National Oilwell Varco has been manufacturing reciprocating pumps since the early 1900's. In 1987 National Supply and Oilwell Supply merged combining National and Oilwell competing pump lines. In 2000 National Oilwell acquired Wheatley Gaso from Halliburton and adds Wheatley, Gaso, and Omega pump lines. The combination of the five lines makes for the most extensive reciprocating pump product mix in the industry.

A single acting pump is a pump in which the liquid in each cylinder is discharged only during a head-end or crank-end stroke during one-half a revolution. A continuous duty pump is rated for 8-24 hours of service per day fully loaded or at max rating. Continuous Duty Single Acting pumps have improved performance capabilities over Continuous Duty Double Acting through its superior design. The single acting design allows for higher pump speeds and higher pressures in continuous duty applications.