One common question is: What pressure can PPR pipes withstand? However, the term "pressure" can refer to different aspects of a PPR pipe system, and if the terminology is not clearly understood, it can lead to confusion and misinterpretation.
Commonly mentioned pressure names in PPR pipe systems include: nominal pressure, operating pressure, and design pressure.
Nominal pressure refers to the commonly used PN pressure, which is usually indicated onPPR pipeOn the pipe walls. The nominal pressure is a designated pressure specified for ease of design, manufacturing, and use. The nominal pressure of PPR pipes is conditional, such as PN20, which means that the PPR pipe can operate at 20°C water temperature for 50 years and withstand a working pressure of 20 bar (20 bar = 2 MPa). If the water temperature is between 25°C and 45°C, the working pressure should be reduced according to the corresponding temperature drop coefficient.
Many people believe that 2 MPa is the maximum pressure that PPR pipes can withstand, which is incorrect. This explanation clarifies the difference between working pressure and design pressure.
Working pressure refers to the maximum pressure specified for a PPR pipe system to operate safely over a certain period of time, based on the highest operating temperature of the transported medium at each level. This is commonly denoted as "Pt". When operating under the specified working pressure, PPR pipes are generally designed to last for 50 years.
The design pressure refers to the maximum instantaneous pressure exerted by the PPR water pipe system on the inner wall of the pipe. This is typically calculated as the sum of the operating pressure and the residual water hammer pressure.
What factors determine the maximum instantaneous pressure that the inner wall of a PPR pipe can withstand?
The most significant influencing factor is the wall thickness of the PPR pipe; the thicker the wall thickness, thePPR pipeThe maximum instantaneous pressure it can withstand is also greater.
Secondly, the mechanical properties of the raw materials themselves are also a significant factor. Even when using the same PPR raw material, different manufacturers produce materials with varying properties. These differences in mechanical properties ultimately affect the ultimate pressure resistance of the PPR pipe.
Additionally,PPR pipeThe production process also influences its compressive strength. If there are inconsistencies in the mixing of materials during production, the PPR pipe will have limitations in its mechanical properties.
Secondly, there is the concept of pressure levels for the piping system. Our piping systems are typically classified into four levels: low pressure, medium pressure, high pressure, and ultra-high pressure.
Low-pressure pipelines: Nominal pressure not exceeding 2.5 MPa;Medium-pressure pipe: Nominal pressure of 4-6.4 MPa;
High-pressure pipes: Nominal pressure ranges from 10 to 100 MPa.
High-Pressure Pipelines: Nominal pressure exceeding 100 MPa;
based on this pressure level classification, water pipelines generally fall under low-pressure pipeline systems, and therefore, the nominal pressure typically does not exceed 2.5 MPa.
Common pressure units include bar (Pascals), MPa (megapascals), and kgf/cm² (kilograms of force per square centimeter). Bar is a commonly used unit in engineering, MPa is the international standard, and kgf/cm² is a unit frequently used in China to represent pressure. The conversion relationships between these units are:
1 bar = 0.1 MPa = 1.01971621 kgf/cm²