ATS-MS1 Mechanical Seal - The pantograph type mechanical shoe seal is the most widely used design on external floating roof tank and provides long service life. The metallic band is formed as a series of shoes that are overlapped together to form a ring and held against the tank shell by pantograph type mechanical device. The counterweight assembly and arm exerts a constant pressure to push the shoe against the tank shell. The continuous seal covers the vapor space between the shoe and roof from the atmosphere.