Specifying a hydraulic power unit starts with three hard numbers — operating pressure in bar, nominal flow in l/min, and the driving motor's kW — and then layers in tank volume, duty cycle and the prime-mover class (electric, air-driven, diesel/gasoline) [S1][S2].
DirectIndustry's catalogue lists 22 manufacturers offering 33 air-driven power units and 12 manufacturers covering 29 construction-class packs, with electric drives accounting for roughly two-thirds of construction units and combustion engines plus air-drives splitting the remainder [S1][S2].
Pressure Class and Flow Envelope by Drive Type
Air-driven hydraulic power packs span the widest pressure range on the market, with one Maximator-style product line covering 100, 600, 1000, 2000 and 4000 bar stages for clamping and test rigs, and the PP-series pneumo-hydraulic units reaching 4000 bar at 0.01–0.25 l/min from a 5–10 l tank [S1].
Electric construction units sit in a much tighter envelope: BAUER's HD 470 delivers 320–350 bar at 470–640 l/min from a 261 kW motor, while the smaller HD 250 produces 320 bar at 250–380 l/min from 176 kW, and HPU-18 reaches 200 bar at 85 l/min from a 30 kW motor [S2].
Combustion-engine packs trade peak pressure for portability — the ASPID and Super ASPID deliver 140–210 bar at 20–30 l/min, and the SUPER RAPTOR 23 HP twin-cylinder gasoline unit produces 150 bar at 20–45 l/min [S2].
Reservoir Sizing, Cooling, and the Heat-Balance Constraint
Reservoir capacity is the dominant thermal buffer: HYTORC's HY-Air air-driven pack is offered with 5.1 or 7.6 l tanks for torque-wrench duty, and air-driven PP-series units ship with 5–10 l reservoirs sized for short, intermittent tool cycles rather than continuous run [S1].
For continuous industrial use, the e4training hydraulic power-unit simulation models power-in, power-out, cooling power and radiated heat loss to predict when off-line cooling is required to stabilise bulk oil temperature [S7].
Otis elevator power units use a submerged motor configuration specifically to cut external oil leaks and to keep the pump and motor below the oil surface, which reduces wear and damps radiated noise in passenger-building applications [S9].
Prime-Mover Selection: Electric, Air, or Combustion
Electric drives dominate where three-phase mains are available and ambient noise is regulated: 19 of the 29 construction units in the DirectIndustry index are electrically powered, versus 6 combustion-engine units and 3 air-driven units [S2].
Air-driven hydraulic power units are specified where electricity is unavailable, restricted or intrinsically unsafe — typical use cases include gas-sensitive tunnels, offshore modules and torque-wrench bays with existing compressed-air reticulation [S1][S2].
Diesel and gasoline packs remain the only practical option for mobile rescue, civil-protection and remote pipeline work: Hycon's HPP13D FLEX pairs a 10 hp single-cylinder KOHLER KD15-440 diesel with 11 l tank capacity to drive any 20–30 l/min hydraulic tool in confined or gas-sensitive environments [S2].
Application-Fit Comparison Across the Main Variants
On four decision criteria — pressure ceiling, flow ceiling, mobility, and intrinsic safety — the variants split cleanly. Electric construction units lead on flow (up to 640 l/min on the HD 470) and on pressure-to-flow efficiency, but require grid power [S2].
Air-driven units lead on pressure ceiling (up to 4000 bar) and on use in electrically classified areas, but trail badly on flow — the PP-series is capped at 0.25 l/min [S1].
Combustion-engine units lead on mobility and grid-independence but cap out near 210 bar and 45 l/min, which rules them out of high-pressure clamping and high-flow foundation work [S2].
Cost Drivers and Build Specification Levers
Zeus Hydratech's buyer-facing guidance identifies project scale, scope, component specification and customisation as the dominant cost levers, with motor power, pump type, reservoir size, valve manifold and certification requirements each moving the price band independently [S8].
For low-voltage shop equipment, Jiangsu VIBO's tyre-changer power unit bundles a 380 V, 1.5 kW, 1400 rpm three-phase motor with a 3.3 cc/rev pump at 16 MPa (160 bar) max, a horizontal G1/4" oil port and a CMC manifold — a compact reference build for 140–160 bar intermittent duty [S10].
Weihai Forward Hydraulics, Hanzhuoli Hydraulic Technology (Jinan) and Jiangsu VIBO all list hydraulic power units alongside gear pumps, reservoirs and telescopic cylinders, signalling that Chinese tier-1 suppliers treat the HPU as a configurable sub-assembly rather than a fixed SKU [S3][S6][S10].
Who Should Not Pick the Default Electric Unit
If the duty cycle is mobile, the site has no three-phase supply, or the surrounding area is electrically classified, an electric pack is the wrong default — air-driven or diesel-driven units should be specified instead, with the air-driven option adding a 4:1–10:1 pressure-amplification benefit at the cost of flow [S1][S2].
For high-flow continuous industrial machines, the hydraulic power unit must be sized against actuator demand using a hydraulic cylinder load profile, with valve logic handled through a dedicated FRL unit on the pneumatic supply line and motion delivered by a matched hydraulic actuator.
Buyers integrating HPUs into skids with hazardous-area certification should cross-reference the hazardous-area skid hydraulic valve selection criteria guide, since valve and manifold approvals often dictate the certification route for the whole pack.
Selection Checklist and Trackable Signals
Run a four-line check before commissioning any HPU: (1) confirm required pressure and flow against the actuator's worst-case load, (2) size the reservoir to at least 3× nominal flow-per-minute for continuous duty, (3) match the prime mover to the site's power and safety classification, and (4) verify the hydraulic power unit cooling path against the [e4training simulation model](https://www.e4training.com/hyd_powerunits/powerunit3.php) to avoid thermal runaway. [S1]
Yuken Projects' Hydraulic Powerpack Configurator is one trackable engineering tool for aviation, construction, energy, industrial and marine HPUs, and direct-engineering dialogue with tier-1 Chinese suppliers (Weihai Forward, Hanzhuoli, Jiangsu VIBO) remains the fastest path to a custom build at the 30–200 kW / 80–350 bar band [S3][S5][S6][S10].