KNOWLEDGE / 2026.09.04

Hydraulic Power Unit Sizing Guide

Start with what your machine needs to move and hold. Record the pressure, flow and cycle time. Then check the power supply, available space, ports and required documents with an engineer.

Published: 2026-09-04

Revised: 2026-09-26

Describe the equipment and motion first

Describe each machine action in order: move, clamp, hold and release. For a machine builder or fixture buyer, this sequence helps explain the job the power unit must do.

For workholding, record movement time and holding time separately. Do several stations move at once? What pressure must each clamp hold? Add the electrical supply and available space to the same note. These details help the engineer assess the whole cycle.

Prepare the operating inputs

Bring the known values to the first engineering conversation. Unknown items can be identified for follow-up rather than assumed.

Minimum data set

Equipment and motion description
Operating pressure and required pump flow rate, with units
Duty cycle and pressure-holding requirement
Power supply
Available installation space and port details
Destination-market documents and requirements

Keep the selection boundary visible

Use the SC-QT manual to make a shortlist. Before ordering, confirm the model, ports, power supply and required documents with engineering. A listed configuration does not fit every machine.

FAQ

Frequently asked questions

Can we start before every value is known?

Yes. Submit the known equipment, motion, pressure, flow and duty information first; missing inputs should be confirmed during project review.

Is a current manual configuration an automatic match?

No. Manual-listed configurations support pre-selection only. Final fit requires confirmation of the project boundary and documents.

Hydraulic power pack selection: from motion to configuration

Separate measured inputs from unknowns

Note the unit and source of each value. Was it measured or estimated? Record the machine condition too. Mark missing pressure, flow, voltage or port details as unknown. Send this sheet with the model code, circuit drawing and available installation space. This helps purchasing and engineering work from the same facts.

How to size a hydraulic power unit for the load

Start with the load requirements: what must move, at what speed, and for how long? Note which stations move together and how long each clamp must hold. Record working pressure and any known pressure peaks. For high pressure duties, have the engineer check the ratings of hoses, valves and fittings as well as the power unit. A higher pressure setting is not a substitute for this review.

How to calculate hydraulic power unit requirements

Hydraulic output power in kW = pressure difference in bar × actual flow in L/min ÷ 600, or MPa × L/min ÷ 60. Illustrative example: 5 MPa × 12 L/min ÷ 60 = 1 kW of hydraulic output. This is not a 1 kW motor recommendation or a confirmed SC-QT configuration. Pump losses increase the required shaft power; motor losses also affect electrical input. Check starting load, duty cycle and heat with engineering before choosing the drive.

Flow units: gallons per minute or litres per minute?

Use one unit throughout the input sheet. If flow is given in gallons per minute (gpm), state whether the gallon is US or Imperial. For US units, multiply gpm by 3.78541 to get L/min. For example, 5 US gpm is about 18.93 L/min. This is a unit conversion, not a product rating. Keep peak movement flow separate from the flow needed during a hold.

Check the hydraulic reservoir and usable oil volume

The hydraulic reservoir stores oil and helps release heat and trapped air. Ask the engineer to review tank size, oil level changes through the cycle, return and suction positions, and access for service. A rule of thumb based only on pump flow is not enough to approve a tank. In hydraulic systems with short movements and long holds, review the full cycle before choosing a listed reservoir option.

Specify hydraulic fluid and fluid temperature

Record the hydraulic fluid type and viscosity grade already used by the machine. Note the cold-start temperature, normal fluid temperature and the highest measured value, including where it was measured. Temperature affects oil viscosity. Check the permitted oil and temperature range against the selected pump, valves and seals. Do not assume that one oil grade or temperature limit suits every SC-QT configuration.

Review heat dissipation before choosing cooling

For a cooling review, provide the duty cycle, highest ambient temperature, oil flow and target oil temperature. Include measured heat load if available; otherwise mark it as unknown. Leave room for airflow and service. Ask engineering whether the tank can release enough heat or a cooler is needed. Do not infer cooling capacity from motor power or tank volume alone, or assume a cooler is included in the quote.

Confirm the complete hydraulic power pack design

Include the reservoir, ports, control sequence, electrical supply and space for service in the review. Request the configuration drawing and agreed supply scope with the quotation, then use the factory acceptance checklist to verify the same requirements before dispatch.

Calculation reference: Parker HY29-0026/UK, p. 5 (PDF)

Engineering references: Parker: reservoir functions (PDF, p. 5); Parker: cooler sizing inputs (PDF); NIST: unit conversions. These support the general guidance above; they do not specify Shanchuan product configurations.

ENERGY INTO VALUE

Less idle running. More value.

Make each holding phase count. Stop the motor after motion, then recharge when pressure reaches the set threshold, reducing energy use and heat from continuous idle running.

Save 75% or more in short-motion, long-hold applications. Turn reduced electricity use into lower running costs and get more value from every clamping cycle.

Annual electricity cost savingkWh avoided × electricity tariff

Review the savings potential of your machine →

Hydraulic power unit selection: prepare one input sheet

To choose a hydraulic power pack, record movement flow, holding pressure, simultaneous stations, electrical supply and available space. Identify measured values and unresolved inputs before comparing configurations. The calculations in this guide support an engineering review; they do not approve a particular motor, tank or pressure setting.