Sealing high pressure flow devices

A fluid end assembly, comprising:

• a housing having an external surface and 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, each section independently interconnecting the internal chamber and the external surface;
• a corner section formed in a wall or walls defining the third section and extending concentrically around the third section;
• a tubular sleeve installed within the third section, the sleeve of single-piece construction and comprising a first portion joined to a second portion, the second portion having a greater outer diameter than the first portion;
• and in which the sleeve has a first surface joined to the first portion and a second surface joined to the second portion, the first and second surfaces joined by an outer intermediate surface that extends along a length of the sleeve;
• in which the length of the sleeve is bounded by the first and second surfaces;
• in which no threads are formed in the outer intermediate surface of the sleeve;
• and
• in which no grooves for housing a seal are formed in the outer intermediate surface of the first portion;
• an annular seal positioned within the corner section and engaged with the outer intermediate surface of the first portion;
• a plurality of packing seals installed within the second portion and abutting an internal shoulder formed within the second portion;
• a retainer engaging the second surface of the sleeve and defining a threaded central opening;
• and
• a packing nut installed within the threaded central opening of the retainer and engaging the plurality of packing seals.