Internal gear pump Model HD51ER-1U33B - P/N 2559 HD: Heavy Duty, bare shaft pump in cast iron 51: Pump size DN 50 - 2" E: Suction/Discharge connection in-line R: Safety valve, single acting for protection against excess pressure 1: Casing & cover: GG-25, Rotor/Idler: GG-25, Shaft: St.60.2 U: Idler bearing and main bearing lubricated by pump medium 3: Idler bush: carbon, idler pin: Hardened 16 MnCr5 3: Bearing bush: Carbon, Shaft: St.60.2 B: Shaft seal: Teflon-impergenated, non-asbestos packing