How to design a PPR Valve that can operate stably for a long time under high temperature and high pressure environment?

To design a PPR valve that can operate stably for a long time under high temperature and high pressure environment, it is necessary to comprehensively consider material properties, structural design, manufacturing process and environmental factors in actual application. The following are detailed design steps and key technical points:

1. Clarify requirements and working conditions
Before designing, the specific application scenarios and technical requirements of the valve must be clarified:
Operating temperature: Determine the maximum operating temperature (such as 70°C, 95°C or higher) and ensure that the material can withstand this temperature for a long time.
Operating pressure: Determine the maximum pressure bearing capacity (such as PN16, PN20 or higher), and select the appropriate wall thickness and structure according to the pressure level.
Media type: Understand the properties of the conveying medium (such as hot water, cold water, chemical solution, etc.) to evaluate the corrosiveness or other effects on the material.
Use environment: Consider whether it is exposed to ultraviolet rays, low temperature shock or other external environmental factors.
2. Material selection
The selection of PPR materials is the key to the design, which directly affects the temperature resistance, pressure resistance and anti-aging performance of the valve:
PPR material grade:
Choose PPR materials with high heat resistance and high creep resistance, such as PPR80 or PPR100 (referring to the MRS value of the material is 8.0MPa or 10.0MPa).
For high temperature and high pressure environments, it is recommended to use reinforced PPR materials (such as glass fiber reinforced PPR or nano-composite PPR) to improve mechanical strength and durability.
Sealing material:
The valve seals are usually made of high temperature resistant EPDM (ethylene propylene diene monomer rubber) or silicone to ensure good elasticity at high temperatures.
If the medium is corrosive, PTFE (polytetrafluoroethylene) can be selected as the sealing material.
3. Structural design
The structural design of the valve needs to take into account the pressure bearing capacity, sealing performance and operational convenience:
Wall thickness design:
According to ISO 15874 or GB/T 18742 standards, calculate the minimum wall thickness of the valve body to ensure that it can withstand the design pressure and temperature.
Under high temperature and high pressure conditions, appropriately increase the wall thickness to offset the creep effect of the material due to long-term use.
Valve body shape:
Design a streamlined valve body to reduce the flow resistance of the medium while avoiding stress concentration areas.
Ensure that the internal surface of the valve body is smooth to reduce the possibility of medium retention and scaling.
Seal structure:
Adopt a double-layer sealing design (such as O-ring + flat seal) to improve sealing reliability.

Under high temperature and high pressure environment, add anti-loosening design (such as thread locking or spring washer) to prevent the seal from failing due to thermal expansion or vibration.
4. Thermal expansion compensation
PPR material has a high thermal expansion coefficient and is prone to deformation in high temperature environment. Therefore, the following measures need to be taken:
Flexible connection:
Use flexible joints (such as bellows or rubber joints) between the valve and the pipeline to absorb the displacement caused by thermal expansion.
Reserved gap:
Reserve appropriate expansion gap during installation to avoid stress concentration caused by thermal expansion.
Reinforcement rib design:
Add reinforcement ribs to the valve housing to improve overall rigidity and reduce the impact of thermal expansion on the structure.
5. Manufacturing process
The manufacturing process of PPR valves directly affects its quality and performance:
Injection molding:
Optimize injection molding process parameters (such as melt temperature, injection pressure, cooling time) to ensure that the material fully fills the mold and reduces internal stress.
Use high-precision molds to ensure the consistency of valve body size and surface quality.
Welding process:
For valves with welding parts, hot melt welding technology is used to ensure the strength and sealing of the weld.
Control the welding temperature and time to avoid overheating causing material degradation or overcooling causing loose welding.
Post-processing:
Anneal the finished product to eliminate internal stress and improve the creep resistance of the material.
6. Durability and testing
To ensure that the valve can operate stably and for a long time under high temperature and high pressure environment, strict tests are required:
Pressure test:
According to standards (such as ISO 15874 or GB/T 18742), the valve is subjected to hydrostatic test to verify its pressure bearing capacity.
Temperature test:
The valve is placed in a high temperature environment (such as 95°C or higher) for a long time aging test to evaluate its performance changes.
Fatigue test:
Simulate actual use conditions and perform multiple switching operations on the valve to verify its durability and sealing performance.
Burst test:
Test the valve's breaking point under extreme pressure to ensure its safety margin.
7. Installation and maintenance
Proper installation:
Use special hot melt tools for welding, and ensure that the welding temperature (usually 260°C) and time meet the requirements.
Avoid excessive bending or stretching of the pipe to prevent additional stress on the valve.
Regular inspection:
Regularly check the valve's sealing performance and operational flexibility, and replace aging or damaged parts in time.
Antifreeze protection: In cold areas, take insulation measures (such as wrapping insulation cotton or electric heating tape) to prevent the valve from being damaged due to low temperature brittleness.
8. Innovation and intelligence
With the development of technology, more functions can be added to PPR valves:
Intelligent monitoring: Integrated sensors monitor the pressure, temperature and flow of the valve in real time, and transmit the data to the central control system.
Remote control: Add electric or pneumatic actuators to achieve remote switching and adjustment functions.
Antibacterial materials: In drinking water systems, antibacterial PPR materials are used to inhibit bacterial growth.

Designing a PPR valve that can operate stably for a long time under high temperature and high pressure environments requires optimization from multiple aspects such as material selection, structural design, manufacturing process, and thermal expansion compensation. Through reasonable design and rigorous testing, high-performance and high-reliability PPR valves can be created to meet the needs of various complex working conditions.