Impact Wrench Cfm: Understanding Air Power Requirements

Air impact wrenches are commonly used in the automotive industry to fit or remove lug nuts on a car. Pneumatic impact wrenches are often preferred to electric ones because they are more lightweight and powerful, and they do not carry the risk of sparks or electric shocks. The torque of an impact wrench depends on the pressure of the air fed by the air compressor. The typical CFM (cubic feet per minute) ratings for different drive sizes are as follows: 3/8” – 3 CFM @ 90 psi, 1/2” – 4-5 CFM @ 90 psi, and 1” – 8-10 CFM @ 90 psi.

CFM requirements for continuous vs intermittent use

The CFM (cubic feet per minute) requirements for air tools depend on whether they are used continuously or intermittently.

If you are using an air tool, such as an impact wrench, continuously, you will need an air compressor with a 100% duty cycle so that you can operate the tool without interruption.

On the other hand, if you are using a tool intermittently, in quick bursts with short breaks in between, a less powerful air compressor may suffice. This is because the compressor has time to catch up between uses.

When determining the CFM requirements for your application, it is important to consider the duty cycle, which refers to the percentage of time an air compressor can run before it needs a break. The average CFM rating for air tools is based on a 25% duty cycle. Therefore, it is often recommended that your compressor's CFM rating is 1.5 times that of your air tool to prevent overworking the compressor.

For example, a 1/2" drive impact wrench typically requires about 5 CFM of airflow at 90 psi. To ensure continuous operation, the airflow rating of the air compressor should be 7.5 CFM (3/2 x 5 CFM).

Additionally, the size of the air compressor's tank will determine how long you can use the tool continuously without switching on the motor. For instance, a compressor tank with a capacity of 25-30 litres (6-8 gallons) will allow for approximately one hour of continuous operation of an impact wrench with a 5 CFM airflow requirement.

It is also worth noting that if you are running multiple tools simultaneously, you will need to add the CFM requirements of each tool to determine the total CFM demand.

In summary, when considering CFM requirements for continuous vs intermittent use, factors such as duty cycle, tank size, and the number of tools being used simultaneously will influence the CFM rating needed for your air compressor.

Air receiver tanks

An air receiver tank, also known as an air compressor tank or compressed air storage tank, is an integral part of any compressed air system. Its main function is to act as temporary storage to accommodate peak demands from the system and to optimise the efficiency of the plant.

• Moisture removal: Air tanks cool the air within the compressor system to remove water, preventing corrosion and maintaining the integrity of the system.
• Pulsation reduction: Air compressor tanks can reduce or eliminate pulsations or vibrations in the system.
• Improved torque and speed: Air tanks can improve the torque or speed of pneumatic-powered equipment by helping to maintain a continuous pressure level.
• Supplementing high-flow applications: Tanks can supply compressed air to meet the needs of high-flow-rate applications and multiple sources of demand.

There are two types of air receivers: wet air receivers and dry air receivers. Wet air receivers are installed between the compressor and the air dryer, while dry air receivers are placed after the compressor and air dryer. Their primary function is to maintain the integrity and quality of the dried air, ensuring consistent system performance and reliability.

When choosing an air receiver tank, it is important to consider the compressor output, system size, and air demand cycles. The size of the tank should be based on these factors to ensure it meets the needs of the application.

Airflow requirements for different drive sizes

The drive size of an impact wrench is an important factor in determining the airflow requirements of the air compressor needed to power it. The airflow required by an impact wrench is measured in CFM (cubic feet per minute). Most air tools require a certain CFM of airflow at 90 psi pressure while running free.

• 3/8” drive: 3 CFM @ 90 psi
• 1/2” drive: 4-5 CFM @ 90 psi
• 1” drive: 8-10 CFM @ 90 psi

It is important to note that these are the minimum CFM values. The air compressor you choose must be able to deliver at least this amount of airflow at 90 psi pressure for the impact wrench to run freely. As a rule of thumb, the airflow from the air compressor should be at least 3/2 times the minimum requirement of the impact wrench.

For example, a 1/2" drive impact wrench typically requires around 5 CFM of airflow at 90 psi. Therefore, the airflow rating of the air compressor should be 3/2 x 5 = 7.5 CFM or higher.

When selecting an air compressor, it is crucial to consider not only the CFM rating but also the size of the compressor's tank, as this will determine how long you can use the impact wrench continuously without having to switch on the motor.

Additionally, the intended use of the impact wrench and the number of tools being used simultaneously will also impact the airflow requirements. If you plan to use the impact wrench for extended periods or have multiple tools in use at the same time, a larger industrial air compressor with a higher CFM rating may be necessary.

It is always recommended to refer to the manufacturer's specifications and guidelines when determining the airflow requirements for your specific impact wrench and air compressor setup.

Impact wrench torque

The torque delivered by an impact wrench depends on the tool and the pressure of the air fed by the air compressor. The torque delivered increases the longer you hold the trigger. Therefore, if you have the dial on '3', you might get 100 ft/lbs if you hold the trigger for 2 seconds, and 120 ft/lbs of torque if you hold the trigger for 4 seconds.

The amount of torque delivered by an impact wrench is not intended to deliver specified torque values. Counting the number of impacts is one way to estimate the amount of torque being applied.

If you want to tighten something to a specified torque, you will need a torque wrench or torque sticks. Torque sticks are a good investment if you are using the gun for a variety of tasks. They are accurate and consistent when used with the same impact wrench.

Air compressor tank size

The size of an air compressor tank is an important consideration when choosing an air compressor to run an impact wrench. The tank size determines how long you can use the impact wrench continuously without switching on the motor.

Air compressor tanks can vary in size, from small tanks (2 gallons) to medium-sized tanks (6-16 gallons) and large tanks (over 30 gallons). You can also find tanks that can hold 80-100 gallons of air. The optimum tank size depends on how long you want to use the air tool. As a rule of thumb, it is recommended to have a tank size of at least 5 to 6 times the airflow requirement of the tool.

For example, if an impact wrench has an airflow requirement of 5 CFM, then the tank size of the air compressor should be at least 25 to 30 liters (6-8 gallons). This would allow the impact wrench to operate for about an hour or an hour and a half.

It is important to note that these are just recommendations. If you use multiple tools simultaneously or have a large garage or workshop, a larger tank size and a more powerful air compressor may be more beneficial.

When choosing an air compressor, it is crucial to consider the CFM (cubic feet per minute) rating, which indicates the volume of air produced or required. Air compressors for powering tools typically fall within the 10 to 110 CFM range. Lower CFM ratings are suitable for small tools, while higher CFM ratings are designed for industrial applications and larger tools.

In summary, when selecting an air compressor for an impact wrench, consider the tank size, the CFM rating, and your specific usage requirements to ensure you have sufficient airflow and continuous operation for your tasks.

Frequently asked questions