At CONSTRUTEC we have pipes with a DC-FLEX® joint from diameter DN 80 to DN 250, with a large upper opening and a small lower opening:
DC-FLEX® DN 80 to DN 250 Bolted Joint
With high pressure closure "R"
The DC-FLEX® bolted joint for pipes from DN 80 to DN 250 has two different opening sizes. The upper opening is greater than the lower opening.
The high pressure closure is used in bolts with DN 80 to DN 250 for pipes that are exposed to high internal pressures and is used if the application of trenchless techniques is required, by traction.