By Derrick Taylor, Director, Fluid-Aire Dynamics
What is the best pipe material to use for a compressed air system? Manufacturers have many options when it comes to compressed air piping materials. As with most decisions, the choice in piping material comes down to tradeoffs between cost, performance, longevity and aesthetics. Here are some of the most common materials used for compressed air piping and the pros and cons of each.
Plastic compressed air piping is cheap, lightweight, easy to install and non-corrosive. However, not all plastics are the same. If you are using plastic piping, it is important to make sure it is durable enough to stand up to years of use and will not be damaged by contact with oils and lubricants from your compressed air system. Most critically, you must make sure that the plastic piping you choose is OSHA-approved for use in compressed air systems.
PVC and CPVC Piping: Not OSHA-Approved for Compressed Air Systems!
PVC and CPVC are highly cost-effective and easy to work with. These characteristics have made them very popular for use in plumbing and other applications. Unfortunately, OSHA has banned PVC and CPVC piping for use in compressed air systems.
The reason OSHA does not allow PVC or CPV in compressed air piping is that these plastics are not strong enough to withstand high-pressure applications such as compressed air distribution. In addition, these plastics will degrade when they come in contact with oils and lubricants from the air compressor, leading to fractures and splintering. Over time, this degradation will lead to excessive air leakage and an increased risk of a sudden dangerous rupture. Injuries caused by early installations of PVC and CPVC piping in compressed air systems led to OSHA banning the use of the materials for these applications.
ABS, PE and HDPE for Compressed Air
There are several other options when it comes to plastic compressed air piping, including Acrylonitrile butadiene styrene (ABS), polyethylene (PE) and high-density polyethylene (HDPE). These materials retain many of the benefits of PVC and CPVC but are more durable and do not degrade when exposed to oils and lubricants.
ABS, PE and HDPE plastics are appropriate for use in compressed air piping systems and have some benefits over metal.
- The materials are lightweight and easy to work with, requiring no special bracing or supports.
- Plastics can be easily cut and fit using standard tools and can be glued together rather than welded.
- The interior surface is smooth for maximum laminar flow.
- Plastic does not corrode, so plastic piping minimizes the risk of particulates making their way into the airflow.
On the other hand, even high-quality plastic pipes will not match the strength and durability of a metal compressed air piping system. The cement used for connectors may also be more prone to failure and air leaks than welded metal piping. However, a well-designed plastic system with the right cements can offer similar performance to metal pipes if treated with care.
Piping options made from various types of metal are the more traditional choice for compressed air distribution. Metal pipes are stronger and more resistant to blowouts, cracks and splits. They are not degraded by contact with oils and lubricants. They are also less likely to warp than plastic piping. For these reasons, metal is the most popular choice for compressed air system piping.
Metal pipes are more expensive than plastic and some may take a bit longer to install. But once they are in place, they are likely to last a long time. There are many different types of metal compressed air piping systems to choose from. Each material has its own set of advantages.
Black Iron Pipe
Black iron piping has long been considered a standard for compressed air delivery. You’ll find black metal piping in many older installations. Iron is very strong and durable, so it will hold up to a lot of abuse. These pipes use traditional joining techniques (threading and/or welding), so they can be installed by any plumber with fittings that are easily available from the local hardware store.
Iron piping does have a few drawbacks.
- Iron pipes are very heavy, so anchoring must be used with suspended piping systems.
- Iron can be difficult to cut and join, requiring a skilled plumber or welder to install. Leaks often develop along joins or welds.
- Most critically, black iron piping is highly susceptible to corrosion when it comes into contact with moisture from the air compressor.
- When rust develops inside iron piping, it can cause blockages or make its way into the compressed air stream, fouling the air lines and causing problems for production processes.
Galvanized Steel Pipe
Galvanized steel piping has many of the same advantages and disadvantages of its black iron counterpart, with one major exception: galvanization significantly reduces corrosion. This makes it a popular choice for compressed air systems.
If you are using galvanized piping, you should be aware that the galvanized coating will degrade over time. As the zinc coating degrades, it can flake off inside the piping, causing blockages or fouling in the air lines. Sharp flakes are also a safety concern when they are blown out of the air lines at high speeds.
Stainless Steel Pipe
Stainless steel is highly durable and resistant to corrosion, making it the longest-lasting (and most expensive) choice among the steel and iron piping alternatives. Stainless steel piping does not degrade or corrode like black iron or galvanized piping, making it a good choice for applications where it is essential to keep rust and particulates out of the air stream. It also looks great.
However, stainless steel is difficult to cut and work with, requiring specialized installers with the right tools and training for the job. It is just as heavy as traditional iron and also prone to the same leakage around joints and welds. Due to its high cost and other drawbacks, it is one of the least common choices for compressed air system piping.
Copper pipe is another corrosion-free choice for compressed air piping. It is lighter than iron and easier to install than stainless steel. Like iron, copper piping uses readily available fittings and standard joining techniques. The same properties that make copper a popular choice for plumbing make it attractive for use in compressed air systems.
The main drawback of copper is cost. The cost of copper has risen dramatically in recent years, making its use in compressed air system design less appealing. In addition, you will need a skilled plumber or welder to install or make changes to the system.
Aluminum Pipe Systems
Aluminum compressed air piping systems have grown in popularity over the last 10 to 15 years, and with good reason. Aluminum offers a number of benefits, including:
- light weight (three times lighter than iron piping),
- zero corrosion,
- high leak resistance, and
- ease of installation.
Modular compressed air piping systems made of aluminum are easy to install and modify. Modern modular piping systems require minimal tools for installation and do not need heavy supports or anchoring. These systems can be installed without threading, brazing or welding, so they do not require a hot work permit. Modifications with these systems are easy, too, and can often be completed in-house without hiring a plumber or subcontractor.
Fluid-Aire Dynamics prefers the Unipipe Modular Aluminum Piping System. This modular aluminum system is lightweight, corrosion-free and very easy to install and modify. The flexible and versatile system offers the widest product range for the transport of compressed air, inert gases and vacuum as well as high-pressure air and fluids. It is available in a broad range of sizes, pressures and fittings. Here are some other advantages of the Unipipe system:
- All piping and fittings are 100% aluminum.
- It is available in the broadest range of sizes on the market: ¾” to 10” diameters.
- It is suitable for very wide pressure ranges, from high vacuum to 1000 PSI, and offers a range of working temperatures from -4°F up to 212°F.
- No special tools are required for assembly or installation, and no grooving or crimping are necessary. All pieces connect together quickly and easily.
Choosing the Best Compressed Air Piping for Your System
Fluid-Aire Dynamics can help you select, install and maintain your compressed air piping. We can also help you design your piping layout for maximum performance and determine the right size compressed air piping for your needs.
Need help installing or updating your compressed air system piping? Contact us to set up a consultation with a compressed air system engineer.
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