148 with respect to the lockout groove 151 the retainer groove 167 and or stop dimple 88 may only be provided circumferentially around a portion of the outer surface of the lockout pin adapter 154 such as substantially ninety degree portions of the lockout pin adapter 154 the riser valve lockout assembly 150 functions similar to the riser disconnect lockout disclosed above as lockout pin 148 is rotated such as by rov or diver within one of the upper or lower circular portions of the lockout groove 151 to the valve locked orientation the upset shoulders 147 are oriented so as not to be axially moveable through the narrow portion of the lockout groove 151 the resulting inability of the lockout device 153 to move axially along the lockout groove 151 provides the capability to lock the valve 20 in either a valve opened or valve closed position depending upon whether the lockout device 153 is engaged in the upper or lower circular portion respectively of the lockout groove 151 this assembly may provide the ability to install the riser valve assembly 20 in either a valve opened or a valve closed position in an alternative embodiment a valve sealing member may be generally positioned within a valve housing which includes component variations from a valve housing discussed above that includes the upper 114 and lower 110 valve housings and the central valve housing 112 in an alternative embodiment a central valve housing may be included as an integral portion of a lower valve housing or an upper valve housing the subsea riser valve assembly 20 is preferably an independent.