Assembly a homemade compressor based on a unit from an old refrigerator is a popular solution for garage workshops. The main element of such a system, in addition to the motor itself, is a container for storing compressed air. It is this unit that ensures stable pressure and cuts off pulsations that occur during operation of the piston group.
Many craftsmen wonder what kind of container can be used as receiverso as not to risk their safety. The choice of material and design of the tank directly affects the durability of the entire installation. An incorrect approach to this stage can lead to depressurization or even explosion of the pressure vessel.
In this article we will analyze in detail which containers are suitable for this purpose, and which should be discarded immediately. You will learn about the technical requirements for materials, methods of their preparation and the nuances of installing additional equipment. Safety when working with high pressure is the number one priority for any self-taught engineer.
Requirements for the material and design of the receiver
The main task of the receiver is to buffer the air flow. It smoothes out pressure surges that are inevitable during work piston compressor. In addition, the air is cooled and moisture condenses in the tank, which protects the pneumatic tool from water ingress.
The manufacturing material must have high tensile strength and resistance to cyclic loads. Steel is the most common choice due to its mechanical properties. However, it is important to consider that ordinary structural steel can rust from the inside, which reduces the resource.
⚠️ Attention: It is strictly forbidden to use containers containing flammable liquids (gasoline, solvents) without prior and thorough treatment with steam or burning. Residual vapors can ignite from a spark or heat when air is compressed.
The thickness of the walls of the selected container must be sufficient for the operating pressure. For household compressors from refrigerators, the pressure rarely exceeds 8-10 atmospheres, but the safety margin should be multiple. Thin-walled canisters or plastic bottles are unsuitable for these purposes.
Fire extinguishers as an ideal receiver option
The most popular and safe material for creating a receiver are decommissioned fire extinguishers. Their housings are initially designed for high pressure and undergo strict quality control during production. This makes them ideal candidates for conversion.
Most often, craftsmen use powder fire extinguishers of the OP series with a volume of 10 liters or more. The metal in them is quite thick, and the shape of the case is convenient for installation on the frame. Before use, you must ensure that there is no through corrosion.
- 🔥 Availability: Decommissioned fire extinguishers can be easily found at car markets or in organizations that hand them over for recharging.
- 🛡️ Safety: The factory test pressure of such cylinders significantly exceeds the working pressure refrigeration compressor.
- 🔧 Convenience: The presence of a ready-made threaded hole for the locking mechanism simplifies the insertion of fittings.
The process of preparing a fire extinguisher begins with removing the remaining powder. To do this, rinse the container with water under pressure until the contents are completely washed out. After drying, it is recommended to treat the inner surface with an anti-corrosion compound or primer.
Use of gas cylinders and air conditioning systems
The second most popular option is old propane cylinders or freon containers. Propane cylinders with a volume of 5, 12 or 27 liters have excellent durability characteristics. However, their use requires special precautions when cutting and welding.
Freon cylinders, especially copper or aluminum, are often used in mobile installations. Copper receivers do not rust, but have lower mechanical strength compared to steel counterparts. Aluminum containers are lightweight, but require careful welding with argon.
| Container type | Material | Max. pressure (atm) | Difficulty of processing |
|---|---|---|---|
| Fire extinguisher OP-10 | Steel | 25-30 | Low |
| Propane cylinder 12l | Steel | 16-20 | Medium (pressure relief required) |
| Freon cylinder | Steel/Aluminium | 15-25 | High (special welding required) |
| Truck receiver | Aluminium/Steel | 12-15 | Medium |
When working with gas cylinders, it is critical to completely remove any remaining gas. Even a small concentration of propane mixed with air and oil from the compressor creates an explosive mixture. Before any mechanical treatment, the cylinder must be filled with water or inert gas.
Alternative options: receivers from trucks and air suspension
An excellent source of ready-made receivers are the air brake systems of trucks and buses. Such containers already have the necessary threaded holes, mounting brackets and are often equipped with a condensate drain valve. They are specially designed to work under conditions of vibration and temperature changes.
Receivers from the air suspension of passenger cars (for example, some Mercedes or Audi models) are compact in size. They are ideal for creating mobile compressor units that need to be transported in the trunk. However, their volume is usually small, which limits the time of continuous operation of the tool.
Why are receivers from trucks better than homemade cylinders?
They already have a factory anti-corrosion coating on the inside, the correct geometry to minimize condensation and are certified to work with pressurized air. They do not need to be hydraulically tested before use if they do not have visible damage.
When choosing a used car receiver, inspect it for deep corrosion on the outside. It is more difficult to check the internal condition, so it is better to choose options with a shorter service life. The presence of a standard protection valve simplifies the assembly of the circuit.
Technology for inserting fittings and preparing the container
Preparation of the selected container requires sequential operations. First, paint and rust are removed from the welding areas. Then the holes for the inlet and outlet pipes, pressure gauge and drain valve are marked.
For inserting fittings, it is best to use ready-made bosses or couplings. They are welded to the body or screwed into pre-prepared threaded holes. The use of cold welding for fastening fittings under pressure is unacceptable - only high-quality electric welding or reliable threads.
- 📏 Marking: Accurately determine the drilling locations to ensure convenient connection of the hoses.
- 🔩 Thread: Use taps of the appropriate diameter to cut threads in welded couplings.
- 💧 Drain: At the lowest point of the receiver, be sure to install a tap to drain condensate.
After installation of all fittings, pressure testing is carried out. The receiver is filled with water under pressure 1.5 times higher than the working pressure and checked for leaks. Only after a successful hydraulic test can the container be considered ready for operation.
☑️ Preparing the receiver for operation
Assembling the system and installing safety elements
The assembled receiver must be integrated into the overall system. A check valve is installed between the compressor and the receiver, which prevents air from escaping back into the cylinder when the engine is stopped. This makes it easier to start the engine the next time.
The required element is safety valve. It will work if the automatic shutdown fails and will prevent the tank from rupturing if the critical pressure is exceeded. A reducer is also installed at the outlet to reduce the pressure to the operating level of the tool.
⚠️ Attention: Do not ignore the installation of the pressure gauge. Visual pressure monitoring allows you to quickly notice a malfunction of the pressure switch or a leak in the system.
All connections must be tight. To seal threaded connections, use anaerobic sealants or flax tow with paint. FUM tape may not withstand vibration and thermal expansion in the long term.
Operation and maintenance of a homemade compressor
Proper operation will extend the life of your installation. Open the drain valve regularly, at least once a week, to remove accumulated condensate. Moisture inside the tank is the main cause of corrosion and failure of pneumatic tools.
Periodically check the tightness of the bolt connections and the condition of the hoses. Vibration from a running motor can weaken the fasteners. If you notice a decrease in performance or unusual sounds, stop the compressor and carry out diagnostics.
Timely replacement of oil (if the compressor is oil-based) and air filters is also important. Clean air at the inlet reduces contamination of the receiver from the inside and reduces wear on the piston group. Monitor the temperature of the receiver body - excessive heating may indicate problems.
Frequently asked questions (FAQ)
Can a plastic oil can be used as a receiver?
No, plastic containers are not designed to work under compressed air pressure. Even if the plastic seems durable, it can break under stress and temperature changes, causing injury. Use only certified metal cylinders.
What volume should the receiver for the refrigerator compressor be?
The optimal volume is from 10 to 50 liters. A smaller volume will result in the motor turning on frequently, which will shorten its life. A larger volume will allow you to turn on the compressor less often, but will take up more space. For painting and inflating tires, 10-20 liters are enough.
Is it necessary to paint the inside of the receiver?
It is advisable to coat the inner surface with a specialized primer that is resistant to oil and water. This will slow down the corrosion process. However, ordinary paint can peel off over time and clog pneumatic tools, so it is better to use special compositions for receivers.
What is the maximum pressure that a fire extinguisher can withstand?
Standard OP-10 fire extinguishers are designed for a working pressure of about 16 atmospheres and a test pressure of up to 25-30 atmospheres. Refrigerator compressors rarely create pressure above 10-12 atmospheres, so the safety margin of the fire extinguisher is more than sufficient.