1. Raw Material Quality Control
Core Raw Materials: CPVC resin is used, with chlorine content being a key indicator, typically ranging between 60% and 70%, and extremely low levels of impurities.
Additive System: Heat stabilizers, lubricants, and processing aids must be used; for example, calcium-zinc stabilizers are used in place of traditional lead salts to meet environmental requirements.
Mixing Process: A two-step "hot-cold mixing" process is required to ensure uniformity of the material. The hot mixing temperature is approximately 110–125°C, and the cold mixing temperature is approximately 40–50°C.
2. Full-Process Control of the Production Process
Drying and Pre-treatment: CPVC resin is highly hygroscopic and must be dried in an 80°C oven for 2–4 hours prior to production.
Extruder Requirements: A twin-screw extruder must be used, with screw designs adapted to the high viscosity characteristics of CPVC.
Melt Temperature Control: This is the most critical step. The melt viscosity of CPVC is significantly higher than that of PVC, typically ranging between 180–220°C. Temperatures that are too low or too high will cause a sharp decline in pipe quality. Modern production lines employ precise segmented control to maintain stable temperatures in each zone.
Cooling and Setting: After extrusion, the material must be cooled rapidly and uniformly; improper cooling can easily generate internal stress, affecting the strength of the pipe.
Cutting and Marking: After precisely cutting the pipe to length as required, clearly mark specifications, standards, production batch numbers, and other information using inkjet coding equipment.
Process Monitoring: Monitor dimensions in real time using equipment such as online thickness gauges; operators must conduct regular inspections and immediately address any abnormalities, such as smoke, in accordance with procedures.
3. Final Product Quality Inspection
Appearance and Dimensions: The inner and outer walls of the pipes should be smooth and free of defects such as bubbles or cracks. Use tools such as a micrometer to measure the outer diameter, wall thickness, and ovality.
Physical Properties: As previously mentioned, these include Vicat softening temperature, drop weight impact test, hydrostatic strength test at 2.5 MPa or higher, as well as flattening test, ring stiffness test, and longitudinal shrinkage rate.
Chemical and Composition Analysis:
Chlorine Content Determination: Verify that the chlorine content of the pipes meets the specified standards.
Chemical Resistance Testing: Evaluate chemical stability through immersion in acids, alkalis, and salts.
Thermal Stability Analysis: Evaluates long-term heat resistance through thermal aging tests and thermogravimetric analysis.
Special Performance Testing: When used in drinking water applications, hygiene performance tests such as heavy metal migration must be conducted.
Full Process Traceability: Finished pipes must be clearly marked with a production batch number to ensure that any quality issues can be traced back to the raw materials, production date, process parameters, and operators.
4. Establish a Comprehensive Quality Management System
Implement Institutionalized Controls: Establish a "five-tier quality assurance" system covering all employees, with clearly defined responsibilities and strict performance evaluations for key business processes.
Implement Lean Production: The Lean Production philosophy emphasizes full employee participation in quality control. Through statistical analysis of key production parameters, deviations are identified and proactively prevented.
Obtain System Certification: Certification signifies that the company has achieved internationally recognized standards in quality management and product consistency.
Conduct Supply Chain Audits: Conduct factory and product inspections of suppliers, evaluate their quality systems on-site, and collaborate with multiple suppliers to diversify risk.