It is important to understand Off/off and on/off terminology to ensure proper assembly and function. When there are two or more flanges welded to the same piece of pipe or where two sets of bolt holes are drilled and tapped in a flange (such as in a reducing flange) the holes must align with each other.
OFF/OFF
On the same Alignment such as the case with our standard fittings we supply. Also known as “two holes top”. The this is where the bolt holes are straddling the natural centerlines.
ON/OFF
This is commonly seen on reducing Flanges. The bolt holes are with one set on centers whilst the other is off centers, therefore on/off center.
