II. FUNDAMENTALS OF OPERATION
B. Plunger or Piston Rod Load
Plunger or piston rod load is an important power end "design" consideration for WGI reciprocating pumps. Rod load is the force caused by the liquid pressure acting on the face of the plunger/piston. This load is transmitted through the adapter or piston rod to the crosshead, then to the crosshead pin, wrist pin bushing, connecting rod, crank shaft, main bearings and power frame. This load is directly proportional to the discharge gauge pressure and the square of the plunger/piston diameter.
Occasionally, allowable liquid end pressures limit the "allowable" rod load to a value below the "design" rod load. It is important that liquid end pressure DOES NOT exceed WGI's latest published recommendations.
Rod loads are not generally used when "applying" the pump. They are used to establish the power frame design - not to determine the allowable pressures, in most cases, for each size plunger/piston.. Also see the Sizing pumps in high inlet pressure conditions section.
