How to Select the Best Hydraulic Suction and Return Hoses

In a hydraulic system, the return of working fluid rarely follows the exact same path it took when pressurized (such as in a simple hydraulic jack). More commonly, fluid is pumped through one line, completes its work, and then flows back to the reservoir through a separate suction and return hose. This is where hydraulic return hoses come into play.

Return hoses are typically made of flexible rubber materials, often referred to as hydraulic oil return hoses. Unlike pressure lines, return hoses are not exposed to extreme pressures, but they must offer excellent resistance to oil and compatibility with various types of hydraulic fluids and oil-based media. For this reason, return hoses generally do not use steel wire reinforcement. Instead, they rely on textile braids or fabric layers, sometimes combined with helical steel wire for additional flexibility and structural integrity.

When designing or maintaining a hydraulic system, selecting the right suction and return lines is critical to achieving reliable performance. These hoses ensure efficient fluid transfer between components while minimizing the risk of contamination, cavitation, and system failures. In this guide, we will explore what hydraulic suction and return lines are, their functions, and how to choose the most suitable option for your system.

What Is a Hydraulic Suction Hose?

A suction line connects the hydraulic reservoir to the pump, allowing fluid to flow smoothly into the pump. Its primary function is to ensure a continuous supply of hydraulic oil at low pressure, preventing interruptions that could lead to pump damage.

Key Considerations for Suction Hose

1. Material and Construction
Suction hoses are typically made from reinforced rubber or thermoplastic materials designed to withstand vacuum conditions. The construction must be both flexible and durable to prevent collapse when the pump draws fluid under suction.

2. Inside Diameter (ID)
The internal diameter of the suction line should be sufficiently large to prevent cavitation and minimize pressure drop. An undersized hose can restrict flow, leading to pump starvation, cavitation, and premature pump failure.

3. Compatibility
Always ensure that the hose material is compatible with the type of hydraulic fluid used. Incompatibility can result in swelling, degradation, reduced performance, and system contamination.

4. Operating Temperature and Pressure
Suction hoses must withstand the temperature range and vacuum levels of the hydraulic system. Before installation, verify the hose’s rated temperature and pressure capabilities to ensure reliable performance under working conditions.

What Is a Hydraulic Return Hose?

A return line carries hydraulic fluid from system components back to the reservoir. Unlike pressure lines, return hoses typically operate under low pressure but must be capable of handling high flow rates.

Key Considerations for Return Hoses

1. Flow Capacity
Return hoses must be sized to handle high fluid volumes without causing excessive back pressure. Choosing a hose with an adequate inside diameter ensures smooth flow and prevents system inefficiencies, especially during peak flow conditions.

2. Pressure Rating
Although return lines operate at lower pressures compared to supply or pressure hoses, they should still be rated according to the system’s operating conditions. This is particularly important in systems subject to pressure surges or fluctuations.

3. Filtration
Installing return-line filters helps capture contaminants before the fluid re-enters the reservoir. Cleaner oil reduces wear, improves system reliability, and extends the overall service life of hydraulic components.

4. Material Durability
Return hoses are often exposed to challenging environmental conditions. Selecting hoses with abrasion-resistant covers and weather-resistant materials ensures long-term durability and reduced maintenance requirements.

Key Differences Between Suction and Return Hoses

Pressure Conditions

Suction lines: operate under vacuum/low pressure, risk of collapse

Return lines: low pressure but constant flow, need oil resistance

Fluid Compatibility

Both must withstand hydraulic oils and additives

Reinforcement Structure

Suction hoses: usually reinforced with helical wire to prevent collapse

Return hoses: reinforced with textile braids or fabric layers, sometimes light steel helix

Functions of Hydraulic Suction and Return Hoses

1. Ensuring Fluid Circulation
In a hydraulic system, oil is delivered from the reservoir to actuators (such as hydraulic cylinders) to perform work. After completing its function, the fluid must return to the reservoir to allow the pump and other components to continue operating. The primary role of the return line—such as those used in excavators—is to channel hydraulic fluid back to the reservoir, ensuring continuous circulation and proper system operation.

2. Pressure Balancing
Return lines also play an important role in pressure stabilization within the hydraulic system. When actuators are in operation, hydraulic fluid is subjected to varying pressure levels. To maintain system stability and safety, these pressures must be equalized. The return line helps dissipate excess pressure and balance conditions throughout the circuit, contributing to reliable and smooth system performance.

3. Heat Dissipation
Hydraulic fluid naturally generates heat during operation. Without proper cooling, the fluid temperature may rise excessively, reducing system efficiency and shortening component lifespan. By directing the oil back to the reservoir, the return line facilitates cooling, either directly in the tank or through external heat exchangers, helping to maintain optimal operating temperatures.

Return lines are essential for the safe and efficient operation of hydraulic systems. They ensure continuous fluid circulation, help stabilize pressure, and assist in cooling the hydraulic oil. Regular inspection and maintenance of return hoses are crucial to prevent failures, reduce downtime, and extend the service life of hydraulic equipment such as excavators.

How to Determine the Right Hydraulic Suction and Return Hoses

Selecting the best suction and return hoses requires balancing system requirements, hose specifications, and operating conditions. Here is a step-by-step guide:

1. Understand System Requirements

• Identify the working pressure and operating temperature.

• Measure the maximum flow rate in both the suction and return lines.

• Evaluate environmental factors such as exposure to heat, cold, abrasion, or chemicals.

2. Choose the Correct Hose Size

• Use hose ID charts to match flow rate and pressure requirements.

• For suction lines, prioritize minimizing pressure drop to prevent cavitation.

• For return lines, ensure the hose can handle peak return flow without causing back pressure.

3. Pay Attention to Compatibility

• Verify that the hose material is compatible with the hydraulic fluid used.

• Select hoses designed for specific fluids, whether petroleum-based, synthetic, or biodegradable oils.

4. Check Certifications and Standards Compliance

• Choose hoses that meet industry standards such as SAE (Society of Automotive Engineers) or ISO (International Organization for Standardization) for reliability and safety.

5. Consider Hose Assembly Requirements

• Use high-quality fittings and connectors to minimize the risk of leakage.

• Secure hoses properly with clamps or brackets to reduce vibration, abrasion, and premature wear.

Common Mistakes to Avoid When Selecting Suction and Return Hoses

1. Using Undersized Hoses
Installing hoses with an inside diameter smaller than recommended can cause different problems depending on whether the hose is a return line or a suction line:

• Return Lines

  • Restricted flow can create back pressure in the return hose.

  • Increased back pressure limits upstream pressure, potentially causing overheating, reduced efficiency, and component damage.

• Suction Lines

  • Flow restriction at the pump inlet may create negative pressure or vacuum conditions in the suction line.

  • This can lead to pump cavitation, resulting in pump damage, reduced system performance, and lower overall system pressure.

2. Ignoring Pressure Ratings
Even though suction and return hoses typically operate at lower pressures than supply hoses, exceeding their rated pressure can cause failures or hose rupture.

3. Neglecting Filtration
Failure to install return-line filters allows contaminants to circulate, increasing wear on system components and reducing the service life of the hydraulic system.

Common Applications of Hydraulic Suction and Return Hoses

Hydraulic hoses are designed to transport various types of fluids and operate under the specific conditions of different systems. Choosing the right hose based on fluid type and application can significantly impact both system performance and hose longevity. Below are some common applications of hydraulic suction and return hoses categorized by fluid and system type:

1. Water-Based Hydraulic Fluids
Water-based hydraulic oils are often used in fire-resistant applications, such as mining or industrial environments. Hoses compatible with these fluids must resist water absorption and remain flexible at low temperatures. They are typically used in systems requiring safer, non-flammable hydraulic fluids.

2. Thermal Fluid Heating Systems
In thermal fluid heating systems, hoses are exposed to high temperatures while conveying heated fluids to maintain system efficiency. These hoses must withstand extreme heat without performance degradation. Typical applications include industrial heating processes or specialized machinery such as plastic molding equipment.

3. Petroleum-Based Fluids
Hoses for petroleum-based fluids must resist the chemical properties of oils and other hydrocarbons. These hoses are critical in applications such as oil and gas extraction, transport, and storage, where durability and fluid compatibility are essential for safe and reliable operation.

4. High-Pressure Applications
Certain hydraulic systems, such as industrial presses or heavy-duty mining equipment, operate under extremely high pressures. Hoses designed for high-pressure applications are reinforced to prevent failure and ensure safety in demanding environments.

5. Transmission Oil Cooler Lines
Hoses used in transmission oil cooler circuits are designed to handle high-temperature oil flow and provide effective cooling to prevent system overheating. These hoses are commonly found in automotive and industrial machinery, where maintaining proper transmission function is critical.

Maintenance of Hydraulic Suction and Return Hoses

1. Regular Inspections

• Check hoses for signs of wear, such as cracking, abrasion, or leaks.

• Inspect the tightness of connections and fittings to ensure secure installation.

2. Timely Replacement

• Replace hoses immediately if any damage is detected or when they reach the end of their service life.

• Always use OEM (Original Equipment Manufacturer) or high-quality aftermarket hoses and fittings to ensure reliability.

3. Maintaining System Cleanliness

• Regularly flush the hydraulic system to prevent contamination buildup.

• Maintain proper fluid levels and remove contaminants through effective filtration.

4. Filter Selection and Maintenance

• Using return-line filters with incorrect flow ratings can create back pressure, reducing efficiency and potentially damaging system components.

• Regular maintenance of filters is crucial to prevent clogging, which can increase back pressure and system load.

Select Sinopulse SAE 100R4 Suction and Return Hoses

This R4 hose combination meets a variety of suction and return application needs.

SAE 100R4 Suction and Return Line Construction
Inner Tube: Synthetic Rubber
Reinforcement: Multiple layers of fiber braid and one helical wire (the spiral withstands vacuum conditions up to 25 inches/Hg to prevent collapse).
Cover: Synthetic rubber, MSHA compliant

Features
Bend radius up to half the SAE minimum bend radius, suitable for standard and high-temperature applications, petroleum-based hydraulic fluids and lubricants
Meets or exceeds SAE 100R4 standard requirements
Interchangeable with Aeroquip FC318, Gates G4, Parker 881, and Weatherhead H039
Compatible with 188-24 - Hydraulic Suction and Return Lines Male NPTF valve stem, designed and engineered specifically for hydraulic suction line applications using SAE100R4 hydraulic hose. High-visibility laying line
Suitable for vacuum applications from 25 to 28 inches/Hg
Oil-resistant and weather-resistant synthetic rubber cover
811 petroleum-based hydraulic fluid with a high temperature range of -40°F to +257°F

Specification

Conclusion

Selecting the right hydraulic suction and return hoses is essential for the smooth operation of any hydraulic system. By understanding system requirements and considering hose size, material compatibility, and pressure ratings, you can ensure optimal performance and long service life. Regular maintenance and proper installation further reduce the risk of system failures and extend the lifespan of both hoses and hydraulic components.

Need help?

Contact your Sinopulse sales representative or email us to speak with a member of our hose expert customer service team.