Using old household equipment to create new ones useful tools - excellent practice for a home craftsman. Often, units that can still serve are idle in garages or cottages. For example, compressor from the refrigerator becomes a reliable source of compressed air for painting work, inflating tires or blowing out mechanisms. This solution saves the budget and gives a second life to components that would otherwise go to a landfill.
The main element of the future installation is piston compressorextracted from the refrigerator body. It is designed for long-term operation, is quiet and does not require complex maintenance. However, for it to work properly, it needs a receiver, the role of which is often played by an old gas cylinder. It is important to understand that a simple combination of a motor and a container is only the beginning of the journey. The operating pressure of a homemade system usually does not exceed 6-8 atmospheres, which is sufficient for most household tasks, but not enough for industrial use.
Before starting assembly, it is necessary to assess the technical condition donor. The engine should start without humming or vibration and perform as expected. In this article we will examine in detail the process of creating an effective device, paying special attention to the safety and tightness of connections. You will learn how to turn a set of metal parts into a functional tool.
Selection and preparation of necessary materials
The first stage of creating a homemade installation is the search for high-quality components. The heart of the system is the compressor unit from the refrigerator. Units from Soviet models, such as ZIL or Biryusaare best suited, as they are known for their reliability and maintainability. Modern imported motors are also applicable, but may have a shorter resource when operating in continuous mode.
The second critical element is the receiver. The ideal option is a 50-liter metal propane cylinder or a smaller 12-liter cylinder. An alternative is fire extinguishers or receivers from trucks. The main requirement is the absence of corrosion inside and the ability to withstand high pressure. A rusty cylinder must absolutely not be used.
- 🛠️ Compressor unit from the refrigerator (complete, with tubes).
- ⚙️ Receiver (gas cylinder, fire extinguisher) with a volume of 10 liters or more.
- 🔩 Fittings, hoses, clamps and a pressure gauge for monitoring pressure.
- ⚡ Pressure switch (pressostat) to automate engine operation.
You will also need a set of tools: a drill, taps for threading, wrenches and a soldering iron. Do not forget about oil if the compressor design requires its replacement or topping up after a long period of inactivity. Preparing all materials in advance will avoid interruptions during the assembly process.
⚠️ Attention: Before drilling or welding a gas cylinder, make sure it is completely empty and free of gas residue. The best way is to fill it with water, let it settle, and only then begin work. A spark during drilling can ignite the remaining propane.
Removing the compressor and checking its functionality
The process of removing the compressor from the refrigerator requires care. You should not immediately saw off the tubes with a grinder, as metal shavings may get inside the mechanism. It is better to use a pipe cutter or carefully cut the copper tubes with wire cutters, leaving a margin of length. After removal, the motor must be cleaned of dirt and old paint in order to conduct a visual inspection.
The next step is to check the electrical part. Refrigerator compressors often have a start relay that must be maintained. Plug in the unit briefly to make sure it starts and produces air flow. At this stage, it is important to determine which of the three tubes is suction and which is discharge. Typically, the discharge tube is hotter and air blows out of it, and the suction tube is cooler and draws in air.
If the engine hums but does not start, the piston group may be stuck or the start relay has failed. In some cases, replacing a capacitor or relay with a similar one helps. Tightness The motor housing is also important: if there is smoke coming from the motor shaft or a burning smell is felt, it is better not to use such a unit.
Checking performance is carried out using a simple method: put a hose on the discharge tube and try to block the outlet with your finger. A working motor should create noticeable resistance. If air flows freely even when shutting off, the piston rings may be worn out, and such a compressor will not hold pressure.
Preparing the receiver from a gas cylinder
Preparing the cylinder is the most important and dangerous stage. As mentioned, removing residual gas is the number one priority. After washing with water, it is necessary to remove the paint from the top of the cylinder, where the holes for the fittings will be drilled. This will allow for high-quality welding of elements or cutting threads.
Several fittings must be installed in the upper part of the cylinder (in the “heel” or through existing holes). The minimum set includes: an air inlet from the compressor, an air outlet to the consumer, a hole for a pressure gauge and a hole for draining condensate. It is difficult to cut threads in the thin walls of a cylinder, so the method of welding bosses with ready-made internal threads is often used.
| Element | Purpose | Type of connection |
|---|---|---|
| Inlet pipe | Air supply from the compressor | Thread 1/2 or 3/4 inch |
| Outlet pipe | Connecting the hose to the tool | Thread 1/2 or 3/4 inch |
| Drain valve | Removal of moisture and oil | Ball valve with thread |
| Pressure gauge hole | Pressure control in the system | Thread for pressure gauge |
After installing all fittings, the receiver must be tested for leaks. To do this, you can pump water into it under pressure or use a soap solution when supplying air. Bubbles will indicate places where additional sealing or overwelding of seams is required. Ignoring this stage may lead to rupture of the pressure container.
Assembling the automation and control system
For comfortable operation of the compressor, an automatic on and off system is required. The main element here is pressostat (pressure switch). This device opens the electrical circuit when a predetermined upper pressure limit is reached and closes it when the pressure drops to a lower value. Without a pressure switch, you will have to constantly monitor the pressure gauge and manually turn on the motor.
The connection diagram of the pressure switch is quite simple, but requires care. Electric current from the network goes to the relay input, and from the output to the compressor. Inside the relay there are contacts that open under the influence of air pressure supplied through a special pipe. It is important to correctly set the difference (delta) between turning on and off so that the motor does not jerk too often.
Setting the pressure delta
Usually the factory setting is 2 atmospheres. For example, switching on at 4 atm and switching off at 6 atm. For adjustment, there are two springs inside the relay: the large one is responsible for the upper threshold, the small one for the difference (delta).
In addition, the system must be equipped check valve. It is installed between the compressor and the receiver. Its task is to prevent compressed air from escaping back into the compressor after it stops. If there is no check valve, air from the receiver will go into the engine cylinder, which can lead to it turning in the opposite direction and damage the next time it is started.
Installing the structure and connecting hoses
When the main components are ready, it is time for assembly. The compressor and receiver are usually mounted on a common frame. To do this, you can use a metal corner or thick plywood. It is better to secure the motor through rubber gaskets to dampen vibrations that inevitably arise during operation of the piston group. The noise from such a compressor is much lower than from industrial analogues, but vibration can loosen the fastenings.
The connection of the copper tubes of the compressor with the steel fittings of the receiver is best done through oil- and gas-resistant hoses or special adapters. Direct joining of copper and steel is not recommended due to differences in thermal expansion and vibration. All connections must be tightened with clamps with a screw tightening; conventional worm clamps may not provide the required tightness.
☑️ Final check of the assembly
Do not forget about organizing condensate drainage. When air is compressed, moisture is released from it, which accumulates at the bottom point of the receiver. If it is not drained, it will get into the paint during painting or cause corrosion inside the cylinder. Therefore, a tap must be installed at the lowest point of the receiver.
Test launch and maintenance of the device
The first launch should be carried out with caution. Turn on the compressor and monitor the pressure gauge readings. The pressure should increase smoothly. When the arrow reaches the operating value (for example, 6 atmospheres), the pressure switch should click and turn off the motor. If this does not happen, immediately turn off the device from the network and check the relay settings.
During operation, monitor the temperature of the compressor housing. Refrigeration motors get hot, but they are not designed to overheat above 90 degrees Celsius. If the housing becomes hot, the ventilation may be poor or there may be insufficient oil. In this case, it is worth providing additional airflow or an intermittent operating mode.
⚠️ Attention: Never leave a running compressor unattended for a long time. Despite the automation, the risk of depressurization or fire of wiring when using homemade devices is always higher than with factory-made analogs.
Regular maintenance will extend the life of your installation. This includes checking the oil level (if the design allows), draining the condensate after each use and checking the belt tension (if a belt drive is used, although in refrigeration compressors it is usually direct). Also periodically check the integrity of the hoses, which may dry out over time.
Frequently asked questions (FAQ)
What kind of oil should be poured into a refrigerator compressor?
In most cases, refrigerator compressors are already filled with oil at the factory and are sealed. If replacement is required, use special compressor oil, for example Friezer Oil or analogues recommended by the manufacturer. Conventional motor oil may foam and not provide the necessary lubrication.
Can this compressor be used for sandblasting?
For a full-fledged sandblasting machine, the power of one refrigeration compressor is usually not enough. They provide a small volume of air (performance) at decent pressure. Sandblasting requires a large air flow, so one motor will not be enough; you will need a cascade of several compressors or a more powerful unit.
Why does the compressor get very hot?
Heating up to 70-80 degrees Celsius is normal for piston compressors. If the temperature is higher, check the cleanliness of the cooling fins, the presence of ventilation and the oil level. Also, the cause may be wear of the piston group or a malfunction of the starting capacitor.
Is it necessary to change the oil in the receiver?
The oil in the receiver does not change, it is not poured into it. However, condensate with oil impurities accumulates in the receiver, which is carried away from the compressor. This mixture must be regularly drained through the tap at the bottom of the cylinder to avoid corrosion and oil getting into the pneumatic tool.