An improved rotary drill head is provided having two lip seals installed in a seal cavity to provide a long lasting dynamic seal. The first lip seal is installed with the heel first and the second lip seal is installed with the lip first. Lubricant is maintained between the two seals at a pressure greater than the operating pressure of the rotary drill head. The lubricant pressure energizes the two lip seals. The abrasive fluid from the borehole is prevented from leaking past the seals because of the pressure differential. An infinitesimal amount of lubricant will leak past the lips of the seals thereby lubricating the seal.