Throughout my career, I have assisted many people who wanted to review their entire compressed air system. The first thing to do is a complete inspection of the system, starting with the compressor room. This leads me to want to share with you today my knowledge of a key component of the system: the compressor. Specifically, I will discuss two topics related to stationary compressors, which are often used in companies.
Which compressor to choose
The two largest families are piston and screw compressors.
The piston compressor
If you are familiar with car mechanics, the principle of this compression is easy to understand. 
- A piston sliding in a cylinder successively sucks in and compresses a quantity of air.
- The volume contained in the cylinder chamber enters under atmospheric pressure and is sucked in by the descent of the piston.
- As the piston moves upwards, the inlet valve closes and the air volume is compressed.
- The air finally exits through a second valve, the exhaust valve.
The two valves allow either the entry or the exit of air. The inlet passage is wider than the outlet passage. The pressure switch installed on the vessel controls the starting of the piston compressor. It has a minimum and maximum pressure limit.
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The screw compressor
Screw compression is a more recent technology than piston compression. The general idea is to compress a volume of air by reducing the space in which it is contained. Here, instead of forcing a piston to crush the air, we work lengthwise.
- The screw rotates continuously and generates an airflow between the inlet and outlet.
- The outside atmospheric air is drawn in by the air intake from the high-speed rotation of the screw.
- As the pitch of the screw decreases significantly between the beginning and end of the screw, the air is pushed towards the outlet and increasingly compressed between the threads.
A special feature of screw compressors is that the tank pressure switch often does not control the motor. Instead, a valve at the inlet, called a relief valve, cuts off the air inlet and stops the compression process. This leaves the screw running idle. The motor effort to turn the screw is much less than that produced to push a piston. As the assembly rotates at no load between each compression phase, the torque will be felt much less during the restart and the power consumption will be much lower. As a result, the machine's motor will have a much longer life since it works much less intensely.
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Things to remember when choosing a compressor
Whether the compressor is a reciprocating or rotary screw, don't forget the cooler. Most of the time, the air must be treated with a dryer. The temperature of the air must be controlled (around 40°C) for efficient operation, regardless of the type of dryer used. It is therefore essential to choose a compressor with an integrated air cooler. In the absence of a built-in cooler, a small compressor (10 HP or less) can benefit from some air cooling if it is installed directly on a tank.
To learn more about refrigeration dryers, see the article Why and How to Dry Compressed Air.
If you are on a tight budget, a piston compressor may be more suitable for your situation. If your air requirement is more than 20 HP, then the best option might be the screw compressor. If you choose a well-known and reputable brand-name product, then you should be quite satisfied with your new machine, regardless of the technology you select. The most important thing to consider is your airflow and pressure requirements (SCFM and PSI). Remember, there is no perfect solution.
Now that you know more about which compressor is right for you, you need to know the best place to install it...
Where to Install the Air Compressor
Whether it's because it's too old, too low capacity, or has stopped working, changing a compressor is not a common occurrence in the life of a business. Unfortunately, when it does happen, it is never the right time. The installation of a new compressor is therefore often done in a hurry. However, it is an opportunity to review the layout of your premises and perhaps rethink it differently. You can take advantage of this opportunity to :
Analyze the evolution of compressed air needs
Consider whether the location of the compressor still corresponds to the current or future way of working. If the location was appropriate in the past, it is quite possible that after many years the geography of the building has changed. This has probably been the case with the various expansions that have followed the increase in production. This is a good time to list your plans: new production line, new paint booth, plans to build an annex... And many other possibilities may interfere in the near future.
Question location based on air consumption
The location of the compressor in relation to the air system is very important for proper compressed air distribution. The compressor is the heart of the network structure. When possible, positioning the compressor in a balanced way in relation to the air consumption will provide faster and better air distribution. The compressor should be located as close to the application as possible, prioritizing the applications that consume the most air.
The compressor room and its layout
The compressor is often overlooked and relegated to a corner of the shop floor. Under these conditions, there is no doubt that it will not perform optimally and may overheat. The ideal is to have a compressor room.
A separate room for the compressor
The compressor room should, as far as possible, be independent of the rest of the workshop. It is thus isolated from the dust particles in suspension in the main building. It is also not a place to store various chemicals whose fumes could inevitably end up in the compressed air.
- Choose a small building that backs onto the main building, but is large enough to allow you to move around the machines very easily.
- If you have the possibility, plan the building on the north side to avoid the high summer heat.
- Consider insulating this room.
Good ventilation
Ventilation of the compressor room is an important consideration. Provide a large, low inlet that will allow a significant flow of air as well as an air outlet at the top (about 20% smaller than the inlet). This way, the air will circulate well in the room and will supply the machine.
This ventilation will help you maintain an ambient temperature between 5 and 25°C (40 and 80°F). If you can maintain this range, the flow rate and pressure will be more constant and the air temperature will remain stable and easier to handle. To maintain this temperature, consider installing dampers that can be adjusted in winter, for example.
Some additional tips and tricks
- To prevent clogging of the building's ventilation grille, do not lay the grille directly on the floor. Raise it up to create a space at the bottom of the building where any debris can pile up.
- To facilitate quick maintenance of the interior of the room, install everything (tank, filters, dryer, etc.) with bypass lines that will allow equipment to be removed from the line and changed while the air supply continues.
- Install each machine on sturdy pallets. This will allow you to move them very quickly and effortlessly.
- Consider connecting your larger equipment with flexible anti-vibration hoses so that you can move them slightly if necessary.
- Allow enough space to move the equipment.
Connecting to the network
If the compressor room is a separate building, it must be connected to the rest of the network. To do this, avoid connecting the compressed air lines via an overhead pipe, as there are many risks: exposure to bad weather, risk of breakage by passing vehicles, etc.
Ideally, the pipe should be run in an open trench covered with removable plates. In the event of an intervention, these plates allow full access along the entire length. Use effective insulation to protect the pipe. Finally, since the pipe is at a low point in the trench, install an automatic drain at its entrance or exit to evacuate condensation that could freeze in winter and completely obstruct the air network.
In conclusion
With these valuable tips, you are ready to choose your compressor and build your compressor room, or simply review your installations. Many of the points outlined in this article are logical and inexpensive to implement... They are all details that, when added together, will greatly benefit your compressor. The life of the compressor will be extended and, above all, the quality of your compressed air will be greatly improved! If you would like more information, please contact your Topring representative. I'm sure he or she will be able to guide you.
