The spectacle flanges have three types:spacer,spade(paddle flange),spectacle blind flange.A spectacle blind flange is a combination of a spade and a spacer.
All these three types of spectacle flanges are used in piping systems or pressure vessels where the flow needs to be interrupted from time to time.They are installed between one pair of pipe flanges and able to rotate or ‘swing’ into and out of position to interrupt or allow the flow,they are used in the piping system as “Open” and “Closed” function.
Maintenance on a pipe system can be a reason to temporarily replace a Ring Spacer for a Spade.By loosening of all bolts,and half of the bolts temporarily remove,the Spade or Spacer can be placed.After replacing the gaskets,the bolts can be re-assembled and tightened.It is necessary that the pipeline should be valved off and pressure relieved before loosening the flange bolts.
To prevent unnecessary weight to a flange connections,designer usually will choose the seperated two parts (spacer and spade) instead of the spectacle blind flange.
