Glossary Of Terms

The main objective of this glossary is to define some of the terms that are used throughout the Offset Selection Chart

Advance: This is the distance that an offset covers in a straight line through the offset. Generally measured from center to center but can be measured face to face, or center to face depending on the offset. Sometimes this is called the run.

Center to Center: This is a measurement term for a pipe fabrication or a distance measured from the center of one pipe fitting to the center of another.

Center to Face: This is a measurement term that describes the distance from the center of one pipe fitting to the face of another.

End to End: This is a measurement term that describes the distance from the end of one piece of pipe to the end of another.

Face to Face: This is a measurement term that describes the distance from the face of one pipe fitting to the face of another.

Fitting to Fitting: This is an offset configuration that allows the pipefitter to make the desired offset dimension. It uses only the fittings, without a pup piece. This method saves time, labor, and can be aesthetically pleasing. (Offsets H-L)

Fixed Run: This is a measurement term that describes the distance in a straight line that an offset must be to achieve a desired result. Sometimes this is called the advance, it can be measured as center to center, center to face, or face to face. This dimension is required to solve some of the offsets on the Offset Selection Chart. (Offsets M-Q)

Inside Arc Length: This is a term that is used when laying out a mitered fitting from a standard 90 degree elbow. It is the length of the throat of the fitting, measured along the radius of the fitting for a given angle.See fitting lay out

Outside Arc Length: This is a term that is used when laying out a mitered fitting from a standard 90 degree elbow. It the length of the heel of the fitting, measured along the radius of the fitting for a given angle.See fitting lay out

Parallel Offset:An obstruction in the way of a run of pipe frequently results in the pipe being continued parallel to the original run, but no longer in the same line, i.e.; the pipe is offset.

Perpendicular Offset:This offset uses a 90 degree fitting in conjuction with a fitting less than 90 degrees to offset perpendicular to the original line. It allows the pipefitter to change direction as well as planes at the same time, i.e.; a 90 degree elbow rolled at 45 degrees and straightened out with a 45 fitting.

Radius: This is a term as it applies to a 90 degree weld elbow. It is the distance from the face of the 90 to it's center line. Sometimes it is refered to as the take off of the fitting. This can be found by multiplying the pipe size by 1.5; Ie. 6" 90 degree weld elbow x 1.5 = 9" radius or the take off.

Rise: This is a term I use when laying out a mitered fitting from a 90 degree weld elbow. It is the distance from the face of the fitting to a reference mark at the center line of the 90. It establishes a layout point for the desired angle on the center line.See fitting lay out

Run: This is a term I use when laying out a mitered fitting from a 90 degree weld elbow. It is the distance from the opposite face of the fitting to a reference mark at the center line of the 90. It establishes a layout point for the desired angle on the center line. (This should not be confused with the term fixed run, used in the Offset Selection Chart representing the advance.) See fitting lay out

Set Back: This is the same as the take off of a fitting.

Take Off: This is the distance from the face of a fitting to it's center line for any given angle.See fitting take off

Travel: This is the distance of the diagonal portion of an offset. When there is a pup piece in the travel, the center to center, and end to end dimensions are important information to the pipefitter. If the travel is going to be fitting to fitting, this distance is the length of the take off of the angled fitting or fittings plus the take off of the 90 degree weld elbow or tee. Its length is not as important when going fitting to fitting.