Eccentric Reducer

One uses geometry to figure out where to cut out some tapered strips and wedges so that the remaining part of the pipe can be curled a bit tighter to form the desired shape. There is a "Frankland Pipefitter's Handbook" that explains one method.

Since the dimensions given do not conform to ANSI B16.9/B16.28, you may wish to consider fabricating the reducer from 12mm thick plate - in two symmetrical parts - by plate development - to be rolled/folded/bent.

There exists an inexpensive software application known as "Plate-n-Sheet," that I have used successfully for more than 12 months. All that one does is input the dimensions, including the plate thickness, the length, O.D., I.D. and the offset - in this case, 100mm.

You will also need a CAD package to draw the templates produced by, "Plate-n-Sheet."

Good luck

Sunil.....

What kind of pressures & temperatures does your piping system operate under ?

What is your reducer material ?

What, if any, piping code are you following ?

Pipe material : MS

Water Pressure : 15 bar

Pipe thickness : 11 mm

OD : 1120 mm

sunil.rai-

Get yourself what welders call a "wizard wrap" or "wrap around". Get the largest size you can. These are available at all welding stores/supply houses

This is wrapped around the pipe and gives you the markings and dimensions to make the eccentric reducer you want. They are most often used for smaller pipes but are available in the size range you need. That size is usually used by pipeline welders.

They also have the patterns and dimensions for all sorts of welding configurations, cutting in T's and 45o T's of the same or different sizes, reducers and many others.

Good Luck, Old Salt

Very interesting....Eccentric reducer can be fabricated from plate.But I am not sure ,how to fabricate it from pipe.

Mark large diameter, small diameter and required offset angle on plate.Cut the profile, roll it and join it by welding.

Does anyone know how to make eccentric reducer from pipe with same diameter on both ends?

Not even God know how to do that, because it is no longer a reducer at all.

A very common way it is done in the field is to make a "trial and error" model of it from cardboard, linoleum, sheet metal, thin Styrofoam sheets, stiff rubber sheeting or other similar materials that are semi-rigid and can be cut easily. Combine this with a roll of duct tape, a tape measure, scissors or tin snips and you can do it is a short time.

Take a sport piece of the large diameter pipe (similar to a ring) and the same of the smaller pipe. Space them apart the length that you want the eccentric reducer to be. Tape the sheeting around the end of the large pipe and start cutting it into wedges of the shape want the reducer to be. The more and slimmer wedges the smoother the surface of the reducer but the more welding involved. If you make errors and cut too much of the sheeting off, simply tape another piece on to the over cut piece and continue on with the cutting/shaping. When you have the configuration you want tape the adjacent wedges together and cut an appropriate length of the larger pipe to match the model.

Hammer the wedges so that they are adjacent to each other with the appropriate welding gap width between them. Chamfer the edges of the wedges and hammer them to the appropriate width again.

Put the shield and leathers on and strike an arc! Continue and it will be done. One very important suggestion though, welds the wedges in a pattern similar to a "star pattern". Welding adjacent pieces continuously will warp and distort the materials and end up warping the resultant piece.

This cut and tape method is used extensively for field generated butt weld fittings and in the sheet metal industry. Make an easily adjusted model, take the dimensions, cut the final pieces and assemble.

Good Luck, Old Salt