... The hydraulic clamp consists of main clamp and back-up tong, light and high efficiency.2. Main clamp ... and back-up tong make the linkage, it operate manually ... operated directional valve on the main clamp, the back-up tong can clamp or loosen the tubular pile, ... . hang main clamp, the back-up tong float down the main clamp. The back-up tong connect the main clamp ...