The key functional property of the TPC Compact Flange, is that it is a static connection which means that there is no relative movement between the two flange halves when in service. Due to the static condition, a leak cannot develop over time. The static behaviour also makes the flange 100% maintenance free.
The flange face includes a slightly convex bevel with the highest point, called the heel, adjacent to the bore and a small outer wedge around the outer diameter of the flange. The NCF5 is made up by tightening/tensioning the flange bolting which pulls the two connector halves together.
For the seal ring, axial forces are exerted on the taper of the metal seal ring and translated into a sealing force. Furthermore with increased pre-load, the bevel is closed and face to face contact is achieved at the outer wedge while most of the bolt pre-load is transferred as compressive forces between the flange faces at the heel.
The principle design of the flange face includes two independent seals. The first seal is created by application of seal seating stress at the flange heel. The flange also remains in contact along its outer circumference at the flange faces for all allowable load levels. The main seal is the seal ring. The seal ring force is provided by the elastic stored energy in the stressed seal ring. Any heel leakage will give internal pressure acting on the seal ring inside intensifying the sealing action.
The design aims at preventing exposure to oxygen and other corrosive agents. This prevents corrosion of the flange faces, the stressed length of the bolts and the seal ring.
The back face of the flange in the made-up position is parallel to the flange face in order to prevent bending of the bolts in the assembled condition.