Let me guess, you just took the physics class because you had to, and have no memory of hydraulics whatsoever?

Same here.

But now that you suddenly need to know about the workings of a hydraulic pump – I’ll go to school on the subject and give you the cliff notes.

Simply put, a hydraulic pump converts the mechanical energy of the fluid into hydraulic energy (flashback to the law of energy conversion). It does so by generating enough flow to create pressure that creates resistance to fluid flow in the system. This helps overcome pressure due to the load of the system.

Hydraulic Pump
Hydraulic Pumps convert mechanical energy to hydraulic energy

Let’s take a closer look at how this works.

Ready? Let’s go!

How an Air Hydraulic Pump Works

I do my best to avoid technical jargon. But you’ll need to bear with me a bit in this post.

Hydraulic Pump Process
Hydraulic pump process diagram

Here’s a step-by-step on the air hydraulic pump process:

  1. Air flows from the air post to the bottom of the air piston (11) through a space called the spool valve (10).
  2. The air piston in the driving unit moves to the right, causing the pump to perform a suction stroke.
  3. Next, through this space called the inlet valve (3), the fluid moves into the high-pressure piston system.
  4. Then, through the suction port (2), the fluid is sucked in.
  5. As a feedback control, the air moves from the air port to the spool valve. This causes the valve to switch positions.
  6. The spool valve then connects a silencer to the chamber (located below the air piston). Then through a port R, the air is allowed to escape and reaches the top of the air piston.
  7. As a result of a pressure stroke, the air piston in the drive unit moves to the left. Ultimately, the inlet valve is closed.
  8. All these actions finally lead to the opening of the pressure valve. The high pressure piston then drives the fluid (pumped in earlier).
  9. All of this in turn leads to energy production.


Try to map these steps to the diagram above. That’ll help you understand things a bit better.

Air Driven Hydraulic Pump vs Pneumatic Pump

Heard about different kinds of hydraulic pumps before? Then you might know there are two main types. Pneumatic, and hydraulic pump.

A pneumatic pump, as the name indicates, is a confined pressurized system that uses air or other compressible gases as fluid.

It’s usually designed as an open system and is not as affected by leakage. And it generally requires a compressor for proper functioning. This kind of pump is often used in the drills used by dentists, the dentist chair, brakes in different buses and cars, and even in nail guns.

A hydraulic pump, as we discussed above – is a pressurized system that uses moving liquids. Since liquids are less compressible, the movement and force are usually much faster.

However, since gases are compressible there’s a slight delay in movement and decrease in force. The hydraulic pump is usually designed as a closed system and is prone to slowing down due to leakage.

The advantages of both types largely depend on the application and its requirements.

A pneumatic system is preferable for pumps that don’t require a high output force. They’re more affordable and lightweight.

These kinds of pumps are less combustive and less prone to leak-damage. However, they’re not suitable for applications that require a stronger force. They’re also more prone to corrosion and need frequent lubrication.

In contrast, an air driven hydraulic pump produces a high output force and produces a continuous variable transmission.

It’s less prone to corrosion due to its automated lubrication. However, it is more prone to malfunction due to leakage.

Types Of Hydraulic Pumps

There are three main types of hydraulic pumps; gear, piston, and vane. The air-driven hydraulic pump is a type of piston pump. They’re further classified based on their function. here are some common types:

  1. Gear Pumps: This is one of the most common designs for hydraulic pumps. It’s also more affordable than other types. They usually use a fixed, positive displacement pump.

    This pump transports oil around the circumference of the gear cavity and forces it through its outlet port. It’s easy to maintain and more contaminant resistant.
  1. Piston Pumps: These are usually used in settings that deal with high operating pressures. They usually have a fixed or variable displacement design that uses pistons to move up and down drawing oil from the supply port and driving it through the outlet. They’re usually more expensive and more sensitive to contamination
  1. Vane Pumps: The vane pump has been largely replaced by gear pumps nowadays. It has an input shaft that rotates causing oil to be drawn into the vanes and transported to the outlet. They were usually seen in high utility vehicles before gear pumps came along.
  1. Clutch Pumps: These are small-displacement pumps that are belt-driven. They’re commonly seen in low-force applications like hay spikes, aerial bucket trucks, and wreckers.
  1. Dump Pumps: You may have seen these types of pumps before. It has an integrated 3-position 3-way direction control valve. They’re specifically used in dump trucks.

Uses Of an Air Hydraulic Pump

Now that we’ve looked at different kinds of hydraulic pumps and their applications, let’s see what air-driven hydraulic pumps are usually used for:

  • For pressure testing, while installing oil and gas pipelines
  • They’re used in the CNG industry for certifying correct storage and associated equipment
  • They’re used in the fire fighting industry to test extinguisher pressures and to fill them with carbon dioxide gas
  • For certification of pressure vessels during manufacturing
  • They’re used during refrigerator manufacturing for evacuation and refilling of gases
  • Used in the defense industry for pressure testing of equipment

There are many more uses of air-driven hydraulic pumps. But they’re mainly used for their pressure-testing ability.


Air driven hydraulic pumps are used widely thanks to their high-pressure capabilities. Now you have a much better idea how they work. That gives you a better working understanding of machines utilizing such hydraulic pumps.

This will also help you better diagnose problems if you work with a machine that uses such pumps.

I hope this post simplified one of the more technical things we talk about. Feel free to check out similar articles on our site.

Thanks for reading. Have a great day!