Talk about the triangular relationship between nominal pressure, design pressure and working pressure

1. What is the nominal pressure PN (MPa)?

The reference value related to the pressure resistance capacity of piping system components refers to the design given pressure related to the mechanical strength of piping components. The nominal pressure is generally expressed by PN.

(1) Nominal pressure – the compressive strength of the product at the reference temperature, expressed in PN, unit: MPa.

(2) Reference temperature: Different materials have different reference temperatures. For example, the reference temperature of steel is 250°C

(3) Nominal pressure 1.0Mpa, denoted as: PN 1.0 Mpa


2. What is work stress?

It refers to the maximum pressure specified according to the maximum working temperature of the pipeline conveyed medium at all levels for the safety of the pipeline system. Working pressure is generally expressed in Pt.


3. What is the design pressure?

Refers to the maximum instantaneous pressure of the water supply pipeline system acting on the inner wall of the pipe. Generally, the sum of working pressure and residual water hammer pressure is used. Design pressure is generally expressed in Pe.


4. Test pressure

The pressure to be reached is specified for the compressive strength and air tightness test of pipes, containers or equipment. The test pressure is generally expressed in Ps.


5. The relationship between nominal pressure, working pressure and design pressure

Nominal pressure is a nominal pressure artificially specified for the convenience of design, manufacture and use. The unit of this nominal pressure is actually pressure, and pressure is a common name in Chinese, and the unit is “Pa” instead of “N”. Nominal pressure in English is nominal pres-surenomina: l in name or form but not in reality (nominal, nominal). The nominal pressure of the pressure vessel refers to the nominal pressure of the flange of the pressure vessel. The nominal pressure of the pressure vessel flange is generally divided into 7 grades, namely 0.25, 0.60, 1.00, 1.60, 2.50, 4.00, 6.40MPa. Design pressure=1.5×working pressure.

The working pressure is derived from the hydraulic calculation of the pipe network.


6. Relationship

Test pressure>nominal pressure>design pressure>working pressure

Design pressure = 1.5 × working pressure (usually)


Post time: Jun-06-2022