PIPE REDUCERS AND CAPS (BUTT WELD)


Pipe reducers are used to change the bore size of a pipeline (increase or reduce) and are available in two configurations, concentric and eccentric, which are used for different applications. PIpe caps, instead, are used to blind a pipe permanently or for temporary maintenance works. Both products belong to the butt weld fittings family and are manufactured according to ASME B16.9 (carbon and alloy) and MSS SP 43 (stainless steel and higher grades). In this article, we give a short overview of these two widely used types of welded fittings.


WHAT ARE PIPE REDUCERS?

Butt weld reducers are used to decrease or increase the bore size of a pipeline or a pipework.

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). For more information about the available material grades, their chemical composition and, mechanical properties, refer to this article.

There are two shapes of butt weld reducers, both produced according to ASME B16.9 (carbon and alloy) and MSS SP 43 (stainless steel and nickel-alloys):

CONCENTRIC REDUCERS

The open ends of concentric reducers are aligned and centered one to the other. Generally, this type of reducers is used to modify the bore size of the pipeline by two (maximum three) measures, to avoid an excessive pressure drop. If the required size reduction is larger, a series of fittings (in sequence) have to be used to have a smooth and gradual adjustment of the flow capacity of the pipeline.

 

Butt Weld concentric reducer

 

ECCENTRIC REDUCERS

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

 

Butt Weld Eccentric Reducer

 

TOP/BOTTOM FLAT ECCENTRIC REDUCERS

Eccentric reducers can be top flat (“TF”) or bottom flat (“BF”). The bottom flat 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 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 or bottom flat eccentric reducers

PIPE REDUCERS MANUFACTURING PROCESS

 

manufacturing process of concentric reducers

PIPE REDUCERS DIMENSIONS

Butt weld reducers dimensions and weights are shown in this article.


BUTT WELD PIPE CAPS

Butt weld caps are used to blind the pipeline, permanently or temporarily (example during maintenance and reparation works).

Butt weld pipe caps are manufactured out of steel plates in most sizes and materials (ASTM A234 and ASTM A420 for applications requiring carbon steel materials, ASTM A403 for services requiring stainless steel materials). Bw caps 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 these caps is ellipsoidal and conforms to the requirements set by the «ASME Boiler and Pressure Vessel» code.

 

Butt Weld Pipe Cap

 

PIPE CAPS MANUFACTURING PROCESS

 

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.