Pumping Low Specific Gravity Hydrocarbons: Why API 610 Specifications Make Vertical Turbine Pumps the Right Choice

December 15, 2025

Pumping low specific gravity hydrocarbons is rarely straightforward. These fluids combine low density with high vapor pressure and tight NPSH margins, leaving little room for error in pump and system design. Refineries, terminals, and pipelines need solutions that handle volatile liquids reliably while meeting strict safety and environmental expectations. Oil and gas, refinery, and terminal operations depend on pump designs that can manage these challenging fluid properties safely and efficiently.

Specific gravity compares a fluid’s density to water, and many light hydrocarbons are significantly lighter than water. This affects how head converts to pressure and how much power the pump absorbs, even though a centrifugal pump develops the same head in feet regardless of fluid density. Because light hydrocarbons also tend to have higher vapor pressure at elevated temperatures, the margin between system pressure and vapor pressure can shrink quickly, increasing the risk of cavitation.

Net positive suction head (NPSH) becomes a critical design variable. Engineers must carefully evaluate NPSHa versus NPSHr and maintain sufficient margin across operating conditions. Misjudging NPSH, suction piping, or operating range can lead to cavitation, causing noise, vibration, efficiency loss, and long-term damage to impellers, bearings, and seals.

Vertical turbine pumps built to API 610 specifications are widely used in these services because they offer flexible arrangements and robust construction. In VS1 (wet-pit) and VS6 (canned configurations), the bowls and first-stage impeller can be set below grade or inside a barrel, increasing NPSHa by placing the hydraulics deeper in the fluid. Multistage designs, low-NPSH impellers, and engineered bearing and thrust assemblies support stable operation when pumping volatile, low specific gravity hydrocarbons.

Typical applications include LPG and light-ends transfer, terminal loading and unloading, pipeline booster service, and critical fueling systems. National Pump Company’s API 610 compliant vertical turbine portfolio, including VS-0, VS-1, and VS-6 configurations, is designed for these demanding duties. Our engineering team works with customers to review fluid properties, verify NPSH, and specify configurations that deliver reliable, long-term performance in low specific gravity hydrocarbon services.