Excessive heat causes oil viscosity to drop, leading to internal
leakage,
seal degradation, and component failure. Implementing an effective cooling
strategy—whether
through air blast coolers or plate heat exchangers—is
vital for system longevity.
Heat Load Formula
Ploss = Pin × (1 - η)
Ploss: Heat to dissipate (kW) | Pin: Input Power
(kW)
| η: System Efficiency
1. Air Blast Coolers
Utilizing ambient air to remove heat from the oil, air blast coolers are ideal for
mobile applications or facilities where water is scarce. They consist
of a
radiator core and an electric or hydraulic fan.
- Plug &
Play: Easy
installation with minimal infrastructure.
- Reliability:
Robust
design suitable for harsh environments.
- Noise: Fan
noise
must be considered in indoor settings.
2. Water-Cooled Heat Exchangers
For high-power industrial units, water cooling offers superior density. Plate
heat
exchangers (PHE) provide high thermal efficiency in a compact footprint,
while
Shell & Tube designs offer lower pressure drops for viscous fluids.
3. Thermal Bypass Valves
Starting a cold system with full cooling flow can damage the cooler core due to pressure
spikes (viscous oil) and delay the system reaching operating temp. Use a thermal
bypass valve to circulate oil back to the tank until it reaches ~40°C.
"Cooling isn't an accessory; it's a life support system. A 10°C rise above 60°C cuts
oil
life in half."
— BRS PROSES Engineering
4. BRS PROSES Solutions
We integrate smart cooling solutions into every HPU we design:
- Thermostatic
Control: Fan cycles only when needed to save energy.
- Integrated
Pump:
Independent circulation circuits for constant cooling flow.
- Sizing Service:
Accurate calculation based on your duty cycle and ambient conditions.
6. Mathematical Thermal Balance Modeling in Industrial HPU Reservoirs
Operating hydraulic oil above 60°C accelerates fluid oxidation, sludging, and elastomer degradation (doubling chemical aging rate for every 10°C increase based on the Arrhenius rate law). Designing a cooling system requires calculating steady-state heat generation ($P_v$):
P_{\text{heat}} = (1 - \eta_{\text{total}}) \cdot P_{\text{installed}} \quad [kW] \quad \text{with} \quad P_{\text{heat}} \approx 0.20\text{ to }0.35 \times P_{\text{electric}}
The natural heat dissipation ($P_{ ext{natural}}$) radiating through the steel reservoir shell depends on fluid-to-ambient temperature delta ($Delta T = T_{ ext{oil}} - T_{ ext{ambient}}$) and tank wetted surface area ($A_{ ext{tank}}$). If $P_{ ext{heat}} > P_{ ext{natural}}$, an external heat exchanger must be integrated to dissipate the net thermal surplus.
7. Air-Oil Blast Coolers vs. Plate Water-Oil Heat Exchangers
Selecting the cooling medium dictates plant piping infrastructure and operational stability during extreme summer heatwaves:
| Cooler Technology |
Heat Transfer Coefficient |
Cooling Medium Requirement |
Optimal Factory Environment |
| Air-Oil Radiator with 24V/380V Fan |
20 – 40 W/(m²·K) |
Ambient air (No water supply needed) |
Mobile machinery, standalone factory units |
| Brazed Plate Water Exchanger (AISI 316) |
1,000 – 2,500 W/(m²·K) |
Plant cooling tower water (15–25°C) |
Heavy continuous presses, hot forging mills |
| Thermostatic Bypass Valve Integration |
Eliminates cold-start backpressure |
Bypasses cooler until oil reaches 45°C |
Prevents over-cooling and saves radiator fan energy |
Thermal Balance Calculation & Cooler Sizing (Air-Blast vs Water-Cooled)
A hydraulic system that operates above 60°C experiences accelerated oil oxidation, rapid seal hardening (loss of elastic memory), and severe breakdown of the hydrodynamic lubricating film between pump components. In industrial hydraulic power packs, sizing heat dissipation equipment requires an accurate determination of continuous power loss:
P_loss = P_installed × (1 - η_overall)
For standard industrial systems, overall hydraulic efficiency ((η)) ranges from 70% to 80%. Thus, 20% to 30% of total installed electric motor power must be continuously rejected into the atmosphere or water circuit as thermal energy.
Selection Criteria: Air-Blast Radiators vs Brazed Plate Heat Exchangers
- Air-Oil Coolers: Ideal where cooling water is unavailable or expensive. Sizing factor: (Q / Delta T) [kW/°C]. Requires sizing for worst-case summer ambient temperatures (e.g. 40°C), resulting in a permissible oil temp of 55°C ((Delta T = 15°C)).
- Water-Oil Plate Exchangers: Delivers superior heat transfer efficiency (up to 4x more compact than air coolers) and consistent oil temperatures regardless of ambient weather, but requires water treatment to prevent calcium scale clogging.
- Thermostatic Bypass Valves: Critical during cold morning startups. The bypass valve routes oil around the cooler until fluid reaches 45°C, preventing over-cooling and high pump cavitation risks.
Technical Field Inspection & Commissioning Protocol
Prior to signing off on any fluid power retrofit, system upgrade, or routine component overhaul, technical commissioning engineers must rigorously complete the following verification procedures to ensure full compliance with ISO machinery safety standards:
- Static Hydrostatic / Pneumatic Pressure Proof Test: Pressurize circuit to 1.5× maximum design working pressure for 15 minutes, inspecting all welded flanges and fittings for micro-weeping.
- Contamination & Fluid Particle Verification: Draw dynamic fluid samples under working temperature and confirm ISO 4406 cleanliness classes (or ISO 8573-1 air dew point classes) before activating sensitive proportional spool valves.
- Thermal Baseline Profiling: Record continuous thermal infrared scans of pump casings, valve manifold manifolds, and accumulator bodies across 4 hours of full-load production cycles to confirm proper thermal dissipation.
- Failsafe & Emergency De-energization: Verify manual LOTO isolation valves, dump valves, and accumulator vent blocks discharge trapped hydraulic/pneumatic kinetic energy to 0 bar within 2.0 seconds of emergency e-stop triggering.
