seal ring 120 is carried by a seal holder 122 which is connected to end 124 of resilient bellows 126 the other end 128 of bellows 126 is connected to a flange 130 which is secured to casing 102 by bolts 132 a seal 134 seals between casing 102 and flange 130 bellows 126 through carrier 122 urges seal ring 120 against ring 110 a pin 140 secured in holder 122 is loosely engaged in an opening 142 in seal ring 120 to prevent the rotation of the seal ring as thus described the structure is conventional and need not be further detailed the sealing face 150 of seal ring 120 has a circumferential raised portion 152 which seals between the seal ring 120 and mating ring 110 the sealing face 150 also carries four spaced raised pocket pads 154 each having a raised entrance rail 156 forming an entrance surface a raised side rail 158 and a raised side rail 160 the top surfaces of rails 156 158 and 160 are co planar with the surface of raised portion 152 the surface 162 of each pad 154 within the aforesaid rails is depressed a small distance below said plane typically in the range of from about 0 002 to about 0 03 cm the surface 162 is situated above the face 150 of the seal ring 120 by a typical distance of 0 15 to 0 30 cm when the chamber 104 is filled with a liquid under substantial pressure.