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Buttweld Fittings, Pipe Fittings, Technical Library

Buttweld Pipe Reducer and Cap

Buttweld Pipe Reducer and Cap

A butt weld pipe reducer is used to increase or decrease the bore size of a pipeline or of a piping system. There are two shapes of butt weld reducers, concentric and eccentric, manufactured according to the ASME B16.9 (carbon and alloy) and MSS SP 43 specifications (stainless steel and nickel alloys). Pipe reducers are available in sizes from 1/2 inch to 48 inches and in multiple material grades, as carbon steel (ASTM A234 WPA, WPB, WPC), alloy steel (ASTM A234 WPxx) and stainless steel (ASTM A403 and ASTM A815 for duplex and super duplex materials). 


Pipe reducers are manufactured in multiple dimensions to fit ASME B36.10 carbon/alloy steel pipes and ASME B36.19 stainless steel and nickel alloy pipes. The most common material grades for concentric and eccentric reducers are the ASTM A234 WPB and WPC (carbon and alloy steel reducers), and the ASTM A403 (stainless steel reducers).



Pipe reducers can be either concentric or eccentric:


The open ends of a concentric reducer are aligned and centered one to the other. Generally, this type of pipe reducer is used to modify the bore size of the pipeline by two (maximum three) measures, to avoid an excessive pressure drop in the pipeline.

If the required size reduction is larger, a cascade of butt weld fittings (multiple pipe reducers in sequence) has to be used to have a smooth and gradual adjustment of the flow capacity of the pipeline.


Concentric reducer



The open ends of an eccentric reducer are in an “offset” position one to the other. Eccentric reducers are used, generally, for pipelines installed in a horizontal position (whereas concentric reducers are used for pipelines installed vertically or for the inlets of suction pumps, as top flat eccentric reducers).


Eccentric Reducer



Eccentric reducers can be top flat (“TF”) or bottom flat (“BF”). The bottom flat eccentric reducer type is used for pipe-racks (the bottom of the reducer is flat and at the same level of the bigger sized run pipe), while the top flat pipe reducer type is used at the inlet of piping suction pumps as shown in the image below (this setup prevents the formation of vapor traps in the pipeline):

Top flat and bottom flat eccentric reducer for suction pump



The key difference between concentric vs eccentric reducer is the centricity of the inlet vs. the outlet of the fitting, which is perfect for a concentric reducer and offset of an eccentric reducer.



The manufacturing process of pipe reducers is shown in the image below.

manufacturing process of concentric reducers


A butt weld pipe cap is used to blind or isolate the pipeline, permanently or temporarily (for example during the execution of maintenance and reparation works). A pipe cap can be manufactured using steel plates for most sizes and materials (ASTM A234 and ASTM A420 for applications requiring carbon steel materials, ASTM A403 for services requiring stainless steel materials).

The pipe cap dimensions and tolerances are set by the ASME B16.9 (carbon and alloy steel caps) and MSS SP43 (stainless and nickel-alloys caps). The shape of a pipe cap is ellipsoidal and conforms to the requirements set by the «ASME Boiler and Pressure Vessel» code.


buttweld pipe cap asme b36.19



manufacturing process of butt weld caps

Read this article to learn more about the materials grades for pipe caps. Dimensions and weights charts for pipe caps are shown in this other article.



Looking for the price of pipe reducers? Click on the image and check our online steel reducer price estimation tool!

price eccentric concentric reducer

The tool estimates the price for pipe reducers manufactured in Europe and Asia.

Even if our price estimates are reliable, prices shall always be double checked with butt weld fittings manufacturers and distributors.



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