In your search for information about hydraulic vs pneumatic torque wrench, you will find out both are used in heavy industrial application.
Controlled torque in industrial applications is very important. In the industrial setting, we do not use the small tools such as click torque wrenches, since their maximum torque is too limited.
The two main tools used in heavy torque applications are the hydraulic and pneumatic torque wrenches.
In heavy construction, motor vehicle assembly, metalwork, oil rigs and large ships, there are heavy-duty fasteners. To tighten such nuts and bolts, you need to torque them to the recommended pressure/force.
This is where the hydraulic, pneumatic and electric torque wrenches come in.
These tools may be intended for the same purpose, which is the application of precise force on fasteners. However, they still have some differences.
By design, the pneumatic one uses air for power while the other one uses hydraulics (fluid). Physically, the two power tools look very different.
What is a hydraulic torque wrench?
These are two different tools; otherwise, they would have the same name. The hydraulic torque wrench comes in two types. There is the low profile one and then there is the one that comes with a square drive.
If a tool uses hydraulics for power, it means it is using pressurized fluid. A small amount of fluid can be subjected to a lot of pressure to produce a lot of force.
In this case, hydraulic powered torque wrenches can be used to apply torque levels of more than 20,000 ft-lb. A typical torque range for hydraulic-type torque wrenches is 150 to 29,000 ft-lb.
Compared to a digital torque wrench that has a torque range of 5 to 200 ft-lb, you can see just how powerful a hydraulic powered torque wrench is.
Water-soluble oil is the main fluid used in hydraulic systems. It is pressurized and circulated under controlled conditions to the motor, where it is then converted to mechanical energy.
Low profile hydraulic torque wrench
What is low profile torque wrench? As the name suggests, this is a small hydraulic-powered tool that fits over bolts in tight spaces.
The main parts of the low profile hydraulic-powered wrench are the cassette that can fit a given fastener size.
The cassette is not a permanent feature because you can change the cassettes depending on the fasteners that you want to tighten.
Another part of the torque wrench is the drive, which connects to the hydraulic pump. This is the power source that powers this tool.
Low-profile hydraulic torque wrenches slip over a bolt in tight or recessed spaces. This torque wrench consists of a cassette that fits a specific bolt size and a drive that connects to a hydraulic pump to provide power. Cassettes can be changed to match the bolt shape and diameter.
Square drive hydraulic torque wrench
From the name, perhaps you can already tell that this torque wrench comes with a fixed square head, just like a manual torque wrench.
To use this type of torque wrench, you will need a square or hexagonal adapter. Adapter just means socket, the same way you would need one with a click or manual torque wrench.
The square drive is fixed and it is on one side. It increases the bulkiness of the wrench, which makes it harder to reach fasteners in squeezed spaces.
Please note that the main difference between the square drive hydraulic type torque wrench and the low profile one is that the latter slips onto the bolt that it is tightening or loosening.
How a hydraulic torque wrench works
Knowing the best hydraulic torque wrench to buy is not enough. You must also know how it works so that you can get the full value of your money out of it.
There is a learning curve, so you need to read the user manual keenly. Some companies will even take you for training to know how to use these tools.
You should not take the information here as your main guide because every tool is different. What we will bring you here are just guidelines for how a hydraulic tool works.
To get the full effectiveness of this tool, first, there are a few things to take care of. You must know the recommended torque of the fasteners that you are tightening.
You can ask your company engineers or you can read the service manual (if you are working on a truck or bus).
Read the user manual to know how to connect the tool to the hydraulic pump, and how to set the torque on the torque wrench. The torque that you set must match that of the fastener.
Wear the appropriate protective gear when working with this tool. It is heavy and it uses a source of power. These are high-pressure tools since they use hydraulic fluid under high pressure of up to 10,000PSI. Equally, they have a high torque output of up to 50,000 ft-lb.
Remember also that the hydraulic pump is not the main source of power. Electricity or an air compressor power the hydraulic pump and in return, it powers the torque wrench.
Follow the guidelines; give the machinery a visual check to ensure that everything is in good order.
What is a pneumatic torque wrench?
This is one of the most advanced torque wrenches in the market. Like the hydraulic type, it comes with a motor, which provides the power to tighten fasteners. However, in the pneumatic style torque wrench, the motor is powered by air pressure from a compressor.
This tool can perform high-speed rotations and tighten high-torque fasteners faster. This is why this type of torque wrench is used in automotive garages, factories, aircraft hangars and other industrial settings.
This kind of high power torque wrench also comes with a planetary gearbox. This kind of gear is used in systems that are restricted to small sizes but have to have a high torque output.
On the same note, this type of gearing is also safer for the tool, the user and the equipment they are working on.
Types of pneumatic torque wrenches
Pneumatic torque wrenches come in two main types. These are stall torque nutrunners and shut-off nutrunners.
Shut-off nutrunner
This kind of torque wrench runs continuously until you achieve the torque that you had set and then it stops tightening.
This is the safest type of a pneumatic-style wrench to use because it leaves no room for error. Once it tightens the nuts to completion, it just stops completely.
If you do not have experience using this kind of a power tool, this one will be easy to use. It is especially good for uniform tightening jobs and it can help you work speedily.
Stall torque nutrunners
To use this kind of pneumatic torque wrench, you should set the air pressure because of the torque. If you set a high air pressure, the wrench will tighten harder and longer.
These tools give continuous rotation but the torque applied on the fastener will depend on the air pressure that you have set.
To set the torque that you want to tighten your fastener to, you ought to know the correct air pressure level to reach that torque.
You should also be careful because varying the air pressure will definitely change the torque applied on a fastener.
As you can see, the stall torque nutrunners have a learning curve, so they may not be too good for beginners.
How does pneumatic torque wrench work
Using a pneumatic torque wrench requires some learning. There is some setting up to do to connect the air hoses and all.
To know how this torque wrench works, you need to know how it is built. Inside, a turbine-rotor turns a shaft inside the gearbox.
On the end of the shaft, there is an adjustable clutch that will fall when it reaches a given tension (the preset torque level).
On the other end of the shaft, you can attach the socket that you are using to tighten your fasteners. What happens here is that when you tighten the nut, the clutch holds until you reach the final torque. When that happens, the clutch is released and the wrench stops tightening.
Air-powered torque wrenches are light in weight. Therefore, they are used in automotive garages. They can also be used on the delicate car parts in the engine bay. If it can fit in the space, use it because it is very accurate.
Even for heavy-duty nuts and bolts that require a large amount of torque, you can use the pneumatic wrench because it absorbs all of the vibration so your arms will not feel a thing.
Hydraulic vs Pneumatic Torque Wrench: How They Compare
If you are wondering what to get between the pneumatic and hydraulic torque wrench, well, it is best to compare the two side-by-side, so that you can take the one with the most features.
Here, we are going to look at the performance of the two tools, at different factors such as speed, accuracy, usability, price and size/weight.
Accuracy: Hydraulic wins
The accuracy of a precision tool is very vital. That is the entire point behind buying a torque wrench rather than using a regular spanner for the job.
The complex working mechanism of the hydraulic torque wrenches makes them more accurate, with an accuracy rating of +/-3%.
Pneumatic torque wrenches on the other hand have a lower accuracy rating of +/-5%. While this is not too bad, if you want the torque to be as close to 100% of the set value as possible, you had better use a hydraulic powered torque wrench.
You will also find that repeatable torque accuracy differs between the two tools. The accuracy of the repeatable torque of the hydraulic torque wrench is +1% while that of the pneumatic one is 2%.
Usability: Pneumatic wins
If you are a beginner and the only choice you have is between these two types of torque wrenches, go with the pneumatic one.
It has a shorter learning curve. It is light in weight and even connecting it to the air compressor and tweaking the regulator and the gauges is simple enough.
The hydraulic torque wrench is a bit complicated to use. Even the setup is a bit complicated, so you will have to refer to the manual at every step.
You can get a pneumatic torque wrench with a digital display so that you can set the torque easily, and so you can watch the pressure and everything.
You can also get a hydraulic type wrench that has a display so you can see the pressure of the hydraulic fluid and your real-time torque.
You can use both tools to tighten and loosen fasteners.
Size and weight: Hydraulic wins
Pneumatic adjustable torque wrench looks bulbous and big. It is bulky and heavy, sometimes weighing even up to 25 pounds. However, if you are strong, you can still use it for long hours without feeling too cramped at the wrists.
Hydraulic adjustable torque wrench is smaller, lighter and the low profile one can be used to tighten industrial fasteners in squeezed spaces. Most of the hydraulic type wrenches weigh less than 10 pounds.
Don’t also forget that both tools use pumps, one for air and the other for hydraulic fluid, as their power source. If you are thinking about weight and portability, it can be a headache to travel with the different components.
Working speed: Pneumatic wins
The pneumatic wrench works fast because it can run at 10 or higher RPM (for the very advanced ones).
The hydraulic torque wrench can barely get up to 3 RPM. If you are doing a lot of repetitive work at the garage, you might want to choose the pneumatic over the hydraulic torque wrench.
Cost: Pneumatic is cheap
Cost is one of the determining factors for what to get between pneumatic torque wrench vs hydraulic wrench. And the pneumatic one can be as cheap as 50% compared to the cost of the hydraulic wrench.
The hydraulic wrench must come with a hydraulic pump so that it can work. The pneumatic one requires no such thing.
Even buying the electric hydraulic pump itself is more expensive than an electric air compressor for working with your air-powered torque wrench.
Wrapping Up
Your choice of a heavy-duty torque applicator is not limited to the hydraulic vs pneumatic torque wrench.
There is also the electric torque wrench. However, eventually, for industrial torque applications, the choice comes down to pneumatic or hydraulic torque wrench.
Both will give you good value for money. However, they require keener maintenance, storage and usage than the smaller torque wrenches.
Using pneumatic and hydraulic torque wrenches follows just about the same process. It goes as follows:
- Assembling the components (mostly for the hydraulic one since it comes dismantled)
- Setting the torque value that you require
- Use the right socket for the fastener you are tightening. For the hydraulic one, you will use a cassette matching the fastener you want to tighten.
Hydraulics work very differently from pneumatic systems, so the process will never be exactly the same. Learn how each tool works carefully before you use it.