Oil purge valve Design characteristics The 8 mm oil purge consists of : - a purge valve body (weldable steel : TStE 285-DIN 17102 or equivalent) with impact strength certificate to -50°C, - a nipple (hardened steel) - and a sealing O-ring. Operation To open that oil purge, unscrew the nipple by two turns. The oil will then flow through the valve and nipple. To close, screw in the nipple.