A single spring bi-directional seal is independent of the direction of rotation due to unique positive drive lug design, which avoids any torsional load on the spring. This increases spring life many times more and minimizes the drag on the rotary seal face. With sturdy and long spring design, the seal can tolerate greater amount of misalignment, vibrations, thermal expansion and axial play of the pump shaft. It has low starting torque and therefore, most suitable for viscous fluids and abrasives slurries. Hard face combination can be provided for handling abrasive slurries upto moderate concentrations.