CPVC piping is commonly employed in the chemical industry. CPVC resin is created by post-chlorination of PVC polymer.
CPVC has excellent chemical resistance to wide range of corrosive fluids. It's chemical resistance is almost identical to that of PVC. The additional chlorine in CPVC polymer extends its maximum service temperature from 140°F to 210°F.
Physical properties of CPVC piping
CPVC is used for hot water distribution systems, hot corrosive fluids where PVC cannot be used due to its low strength at higher temperatures. The design stress of PVC as well as CPVC piping is 2000 psi at 73°F. However, the strength of CPVC is reduced to 500 psi @ 180°F, when compared to 400 psi @ 140°F for PVC. Because of higher strength at higher temperatures, CPVC piping can have larger support spans.
UV resistance of CPVC piping
CPVC piping undergoes surface oxidation and embrittlement by exposure to sunlight over a period of time. The color of pipe changes from gray to white. The strength of piping is not reduced, however it becomes more susceptible to impact damage. UV protection can be provided by applying a thick coating of latex paint.
Heat tracing of CPVC pipe
It is possible to heat trace CPVC piping to maintain a constant elevated temperature. Electric tracing is recommended. The maximum heat trace temperature should not exceed the pressure temperature rating of the piping system.
Pipe supports
Pipe saddle cut from CPVC pipe are recommended at support locations. CPVC pipe must not rest directly on steel. Supports must be provided on or close to inline items such as valves. CPVC piping connected to vibrating equipments such as pumps must be isolated using teflon or rubber expansion joints.
Joining Methods
- Solvent Welded Joints
- Flanged Joints
- Threaded Joints
Solvent cementing is a preferred method of joining CPVC pipe and fittings. The OD of the pipe and ID of fitting are primed, coated with special cement and joined together. Most solvent cement joints fail due to lack of solvent penetration or inadequate primer application.
Applicable Standards
- ASTM D2846 - Standard Specification for Chlorinated Poly(Vinyl Chloride) (CPVC) Plastic Hot- and Cold-Water Distribution Systems
- ASTM F437 - Standard Specification for Threaded Chlorinated Poly(Vinyl Chloride) (CPVC) Plastic Pipe Fittings, Schedule 80
- ASTM F439 - Standard Specification for Chlorinated Poly (Vinyl Chloride) (CPVC) Plastic Pipe Fittings, socket type - Schedule 80
- ASTM F441 - Standard Specification for Chlorinated Poly(Vinyl Chloride) (CPVC) Plastic Pipe, Schedules 40 and 80
- ASTM F493 - Standard Specification for Solvent Cements for Chlorinated Poly(Vinyl Chloride) (CPVC) Plastic Pipe and Fittings
CPVC vs Carbon Steel
| Property | Unit | Carbon Steel | CPVC |
|---|---|---|---|
| Density | kg/m³ | 7860 | 1550 |
| Coefficient of Thermal Expansion | in/in °F x 105 | 0.06 | 3.8 |
| Thermal Conductivity | BTU/hr/ft2/°F/in | 290 | 0.95 |
| Modulus of Elasticity @ 73°F | psi x 105 | 290 | 4.2 |
| Tensile Strength | psi | 60,000 | 8,400 |
| Working Stress @ 73°F | psi | 20,000 | 2,000 |
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