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Hydraulic Systems

Thermostatic mixing and diverting valves regulate hydraulic fluid temperature to maintain viscosity and protect system components.

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Hydraulic Fluid Temperature Control

Hydraulic systems generate heat as fluid moves through pumps, valves, and other components. Hydraulic system temperature control helps keep the fluid within the viscosity range required for reliable operation.

As fluid temperature rises, viscosity decreases. When temperatures exceed recommended limits, the resulting changes in fluid properties can reduce lubrication, affect sealing, increase the risk of pump cavitation, and shorten component life. Cold hydraulic fluid creates different challenges. Higher viscosity increases resistance to flow and can place additional load on the system during start-up.

Maintaining the required operating range helps preserve fluid properties and component life, support consistent system performance, and reduce temperature-related maintenance and downtime.

Below Recommended Range

  • Higher fluid viscosity 
  • Increased resistance to flow 
  • Higher pressure drop 
  • Greater start-up load

Above Recommended Range

  • Lower fluid viscosity 
  • Reduced lubrication 
  • Increased internal leakage 
  • Higher pump cavitation risk 
  • Accelerated fluid degradation and varnish formation 
  • Seal and component deterioration

How Thermostatic Valves Control Hydraulic Cooling

ThermOmegaTech® thermostatic control valves respond directly to fluid conditions to regulate the cooling circuit without external power, sensors, or electronic controls.

Depending on the system layout, hydraulic fluid can be mixed, diverted, or routed through a bypass with integrated pressure relief. By adjusting cooling flow automatically, these valves help reduce temperature-related component wear, maintenance, and unplanned downtime.

Mixing Mode

A 3-way thermostatic mixing valve combines two incoming fluid streams at different temperatures and proportions the flow to maintain the required outlet condition.

Diverting Mode

A 3-way diverting valve directs one incoming fluid stream between the oil cooler and bypass path based on fluid temperature.

Thermal Bypass with Pressure Relief

Some systems require both automatic temperature control and protection from excessive pressure across the oil cooler or heat exchanger. The TBV-PR combines thermostatic bypass with integrated pressure relief. If pressure exceeds the predetermined relief setting, the valve opens the bypass path to reduce pressure and protect the cooler and system from excessive pressure buildup.

Explore Thermal Bypass

Common Hydraulic Applications

Self-actuating temperature control valves (TCVs) can be incorporated into industrial hydraulic systems including:

  • Hydraulic power units – Hydraulic oil temperature control for varying system loads
  • Hydrostatic drive systems – Fluid management during start-up and continuous operation
  • Mobile hydraulic equipment – Automatic control across changing loads and ambient conditions
  • Industrial machinery – Hydraulic systems with continuous or variable-duty cycles
  • Hydraulic cooling circuits – Oil coolers, heat exchangers, and other bypass arrangements

Related Products

Product Title Industry Application
TBV-PR Thermal Bypass Valve with Pressure Relief Industrial Thermal Bypass
M/D Thermostatic Mixing & Diverting Valve Industrial, Aerospace & Defense Thermal Bypass, Avionics & Electronics Cooling, Fuel & Oil Thermal Management

Need Help with Your System?

For standard valve selection, availability, and ordering, contact a ThermOmegaTech® Industrial Distributor.

For OEM or application-specific systems, ThermOmegaTech® can review your fluid, operating range, flow, pressure, and cooling circuit to help determine the appropriate mixing, diverting, or bypass solution.