Hydraulic Gear Pump

In an industrial Hydraulic Power Unit (HPU), the pump is the primary component that converts mechanical energy from the electric motor into hydraulic energy (flow × pressure) delivered to the circuit. Three technologies compete in this role: external gear, vane and axial piston. Each has a distinct application envelope. The external gear pump is the standard choice for medium-pressure applications (up to 200 bar in heavy industrial versions, up to 22 kgf/cm² ~22 bar in the standard FBE line) with requirements of robustness, contamination tolerance and low maintenance cost. Volumetric efficiency is 85-95% on ISO VG 32-68 oil, gradually declining over service life from tooth and clearance wear. Compared to vane, it is more tolerant of cold start and pressure spikes. Compared to axial piston, it is dramatically cheaper (between 1/4 and 1/3 the price) and does not require the 10-micron filtration that piston demands. The hydraulic FBE niche covers small-to-medium HPUs (up to 100 kW), auxiliary circuits in machine tools, forced lubrication systems in industrial gearboxes, service-pressure circuits in hydraulic presses, elevators and platforms, slewing systems in cranes, and lubrication in large planetary gearboxes (steel, mining, cement). For applications above 100 kW or sustained pressure above 200 bar, the correct technology becomes axial piston — outside the FBE scope.

• Small/medium Hydraulic Power Unit (HPU) — FBE 3/4" to 3", 1,150-1,750 rpm
• Industrial gearbox forced lubrication — FBE 1/2" to 2", low pressure
• Service hydraulic press (up to 200 bar) — robust FBE 2" to 4"
• Machine tool (lathe, CNC mill) — FBE 1/2" to 1" with very low noise
• Crane / platform slewing system — FBE 1" to 2" in carbon steel
• Auxiliary circuit in large gearbox (steel/mining) — FBE with external bearing

Pump sizing for a hydraulic power unit follows four chained parameters: useful flow (Q), working pressure (p), rotation (n) and drive power (P). Useful flow is determined by the speed and area of hydraulic actuators (cylinders, hydraulic motors) the circuit must feed, discounting typical 90% volumetric efficiency and return-to-tank flow. Working pressure is the maximum value the circuit demands in regime — generally 80-90% of the limiting-valve opening pressure. For pressures up to 22 kgf/cm² (~22 bar), standard FBE serves. Above that, manufacturing is custom with reinforced gears and specific bearings. Rotation is calculated by FBE manual Table 2 as a function of hydraulic oil viscosity: ISO VG 32-46 allows 1,750 rpm, ISO VG 68-100 limits to 1,150 rpm. Drive power follows the formula P (kW) = Q (L/min) × p (bar) / (600 × η), where η is pump overall efficiency (volumetric × mechanical), typically 0.80 for FBE. Practical example: 50 L/min HPU at 150 bar with FBE 2" at 1,150 rpm requires motor of P = 50 × 150 / (600 × 0.80) = 15.6 kW ≈ 20 HP. Slight oversizing is standard practice to handle transient peaks and cold start.

Hydraulic oil is the most decisive component for gear-pump service life — more than the mechanical construction itself. ISO VG 32 oils are typical for HPUs in cold environments (underground garages, uncontrolled-temperature factories), enabling ambient-temperature start-up of 5-10 °C. ISO VG 46 is the most common specification in industrial applications in climate-controlled environments (25-35 °C). ISO VG 68 is used in presses and heavy circuits with high sustained pressure (50-60 °C regime operation). Modern hydraulic oils fall into three main categories. HLP (DIN 51524-2) is the classic category with anti-wear, antioxidant and antifoam additives — refined mineral base. HVLP (DIN 51524-3) adds viscosity-index improver (dissolved polymer) that reduces viscosity variation with temperature — more stable but with shear that degrades the polymer over time. HEES biodegradable oils (synthetic esters) and HEPG (polyalkylene glycols) are required in equipment near water courses or in regulated environments. For each category, sealing-elastomer specification is distinct. Standard HLP and HVLP: standard viton. Biodegradable HEES: special viton GLT-S. HEPG: EPDM (viton is incompatible). FBE is supplied with appropriate elastomer upon oil specification — common error is specifying standard viton for HEPG circuit, causing seal failure in 30-90 days. Typical type-21 seal service life on properly filtered HLP hydraulic oil is 18-36 months in continuous operation.

The number-one cause of premature failure in hydraulic gear pumps is oil contamination — solid particles, water and dissolved air. ISO 4406 classifies cleanliness by particle count in three size ranges; for hydraulic FBE, recommended class is 20/18/15 (acceptable) to 18/16/13 (ideal). Levels above 21/19/16 accelerate tooth and bushing wear by 3-5 times. Three typical contamination sources are: internal wear particles (tooth, bushing, seal fragments); environmental ingress (dust, moisture through tank cover); and manufacturing residues (swarf, foundry sand, cleaning solvents). Correct specification includes suction filter with β₂₀ ≥ 100 rating (retains 99% of particles ≥ 20 µm) and, in critical systems, pressure filter β₁₀ ≥ 200 on the discharge. Tank-admission mesh eliminates particles above 150 µm. Water contamination is especially damaging. Dissolved water (<0.5% by volume) is tolerated by most HLP oils, but free water (emulsified or settled) produces gear rusting, hydrolysis of anti-wear additives and sludge formation. Control is done via heat exchanger (keeps oil below 60 °C, avoiding condensation in the reservoir), silica-gel breathers and periodic exchange per physicochemical analysis. For circuits where process water can leak into oil (machining with coolant, presses with spray), installing a vacuum purifier is mandatory.

FB Bombas has supplied gear pumps for Brazilian industrial hydraulic circuits for over 70 years. The FBE line is specified in steel projects (forced rolling-mill lubrication, hydraulic closing systems), mining (crusher, ball-mill and conveyor-belt reducer lubrication), cement plants (kiln and mill planetary gearboxes), pulp and paper (roll-press hydraulic systems), and industrial equipment manufacturers (mechanical and hydraulic presses, plastic injection machines, machine tools). The technical advantage versus imported hydraulic pumps (Bosch Rexroth, Parker, Eaton Vickers) is specific: for the up-to-22 kgf/cm² (~22 bar) range in auxiliary circuits and small-to-medium HPUs, FBE delivers functional equivalence at 40-60% lower cost and 100% domestic spare parts. For sustained pressures above 200 bar or flows above 500 L/min, the correct technology is axial piston — in that case, FB's recommendation is the manufacturer's original pump, since external gear operates outside its optimal envelope. Technical support includes analysis of the complete hydraulic circuit (not just the pump), filtration recommendation, reservoir-tank sizing and heat-exchanger specification when needed. For replacement of end-of-life pumps, sending nameplate and circuit data to comercial@fbbombas.com.br returns an equivalent FBE specification in 48-72 hours. Active Petrobras CRCC enables direct supply to refineries.