeline.
However, still other factors exist that will affect your decision when it comes to choosing the right valve size. The two major factors are:
- The maximum flow rate
- The acceptable pressure drop
Furthermore, it is important to note that valve types such as globe valves and ball valves are available in both – full bore and reduced bore. It is important to ensure if there is a requirement for maximum acceptable pressure drop prior to selecting the right globe valve.
For example, if a globe valve is used in a steam system that is meant to generate steam for a turbine, the pressure drop requirements will be critical when it comes to the turbine’s optimum performance.
As a result, a full bore globe valve is strongly advised. A reduced bore valve, on the other hand, is preferred if a valve is used to drain water at the pipeline’s tip. This is due to the fact that pressure drop is not a controlling factor.
5. End Connections of the Valve
Flanged, welded (BW or SW), and screwed end connections are the most commonly used industrial valve end connections. A common example is NPT.
In general, the end connection is selected based on the design and construction of the complete piping system. Safety along with maintenance and emission factors are also taken into account.
Below are some of the common end connections that are used in some industries:
- Water and wastewater treatment plants – flanged
- Steam power plants – welded
- Gas systems – welded
- Refineries – flanged
6. Type of Actuation
When choosing your globe valve, don’t forget to determine how you want to operate the valve. Here are some simple and common ways on how to actuate your globe valve:
- Manual (handwheel/lever)
- Pneumatic actuator
- Electric actuator
7. Trim Materials
The trim (disc/stem/seat) materials consisting of your globe valve should be compatible with the body materials.
The selected materials also significantly depend on the process media. Not only this but system conditions, maximum allowable leakage, and some other aspects are also important.
Take Away
We assume this guide was useful in choosing the best global valve when it comes to industrial applications. With all the above-mentioned points and factors in mind, choosing the ideal entity will be a no-brainer, even if you are a beginner.
