The basic difference of outside-vent coring tool from conventional one is that it has a special outside-vent joint installed between safety joint and swivel assembly.

The wash pipe packing of drilling swivel showed wear-and-tear continually in drilling process due to its structural design. The packing assembly was often torn by high pressure mud.

Swivel packing seal assembly is the key of the swivel, whose function directly influences its service life, further more, and affects the drilling speed.