Abstract: An improved progressive cavity (pc) pump is provided. In a first aspect, the pc-pump comprises a rotor connected to a motor via a drive shaft that is isolated from the material flowing through the suction chamber of the pump, thereby preventing the pumped material from reaching the joints of the drive shaft through faulty seals. In another aspect, the pc-pump comprises a rotor assembly comprising a rotor shaft that is joined to a rotor member by means of a connecting member featuring a thermally-induced structural failure capability that provides a tamper-proof fail-safe mechanism against overheating. In a preferred embodiment the connecting member is made of low temperature melting alloy that converts into the liquid state at a temperature beyond which the operation of the pump may no longer be safe. If the pump overheats, as a result of deadhead operation or dry pumping, the connecting member melts thus terminating the driving relationship between the rotor shaft and the rotor member.