Mastering Hydraulic Systems: A Comprehensive Guide to Calculating Pressure and Flow Requirements for HPU Pumps

Delta Hydraulics has you covered when calculating pressure and flow requirements for a hydraulic pump on your hydraulic power unit. Our team of hydraulic repair specialists is well-versed in all aspects of hydraulics. Hydraulic power units (HPUs) are vital in various industrial applications, powering hydraulic systems that operate heavy machinery and equipment.

Determining the pressure and flow requirements for HPU pumps is essential for ensuring optimal performance and efficiency. In this blog post, we will explore the factors to consider when calculating pressure and flow requirements with tips from our experts! 

Understanding Pressure and Flow Requirements

Pressure and flow are two fundamental parameters that influence the performance and functionality of hydraulic systems. Pressure is the force exerted on the fluid, measured in pounds per square inch (psi) or bar, while flow refers to the rate at which the fluid moves, typically expressed in gallons per minute (GPM) or liters per minute (LPM).

Quick Tips for Calculating Pressure and Flow Requirements:

  • Consider the size and velocity of the actuators.
  • Account for efficiency in your calculations.

Calculating Pressure and Flow Requirements

Before choosing a pump for your HPU, it is essential to calculate the pressure and flow requirements accurately. To determine the flow required by your hydraulic pump, you must know the size and velocity of the actuators it will power. Calculating the maximum flow required during simultaneous actuator operation is crucial, such as when a motor and cylinder work in tandem.

Additionally, always factor in efficiency during your calculations to avoid disappointment during commissioning. While calculating the flow requirement for a hydraulic motor is easier, cylinders present a challenge due to their cycling with differential volumes.

Calculating Pressure Requirements

Determining the pressure requirements for HPU pumps involves considering the specific hydraulic applications and their operating conditions. Here are some key factors to keep in mind:

System Load: Evaluate the maximum load or force the hydraulic system needs to generate. This includes the equipment’s weight, the required force to perform a specific task, or any resistance encountered in the system.

Safety Margin: Incorporate a safety margin for unexpected or transient loads. It ensures the hydraulic system can manage occasional peak demands without compromising performance or causing damage.

Pressure Drops: Consider pressure drops caused by valves, filters, hoses, and fittings. These pressure losses must be accounted for to maintain the desired pressure at critical points within the system.

Calculating Flow Requirements

To determine the flow your hydraulic pump requires, it is essential to know the size and velocity of the actuators it will power. 


Motor Flow Requirements

Delta Hydraulics offers a simplified calculation method for hydraulic motor flow requirements, as follows:

Flow Required (in gallons per minute, GPM) = (Cubic Displacement (CID) x Efficiency (eff) x RPM) / 231

Here’s an example:

Cubic Displacement (CID): 2.5 in² Efficiency (eff): 0.8 Revolutions per Minute (RPM): 1200

Flow Required = (2.5 x 0.8 x 1200) / 231 = 10.4 GPM

It’s important to note that the motor’s efficiency rating can change with varying speed and pressure, so conducting thorough research is necessary to ensure accurate calculations.

Calculating Cylinder Flow Requirements

Calculating cylinder flow requirements involves more complex calculations due to differential volumes. Here’s a step-by-step guide provided by Delta Hydraulics:

Calculate the volume of the cap side: Cap Side Volume = (πr²) x Stroke

Calculate the volume of the rod side: Rod Side Volume = Cap Side Volume – Rod Volume

Example: Cylinder Bore: 4 inches Stroke Length: 12 inches Rod Diameter: 1 inch

Cap Side Volume = π(2²) x 12 = 150.8 in³ Rod Side Volume = 150.8 – (π(0.5²) x 12) = 94.2 in³

Determine the required volume to achieve the desired stroke time: GPM Required = (Volume / Time) / 231

Example: Desired Stroke Time: 3 seconds

Cap Side Flow Required = (150.8 / 0.05) / 231 = 13 GPM Rod Side Flow Required = (94.2 / 0.05) / 231 = 8 GPM

Considering the combined volumes of all simultaneously operating actuators is crucial to determine the ideal pump flow. In certain situations, compromises may be necessary.

Proper flow calculation ensures that the hydraulic system operates optimally and delivers the necessary performance. Consider the following factors when calculating flow requirements:

Actuator Speed and Volume: Evaluate the speed at which the hydraulic actuators need to move and the volume of fluid required to achieve the desired motion. This information is crucial in determining the flow rate required from the HPU pump.

Multiple Actuators: If the hydraulic system operates multiple actuators simultaneously, sum up their individual flow requirements to determine the total flow rate needed.

Efficiency Considerations: Account for system inefficiencies, such as pressure losses, fluid leakage, and volumetric losses in valves or cylinders. These factors affect the flow rate required and help choose the appropriate pump capacity.

Let Delta Hydraulics Do the Calculations for You

Delta Hydraulics excels in calculating flow requirements for HPU pumps, ensuring their customers receive the optimal pump size for their hydraulic systems. Our engineers can estimate the required flow rates accurately by considering actuator speed, volume, and system efficiencies. This attention to detail allows Delta Hydraulics to deliver high-performance HPUs that enhance the overall efficiency and productivity of their customer’s operations.

Phillip and Jeffrey in Delta Hydraulics Shop

On-Site Hydraulic Repair, Field Service, and Consultation

Our field technicians perform on-site inspection and repair services. If your operation has hit a roadblock, we can swiftly restore your pump’s functionality. Our reliable and experienced team can provide diagnostic services and perform minor repairs for equipment and machinery across various industries.

Get In Touch for Your Free Consultation

Calculating pressure and flow requirements for HPU pumps is critical in ensuring optimal performance and efficiency in hydraulic systems. You can ensure that the hydraulic system operates reliably and efficiently by carefully evaluating system load, safety margins, pressure drops, actuator speed, and efficiency considerations. At Delta Hydraulics, we possess the expertise and resources to assist you.

Delta Hydraulics’ expertise in pressure and flow calculations empowers them to deliver tailor-made HPU pumps that meet the precise requirements of diverse industrial applications. By choosing Delta Hydraulics, you can rely on their wealth of experience and commitment to excellence in hydraulic solutions. Whether you require repairs, on-site services, or consultations, our team is dedicated to providing top-notch solutions. Contact us today to benefit from our comprehensive hydraulic services. Remember, when it comes to hydraulics, Delta Hydraulics has you covered.