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Evaluating the Chemical Resistance of Piping Materials

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When chemicals are involved, selecting the right piping system can be a challenging decision for plumbing engi­neers and designers. Finding the answer requires evaluating the chemical resistance of piping materials based on the unique parameters of each application.

“Chemical resistance is a broad term used to describe the ability of a material to resist degradation from chemical exposure or attack,” said Brian Helms, training manager at Charlotte Pipe and Foundry. “In the holy trinity of piping design criteria — pressure, temperature, and chemical resistance — chemical resistance is often the last consideration. Depending on the application, however, the chemical resistance of thermoplastic piping materials may indeed be the most important factor.”

Chemical resistance is a broad term used to describe the ability of a material to resist degradation from chemical exposure or attack.

Plumbing engineers and designers can make informed decisions regarding material selection and system design by doing two things:

  1. Conducting a thorough evaluation of the chemical composition of substances to be conveyed

  2. Knowing of and adhering to the application parameters

How do chemicals attack piping systems?

Depending on the application and exposure, incompatible chemicals can attack both the inside and outside of the piping system. These chemicals infiltrate polymer chains, breaking down weaker bonds on the poly­mer chains and even breaking the molecular chains altogether.

Some of the effects of chemical attacks on plastic piping systems include:

  • Cracking

  • Swelling

  • Splitting

  • Embrittlement

This damage is often further compounded by other stresses the piping system is under such as temperature and pressure.

“Depending on the chemical, type of exposure, environmental conditions, and the stress a system is under, the time to failure may vary,” Helms said. “Ultimately, the result of exposing a plastic piping system to incompatible chemicals is the same: system failure.”

Ultimately, the result of exposing a plastic piping system to incompatible chemicals is the same: system failure.

Piping System Design Considerations

The chemical resistance of piping materials influences a variety of design consider­ations in many different applications, including:

  • Industrial pressure

  • Continuous drainage

  • Laboratory drainage applications

Although both industrial pressure and continuous waste drainage applications are demanding on the chemical resistance of the piping system, the parameters are usually straightforward and easy to identify. For example, engineers and designers often receive a complete list of the chemicals and temperatures that the plumbing will be exposed to, which simplifies specifying a piping system.

“These applications may involve heavily concentrated chemicals at elevated temperatures with no dilution, but the number of chemicals is generally small, and the temperature and pressures are well defined,” Helms said.

In contrast, laboratory drainage piping systems require versatility and must be able to stand up to a broad range of chemicals. Laboratory drainage systems are found in a variety of commercial buildings, each with requirements that vary greatly. Schools — from K–12 to even university chemistry labs — will have different requirements than hospital, pharmaceutical, and microbiological laboratories. Even though dilution is typically present, these systems are exposed to many different types of chemicals.

Chemical resistance is probably the single most important factor for engineers in choosing a piping system in laboratory applications, but it’s not the only one.

“Chemical resistance is probably the single most important factor for engineers in choosing a piping system in laboratory applications, but it’s not the only one,” Helms said. “Mixing chemicals can also produce a chemical reaction that releases energy in the form of heat.”

Therefore, in addition to chemical resistance, design professionals must also consider the temperature capabilities of any system they specify.

Navigating Material Selection

Engineers select piping systems based on several considerations, with experience often leading their decision-making process. The overall installed cost and ease of maintenance for the building owner also factor into an engineer’s decision to specify a certain piping material. Specific application parameters, however, remain at the top of the list of material section considerations for designers.

Chemical resistance, expected temperatures, and other factors — such as whether the piping system will be installed in plenum areas or underground — must be evaluated.

Unfortunately, no piping system is chemically immune to degradation from every chemical or substance ever made: Each piping material has strengths and weaknesses. In addition to proper installation, specifying the material best suited for the application parameters is key for the longevity of any piping system.

Comparing Thermoplastic Chemical Waste Piping Materials

  • CPVC is best known by engineers as a hot and cold domestic water pipe and even a fire protection pipe. However, due to the material’s broad-based chemical resistance, industrial pressure or chemical process applications are the single biggest use of CPVC pipe in the United States. In general, CPVC such as Charlotte Pipe’s ChemDrain® CPVC pipe and fittings exhibits resistance to strong acids and alkalis but is particularly effective with oxidizers and sodium hypochlorite solutions. (Of note, while CPVC is resistant to some dilute water-soluble solvents, it has limited resistance to certain strong, concentrated solvents.)

  • Polypropylene is commonly used in chemical waste and even domestic water applications. This is due to its chemical resistance against weak to moderately strong acids, bases, and water-soluble solvents. However, polypropylene can degrade with long-term exposure to oxidizing chemicals such as hydrogen peroxide or sodium hypochlorite.

  • Polyvinylidene fluoride exhib­its a significant level of chemical resistance to strong acids, weaker bases, solvents, and even oxidizers — but has limited resistance to some concentrated alkalis.

To assist plumbing professionals, Charlotte Pipe’s Tech Tools app features an interactive chemical resistance search tool that allows users to quickly identify what piping material is suitable for specific chemicals, including the maximum recommended temperature.

Explore the Tech Tools app on your desktop computer or download the mobile app via the Google Play store or the App Store.

For more information, learn why Charlotte Pipe’s ChemDrain CPVC is the cost-effective choice for chemical waste disposal.

Additional chemical information can be found at the following links:

National Center for Biotechnology Information’s PubChem site

The National Institute for Occupational Safety and Health’s Directory of Chemical Safety Resources

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