Single Acting vs Double Acting Hydraulic Power Packs: What’s the Difference?

Choosing the right hydraulic power pack starts with one simple question: does your cylinder need hydraulic power in one direction, or in both directions?

The basic difference between single acting and double acting applies to both AC and DC hydraulic power packs. In this guide, we are focusing mainly on Flowfit’s DC single acting and DC double acting hydraulic power pack ranges.

Single acting

Best for lifting and tipping applications where gravity, spring force, or load weight can return the cylinder.

Shop single acting power packs

Double acting

Best for applications that need powered movement in both directions, such as pushing, pulling, clamping, or controlled retraction.

Shop double acting power packs

Quick answer

A single acting hydraulic power pack powers the cylinder one way. A double acting hydraulic power pack powers the cylinder both ways. If you are replacing an existing unit, the cylinder usually gives the first clue: one port often means single acting, while two ports often means double acting.

Jump to:

1) What is a hydraulic power pack?
2) What is a single acting hydraulic power pack?
3) What is a double acting hydraulic power pack?
4) Single acting vs double acting: key differences
5) Single acting and double acting circuit diagrams
6) Which hydraulic power pack do you need?
7) Need help choosing the right hydraulic power pack?

Single acting power packs Double acting power packs

1. What Is a Hydraulic Power Pack?

A hydraulic power pack, also known as a hydraulic power unit, is the part of a hydraulic system that generates oil flow and pressure. It usually includes a motor, hydraulic pump, oil tank, valves, and control equipment.

The power pack sends hydraulic oil to a cylinder or hydraulic component, creating the force needed to lift, push, pull, tip, clamp, or move a load. Hydraulic power packs are commonly used on tipping trailers, tail lifts, scissor lifts, agricultural machinery, loading ramps, presses, and mobile equipment.

Whether the power pack is AC or DC, it is important to know whether the cylinder is single acting or double acting. This affects how the cylinder moves, how many hydraulic lines are required, and what type of control valve the system needs.

2. What Is a Single Acting Hydraulic Power Pack?

A single acting hydraulic power pack is designed to power a hydraulic cylinder in one direction only. In most applications, the power pack uses hydraulic pressure to extend the cylinder, while the return movement is handled by gravity, spring force, or the weight of the load.

A common example is a tipping trailer. The power pack raises the trailer body by sending oil to the cylinder. When the trailer is lowered, gravity brings the body back down and the oil returns to the tank.

Common uses for single acting hydraulic power packs

Tipping trailers
Tipper trucks
Agricultural trailers
Scissor lifts
Lift tables
Material handling equipment
Applications where gravity can return the cylinder

Common choice

Single acting hydraulic power packs are often chosen for lifting and tipping applications where powered movement is only needed in one direction.

Browse Flowfit’s single acting hydraulic power packs if your application needs hydraulic force in one direction and gravity or load weight can return the cylinder.

3. What Is a Double Acting Hydraulic Power Pack?

A double acting hydraulic power pack is designed to power a hydraulic cylinder in both directions. Instead of relying on gravity or a spring to return the cylinder, hydraulic pressure is used to both extend and retract it.

This gives the operator more control over the movement of the cylinder. It is useful when the application needs powered movement both ways, or when the load needs to be pushed and pulled rather than simply lifted and lowered.

Common uses for double acting hydraulic power packs

Hydraulic presses
Machinery clamps
Loading ramps
Plant equipment
Agricultural machinery
Snow ploughs
Applications that need controlled extension and retraction

More control

Double acting hydraulic power packs are usually selected when the cylinder needs positive hydraulic force in both directions.

Browse Flowfit’s double acting hydraulic power packs if your system needs powered movement for both extension and retraction.

4. Single Acting vs Double Acting Hydraulic Power Packs

The main difference between single acting and double acting hydraulic power packs is how the cylinder moves and returns. A single acting system powers the cylinder in one direction, while a double acting system powers it in both directions.

Feature	Single acting hydraulic power pack	Double acting hydraulic power pack
Movement	Powers the cylinder in one direction	Powers the cylinder in both directions
Return method	Gravity, spring force, or load weight	Hydraulic pressure
Cylinder type	Single acting cylinder	Double acting cylinder
Typical number of cylinder ports	One port	Two ports
Best for	Lifting, tipping, and gravity-return applications	Pushing, pulling, clamping, opening, closing, and controlled movement
Common applications	Tipping trailers, scissor lifts, lift tables	Presses, ramps, clamps, plant and agricultural machinery

Simple way to remember it

Single acting = power one way.
Double acting = power both ways.

5. Single Acting and Double Acting Circuit Diagrams

The diagrams below show the basic difference between a single acting and double acting hydraulic circuit. A single acting power pack sends hydraulic pressure to move the cylinder in one direction, while a double acting power pack controls the cylinder in both directions.

Single acting hydraulic power pack circuit diagram showing hydraulic pressure moving the cylinder in one direction — Single acting hydraulic circuit: hydraulic pressure moves the cylinder one way, with gravity or load weight returning it.

Double acting hydraulic power pack circuit diagram showing hydraulic pressure extending and retracting the cylinder — Double acting hydraulic circuit: hydraulic pressure controls both extension and retraction.

6. Which Hydraulic Power Pack Do You Need?

The best way to choose between a single acting and double acting hydraulic power pack is to look at what your cylinder needs to do. The cylinder, application, load, and required level of control all matter.

Check the cylinder type
A single acting cylinder usually has one hydraulic port. A double acting cylinder usually has two hydraulic ports.
Look at how the load returns
If gravity or a spring can return the cylinder, a single acting power pack may be suitable. If the cylinder must be powered back, choose double acting.
Think about control
If you need controlled movement in both directions, a double acting power pack is normally the better choice.
Consider the application
Tipping trailers and lift tables are often single acting. Presses, clamps, ramps, and machinery with powered return are often double acting.
Check pressure, flow, voltage, and tank size
The acting type is only one part of the selection. You also need to match the power pack to the system pressure, oil flow, duty cycle, voltage, and oil capacity required.

If you are replacing an existing power pack, it is also worth checking the motor voltage, pump size, tank capacity, mounting arrangement, valve type, and port connections before ordering.

Expert tip

If your hydraulic cylinder has one hose going to it, it is often single acting. If it has two hoses, it is often double acting. There are exceptions, so check the system layout or ask our team if you are unsure.

7. Need Help Choosing the Right Hydraulic Power Pack?

Flowfit supplies a wide range of DC hydraulic power packs ready to buy online, including single acting hydraulic power packs and double acting hydraulic power packs. Whether you are replacing an existing unit or building a new hydraulic system, our team can help you identify the most suitable option.

Tip: Before replacing a power pack, check the cylinder type, voltage, pressure, flow rate, tank size and port sizes.