ReliefFLOW is our in-house pressure relief software, designed specifically to assist with difficult relief design scenarios. It follows API, ISO, ASME, DIERS and HSE guidance and industrial best practice to rate and size relief systems. It utilises a powerful thermodynamics package to handle thousands of compounds, as well as providing the ability to model custom, proprietary substances.

Relief Sizing

ReliefFLOW calculates both the required rate and the system capacity, along with the inlet and outlet pressure drops for relief valves, and can be used to rapidly size the relief device and all relief pipework of a system. It is extremely useful for many relief calculations, such as:

  • Fire relief
  • Reaction runaway
  • Blocked outlets
  • Solar heating
  • Loss of temperature control

The calculations can be carried out for relief valves, bursting disks, or open vents.

Two-Phase Flow

Added to following industry standards for calculating relief loads, ReliefFLOW has an integrated two-phase flow solver, to allow complex, iterative scenarios to be examined. The software has been used for a variety of two-phase calculations, including:

  • Runaway batch reactions
  • Refinery separators with blocked outlets
  • Flashing sub-cooled relief
  • Boiler blow-down

Dynamic Calculations

ReliefFLOW also incorporates the ability to perform dynamic, time-dependent calculations. These include the effects of emptying a vessel during a runaway reaction, or a supercritical fluid fire relief scenario. By using dynamic calculations, a more accurate picture of the safety case can be built, removing some of the excess conservatism built into traditional calculation techniques. Bringing time into the picture identifies the peak flow, and the rates the relief system against that.


ReliefFLOW is built with engineers in mind. Essential parts of any relief sizing exercise – required rate, capacity, pressure drops – are immediately available. It also provides more detailed numbers, such as fluid velocity, to allow the calculation results to be used in mechanical assessments. Additionally, any calculation template or datasheet can be used, so ReliefFLOW can output directly to a client’s standard documentation, whether it be a PSV datasheet or a relief stream summary.

If you would like to know more, please contact us.

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