Managing Heat Dissipation in Hydraulic Systems
Smart design and maintenance choices to keep your system cool and efficient.
Heat is one of the most common and costly enemies of hydraulic system performance. Excessive heat shortens the life of oil and seals, reduces component efficiency, and leads to unexpected downtime. The good news? You can avoid many overheating issues with the right approach to system design, heat exchanger sizing, and ongoing maintenance.
Don’t Create Excess Heat in the First Place
The best strategy for managing heat is preventing it from being generated in the first place. That starts with smart design decisions, such as avoiding excessive pressure drop (PSID) and properly
sizing your hydraulic power unit(HPU). As we’ve discussed in previous blog posts, undersized components, inefficient flow paths, and unnecessary restrictions all contribute to energy being converted to heat instead of useful work.
Heat Exchanger Basics: Air-Over-Oil vs. Water-Over-Oil
When your application does require heat removal, heat exchangers are the go-to solution.
There are two primary types:
• Air-over-oil (A/O): Uses ambient air to cool hydraulic fluid via forced convection
• Water-over-oil (W/O): Uses circulating water to remove heat through fluid-to-fluid exchange
Each has its place. Air-over-oil coolers are commonly used in mobile or outdoor systems, whereas water-over-oil models are typically found in industrial settings with high cooling requirements.
The Importance of Proper Sizing
Sizing a heat exchanger isn’t a guess; it’s a calculation based on your system’s operating temperature goals and the actual temperature differential available. Many manufacturers’ sizing charts assume a 100°F temperature differential. But in reality, that figure can vary significantly depending on your environment and target fluid temperature.
For air-over-oil systems, ambient air temperature is the critical variable. In hot climates or enclosed spaces, your actual differential may be much smaller than you think. Mounting location matters too; restricted airflow can render even a well-sized cooler ineffective.
For water-over-oil systems, the temperature and flow rate of the incoming water are key. If water is too warm or flow is inconsistent, the exchanger won’t perform as expected.
At FSC, we work closely with our vendor partners to accurately size heat exchangers using manufacturer-specific software, ensuring a match to the exact needs of your application.
Maintenance Matters
Even the best heat exchanger won’t perform if it’s neglected.
• A/O coolers must be kept clear of dust and debris—clogged fins dramatically reduce cooling efficiency.
• W/O systems are vulnerable to calcification and scaling in the tubes, especially when using untreated water.
Routine inspection and cleaning help keep these systems working as intended.
Application Examples
Some systems, such as rear-mount mobile equipment, only require light cooling. Others, like hydraulic test stands, demand far more. In test environments where no useful mechanical work is being done, 100% of the hydraulic horsepower turns into heat. That heat must be removed entirely to keep the system running safely.
Need help selecting or sizing a hydraulic heat exchanger?
Our team of experts is here to help, from application review to vendor-supported sizing tools and long-term support. Contact us today!
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