A compressed air system transfers power in the form of air pressure. A device somewhere else in a workshop can use the energy the compressor creates. The component that connects everything together in a compressed air system is the piping.
The piping in your system can make or break the profitability of your enterprise. Lost power through inefficient or faulty piping can wipe out your profit margin and give your competitors an advantage. Pay attention to the layout, installation and maintenance of your compressed air piping system to control costs and keep your business in the black.
Compressed Air Piping Systems
The basics of compressed air pipework are simple. You just need to attach a compressor to an end-use device via a pipe. However, no matter how easy it looks in the brochure, when you try to apply this to your workshop, you can find it gets a bit more complicated.
Many end-use devices of compressed air require isolation and ventilation. For example, a paint-spraying station needs its own booth, with heavy air filtering. Given these requirements, you’re going to have to place the station near an outside wall. If you’ve got a curing machine, you’re going to need to cool it and will have to place it near an outside wall as well. With many of your devices requiring an outside wall, you’ll find you have long distances you must travel to get compressed air to all of your end-use equipment. Unless your property is donut-shaped, this can be a challenge.
A major drawback of getting all of your compressed air from one source is that you end up sacrificing simplicity in your piping system. All too often, planning the compressed air piping system is the last consideration when organizing a shop floor. The environmental conditions and needs of your factory equipment often outrank the plan to simplify supply lines.
Piping Layout Considerations
When designing a compressed air piping system, you might think you should focus on the connectors. After all, this is where leaks are most likely to occur. Most people believe leaks are the greatest threat to a system’s efficiency. However, that is not necessarily the case.
Three factors can have a more significant impact on your pressure efficiency than leaks:
- Sharp angles
- Obstructions and Blockage
Sharp angles in your piping system impede the speed of flow, reducing pressure. Compressed air flow is actually no different than traffic flow on highways. If you have to make a sharp turn, you have to slow down. Coming out of a bend requires concentration — you need to correct any overcompensation for the turn and account for any unexpected objects on the new road.
Air can’t think or steer, so the redirection of a bend in a piping system sends it ricocheting off the inside of the pipe. It can soon have an undirected course that wastes energy. This type of air flow is called “laminar.” A convoluted air flow path is called “turbulent.”
Turbulence will cause a pressure drop, and it will only worsen if you turn up the output on your compressors. You need to avoid right-angle elbow corners in your piping system wherever possible, because they are going to cause turbulence and decrease your pressure delivery. A straight path in air flow is the most efficient.
The turbulence a 90-degree bend causes can often amount to 3 to 5 PSID of pressure loss. Therefore, eliminate sharp bends and install a series of 30- to 45-degree bends instead.
Water will corrode certain types of pipe, causing rust to flake off into the air stream. That rust, along with vapor, will arrive at the end-use equipment, clogging nozzles and contaminating the material you intend for the compressed air to deliver or apply.
In addition to clogging and contaminating issues, the corroded interior of a rusted pipe creates a rough surface. That is a second cause of turbulence, so moisture has a secondary effect on reducing air pressure.
Moisture is an unavoidable byproduct of air compression. The water that emerges from compression originates in the air taken in by the compressor. All ambient air has a certain level of humidity. When that air is compressed, the water in it condenses from its vapor form into a liquid state.
One solution to reducing moisture in your compressed air piping system is simple: change the supply inlet source where you’re drawing air from. The water that results from compression is heavier than the compressed air, causing it to fall to the bottom of the compressor. Drawing air from the top of the compressor will take less moisture with it.
While this can be an effective way to reduce moisture, drying air before it gets into the compressor can be a better choice. However, taking moisture out in-stream once the air is compressed requires passing your air flow through driers. Those devices can also slow down air flow, reducing pressure.
To address this issue, most compressor installers will recommend you use an aftercooler. Cooling the air as it leaves the compressor will take most of the moisture out before it gets into the piping. Two-thirds of the total water content of compressed air will turn to liquid when the air cools to 104°F. The aftercooler should feed into a filter with a drain to remove the liquid from the system.
With an aftercooler filter, there will be considerably less moisture in your air flow immediately after leaving the compressor. Removing moisture early in the process is preferable to letting it circulate in the piping.
Dryers, coolers and filters are essential elements of compressed air distribution systems. Moisture in compressed air is unavoidable, but that does not mean it is acceptable.
Corrosion in a piping system can break off and accumulate into obstructions. The main restriction points in your piping occur where you have valves, connectors or devices such as dryers or sensors in the circuit. These elements can reduce the diameter of pipe available for the air to flow through, and they also accumulate any particles in your air stream. A buildup of particulates on these devices will lower available pressure downstream and back up pressure upstream.
The unavoidable particulate content of a compressor’s air intake requires air filters. As with dryers, it is better to have effective air filters before the compressor to take out any particles that might circulate in the piping and clog inline devices, valves and end-use nozzles.
A blockage is easy to detect: You will have excessive pressure before it and insufficient pressure after it. You can eliminate many obstructions by choosing the correct pipe materials. Getting piping made of non-corrosive material automatically removes a large potential for obstructions.
An essential first question when planning a new compressed air system is “What type of pipe should I use for my air compressor?” You have two basic options: plastic or metal.
There are a lot of myths surrounding these two pipe materials. There are also pros and cons for each.
Plastic pipes over many benefits over metal.
- They do not corrode, so you don’t have to worry about rust dropping into your air flow. This, in turn, reduces the risk of obstructions.
- The interior surface is smooth and never deteriorates, which encourages laminar flow.
- The pipes are lightweight and easy to transport and fit.
- Cutting through plastic pipes is quick and simple and requires basic tools.
- Plastic pipes can be glued together, which is less costly and quicker than welding metal.
You can’t use just any plastic pipes for compressed air distribution. The most common types of plastic pipe available today are polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC). These are widely used for plumbing applications but are not suitable for high-pressure systems, such as compressed air channels, because they cannot withstand the pressure.
Acrylonitrile butadiene styrene (ABS) is a good material for piping compressed air. You can find ABS in a variety of products, from car fenders to Lego brand toy bricks. Polyethylene (PE) piping is also produced specifically for compressed air systems. Another suitable plastic for compressed air pipes is high-density polyethylene (HDPE).
The early attempts to use PVC and CPVC caused a number of catastrophes, resulting in the Occupational Safety and Health Administration (OSHA) banning them for use in high-pressure systems. However, ABS, PE and HDPE are all OSHA-approved for compressed air piping.
Many air compressors also require lubricating oil that can aspirate out into the air stream. This oil is corrosive to PVC and CPVC pipes. Metal pipe manufacturers will tell you that plastic will degrade in compressed air applications, making them splinter, causing injury and loss of production. However, ABS, PE and HDPE are oil-resistant and will not degrade when compressor lubricants come into contact with them.
Some people believe that plastic piping for pressurized air isn’t a good idea because the cement used in connectors is not strong enough and will fail, causing bursts and leaks. Plastic pipes specifically manufactured for compressed air systems come with OSHA-tested and approved cements that will hold fast for just as long as metal pipe welding.
Traditionalists prefer metal pipes for compressed air distribution systems. Just the look and feel of a metal pipe is more substantial and seems to have greater strength than its plastic equivalent. No matter how advanced engineering plastics become, some people will always feel they have greater strength and safety with metal pipes than plastic ones. There are also many benefits of metal pipes for compressed air.
- The traditional material means more installation technicians know how to fit the pipes.
- Having been in service longer, their strength against blowouts, fractures and splits is better proven.
- Their rigidity guarantees against warping.
- Compressor lubricants will not degrade them.
The category of metal pipes is further broken down into five alternatives:
- Black Steel Pipe — This is the traditional material in compressed air systems. It is strong and durable on the outside, and there is a large workforce of fitters who know how to install it. However, it is susceptible to corrosion. Suspended pipes need strong anchoring because of how heavy it is. It can also be difficult to cut and join. In addition, threaded connectors can slip and leak. Although the pipe itself is unlikely to leak, welded joints frequently fail.
- Galvanized Steel Pipe — This is another widely used material for compressed air systems. It is less susceptible to corrosion. However, the galvanizing coating tends to flake off over time, causing blockages and potential harm when released in air stream applications. As with black steel, it is difficult to maneuver, and threaded or welded joints are prone to failure. It is heavy, requiring higher strength from suspension and fixing methods.
- Stainless Steel Pipe — While this type of metal may be pressed or welded, it has the same connector faults (threading or welding) that black and galvanized steel have. There is no risk of corrosion or degradation on the interior or exterior of these pipes. However, stainless steel is heavy and difficult to fit. Another drawback is the strength requirements if you’re suspending it from supporting structures. Stainless steel is less common in real-world compressed air applications because of its high cost.
- Aluminum Pipe — Aluminum has the same anti-corrosive properties of stainless steel but without the weight. It’s easy to carry around the worksite while installing, and it requires the same skill set as fitting steel pipes. Push-together connectors make these pipes easy to install. Its light weight makes it easy to suspend. However, it can be considered expensive.
- Copper Pipe — This metal is corrosion-free and easy to cut and weld. It is lightweight and has a wide range of fittings available due to its frequent use in plumbing. It is easy to suspend, and a large number of plumbers are familiar with working with this material. However, like aluminum and stainless steel, it can be expensive.
Given that some amount of moisture in compressed air systems is unavoidable, the newer metals — stainless steel, aluminum and copper — are more popular over the traditional galvanized and black steel piping. However, the older metal types are still widely used in new installations even today. They are less expensive, and a large number of installation technicians recommend the materials, with which they are most familiar.
Many new customers of compressed air systems are unaware of pressure-grade stainless steel, aluminum and copper pipes. This is often simply because the companies that install pressurized air systems prefer the other options.
Speak to a Specialist
At Quincy Compressor, we combine legendary performance and reliability. We can help you plan and install a new compressed air piping system or assess your existing system. Contact us to schedule a consultation and find out about the latest technology emerging in piping systems. You can locate a sales representative or service center near you by using our Sales and Service Locator. Quincy Compressor has been trusted in the market for nearly a century. Let’s work together to maximize your compressed air system’s efficiency.