Design Pressure Calculator

Calculate design pressure for pressure vessels, pipes, and equipment based on operating conditions and safety factors. This calculator helps engineers determine safe working pressures according to industry standards.

MPa
Normal working pressure of the system
MPa
Additional pressure due to water hammer or other transient effects
m
Height of liquid column above the point of interest
kg/m³
Density of the fluid (water = 1000 kg/m³)
°C
Normal operating temperature of the system
°C
Additional temperature margin for design conditions

Vessel/Pipe Dimensions

mm
mm
mm
mm
mm

Material Properties

MPa
Maximum allowable stress at design temperature

Design Code Parameters

Weld joint efficiency factor (0.6 to 1.0)
Additional safety factor beyond code requirements
mm
Additional thickness to account for corrosion over service life

Results

Design Pressure

Required Wall Thickness

MAWP

Maximum Allowable Working Pressure

Design Temperature

Stress at Design Conditions

Design Assessment

About Design Pressure Calculation

What is Design Pressure?

Design pressure is the pressure used in the design of a pressure vessel or piping system. It is typically higher than the maximum operating pressure to provide a margin of safety. The design pressure accounts for normal operating conditions, possible pressure surges, static head, and other factors that could increase the pressure in the system.

Design Pressure Determination

Design pressure is determined by considering several factors:

  • Operating Pressure: The normal working pressure of the system
  • Pressure Surge: Additional pressure due to water hammer or other transient effects
  • Static Head: Pressure due to the height of a liquid column
  • Safety Margin: Additional pressure to account for uncertainties

Design Pressure Formula:

Pdesign = Poperating + Psurge + Pstatic head + Safety Margin

Where:

  • Pstatic head = ρ × g × h
  • ρ = Fluid density (kg/m³)
  • g = Gravitational acceleration (9.81 m/s²)
  • h = Height of liquid column (m)

Wall Thickness Calculation

The required wall thickness of a pressure vessel or pipe depends on the design pressure, vessel geometry, material properties, and design code requirements.

Cylindrical Vessels and Pipes (Thin-Wall Theory)

t = (P × D) / (2 × S × E - 1.2 × P) + C

Where:

  • t = Required wall thickness
  • P = Design pressure
  • D = Inside diameter
  • S = Allowable stress
  • E = Joint efficiency
  • C = Corrosion allowance

Spherical Vessels (Thin-Wall Theory)

t = (P × D) / (4 × S × E - 0.4 × P) + C

Maximum Allowable Working Pressure (MAWP)

MAWP is the maximum pressure at which a vessel or pipe can operate safely at its design temperature. It is calculated based on the actual wall thickness, material properties, and design code requirements.

Cylindrical Vessels and Pipes

MAWP = (2 × S × E × (t - C)) / (D + 1.2 × (t - C))

Spherical Vessels

MAWP = (4 × S × E × (t - C)) / (D + 0.4 × (t - C))

Design Temperature

Design temperature is the temperature used in the design of a pressure vessel or piping system. It is typically higher than the maximum operating temperature to provide a margin of safety. The design temperature affects the allowable stress of the material.

Design Temperature Formula:

Tdesign = Toperating + Temperature Margin

Design Codes and Standards

Various design codes and standards provide guidelines for pressure vessel and piping design:

  • ASME Boiler and Pressure Vessel Code (BPVC): Widely used in North America and many other countries
  • EN 13445: European standard for unfired pressure vessels
  • API 650: Standard for welded tanks for oil storage
  • ASME B31.3: Process piping code

Safety Considerations

When designing pressure vessels and piping systems, several safety considerations should be taken into account:

  • Corrosion Allowance: Additional thickness to account for material loss due to corrosion over the service life
  • Joint Efficiency: Factor that accounts for the reduced strength of welded joints compared to the base material
  • Safety Factors: Additional margins applied to ensure safe operation under all conditions
  • Material Selection: Appropriate materials must be selected based on service conditions, including temperature, pressure, and corrosive environment
  • Inspection and Testing: Regular inspection and testing are essential to ensure continued safe operation