Stem Seal And Double Bulb Seal is used for heads exceeding 30 m. The sealing will be obtained due to interference pressure between the seal seat and seal and also behind the seal in space between the seal base plates. The sealing bulb should project 6mm beyond the face of the clamps. The initial interference of 2 to 5mm the plane of the sealing bulb and sealing face of the seal seat is usually provided.

These seals may be used as top, bottom and side seals either by using them with water pressure acting them which is withdrawn before the gate is moved to reduce / eliminate friction load or they may be used with metal or fluorocarbon film to achieve the same purpose. On heavy gates such seals may be well bottom seals where enough mechanical compression becomes available to make a good seal.