Gear Pump for Oil

A gear pump for oil is a rotary positive displacement pump that uses two external helical gears to capture fluid between the teeth and the casing wall, transporting constant volume per rotation — independent of system pressure. It is the correct technology for any oil with viscosity above roughly 150 cSt, the range where centrifugal pumps lose efficiency exponentially. In the FB Bombas FBE line, the design follows API 676 (Positive Displacement Pumps — Rotary, 3rd edition). The body is cast in a single piece with integrated feet and ports opposed at 180°. Oils fill the spaces between teeth without significant shear, preserving lubricant additives and physical-chemical properties. There are six main operational classes the FBE serves: mineral and synthetic lubricating oils, industrial hydraulic oils, rolling and quenching oils in steelmaking, dielectric oils in transformers, vegetable oils in food industry, and residual oils in reuse or disposal cycles.

Each oil class has a viscosity and temperature profile that determines the pump's maximum rotation and construction material. ISO VG 32 to VG 680 lubricating oils typically operate between 200 and 3,500 SSU, served by FBE with direct rotation at 1,150 rpm in cast iron or carbon steel. Hydraulic oils (HLP, HVLP, biodegradable) are generally between 150 and 600 SSU at 40 °C — ideal range for FBE 1/2" to 3" with direct coupling and type 21 mechanical seal. Heavy mineral oils, such as BPF and quenching oils, operate between 2,500 and 7,500 SSU when heated to 60-80 °C, requiring FBE 1" to 6" with direct transmission at 850 rpm. Above 7,500 SSU (ultra-viscous oils or cold residual oils), rotation drops to 500-700 rpm via pulley or reducer, and the FBEI internal gear line becomes preferred due to lower pulsation. Vegetable oils (soybean, palm, sunflower, cocoa butter) have viscosity between 50 and 350 SSU and require AISI 316 stainless casing (ASTM A743 CF8M) to meet food-industry sanitary requirements. Transformer dielectric oils (naphthenic or silicone) operate at low viscosity (~40 SSU) and do not require heating, transferred by small FBE with special sealing to prevent moisture contamination.

• ISO VG 32-68 (light hydraulics): FBE 1/2" to 2", 1,150-1,750 rpm, cast iron
• ISO VG 100-220 (medium lubricants): FBE 3/4" to 3", 1,150 rpm, cast iron or carbon steel
• ISO VG 320-680 (gear, reducer oils): FBE 1" to 4", 850 rpm, carbon steel
• BPF / residual oils (>7,500 SSU): FBE 2" to 6" with reducer, 500-700 rpm
• Food-grade vegetable oils: FBE 1/2" to 3" in 316 stainless, sanitary seal
• Transformer dielectric oil: FBE 1/4" to 1" with special moisture-resistant seal

Table 2 of the FBE technical manual (MTEC-01/01, page 4) rigorously defines maximum rotation as a function of oil viscosity. For the 30 to 250 SSU range, direct drive at 1,750 rpm is allowed on FBE 1/8" to 1" D. From 250 to 2,500 SSU — covering most industrial lubricating oils — rotation drops to 1,150 rpm and the range expands to FBE 1/8" to 5". Between 2,500 and 7,500 SSU (heated heavy oils), nominal rotation is 850 rpm on FBE 1/2" to 6". Above that, drive requires pulley or reducer: 700 to 500 rpm for 7,500-10,000 SSU, 500 to 300 rpm for 10,000-50,000 SSU, and 300 to 150 rpm for 50,000-100,000 SSU. Violating these ranges produces two typical failure modes: suction cavitation from insufficient NPSH (when forcing high flow on very viscous oil) and mechanical overload with motor thermal trip (when actual field viscosity exceeds design). The golden rule is to size at minimum start-up viscosity, not regime viscosity. In heavy mineral oil, viscosity at 20 °C can be four to six times higher than at 60 °C — and cold start is where 80% of mechanical failures manifest.

For mineral, hydraulic and commercial lubricating oils at temperatures up to 80 °C, the standard FBE configuration is cast iron ASTM A48 CL30 casing, SAE 8620 gears, SAE 1045 shafts and sealing by graphite packing or type 21 mechanical seal (ceramic × graphite × viton, AISI 304 spring). This configuration has typical field life of eight to twelve years in continuous operation and is the economically correct choice in 70% of oil applications. For vegetable oils in food industry, sanitary requirements mandate AISI 316 stainless casing and gears (ASTM A743 CF8M), with FDA-type sanitary mechanical seal. For transformer dielectric oils, the priority is to avoid any moisture or ferrous particulate contamination — recommended configuration: stainless casing, double mechanical seal with barrier oil reservoir, and 10-micron filter on the suction. For residual or disposal oils with abrasive particulates, the FBEI internal gear line is preferred for its lower number of metal-to-metal contact points and greater tolerance to suspended solids. In extreme cases (used oils with emulsified water and sediments), silicon carbide bushings can be specified for erosion resistance.

FB Bombas has manufactured external gear pumps since 1944 in Cabreúva, Brazil, and the FBE line is the historical choice of Brazilian refineries, lubricant plants, steelmakers and sugar mills for oil transfer. The real differentiators are three: local manufacturing of spare parts (no import dependency versus Edral, Hidex, RZR, Viking, Netzsch or Maag), direct API 676 3rd edition compliance, and application engineering support in Portuguese directly with the people who design the pump. Active Petrobras CRCC in Family 6 (Rotating Equipment) confirms FBE homologation for direct supply to the Petrobras chain, including refineries where heavy fuel oils and naphtha are pumped 24/7. For industries replacing end-of-life imported pumps, the FBE offers dimensional drop-in replacement compatible with major brands in DN 1/2" to 6" — fast specification, reduced delivery lead time and substantially lower total cost of ownership.