▁as ▁a ▁g asket , ▁an ▁O - ring , ▁compression ▁pack ing , ▁etc . ▁ ▁In ▁this ▁article , ▁the ▁reference ▁is ▁to ▁an ▁end - face ▁mechanical ▁se al . ▁▁▁ ▁One ▁such ▁method ▁of ▁classification ▁cons iders ▁design ▁features ▁or ▁the ▁configuration ▁in ▁which ▁these ▁features ▁may ▁be ▁used . ▁ ▁Classification ▁by ▁Design ▁accounts ▁for ▁the ▁details ▁and ▁features ▁incorpor ated ▁into ▁a ▁single ▁se al ▁ring / m ating ▁ring ▁pair . ▁ ▁Classification ▁by ▁Configuration ▁includes ▁the ▁orientation ▁and ▁combination ▁of ▁the ▁se al ▁ring / m ating ▁ring ▁pair . ▁ ▁Design ▁features ▁ ▁The ▁individual ▁components ▁of ▁end - face ▁mechanical ▁se als ▁may ▁be ▁designed ▁to ▁include ▁features ▁such ▁as : ▁ ▁face ▁treat ments ▁such ▁as ▁hyd rod ynamic ▁features , ▁p ads , ▁etc . ▁ ▁balance ▁ratio ▁ ▁push er ▁or ▁bell ows ▁ ▁spring ▁design ▁ ▁hardware ▁for ▁containing ▁assembly ▁and ▁providing ▁drive ▁mechanism ▁ ▁consider ations ▁for ▁secondary ▁se aling ▁element . ▁In ▁general , ▁design ▁features ▁are ▁not ▁completely ▁independent ; ▁that ▁is , ▁emphas is ▁of ▁a ▁particular ▁feature ▁may ▁also ▁influence ▁other ▁features . ▁ ▁For ▁example , ▁selection ▁of ▁a ▁particular ▁secondary ▁se aling ▁element ▁may ▁influence ▁the ▁shape ▁of ▁the ▁se al ▁ring . ▁ ▁Face ▁treatment ▁▁▁ ▁The ▁most ▁common ▁se al ▁face ▁design ▁is ▁a ▁plain , ▁flat , ▁smooth ▁surface ▁but ▁there ▁are ▁many ▁special ▁treat ments ▁intended ▁for ▁specific ▁applications . ▁The ▁most ▁common ▁objective ▁for ▁the ▁face ▁treatment