Sealing high pressure flow devices

A fluid end assembly, comprising:

• a housing having an external surface and an internal chamber;
• a first conduit formed in the housing and having first and second sections, each section independently interconnecting the internal chamber and the external surface;
• a second conduit formed in the housing, intersecting the first conduit and having third and fourth sections positioned on opposite ends of the internal chamber, each section independently interconnecting the internal chamber and the external surface;
• an endless groove formed within the fluid end housing and surrounding the third section of the second conduit;
• a stuffing box installed within the third section, the stuffing box comprising a first portion joined to a second portion, in which the second portion has a greater outer diameter than the first portion;
• and in which no threads are formed in an outer surface of the stuffing box for engaging the housing;
• an annular seal installed within the endless groove and engaging an outer surface of the first portion of the stuffing box;
• a plunger packing installed within the second portion of the stuffing box;
• a packing nut engaging the plunger packing;
• and
• a retainer engaging the second portion of the stuffing box and having a threaded central opening formed therein;
• in which the packing nut is installed within the threaded central opening.