Methods and apparatuses for pump sealing during leakage events

Abstract

A pump leakage mitigation device includes one or more clamp arms on an outer surface of a pump that can be driven by a biasing element to seat against a shaft of the pump to seal or reduce fluid flow through a breakdown of the pump. The biasing element engages only at threshold temperatures, such as those associated with breakdown orifice failure when additional sealing may be necessary. Clamp arms of any number and shape can be used to achieve the desired seal and based on the pump geometry. A sealant surface and/or keeping mechanism are useable with the leakage mitigation device to enhance fluid flow blockage throughout a pump failure transient scenario. Pump leakage mitigation devices are installed on an outside of a variety of different pump types and can thus be installed, actuated, manipulated, disengaged, and/or removed without having to destroy or disassemble the pump.

What is claimed is: 
     
         1 . An external seal for a nuclear power plant pump having a shaft and breakdown orifice about the shaft, the seal comprising:
 a clamp arm shaped to seat against the shaft at the breakdown orifice so as to seal the breakdown orifice; and   a temperature-dependent biasing element coupled to the clamp arm, wherein the biasing element is configured to drive the clamp arm toward the shaft only at a temperature associated with failure of the breakdown orifice.   
     
     
         2 . The external seal of  claim 1 , wherein the temperature-dependent biasing element is a bimetallic spring. 
     
     
         3 . The external seal of  claim 2 , wherein the temperature is approximately 300 degrees Fahrenheit. 
     
     
         4 . The external seal of  claim 1 , wherein the clamp arm includes a crescent shape matching an exterior of the shaft. 
     
     
         5 . The external seal of  claim 4 , further comprising:
 a sealant surface attached to the clamp arm, wherein the sealant surface is configured to enhance the sealing of the breakdown orifice.   
     
     
         6 . The external seal of  claim 1 , further comprising:
 a keeping device configured to lock the clamp arm in a position sealing the breakdown orifice.   
     
     
         7 . The external seal of  claim 6 , wherein the keeping device includes a ratchet surface on the clamp arm and a ratchet keeper stationary to the clamp arm and positioned to engage the ratchet surface. 
     
     
         8 . The external seal of  claim 6 , wherein the keeping device is configured to be released without dismantling the pump.