Pump seal with thermal retracting actuator

A shutdown seal for a pump having an impeller section which is connected to a motor through a shaft that is rotatably supported between the motor and the impeller with a seal housing interposed around the shaft between the motor and the impeller section, the seal housing surrounding an axial portion of the rotating shaft, the shutdown seal being configured to be supported within the seal housing for preventing a fluid in an annulus surrounding the shaft from leaking past the shutdown seal after rotation of the shaft has slowed or stopped, the shutdown seal comprising:

• a constrictable split ring configured to surround the shaft, the split ring having confronting ends and an inner diameter that will be spaced from the shaft when installed in the pump and the shaft is rotating, the inner diameter defining a portion of the annulus;
• a spacer disposed between the confronting ends of the split ring for maintaining the annular space between the confronting ends during normal operation of the shaft, the spacer is operable to be removed from between the confronting ends when the fluid rises above a pre-selected temperature so the split ring can constrict to narrow or substantially seal a portion of the annulus;
• an actuator for removing the spacer from between the confronting ends of the split ring when the fluid rises above the pre-selected temperature so the split ring can constrict to narrow or substantially seal the portion of the annulus, the actuator comprising:
• a cylinder having an axial dimension;
• a piston axially movable within the cylinder with the cylinder having an upper and a lower end which is sealed around the piston;
• a piston rod extending at a lower end of the piston and having one end connected to the spacer;
• a cavity occupying a space within the cylinder between the upper and lower ends, through which space the piston travels, an axial dimension of the piston extending through the space within the cavity when the spacer is disposed between the confronting ends of the split ring, having at least two separate diameters with a largest of the diameters leading a smaller of the diameters in a direction of travel of the piston to remove the spacer from the confronting ends of the split ring;
• and
• a material occupying at least a portion of the space within the cavity, the material expanding upon an increase in temperature to exert a force on the piston that causes the piston to move in a direction to remove the spacer from between the confronting ends when the material rises above the preselected temperature.

An actuator comprising:

• a cylinder having an axial dimension;
• a piston axially movable within the cylinder with the cylinder having an upper and lower end which is sealed around the piston;
• a piston rod extending at a lower end of the piston and having one end connectable to an operator;
• a cavity occupying a space within the cylinder between the upper and lower ends, through which space the piston travels, an axial dimension of the piston extending through the space within the cavity when the piston is in a first position of its travel, the axial dimension of the piston having at least two separate diameters with a largest of the diameters leading a smaller of the diameters in a direction of travel of the piston to move the piston to a second position, the two diameters occupying at least a portion of the space when the piston is in the first position;
• and
• a material occupying at least a portion of the space within the cavity, the material expanding upon an increase in temperature to exert a force on the piston that causes the piston to move to the second position when the material rises above a preselected temperature.