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PN and MPa both represent pressure, what is the difference?

Release time:

Jun 05,2025

In the field of engineering, PN and MPa are two key concepts related to pressure, but their meanings and application scenarios are fundamentally different. The following is a detailed analysis:

一、PN(Nominal Pressure)

1、Definition

PN is the abbreviation of (Nominal Pressure), which is the symbol used to identify the pressure level of piping system components (flanges, valves, etc.) in the European standards (e.g., DIN, EN), and it indicates the maximum permissible working pressure of the component at room temperature (20°C). Example: PN16 flanges have a maximum capacity of 16 bar (approx. 1.6 MPa) at 20 °C.

2、Features

PN is a class symbol, not a specific pressure value. Only for room temperature conditions, high temperature when the allowable pressure will be reduced (need to check the material temperature pressure table). Commonly used in European standard (such as GB/T, DIN) flanges, valves and other components.

3. Common grades

PN6, PN10, PN16, PN25, PN40, etc.

二、 MPa (Megapascals)

1、Definition

MPa (Megapascal) is the unit of pressure in the International System of Units (SI), 1MPa = 10⁶Pa = 10bar ≈ 145psi. It is used to directly represent the actual pressure value (e.g., the design pressure, the test pressure), and describes the real force exerted on the unit area.

2、Characteristics

MPa is a universal unit of physical quantity, applicable to all engineering calculations. It has nothing to do with temperature and only indicates the magnitude of pressure. It is used globally, with no geographical or standard restrictions.

三、Core differences

Comparison term

PN (nominal pressure)

Mpa (megapascals)

Nature

Pressure class symbol

Pressure unit

Application

Scenario Identifies

the pressure capacity class of flanges and valves

the actual pressure value (e.g. design, test pressure)

Temperature dependence I

Maximum pressure at room temperature (20°C)

Independent of temperature

Conversion relation

1PN=0.1MPa

1MPa=10bar=145psi

Standard system

European standard (GB/T, DIN, etc.)

International common unit

四、The actual application example

Design requirements: working pressure of 2.5MPa, temperature of 100 ℃

Wrong understanding: directly choose PN25 flange (mistakenly thought that PN25 = 25bar = 2.5MPa)

Correct practice:

1, check the temperature and pressure table: PN25 flange at 100 ℃ when the allowable pressure may drop to 1.8MPa

2, the actual pressure of 2.5MPa> 1.8MPa, you need to Select a higher level (such as PN40)

五、Common Misconceptions

Misconceptions 1:PN = MPa(such as PN16 = 16MPa), the correct is: PN16 = 16bar = 1.6MPa

Misconceptions 2: Ignore the impact of temperature on the PN level

The correct : high temperatures need to reduce the permissible pressure (refer to the materials manual).

Misunderstanding 3: Confusing European standard (PN) and American standard (Class).

The correct : American Standard Class150 ≠ PN16, need to be converted (Class150 ≈ PN20)

六、Association with other standards

American Standard (ASME): with Class indicates the pressure level (such as Class150, Class300), and PN conversion need to check the table:

Class150 ≈ PN20 (2.0MPa)

Class300 Class300 ≈ PN50 (5.0MPa)

Japanese Standard (JIS): with the K level (such as 10K, 20K), the approximate corresponding PN level.

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