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Concentric vs. Eccentric Reducer: When to Use Which?

Pipe reducers are one of the many types of fitting that can be used to control the flow within a piping system. In a piping system, there are two major types of reducer: concentric reducers and eccentric reducers. We’re going to talk about both types of reducer, what they are, and when you might use them. For the most part, reducing (and expanding) pipes is fairly straightforward. But there are some exceptions that are important to note for the health of a piping system.

What is a Pipe Reducer?

First, let’s keep it simple: A pipe reducer is a pipe fitting that connects a larger pipe to a smaller pipe. Thus, it reduces the size of the pipe in the pipe system, from one size to another. Pipe reducers may frequently be used to connect pipes of different sizes. There are a variety of reasons why this might be done, and there are a variety of materials that could be flowing through the pipe, which is why there are different types of pipe reducer.

Like other pipe fittings, it can be very complicated to find the right pipe reducer. The fit can be complicated, and materials will matter. But once you find the right pipe reducer, the installation should be fairly simple and fast.

When Would You Use a Pipe Reducer?

Reducers can be used simply to adapt pipes of other sizes, but there are also more complicated uses for them. They may need to be used when the flow has to be limited or expanded in a piping system, such as if the hydraulic nature of the piping system demands it. If you’re using a pipe reducer, you need to consider the consequences for the pipe system as a whole, because there will be changes in both flow and pressure.

Once you know that you need to use a pipe reducer, you need to make the decision between concentric and eccentric reducers. Most people are going to need to use a concentric pipe reducer, but there are some important reasons why an eccentric pipe reducer might be preferred.

Concentric vs Eccentric Reducer: What’s the Difference?

While this may seem complicated, it’s actually quite simple. Concentric reducers reduce the pipe in the center. So, if you’re looking at the reducer head-on, you can see the smaller section is formed in the direct center of the larger side. Eccentric reducers reduce the pipe to the side. So, if you’re looking at the reducer head-on, you can see the smaller section is against one side of the larger side.

This may seem like a very simple change, but it does matter.

The cone-shaped concentric pipe reducer means the pipes have matched center lines, and the eccentric reducer has mis-matched center lines. Both of these have a consequence regarding flow. Most reducers are going to be concentric. Eccentric reducers are used when the pipes have to maintain the same top or bottom level. Eccentric reducers are frequently used to avoid trapping air within the system, so they are often used when both air and liquids may be flowing together.

Most people are going to need a cone-shaped concentric pipe reducer, because they aren’t going to need one side of the reducer to remain flat. But in many applications, either can be used, as long as the bottom of the eccentric reducer is placed correctly. The major concern about eccentric reducers is that they can collect liquids or gasses in one area if they are not properly aligned. When used vertically, there is essentially no difference between a concentric or eccentric pipe reducer.

What About Concentric and Eccentric Expanders?

It should be noted that while they are called reducers, reducers by their very nature are also expanders. They are simply used in the opposite direction as expanders. Thus, expanders can also be both concentric and eccentric, and the consequences of using one or the other to expand rather than reduce are the same. Either way, they are being used when a pipe of one size has to transition to a pipe of another size.

How Are Reducers Installed?

How a reducer is installed depends on the material that the reducer and the pipes are made from. If the reducer and pipes are made from metal, they can be butt-welded together. If the reducers are made of PVC, they will likely be fitted and glued. There are reducers that may have push-to-fit or crimp installations as well. It depends on how the reducer was made, the material, and the goals for the reducer.

To install the reducer, the reducer will be fitted on both pipes, and connected in the appropriate way. But care must be taken with eccentric reducers to ensure that the bottom of the eccentric reducer is properly lined up. In piping liquids horizontally, eccentric reducers need the flat side up, because otherwise gasses can collect. But in piping vapors horizontally, eccentric reducers need the flat side down, because they need to avoid collecting liquids.

The more the pipe is reduced, the more concerns there may be related to flow. If the pipe is only being reduced a little, then there shouldn’t be any complications.

How Do You Find the Right Pipe Reducer?

Let’s say you already know that you need a concentric or eccentric pipe reducer. This isn’t the only thing you will need to know. Because you are connecting pipes, you will also need to know the material. There could be metal reducers, PVC reducers, PEX reducers, and so forth, each with their own method of connection. If you’re connecting two metal pipes, you might want a welded reducer. Otherwise, you might want one that can be fitted and glued.

You also need to know the sizes. Fitting for pipes can be tricky because they don’t go by the universal size of pipe. Instead, they go by the outside measurement for a male pipe, and an inside measurement for the female pipe. So, you need to know your type of pipe, and the exact size, and the exact material. One of the easiest ways to fit pipes is simply to bring the relevant pipes with you to match them up to the fittings.

When it comes to concentric vs eccentric reducer fittings, the initial choice of fitting should be obvious. That being said, finding pipe fittings is always complicated, and using the wrong pipe fitting can be disastrous. If you need to know more about pipe fittings, it’s time to consult with the experts. Check with Steel Forgings today to learn more about pipes and pipe fittings, and how to find the right concentric or eccentric reducers with rapid turnaround.

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