All pipelines require maintenance at some time and for this to be done it is often necessary to isolate and drain off a section of the pipe. Whilst valves can be used to regulate flow, when they are used as a primary means of isolation they suffer from an inherent problems. It is quite common for debris flowing in the pipeline to collect in the valve seating and prevent it closing properly and so ‘let by’.
This can be a serious problem and other means have to be found to isolate the pipeline. For smaller lines spectacle flanges can be used. These consist of two circular plates the size of the pipeline connected by a short piece of steel and as the name implies they look like an old fashioned pair of spectacles. However whilst one side has an open centre the other is blanked off. The connecting piece between the two discs acts as a pivot point. By releasing the flange bolts the spectacle plate can be rotated to bring the closed plate in line with the pipe. The flange bolts are then replaced and this seals off the pipeline.
However on very large pipes this is not a practical solution as the spectacle plate would be too large and heavy to manipulate. In this situation a spade flange plate is used together with a ring spacer. These units sit between two flanges. In normal use the ring spacer is fitted but to shut off the pipeline this is replaced with the blank spade plate. This is fitted with a handle which sticks out between the flanges to flag up that it is in position. Without this it would be easy to forget that it was fitted which could lead to much scratching of the head to find out why there was no flow in the pipeline.
At Chemipetro we manufacture spectacle and spade flanges to any pipe size you need.