Both PVC and CPVC piping offer strength and durability for a relatively low cost, even for chemical applications. While steel piping can become corroded overtime, thermoplastic piping like PVC and CPVC can resist corrosion from acids, salts, and other harsh chemicals, though CPVC may not be the best fit for certain solvents and aromatics. Continue on to learn more about chemical resistance in PVC and CPVC piping.
Why PVC Piping can Handle Chemicals
PVC, or polyvinyl chloride, piping accounts for over 85% of thermoplastic piping today. Known for its strength and rigidity, it’s made even stronger with the use of cement solvents to fuse the pipes together, creating permanent joints and decreasing leakage. These pipes are also lightweight and relatively inexpensive to use. They come in both Schedule 40 (here) and Schedule 80 (here).
PVC piping has a strong chemical resistance and can be used with a broad range of corrosive liquids, including certain acids, salt solutions, and alkalis. This makes it a good fit for chemical drainage, chemical processing, and industrial plating. However, when used in chemical applications, special care should be taken to install the piping properly, to avoid cracking or over-belling. Do not use PVC with ketones, aromatics, or some chlorinated hydrocarbons. It’s also important to note that PVC piping has a maximum service temperature of 140° F.
The allowable span for PVC piping is about half that of its steel counterpart. There’s also not a significant increase in span as the diameter of the piping increases. For a standard 2-inch pipe, the allowable span is 1.8 meters; for 6-inch piping, the span is 2.5 meters; and for 10-inch piping, the allowable span increases to 3 meters.
Benefits of Using CPVC Piping in Chemical Applications
Like PVC piping, chlorinated polyvinyl chloride, or CPVC, piping is a strong thermoplastic with a relatively low cost (view here). This piping is a PVC homopolymer that has undergone a chlorination reaction. This reaction allows the CPVC piping to tolerate higher temperatures and have superior resistance to corrosive chemicals.
For a highly corrosive-resistant CPVC option, view our selection of LabWaste pipes here. These pipes are a great option for drainage systems as well as for corrosive waste, and they can withstand temperatures up to 220° F (10° F higher than the average CPVC pipe, discussed below).
CPVC Can Tolerate Higher Temperatures than PVC
Unlike PVC, whose maximum temperature tops out at 140° F, CPVC piping can withstand temperatures up to 210° F. It is equally effective at lower temperature ranges, as well. While relatively inexpensive, however, it is still more costly than PVC piping, and thus is typically used where higher temperature resistance is required.
CPVC is Resistant to Corrosive Chemicals
The chemical resistance of CPVC has been widely tested by two industry standards: the ISO Evaluation, which determines the Environmental Stress Cracking (ESC) of thermoplastics, and the ASTM Evaluation, which evaluates their resistance to chemical reagents. Both evaluations demonstrate that CPVC piping is extremely resistant to most corrosive chemicals. This means that CPVC can handle salts, caustics, and acids better than metal and other thermoplastics. There is no pH limitation either, which means that it can hold up to large pH swings with no damage.
Be Aware of CPVC Softening
It’s important to note, however, that CPVC is not the right fit for applications where solvents like ketones, ethers, esters, alcohols, and aromatics are used. These can be absorbed into the piping, causing softening to the structure. Overtime, this softening could lead to ductile rupture or other damage. This is not limited to the fluids passing through the CPVC either. Environmental exposure to solvents and plasticizers could also cause softening to occur.
Industries CPVC Piping is Used In
CPVC piping is used today in a wide variety of applications. Due to its high temperature and chemical resistance, CPVC is commonly used in the following industries:
- Food and Beverage
- Wastewater Treatment
- Power Generation
- Metal Finishing
- Chemical Processing
- Mineral Processing
- Chlor-Alkali Industry
Not all CPVC piping is made with the same specifications, including chlorine content and compound additives. For this reason, it is highly recommended for you to work directly with a pipe and fitting manufacturer that can help determine the actual chemical resistance to that particular product and how it may impact your unique application.
Considerations for Using PVC and CPVC Piping in Plants that Handle Chemicals
There are several factors to consider when determining if PVC or CPVC piping is a proper fit in a process that handles chemicals.
Temperature and Pressure Factors
Elevated temperatures could negatively impact thermoplastic piping. Consider the sustained temperature of the liquid passing through it, but also the temperature of the environment. For this reason, it is best not to utilize PVC or CPVC piping near steam lines or hot surfaces. In addition, avoid the possibility of liquid hammer, which occurs when the liquid flow in the pipe stops abruptly, causing a pressure surge, which can easily damage the system.
Proper Support of Plastic Piping
Due to the use of elevated temperatures, the proper support for your CPVC or PVC piping is critical. Refer to the general span guidelines above and determine the specifications given by the piping manufacturer. Common supports include clamps, angles, and saddles. The contacts should be broad and smooth, rather than narrow, to decrease the potential of stress concentration.
For our pipe supports go here.
Vibrations around the Piping
Consistent vibration could cause damage to your PVC or CPVC piping. Before installation, do an assessment to determine the level of vibration that could occur in your system. If a high level of vibration is likely, mitigation efforts will be needed. If attached to a pump, for example, excess vibration may need to be controlled through the use of a vibration isolation device.
Use of Plastic Fittings
Fittings, such as tees, are required for branch connection. The correct fitting should be strong enough to sustain internal and external pressure of the pipe. However, plastic fittings can cause extended stress concentrations that could cause damage to the line. For this reason, it’s always best to consult the fitting manufacturer to ensure the right fit for your application.
Solvent Cement
Solvent cement (here) was designed to create a reliable, permanent bond between the pipe and its fittings. In harsh chemical environments, however, fillers contained in the solvent can dissolve, causing leakage at the joint. If you plan to use PVC or CPVC piping in a plant that handles chemicals, a special solvent cement is needed to withstand the exposure and minimize leakage.
Use of PVC and CPVC Piping in Chemical Applications
Thermoplastic piping like PVC and CPVC have a long successful history of use in chemical applications. Both resist corrosion from a number of harsh chemicals and can withstand higher temperatures, though CPVC may be the better choice for high temperature uses. Whether you’re in metal finishing, chemical processing, wastewater treatment, or even the food and beverage industry, your systems could benefit from the use of PVC or CPVC piping. Keep in mind, however, that each manufacturer may produce a slightly different product, so it’s important to know if the chlorine content and compound additives in the piping are appropriate for your application. Contact Commercial Industrial Supply to learn more about our piping solutions.