Converting an old household appliance into a useful tool for the workshop is not just a way to save money, but also an excellent option disposal of equipment that has failed due to a freon leak or a malfunction of the thermostat. Refrigerator compressor has unique characteristics: it is capable of creating high pressure, operates relatively quietly and does not require complex maintenance, unlike industrial piston analogues. It is these qualities that make it an ideal basis for creating a compact air blower, which is useful for airbrushing, inflating tires or blowing electronics.
However, before proceeding with disassembly, it is necessary clearly understand that the normal operating mode of the refrigeration unit is fundamentally different from the supercharger mode. In a refrigerator, the device operates in an intermittent cycle, managing to cool down during periods of inactivity, while the compressor must pump air almost continuously, which leads to serious overheating. You will need to not only disconnect the tubes, but also completely rework lubrication system and cooling to avoid jamming of the piston group or even an oil fire.
In this article we will analyze in detail the process of creating a full-fledged compressor station, paying special attention to the technical nuances that beginners often ignore. We will consider choosing the appropriate receiver, installation of safety valves and the correct electrical connection diagram. Remember that working with pressure vessels requires strict adherence to safety precautions, since incorrect assembly can lead to rupture of the container.
Preparation of materials and selection of a compressor
The first step is to remove the compressor from the old refrigerator. Units from Soviet refrigerators brand ZIL or Biryusaare best suited, as they are known for their reliability and maintainability, although modern models from Indesit or Atlant will also cope with the task provided there is good ventilation. Before removal, it is necessary to cut the copper tubes at a distance of 10-15 cm from the body in order to maintain the length for subsequent connection, and be sure to drain the old mineral oil, replacing it with a more heat-resistant one or adding special additives.
To assemble a full-fledged installation, you will need a set of tools and additional components, without for which creating a secure system is impossible. The main element, in addition to the pump itself, will be the receiver - a container for storing compressed air, which is often used as old fire extinguishers or gas cylinders. It is also critically important to purchase pressure gauge to control pressure and a reducer if you plan to use a tool that requires precise pressure adjustment.
⚠️ Attention: It is strictly forbidden to use plastic containers, glass bottles or metal fuel cans as a receiver liquids that have not passed hydraulic tests. The air pressure in the system can reach 10 atmospheres or higher, which will lead to an instant rupture of an unsuitable container with flying fragments.
The list of necessary materials for assembling the basic version of the compressor includes not only the main components, but also consumables for sealing and connections. Careful preparation will allow you to avoid situations where the process stops due to the lack of the required fitting or clamp.
- 🔧 Compressor from the refrigerator (intact, without mechanical damage).
- 🛢️ Receiver (metal cylinder with a volume of 10 liters or more).
- 📏 Pressure gauge with a scale of up to 10-15 atmospheres.
- ⚙️ Pressure reducer (to equalize the flow).
- 🔌 Electromagnetic pressure switch (pressostat) or manual control.
Modernization of the lubrication and cooling system
The standard lubrication system of a refrigeration compressor is designed to work in a closed circuit with freon, which carries away some of the oil and returns it back. When operating in air, this mechanism is disrupted: the oil begins to be actively carried away into the air flow, and the level in the crankcase drops, which leads to dry friction and rapid wear of bearings and cylinders. To solve this problem, it is necessary to organize a drop supply of oil or use a special oil separating flask at the outlet of the pump.
The second critical aspect is temperature. When air is compressed, the gas heats up, and if in a refrigerator heat is removed through the condenser and the walls of the case, then in an open compressor heating occurs much faster. Case temperature should not exceed 90-100 degrees Celsius, which is why many craftsmen install an additional blower fan or even water cooling on the outlet pipe. Without proper cooling, the oil will begin to coke, turning into a hard deposit that will jam the piston group.
Can synthetic oil be used?
Yes, synthetic oils for compressors have better thermal stability and less waste, but they cannot be mixed with residues mineral oil. Before changing the type of lubricant, it is recommended to rinse the internal cavity of the compressor with a special solvent or the oil itself several times.
To organize proper lubrication, you can use a simple gravity method or wick feed, but the most effective is to install an oil trap immediately after the compressor. This device is a container with a filler (for example, metal shavings or felt), where the air slows down and the oil settles, returning back to the crankcase through drainage, or is collected in a separate compartment.
Manufacture and preparation of the receiver
The receiver acts as a buffer, smoothing out pressure pulsations created by the piston compressor and accumulating air reserve for peak loads. The most affordable and safe option for a home workshop is to use a fire extinguisher housing with a volume of 10-50 liters, since these containers are initially designed for high pressure and are equipped with a reliable locking mechanism. Before use, the cylinder must be thoroughly cleaned from the inside to remove powder residues, rinsed with water with the addition of detergents and completely dried to prevent corrosion.
The process of preparing the cylinder includes drilling holes for installing fittings, a tap and a pressure gauge. It is important to drill carefully, without strong pressure, periodically cooling the drill so as not to burn the metal or damage its structure. For air inlet, a hole is usually drilled in the upper part of the cylinder (if it is installed vertically), and it must be mounted in the lower part drain valve to remove condensate, which inevitably forms when humid atmospheric air is compressed.
| Tank type | Working pressure (atm) | Advantages | Disadvantages |
|---|---|---|---|
| Fire extinguisher (10 l) | 15-20 | Ready holes, compactness | Small volume, requires frequent purge |
| Propane cylinder (50 l) | 16-25 | Large volume, stability | Heavy, difficult to find empty |
| Spring from a truck | 20-30 | High strength, original appearance | It is difficult to seal the ends |
| Gas cylinder (small) | 10-15 | Availability, low cost | Risk of explosion if improperly prepared |
After installing all fittings, the receiver must be checked for tightness. To do this, it is pumped with air under pressure that exceeds the working pressure by 20-30%, and all joints are generously lubricated with soap solution. The appearance of bubbles will indicate leaks that should be eliminated by replacing seals or additional sealing of threaded connections using FUM tapes or anaerobic sealant.
Assembling the pneumatic line
Assembling a pneumatic circuit requires sequential connection of all elements in the correct order to ensure efficient operation and safety. Air from the compressor must first enter the receiver through a check valve, which will prevent air from escaping back into the compressor when it stops. This is a critical element, since without it the compressed air will spin the piston group in the opposite direction, which can damage the engine at start-up.
After the receiver, the air passes through the cleaning and preparation system. A moisture-oil separator is installed here, which removes residual oil and condensate that falls out when the compressed air in the cylinder cools. Next, the flow is directed to the reducer, where the pressure is reduced to the operating value required for a specific tool (for example, for an airbrush you need 2-3 atmospheres, and for a tire service - 4-6 atmospheres).
☑️ Checking the pneumatic circuit
For connection All elements use copper tubes or special polyurethane hoses that can withstand pressure up to 20 atmospheres. Copper tubes are preferable in the hot compressor area, as they remove heat better and are not afraid of high temperatures, while hoses are best used at the outlet of the receiver for ease of connecting tools. All connections must be made using brass fittings that are resistant to corrosion.
Electrical circuit and automation
Starting and stopping the compressor can be done manually through a regular toggle switch, but this approach requires constant monitoring of the pressure on the pressure gauge, which is inconvenient and unsafe. The optimal solution is to install pressostat (a pressure switch), which automatically opens the electrical circuit when the upper pressure limit in the receiver is reached and closes it when it drops to the lower threshold. This device significantly extends the life of the equipment and frees the operator's hands.
The electrical connection diagram is quite simple: phase and zero from the 220V network go to the input of the pressure switch, and from the output to the compressor motor windings. If the motor power exceeds 1 kW, it is recommended to include a magnetic starter in the circuit to avoid overloading the relay contacts and ensure a reliable start of the engine under load. Do not forget about grounding: the compressor housing and all metal parts must be securely connected to the grounding circuit. starting capacitor and a magnetic starter to avoid overloading the relay contacts and ensure reliable engine starting under load. Do not forget about grounding: the compressor housing and all metal parts must be securely connected to the ground loop.
⚠️ Attention: When connecting the electrical part, make sure that the cross-section of the wires corresponds to the current load of the motor. Using thin wires or strands instead of terminal connections can lead to heating, melting the insulation and short circuit.
For those who want to delve into the topic of automation, it is possible to install a thermal relay that will turn off the compressor if the windings overheat. This is especially true during long-term continuous operation, when standard protection may not be enough. The pressure switch response thresholds are adjusted by rotating the adjusting screws under the cover, which allows you to flexibly adjust the operating pressure range to suit your needs.
First launch and testing of the system
Before the first full launch, it is necessary to conduct a visual inspection of the entire structure for forgotten tools, dangling wires or loose hoses. Make sure that the drain valve on the receiver is open so that the compressor starts without load, and check the oil level in the crankcase through the sight glass or dipstick. It is best to turn it on via an extension cord with an emergency shutdown button, while being at a safe distance from the unit.
In the first minutes of operation, carefully monitor the readings of the pressure gauge and listen to the sounds of the operating mechanism. The absence of extraneous knocks, creaks and vibrations indicates correct assembly. If pressure builds slowly or the pressure gauge needle jerks, check the system for air leaks again using a soap solution. Also monitor the temperature of the compressor housing: if it becomes too hot to touch with your hand, immediately turn off the device and let it cool.
Successful completion tests means your homemade air compressor is ready for use. Regular maintenance, including oil changes, draining condensate and checking filters, will ensure a long service life for the device. Remember that safety is always more important than saving time, so do not neglect preventive inspections.
Frequently asked questions (FAQ)
What pressure can develop compressor from a refrigerator?
A standard compressor from a household refrigerator is capable of creating pressure in a closed system up to 15-20 atmospheres and higher, but the operating range for safe operation is usually limited to 6-8 atmospheres. Exceeding this value requires the installation of a more powerful motor and a reinforced receiver, since standard parts may not withstand the load.
Is it necessary to change the oil in the compressor during refurbishment?
Yes, changing the oil is highly desirable. Refrigerators use mineral oil, which oxidizes faster when exposed to atmospheric oxygen and high temperatures. It is recommended to use synthetic compressor oils or special mixtures designed for operation in air.
Can such a compressor be used for a spray gun?
Yes, it is possible, but with restrictions. The productivity (liters per minute) of refrigeration compressors is low (usually 30-50 l/min), so for continuous operation of a spray gun with a large torch it may not be enough - the pressure will drop. For airbrushing or touching up small parts, the power is quite enough, especially if you use a large volume receiver.
Why does the compressor get very hot and turn off?
Most likely, the thermal protection relay is triggered due to overheating. This may be caused by insufficient cooling, low oil level, clogged air inlet filter, or continuous operation for too long without breaks. Let the device cool and check the ventilation system.