What is a Concentric Reducer?

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  • Written By: Rolando Braza
  • Edited By: J.T. Gale
  • Last Modified Date: 12 August 2019
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A concentric reducer, which is also known as a tapered expansion joint, is a fitting used to connect two pipes or tubes that have different inside diameters. Both tubes need to share a common centerline or alignment in order to facilitate the flow of fluid or a substance. Reducers can be manufactured using rubber, stainless steel, carbon steel, steel alloy, titanium alloy, copper, nickel, cast iron, brass, or other materials that have met the standards of the pipe industry. It is normally used in joining vertical pipes that need to be anchored for safety reasons. Concentric reducers are common in both the onshore and offshore operation of the oil and gas industry where there is a heavy volume of cargo transfer and vapor recovery.

The two ends of a concentric reducer have unequal diameters in order to achieve its purpose of joining two pipes with different diameters. Its smaller end joins with the smaller pipe while the end with the larger diameter joins with the larger pipe. The ends of a concentric reducer are put together by a cone-shaped transition section to form a single assembly. Joining of the two ends of a concentric reducer can either be done through seamless integration or through welding.


Generally, the length of a concentric reducer is short relative to its diameter. This can make the change in flow of fluid or other substances abrupt. A pipeline designer can opt to have multiple concentric reducers if there is a need to avoid abrupt flow change.

A designer must also carefully define the specification of the concentric reducers that will be used in a pipeline project to achieve the most cost-efficient results without compromising safety. Designers typically will decide on the make, size, dimension, and wall thickness of the concentric reducers that will be installed in different sections of the pipeline system. The more important consideration usually should be the compliance of the brand of concentric reducer chosen to global and local standards on specifications, quality, and safety.

Some concentric reducers are manufactured in accordance to international standards and pre-defined specifications; others are fabricated in accordance to customer specifications. They are presented in catalogs that can be obtained from local and foreign suppliers. Several manufacturers and suppliers have websites, some of which have online ordering forms. The lead-time for delivery, especially for customized orders, varies from one manufacturer or supplier to another and from one source to another. Buyers must therefore factor ordering and delivery lead times in the project schedule to avoid installation delays.


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Post 3

@seag47 – That's how I would describe them, too. I also saw a photo of an eccentric reducer, and it looked quite different.

Instead of flaring out gradually, it just bulges out suddenly at the side that fits on the end of the larger pipe. It's not a nice, smooth transition.

I just wonder how someone would know whether to use an eccentric or concentric reducer. Is there a difference in the way they conduct the flow, or can you just use either one?

Post 2

Concentric reducers are cone-shaped, but they have pieces on the ends that resemble cuffs on sleeves. Once the cone ends, so does the flaring. The cuff is straight instead of curved.

Post 1

I'm sure that in the oil industry, it's very important to have someone on staff who knows which type of concentric reducer each pipe needs. I would imagine that choice of material is very important, too.

There are so many things that can go wrong when you are dealing with crude oil. Little parts like concentric reducers are part of a big system to guard against problems.

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