Modular pump cylinder-head having integral over-pressure protection

A modular fluid end assembly for a reciprocating pump having a cylinder housing secured to a crankcase by the tie-bolts having a predetermined yield strength, the modular fluid end comprising:

• a cylinder-head having a head-to-cylinder base joint surface and an oppositely positioned end joint surface;
• a discharge valve assembly being positioned in the cylinder-head in coaxial alignment with a plunger located in the cylinder housing;
• an intake valve assembly located int he cylinder housing at approximately a 90.degree. angle from the discharge valve assembly;
• the base joint surface of the cylinder-head having a bore therethrough;
• a first seal landing proximate to the bore and in communication with the base joint surface, the seal landing having a preselected internal diameter;
• a first radial seal located in the first seal landing for providing a seal between the cylinder-head and the cylinder housing;
• the end joint surface of the cylinder-head having a second bore in communication with the first bore in the base joint surface of the cylinder-head, the bore having a second seal landing region common to the end joint surface, the second seal landing having an internal diameter which is larger than the internal diameter of the first seal landing of the base joint;
• a second radial seal positioned within the second seal landing of the end joint surface;
• an end plate having an outer surface, an end joint surface, and a threaded bore extending through the end plate perpendicular to the end joint surface;
• a valve cover having an inner face, an outer face, and an outer periphery having a seal means extending thereabout, the outer periphery and the seal sized to be accommodated by the second end seal landing of the cylinder-head;
• a cylinder-head cover retainer having a valve cover facing and a threaded outer periphery configured to engage the threaded bore of the end plate;
• a plurality of cylinder-head bolts located about the periphery of the end plate, the bolts passing through the outer surface of the end plate, the end joint surface of the cylinder-head, and the base joint surface of the cylinder-head and the bolts being received by the cylinder housing;
• and
• wherein the cylinder-head bolts are subject to yielding prior to the tie bolts upon the fluid end of the pump obtaining a preselected internal pressure.

A modular fluid end assembly for a reciprocating pump having a cylinder housing secured to a crankcase by tie-bolts having a preselected yield strength, the modular fluid end comprising:

• a cylinder-head having a head-to-cylinder base joint surface and an oppositely positioned end joint surface;
• a first cavity extending into the cylinder-head from the base joint surface;
• a base joint seal landing common to the first cavity and the base joint surface, the seal landing having a preselected nominal internal diameter;
• a second cavity in communication with the first cavity, the second cavity having a bore of a preselected nominal internal diameter;
• a first seal means positioned in the base joint seal landing;
• an end plate having an end joint surface positioned against the end joint surface of the cylinder-head;
• a valve cover positioned against the end joint surface of the cylinder-head to cover the second cavity of the cylinder-head;
• a second seal means positioned between the valve cover and the bore of the second cavity of the cylinder-head;
• an end joint/vent region located between the end plate and the end joint surface of the cylinder-head;
• and
• fastener means for forcing the end plate, and hence the valve cover, towards the cylinder-head to induce a predetermined minimum preload upon the fastener means and the fastener means is configured and constructed of a material having a predetermined yield strength which corresponds to a predetermined maximum operating pressure of the pump whereupon the fastener means yields prior to the tie-bolts yielding to provide internal pressure relief of the pump should an over pressure condition occur.

A method of providing over-pressure protection of a fluid end assembly for a reciprocating pump having a cylinder housing secured to a crankcase by tie-bolts having a preselected yield strength, the method comprising:

• providing a cylinder-head having a head-to-cylinder base joint surface and an oppositely positioned end joint surface;
• providing the cylinder-head with a first cavity that extends into the cylinder-head from the base joint surface;
• providing a base joint seal landing common to the first cavity and the base joint surface, the seal landing having a preselected nominal diameter;
• providing a second cavity in communication with the first cavity, the second cavity having a wall of a preselected nominal diameter;
• positioning a seal means in the base joint seal landing;
• providing an end plate having an end joint surface and positioning the end joint surface adjacent the end joint surface of the cylinder-head;
• positioning a valve cover against the end joint surface of the cylinder-head to cover the second
• cavity of the cylinder-head block;
• positioning a seal means between the valve cover and the wall of the second cavity of the cylinder-head;
• and
• providing fastener means for securing and forcing the end joint surface of the end plate toward the end joint surface of the cylinder-head to at least a preselected minimum preload, the fastener means being configured and constructed of a selected material having a predetermined yield strength which corresponds to a predetermined maximum operating pressure of the fluid end assembly and in which the yield strength of the fastener means is less than the yield strength of the tie-bolts.