Features of the operation of the pneumatic wrench

Every expert is aware that the most time-consuming task when installing constructions or fixing mechanisms is the process of unscrewing and screwing threaded connections. However, when using pneumatic wrenches for these purposes, such work becomes a mere formality. This handy tool has numerous benefits, but it is worth delving into the details of its operation.

The design and principle of operation of the pneumatic wrench

In the diagram provided below, you can observe the detailed configuration of the pneumatic wrench. The device comprises several components that are housed within a robust metal case.

1. A high-performance pneumatic motor.
2. An impact mechanism.
3. An alloy steel chuck, also known as a stop.
4. A torque regulator and reverse mechanism.
5. A start button.
6. A connector for attaching the compressor hose.
7. An air valve.

This tool is significantly lighter compared to its electric counterpart since it lacks a motor. Additionally, the wrench exhibits high torque, ranging from 300 to 2200 Nm (Newtons per meter).

The pneumatic wrench consists of two main power units, each designed for different modes of operation. The first unit is an pneumatic motor that provides rotary motion to the tool head. The second unit is responsible for generating impact loads. The pneumatic actuator rotates when compressed air passes through it, which is supplied through a high-pressure hose from the compressor.

The unit body has two channels, each directing air in different directions relative to the turbine. In one case, the air pushes the turbine in the clockwise direction to tighten, while in the other case, it pushes against the clockwise direction to unscrew fasteners. The distribution of air flows is controlled by a special switch.

The operation principle of the pneumatic wrench is as follows:

• After pressing the start button, the valve is activated, allowing air to flow from the hose into the device and begin moving through the turbine, causing it to rotate.
• From the turbine, the rotary motion is transmitted to the impactor, which functions similarly to a clutch. The impactor consists of two complexly shaped cams that generate impact force when the fastener needs additional torque during release.
• Next, the rotational motion is transferred to the stop (chuck), onto which a nozzle is attached to fit a specific nut size. This allows the fastener to be screwed or unscrewed. In some air wrenches, screwing is done without the use of an impact mechanism, resulting in a quieter operation.
• If the nut becomes stuck, unscrewing it will require more effort, causing the rotation of the stop to halt temporarily.
• The hammers deflect backward and rotate simultaneously.
• In the next stage, the cams skip engagement with the stop and gain inertia as they continue to move.
• As the cams keep rotating, they re-engage with the stop and strike it in the direction of travel.
• The impact impulses persist until the fastener is forcefully dislodged.

Therefore, using an impact pneumatic tool makes the process of loosening tight bolts and nuts easy and quick.

Selecting a compressor for a pneumatic impact wrench

When purchasing a pneumatic wrench, many drivers often wonder which type of compressor they should buy. One of the main factors to consider is the compressor’s performance, as stated in its specifications. However, it is important to note that some compressor manufacturers may list the productivity based on the input instead of the output. For example, the documentation for a certain unit may indicate a capacity of 210 liters per minute. However, this figure should be interpreted as the rate at which air is injected into the compressor itself, rather than the actual output. In reality, the output capacity may decrease by around 30-40%. In this case, the unit would only produce approximately 146-127 l/min at the output.

From the information given, it is clear that if the compressor is specified to have a performance of 210 l/min, it is important to select a wrench with a lower rate of air flow. For instance, if the tool’s working speed requires an air flow of 200 l/min, and the compressor is documented to have a capacity of 210 l/min (actually 146-127 l/min), then this tool will not be suitable for unscrewing or screwing anything.

Moreover, the size of the container also plays a vital role. In residential settings, the tank might only have a capacity of 24-50 liters. In such situations, the impact wrench would not be able to function properly. Even with a container capacity of 50 liters, the pressure within it significantly decreases after a few seconds of tool operation, and one must wait for it to be restored in order to continue working. Consequently, the compressor’s container should have a capacity greater than 50 liters, and the unit itself should be capable of generating a pressure no less than 6.2 kg/cm². Otherwise, the unit will not be able to generate the necessary power.

However, it is important to maintain the system pressure within the recommended limits. Exceeding the recommended pressure can have negative effects on the main components of the tool, causing them to wear out quickly and ultimately leading to the failure of the wrench.

The consequence of this is as follows: if the air tool is designed to operate at a speed of 119 l/min, but the compressor actually produces 135 l/min, then it is possible to easily loosen and tighten fasteners on wheels using the tool. However, it is essential to remember that the tool should have a torque of at least 550 Nm.

Hose selection

It’s essential to understand that the hose that comes with the compressor, particularly if it’s made in China, won’t be suitable for effectively operating the wrench. Typically, these hoses have an internal diameter of around 6 mm. This capacity of the hose will not be sufficient to supply the necessary amount of air to the pneumatic tool. You can use it to blow off dust or for a paint sprayer, but it won’t work for much else. Even inflating tires with it takes a significant amount of time.

Therefore, it’s important to obtain another hose with a larger capacity. Ideally, you can use a gas hose, which can be purchased at a gas equipment store. On it, you will see markings (Propane-Butane) and the maximum pressure it can withstand, as well as the inner diameter measurement.

Why a compressor needs a filter

It is crucial for the air that is released from the compressor to be of high quality, meaning it should be devoid of any impurities that have the potential to harm the wrench. Not everyone is aware that during the process of compressing air, condensation forms within the internal space of the air receiver. Moreover, if the machine’s mechanical components are extensively worn out, oil can also find its way into the receiver along with the compressed air. When oil mixes with condensation (moisture), it forms an emulsion that enters the tool through the hose connected to it. This emulsion is capable of corroding various parts of the machine’s mechanical system. As a result, service shops often encounter wrenches filled with water and rust, accompanied by broken assemblies.

To prevent the tool from reaching such a lamentable condition, it is common practice to fit a moisture separator filter to the compressor. It contains a unique bronze mesh filter, crafted using special technology.

The filter helps to remove impurities and excess moisture from the air as it passes through. A transparent material is typically used to construct the body of the moisture separator, allowing for easy monitoring of the impurities that accumulate over time. Additionally, a valve is situated at the bottom of the sump, facilitating the simple removal of any collected impurities.

If the airflow rate from the filter is poor, you can determine this by the loss of power in the tool. Initially, the wrench operates within the normal range for a few seconds, but then it suddenly slows down and loses power. This phenomenon can be attributed to the fact that the tool initially starts due to the buildup of air in the hose, but then the airflow becomes insufficient due to the filter being clogged. In such situations, it is necessary to remove the filter, clean it using solvent, and then thoroughly blow it out with compressed air. If all else fails, the filter will need to be replaced. It can be purchased from stores that specialize in selling pneumatic tools.

Selection of oil for the wrench

Special attention should be given to lubricating this pneumatic tool. While the unit may be able to function without purified air temporarily, it will quickly fail without proper lubrication. The oil that is supplied to the moving components of the unit decreases friction, as well as removes wear particles in the form of fine dust. This dust has the potential to fill the gaps between the blades and the rotor, resulting in a decrease in movement speed. Consequently, the power of the tool is significantly diminished. To resolve this issue, a lubricator can be installed within the system. The included image showcases the linear type of lubricator.

However, the lifespan of the wrench can be prolonged by installing an "oiler" and filling it with a specialized lubricant that is specifically designed for pneumatic tools and has the appropriate viscosity.

It is advisable to buy wrench oil that is recommended by the tool manufacturer. If this is not possible, synthetic oil can be used as a last resort. Synthetic oil has excellent anti-wear and anti-corrosion properties and does not contain silicone.

It is important not to use transmission or engine oil in the lubricator, as it has a higher viscosity than necessary and can "stick" the pneumatic actuator blades together, causing a loss of power.

Specialized grease can also be purchased from companies that specialize in pneumatic tools.

Lubrication rules

If you are unable to install a lubricator on your machine for any reason, there is a workaround that can help you.

1. Before starting the wrench, unscrew the hose from it and add 3 to 5 drops of grease into the tool’s fitting.
2. Then, reattach the hose and briefly turn on the machine (about thirty seconds will suffice). This will ensure that the oil is evenly distributed to all the moving parts of the device.

This method of lubrication should also be done before storing the tool for an extended period of time. If the machine is being used intensively, oil should be injected into the connection every 3-4 hours.

While this technique is effective in prolonging the lifespan of the wrench, it can be quite impractical. It requires interrupting work and taking the time to clean the tool, specifically the socket area, and preparing the lubricant. Additionally, one must be cautious to ensure that no dust enters the unit during the procedure. It is for these reasons that it is advisable to incorporate a lubricator into the system, which will consistently provide lubricant to the tool as needed.

Tips for using the pneumatic wrench

If you want to prolong the lifespan of your pneumatic tool, it is highly recommended that you heed the advice given by experienced artisans.

1. Take care to prevent the tool from falling.
2. Ensure that the pneumatic tool is kept away from areas where it could be struck by a vehicle.
3. To increase the tightening power, ensure that the system pressure is not exceeded. Exceeding the pressure can lead to rapid wear of the unit.
4. Avoid keeping the impact wrench under load for extended periods of time as this will quickly damage the impact mechanism. If a "stuck" nut or bolt does not loosen within 5 seconds, it is recommended to stop the machine and replace it with a more powerful one. It is also advisable to use penetrating liquids for problematic bolts, such as gasoline, antifreeze, kerosene, motor oil, brake fluid, which are commonly found in a car owner’s toolkit. Applying a specialized liquid, such as WD-40, to the threaded joint is a more appropriate approach.
5. To ensure the longevity of your tool and enhance its performance, it is crucial to avoid storing it near fire or in locations with excessive levels of heat and humidity.

By adhering to these straightforward guidelines, you can ensure that your tool remains a reliable and efficient assistant during strenuous tasks, providing long-lasting service and justifying the investment made in it.