DON’T Use PVC Pipe for Compressed Air Distribution. Here’s Why

• Fluids (liquids): Liquids are essentially incompressible, meaning they do not compress under pressure. When a liquid-filled pipe fails, the liquid’s inability to compress limits the energy released during the failure. Pressure ratings for liquids are based on the material’s strength and its ability to resist internal pressures without failing (bursting) or deforming excessively.
• Gasses: Gasses are compressible, meaning they can be compressed under pressure and will expand when that pressure is released. A gas-filled pipe that fails can release a significant amount of energy as the gas rapidly expands to its uncompressed state. This release can be dangerous and is often more catastrophic than the failure of a liquid-filled pipe, as it can propel pipe fragments and cause damage or injury.

Because gasses can store more energy and have a higher potential for causing damage upon release, the considerations for gas pressure systems are more stringent. Pipes and fittings for gas are often selected with lower maximum operating pressures than their liquid-rated pressures to account for this increased risk. The design and material selection for gas systems also consider factors like the type of gas, its potential for combustion, and the likelihood of sudden pressure increases.

The Problem with PVC Piping for Gas Applications

Can you use PVC pipe for compressed air and inert gas distribution? Usually, the answer is no. PVC and CPVC pipes are designed primarily for transporting water under pressure. Their characteristics, while suitable for liquid transport, pose significant safety risks when used for compressed air.

Brittleness and Failure Mode

PVC, being a relatively brittle material, can fail catastrophically under the high-pressure conditions typically found in compressed air and gas systems. Unlike more ductile materials that might bulge or leak before bursting, PVC can shatter explosively. This failure mode is particularly dangerous because it can send sharp shards of plastic flying at high speeds, potentially causing injury to personnel or damage to nearby equipment.

Impact of Environmental Factors

PVC’s strength and durability can be significantly reduced by exposure to certain environmental factors, such as UV light from the sun and certain chemicals. Over time, these factors can cause the PVC to become even more brittle, increasing the risk of a sudden, catastrophic failure.

Temperature Sensitivity

PVC’s mechanical properties can be adversely affected by temperatures outside a relatively narrow range. Most notably, PVC can become brittle and more prone to cracking in cold temperatures. In contrast, high temperatures can cause PVC to soften and weaken, reducing its pressure-carrying capacity. Compressed air systems can generate significant heat, which may further compromise the integrity of PVC piping.

Energy Storage and Release

Compressed gasses store a significant amount of energy. In the event of a PVC pipe failure, this stored energy is released abruptly, potentially turning the pipe and its contents into projectiles. The risk is considerably higher than with liquids, which are relatively incompressible and thus store much less energy under pressure.

Regulatory and Code Restrictions

Due to these safety concerns, many local, national, and industry-specific codes and regulations explicitly prohibit the use of PVC pipes for compressed air or gas distribution. Compliance with these regulations is crucial for safety, legal, and insurance reasons. OSHA prohibits the use of PVC and CPVC piping for compressed air or gas unless the piping is underground or encased. Failure to comply with OSHA standards and local building codes can result in substantial fines and penalties.

PVC vs. Aluminum Compressed Air Piping

Given these concerns, when designing systems for compressed air or gas distribution, engineers typically recommend materials specifically designed to handle the unique challenges posed by compressed gasses. While some plastics (such as HDPE, ABS or certain types of polyethylene) may be suitable for compressed air or gas distribution systems, metal piping is usually recommended for enhanced safety, durability and longevity. Among the various materials used for compressed air and gas distribution, Unipipe aluminum pipe stands out as an excellent alternative to PVC piping.

Safety

• Resistance to shattering: Unlike PVC, which can shatter explosively under pressure, aluminum piping is not prone to fail in such a catastrophic manner. Aluminum might deform or burst but won’t shatter, significantly reducing the risk of injury to personnel.
• Non-combustible: Aluminum is non-combustible and does not support combustion, making it safer for use in environments where there might be a risk of fire or explosion. PVC, on the other hand, can burn and release toxic fumes if exposed to fire.

Durability and Performance

• Corrosion resistance: Aluminum piping systems are resistant to corrosion, both internally and externally. This resistance helps maintain clean air quality and reduces the risk of pipe degradation over time. PVC can also resist many forms of corrosion but is more susceptible to damage from UV light and certain chemicals.
• Leak resistance: Unipipe aluminum piping systems are designed with smooth interiors and secure, reliable connections that minimize air leakage. Reducing leaks improves the efficiency of the compressed air system and can lead to significant energy savings. Plastic connections may not be as robust, especially under varying temperature conditions, leading to an increased risk of leaks.
• Temperature tolerance: Aluminum has a broad temperature tolerance and maintains its integrity across a wide range of temperatures. PVC pipes have limited tolerance to high temperatures, and their strength and structural integrity can be compromised in varying thermal conditions, making them unsuitable for hot environments.

System Efficiency

• Conductivity: Aluminum’s thermal conductivity is relatively low compared to metals like copper, which helps to reduce the amount of condensation that forms inside the air lines. While PVC also does not conduct heat well, the performance and efficiency of aluminum piping in terms of maintaining air quality and reducing moisture are generally superior.
• Ease of modification: Unipipe aluminum piping systems are relatively easy to modify and expand. New lines can be added with minimal downtime, and the material allows for the straightforward reconfiguration of the system as needs change. PVC systems, while also modifiable, often require more effort and downtime for adjustments and expansions.

Compliance with Regulations

• Regulatory approval: Many jurisdictions have specific regulations and standards for compressed air systems, and aluminum piping is widely accepted and complies with these regulations. The use of PVC for compressed air is restricted or not recommended in many places due to the safety risks it poses.

Upgrade to Safe Aluminum Pipe from Unipipe Today

If you or your clients are currently using PCV piping for compressed air or inert gas distribution, your people and facility may be at risk. Don’t wait for a catastrophic accident or regulatory penalties before making a change. Upgrade to a clean, safe and durable aluminum piping system today.

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