If you are using PVC or CPVC for your compressed air system, you may be putting people and property at risk. PVC is not a safe or approved material for compressed air piping. In fact, the use of PVC piping for compressed air can lead to dangerous or deadly explosions. Here, we’ll explain the problems with PVC, why it should never be used to conduct compressed air, and what you should do if your current system contains PVC.
Why PVC Pipe Should Not Be Used for Compressed Air
Polyvinyl chloride (PVC) and its cousin, chlorinated polyvinyl chloride (CPVC), are synthetic plastic polymers that are widely used in building, construction, and a variety of consumer and industrial goods. PVC and CPVC are versatile, easy to work with, and highly cost-effective to manufacture. These characteristics have made the materials very popular for piping and plumbing fixtures. However, PVC piping that is appropriate for plumbing is not rated for use in compressed air applications.
The Difference Between Moving Liquids and Gases
Many people make the mistake of assuming that a PVC pipe designed for plumbing can also be used for air lines in a compressed air system. However, there is a big difference between moving liquid and moving gases. Unlike liquid, gases are compressible.
When you compress a gas, you are storing energy—after all, that is the whole reason that we can use compressed air to power tools and production lines. While a liquid will simply stop flowing if there is a blockage (think what happens with your hose when it is kinked), a gas will continue to further compress, leading to over-pressurization. When that happens inside a PVC pipe, you have essentially created a plastic pipe bomb.
The Problem with PVC Pressure Ratings
Pressure ratings on PVC pipe can also lead to confusion. Many PVC pipes are rated for 300-600 PSI. Since the average industrial compressed air system is pressurized to 100-125 PSI, this may sound like it is more than enough. However, there are several problems with this assumption.
- The rating is for the pipe itself, not for seals and joins. PVC is notorious for failing at the joints when used for compressed air. Many adhesives used for PVC piping are not compatible with compressor lubricants, making a failure just a matter of time.
- Pressure ratings are highly temperature specific. When the temperature drops below freezing, PVC becomes highly brittle and prone to shattering. Pressure ratings also drop at higher temperatures: the pressure rating at 110°F is typically half the rating for room temperature applications. This is a particular problem for compressed air, because compression of a gas naturally generates heat (known as “heat of compression”).
- Pressure ratings are for new material only. PVC becomes more brittle with age. After ten years in service, PVC pipe is much more prone to failure.
But the biggest problem with PVC is the way it fails. PVC pipe can explode when over-pressurized or hit with a sharp object, sending plastic shrapnel flying in all directions.
The Dangers of PVC Pipe in Compressed Air
PVC is prone to catastrophic failure and explosion due to the properties of the material. PVC pipe is not a ductile material like metal—it doesn’t bend under pressure. It simply shatters. When PVC pipe shatters at high pressures, plastic shrapnel is expelled at high velocities. PVC pipe explosions may cause substantial damage to property, severe injuries and death.
This video from Charlotte Pipe and Foundry, a manufacturer of PVC pipe, explains the dangers of pressure testing PVC pipe with air, which also applies to the use of PVC to conduct compressed air. (Skip ahead to 1:20 if you just want the dramatic bit.)
There have been many documented instances of PVC pipe failures in industrial compressed air systems over the years. At best, these accidents lead to damage to production lines, unexpected production shutdowns and delays. At worst, they lead to serious injuries or death for workers who are standing nearby.
Does OSHA Allow the Use of PVC Pipe for Compressed Air?
Because of the risk of injury and death linked to the use of PVC and CPVC piping in compressed air systems, OSHA has banned the use of PVC and CPVC piping in compressed air systems. An OSHA Hazard Bulletin dating to 1988 limits the use of PVC pipe for compressed air conveyance in above-ground applications. (Buried PVC pipes are considered safer because the surrounding soil will mitigate the dangers of compressed air pipe explosions.)
Failure to follow OSHA guidelines can lead to safety citations, fines and lawsuits. In one case, a company was fined $110,000 for worker injuries due to improper use of PVC for compressed air piping. It would have been much more cost effective to simply use the correct compressed air piping material in the first place!
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Selecting the Right Material for Your Compressed Air Piping System
What materials can be used for compressed air piping? Fortunately, you have options.
Can Any Plastic Pipe Be Used for Compressed Air?
Some plastics are appropriate for use in compressed air systems. Ductile plastics such as acrylonitrile butadiene styrene (ABS), polyethylene (PE) and high-density polyethylene (HDPE) can be safely used for compressed air. These plastics are more durable and less prone to explosive failure than PVC or CPVC.
Other Piping Material Options for Compressed Air
Companies have many options when it comes to metal compressed air piping, including black iron, galvanized steel, stainless steel copper and aluminum. Read more: What is the Best Piping Material for Compressed Air Systems?
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.
Replacing PVC Piping in Your Compressed Air System
If you are currently using PVC piping in your compressed air system, it should be evaluated and replaced as soon as possible. The longer PVC pipe is used, the greater the chances of a dangerous rupture or explosion.
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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