One thing that is found in virtually every industrial environment is an air compressor. Some uses for the compressed air generated are: powering pneumatic tools, packaging, automation equipment, conveyors, controls systems, and various others. Pneumatic tools are favored because they tend to be smaller and more lightweight than electric tools, offer infinitely variable speed and torque, and can be safer than the hazards associated with electrical devices. In order to power these devices, compressed air must be generated.
There are two main categories of air compressors: positive-displacement and dynamic. In a positive-displacement type, a given quantity of air is trapped in a compression chamber. The volume of which it occupies is mechanically reduced (squished), causing a corresponding rise in pressure. Of the positive-displacement variety they are broken down further into two more categories: reciprocating and rotary.
A reciprocating compressor works like a bicycle pump. A piston reduces the volume occupied by the air or gas, compressing it into a higher pressure. There are two types of reciprocating compressors, single or double-acting. Single-acting compressors are the most common and are available up to 30HP at 200 psig.
Their small size and weight allow them to be installed near the point of use and avoid lengthy piping runs. Additionally, the single-acting reciprocating compressors do not need a separate cooling system. All of this leads to much simpler maintenance procedures, making the single-acting reciprocating compressors one of the easiest to maintain.
There are some disadvantages to this style of compressor. Rings have a tendency to wear out over time, if they’re not replaced as needed this can lead to lubricant carry-over into the air supply. These styles of compressor are relatively loud and comparatively cost more to operate than many other types. Because of this, they’re not designed for applications and processes that have a heavy-duty cycle of 70-90%. The single-acting reciprocating compressor should be used in installations where it’s only going to run 50% or less of the time.
At EXAIR we’re committed to providing you with the point of use products that’ll use your compressed air as efficiently and safely as possible. Feel free to reach out to an Application Engineer to discuss how we can help you improve in your processes.
In one of my previous jobs, I was responsible for the operation of the facility. One of my biggest responsibilities was the air compressor because it supplied pressurized air though out the facility to feed the pneumatic systems. Like with many industries, the compressor system is the life blood of the company. If the compressor fails, the whole facility will stop. In this blog, I will share some preventative maintenance items and schedules for your air compressors.
Because the cost to make compressed air is so expensive, compressed air systems are considered to be a fourth utility. And with any important investment, you would like to keep it operating as long and efficiently as possible. To do this, it is recommended to get your air compressor a “checkup” every so often. I will cover some important items to check as well as a recommended schedule for checking. Depending on the size of your air compressors, some items may or may not apply.
1. Intake filter: The intake filter is used to clean the air that is being drawn into the air compressor. Particles can damage the air pump mechanisms, so it is important to have the proper filtration level. But, as the intake filter builds up with debris, the pressure drop will increase. If they are not properly monitored and cleaned, the air flow will be restricted. This can cause the motors to operate harder and hotter as well as reduce the efficiency of the air compressor.
2. Compressor Oil: This would be for flooded screws and reciprocating compressors that use oil to operate the air pump. Most systems will have an oil sight gauge to verify proper levels. In larger systems, the oil can be checked for acidity which will tell you the level at which the oil is breaking down. The oil, like in your car, has to be changed after so many hours of operation. This is critical to keep the air pump running smoothly without service interruptions.
3. Belts and Couplings: These items transmit the power from the motor to the air pump. Check their alignment, condition, and tension (belts only) as specified by the manufacturer. You should have spares on hand in case of any failures.
4. Air/Oil Separators: This filter removes as much oil from the compressed air before it travels downstream. It returns the oil back to the sump of the air compressor. If the Air/Oil Separator builds too much pressure drop or gets damaged, excess oil will travel downstream. Not only will the air pump lose the required oil level, but it will also affect the performance of downstream parts like your air dryer and after cooler.
5. Internal filters: Some air compressors will come with an attached refrigerated air dryer. With these types of air compressors, they will place coalescing filters to remove any residual oil. These filters should be checked for pressure drop. If the pressure drop gets too high, then it will rob your compressed air system of air pressure. Some filters come with a pressure drop indicator which can help you to determine the life of the internal filter element.
6. Unloader valve: When an air compressor unloads, this valve will help to remove any compressed air that is trapped in the cavity of the air pump. So, when the air compressor restarts, it does not have to “work” against this “trapped” air pressure. If they do not fully unload, the air compressor will have to work much harder to restart, wasting energy.
Preventative maintenance is very important, and checks need to be performed periodically. As for a schedule, I created a rough sequence to verify, change, or clean certain items that are important to your air compressor. You can also check with your local compressor representative for a more detailed maintenance schedule.
After stopping, remove any condensate from the receiver tank.
Check oil level.
Inspect cooling fins on air pump. Clean if necessary
Inspect oil cooler. Clean if necessary
Inspect the inlet air filter. Clean or replace if necessary.
Check the belt for tension and cracks. Tighten or replace.
Check differential pressure indicators on outlet compressed air filters.
Replace Air Inlet Filter
Replace the air-oil separator
Test safety valves and unloader valve
Replace compressed air filters
Grease bearings if required
Keeping your air compressor running optimally is very important for pneumatic operations and energy savings. I shared some important information above to assist. Another area to check would be your pneumatic system downstream of the air compressor. EXAIR manufactures engineered products that can reduce air consumption rates. You can contact an Application Engineer to discuss further on how we can save you energy, money, and your air compressor.
Evaluating all of the different types of compressors and which is right for you can seem like a daunting task. Today, I’d like to take some time to talk about the Double-Acting Reciprocating type of air compressor.
Double-Acting Reciprocating compressors are a subset of the larger family of positive displacement compressor types. In positive displacement compressors, air is drawn into a chamber where the volume is then mechanically reduced. The energy used to displace the air volume is converted to an increase in air pressure. Dynamic compressors operate a little differently. They utilize an increase in air velocity to create the change in pressure. Air is accelerated to a high velocity through an impeller. The kinetic energy of the air is converted to an increase in potential (pressure) energy.
The Double-Acting Reciprocating compressor is a close relative to the Single-Acting Reciprocating compressor. In these types of compressors, an “automotive-type” piston driven by a crankshaft provides the compression. In a Double-Acting Reciprocating compressor, air is compressed as the piston moves in each direction. Hence the name, “double-acting”. In a Single-Acting Reciprocating compressor, air is only compressed on each full revolution of the piston. This makes the Double-Acting Reciprocating compressor much more efficient than its brethren.
Double-Acting Reciprocating compressors are also available in much larger sizes. While Single-Acting compressors can be found up to 150HP, generally they’re much less common any larger than 25HP. Whereas a Double-Acting compressor is available from 10HP-1,000HP, making it a better choice for larger plants that require a significantly greater volume of compressed air. While they’re a bit more expensive due to the added mechanisms to produce the double-action compression, this cost is quickly offset by the increase in efficiency. At a performance of 15-16 kW/100 cfm, they’re 32% more efficient than a single-acting reciprocating compressor.
If you’re in the market for a new compressor and are struggling to determine the most suitable compressor, talk with your local compressor sales representative. Once you’re up an running, EXAIR has a wide-range of products that’ll make sure you’re using your compressed air safely and efficiently!