No matter in design, study or on-site, there will always be pressures such as nominal pressure, work pressure, design pressure, etc. So what is the difference between these pressures? Today I will take you to learn together!
Nominal Pressure
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. Nominal pressure is a standard pressure specified for the convenience of design, manufacture and use.
(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 for steel is 250°C.
(3) Nominal pressure 1.0Mpa, denoted as PN 1.0 Mpa
Work Pressure
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. is the pressure set during normal work.
Design Pressure
It is the pressure index proposed in the design, which refers to the set maximum pressure at the top of the pressure vessel, together with the corresponding design temperature as the design load condition, and its value shall not be lower than the working pressure. In the actual calculation, the corresponding design pressure can be determined according to the relevant regulations such as the “Pressure Vessel Safety Technical Supervision Regulations”.
When determining the design pressure of the vessel, the following factors should be considered: (1) When the vessel is equipped with an overpressure relief device, especially when the bursting disc is used as the overpressure relief device, the design pressure shall be determined according to the provisions of Appendix B in GB150.
Reference standard: GB150-2010 “Fixed Pressure Vessel”
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.
Appendix B4.1 of GB150 stipulates: When the container is equipped with a relief device, the design pressure of the container is generally used as the initial pressure for the overpressure limit of the container. The design pressure of the vessel shall be determined according to B6.2 or B7.1 respectively. When necessary, the maximum allowable working pressure of the container can be used as the initial pressure for the overpressure limit of the container. When the maximum allowable working pressure is adopted, 1.25 times, 1.15 times and 1.00 times of the maximum allowable working pressure shall be taken for the water pressure test, air pressure test and air tightness test of the container, and shall be indicated in the drawings and nameplates.
Reference standard: GB150-2010 “Fixed Pressure Vessel”
Relationship between Nominal Pressure, Working Pressure, 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 pressured, 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, and 6.40MPa. Design pressure=1.5×working pressure.
The working pressure is derived from the hydraulic calculation of the pipe network.
Test pressure>nominal pressure>design pressure>working pressure
Design pressure = (1.1-1.5) × working pressure (usually)
