Introduction
Piping and Pipeline Systems are not of uniform size. Depending on process requirement or availability of material, there is a necessity of reducing or expanding the size of pipelines. This can be done with a special pipe fitting called Reducers.
Basically, reducers are available in two styles:-
· Concentric reducers
· Eccentric reducers
Concentric Reducers
In this type of reducers area reduction is concentric and the centerline of the pipe on a bigger end and smaller end remains the same. These styles are normally used for vertical lines.
Eccentric Reducers
In eccentric reducer there is an offset in between the center lines of the bigger end and the centerline of smaller end. This offset or eccentricity will maintain a flat side either on top or on the bottom side. This offset or eccentricity can easily be found out by the following equation:-
Eccentricity = (Bigger end ID-Smaller end ID) / 2
While using this type of reducer the user has the option of orienting the flat side. Usually, for horizontal lines, eccentric reducers are oriented with either the flat side up or down, and the same with deviation is mentioned in isometric. Normally eccentric reducers with the flat side down are preferred for following cases on horizontal lines:-
· On Sleepers and Pipe racks.
· On lines requiring gravity flow
· On the pump suction line which handles slurry
Eccentric reducers with the flat side up are used for all pump suction lines (excluding pumps handling slurry) on horizontal lines. This way one can avoid air getting trapped inside the pipeline during initial venting through pump casing and will help in avoiding cavitation.
Depending on end connections of this fitting with a straight pipe, reducers are grouped as follows:-
· Butt-welded reducers
· Socket welded reducers
· Screwed reducers
· Flanged reducers
Butt-welded reducers
The applicable pressure rating, dimensional and material standards for butt welding reducers are the same as those applicable to butt welding elbows.
Socket welded reducers
As shown in figure, such reducers are available in concentric type only & in the form of coupling with one end socket to fit larger diameter pipe and another end socket to fit smaller diameter pipe. Standards are the same as those applicable to socket welding elbows.
Screwed Reducer
Available only in the concentric type and are in the form of coupling having one end to fit bigger pipe and another end to fit smaller pipe. ASME B16.11 is an applicable dimensional standard. Material standards including pressure ratings are the same as of screwed elbows.
Flanged reducers
Their pressure rating, use, material, and dimensional standards are the same as those applicable to flanged elbows. Regardless of reduction, their face to face dimensions is governed by the larger pipe size.
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