Reciprocating pump packing nut assembly

A fluid end for use with a reciprocating pump assembly comprising a first stay rod and a second stay rod, the fluid end comprising:

• a mounting flange to be coupled to the first stay rod and the second stay rod;
• and
• a packing nut assembly comprising:
• a packing nut threadably engaged with the mounting flange, the packing nut comprising a gear pattern on a portion of the packing nut;
• and
• a retention assembly comprising:
• a collar that extends circumferentially around the first stay rod;
• an alignment arm coupled to the collar and shaped to contact the second stay rod to align the collar and prevent rotation of the collar and the alignment arm in a first direction;
• a pawl pivotally coupled to at least one of the alignment arm or the collar, the pawl positioned via the alignment arm to engage the gear pattern of the packing nut to allow the packing nut to be threaded into the mounting flange and prevent the packing nut from unthreading from the mounting flange;
• and
• a biasing assembly coupled to the pawl to bias the pawl into engagement with the gear pattern of the packing nut.

A packing nut assembly for use with a fluid end comprising a first stay rod and a second stay rod coupled to a mounting flange, the packing nut assembly comprising:

• a packing nut threadably engagable with the mounting flange, the packing nut comprising a gear pattern on a portion of the packing nut;
• and
• a retention assembly comprising:
• a collar sized to extend circumferentially around the first stay rod;
• an alignment arm coupled to the collar and shaped to contact the second stay rod when the packing nut assembly is installed on the fluid end to align the collar and prevent rotation of the collar and the alignment arm in a first direction;
• a pawl pivotally coupled to at least one of the alignment arm or the collar, the pawl positionable via the alignment arm to engage the gear pattern of the packing nut to allow the packing nut to be threaded into the mounting flange and prevent the packing nut from unthreading from the mounting flange;
• and
• a biasing assembly coupled to the pawl that, when the packing nut assembly is installed on the fluid end, biases the pawl into engagement with the gear pattern of the packing nut.