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Flaretot Professional is an integrated solution for all aspects of Flare System design, revamp or auditing.

Advanced Flare System Audit Tool
Because of the integrated approach, Flaretot Professional is highly suitable for carrying out the standard vertical and horizontal checks on major parts of the flare system audits, in particular:
  • Vertical checks including determination of Relief Loads
  • relief device calculations
  • sizing checks on relief device inlet piping
  • establishing minimum temperatures of vessels during depressurisation
  • Horizontal checks including flare network header conformance to sizing criteria (e.g. Mach number)
  • flare drum sizing
  • ensuring all flaring scenarios have been addressed
  • auditing of radiation
  • dispersion and structural steel temperature rise with radiation and flare purge rates etc
Full GUI Interface for Network Design with Data Linking to Modules
At the core of Flaretot, is an intuitive easy-to-use windows style graphic user interface. The point and click and drag and drop design allows for rapid network unit definition and connectivity setup with a minimal amount of user training. The drawing space is also very flexible to allow for changes to the network during the life of a project.

Engineering units for the piping network and all calculations are fully customisable with preset groups for project units and metric / British units.

Selected network properties (Temperature, pressure, mass flow & mach number) can be shown of the network drawing to aid in finding a working solution rapidly give the user visual feedback on design problems or bottlenecks in the flare network.

Colour coding is used to show unit status, for example where data is lacking, a unit is unsolved, encountered an error while solving, or is excluded from the current flaring case (defaults to greyed out).

Properties for the network units and pipes are shown in a customisable format. Data can be exported to csv (Excel compatible format).

Piping Class Estimation & Piping/Flare System Design to Project Criteria
Piping in the flare network is piping class driven to permit rapid selection of pipe sizes. Custom pipe sizes can also be selected from the library of material / pipe schedules and custom wall thickness can be calculated from design conditions.

The piping classes are generated based on standard (customisable) basic mechanical design parameters and piping material with a design pressure/temperature table. While not intending to replace actual detailed design pipe classes, it enables even study phase projects to closely match detailed design piping, thus minimising costly changes during the lifetime of a project.

Individual pipes or selected groups of pipes can be sized automatically to meet project criteria based on velocity, mach number, Rho.v2 or maximum pressure. All these criteria can be specified concurrently or in any combination and the size will be adjusted based on the piping class sizes.

Integrated Component Based Physical Properties and EOS Based VLE
Flaretot has an integral component based physical property calculator with 310 library components, locatable by name, synonyms, formula or CAS number. The module provides fluid property and VLE data for the piping network simulation and all other component based calculation modules. The Peng-Robinson EOS together with API methods for enthalpy are used as well as value corrected density, viscosity & surface tension correlations. The module is designed to operate from the lower pressure ranges (as typical for flare systems), up to the supercritical region (as may be required for depressurisation calculations).

User components or petroleum fractions can easily be created with as much data as is available, from basic to comprehensive. Thermodynamic properties can be specified or generated by any mixture of Petro and Joback group contribution. The Joback group contribution method is presented in a clear diagrammatic form so that even an inexperienced the user is clear on the group contributions.

Liquid property correlations can be can calibrated with actual data and chart based feedback displays the calculated values over the whole range to avoid inappropriate values from being used.

Integrated Relief Load, Relief Valve Sizing and Case Management
Fire, gas blowby & tube rupture relief load calculations provide the relief case data in each source, along with manually entered data.

This relief case data can then be used to size the required relief valves.

A visual tabular approach is used to assign relief case data to any number of network cases so that both design and turndown can be addressed easily.

Advanced Relief Load Calculations
The relief load calculations are rigorous and are to codes & regulations but the user interface is designed to be intuitive and easy to use so that accurate results can be achieved even by inexperienced users. Invalid data is highlighted by colour coding as the data is entered. Physical property data is generated internally so that data import from 3rd party applications is not required.

A significant saving on man-hours can be achieved over hand based or even spreadsheet calculations, without the required over-simplifying assumptions that these methods require in order to be feasible.

The fire relief load calculation for vessels (horizontal, vertical and spherical) uses the API wetted liquid and vapour expansion models as well as a more rigorous multicomponent model with heat transmission to liquid wetted & dry areas. Surrounding system piping / volumes can be included, containing liquid or vapour. Only normal operating conditions are required as the composition at relieving conditions is calculated automatically.

The gas blowby relief load calculation for level control valve failure includes typical values for control valves and bypass (generic globe) valves, and allows for control valve flow calculation using either ISA or the universal gas equation. Control valve attached fittings can also be modelled (when using the ISA equation).

The heat exchanger tube rupture relief load calculation allows for rigorous calculation of relief flow for all types of conditions (two-phase, vapour, liquid or flashing liquid).

The flowrate calculation can also use the conservative assumption that there is insufficient time for liquid or 2-phase flow to reach equilibrium over the tube rupture (frozen composition).

Vaporisation effects where a colder stream encounters a hotter shellside fluid are also modelled.

Rigorous Relief Valve Calculations to Codes
Relief valve (pressure safety valve) sizing and rating is carried out according to API520, in conjunction with design codes ASME VIII or BS5500 for relief valve arrangements and API526 for the relief valve selection. Calculations are carried out automatically for all specified cases to determine the maximum sizing case.

Very little user input is required to achieve a reliable design conforming to codes and standards, which means a minimum man-hour requirement and less possibility of error by inexperienced engineers. Several key factors have been employed to achieve this:
  • Required flow data is obtained directly from the network & does not have to be re-entered
  • The inbuilt database of allowable relief valves for given design conditions ensures the correct relief valve selection, including multiple relief valves, without consultation of external reference material (the selection may be overridden but the user is made aware that the valves are probably not suitable).
  • More complex multi-tiered set-pressure ASME VIII arrangements and supplemental fire valves are automatically generated (if this design code is selected).
  • Calculations provide extensive feedback on the sizing to aid the user in understanding the process of sizing and selection.
  • the final relief valve selection and arrangement includes suggested & selectable alternative arrangements (to code & where applicable) that can reduce area oversizing and thus potential valve chatter.

The sizing / rating calculations cover the basic API vapour, steam and liquid calculations and include the DIERS HEM model (as recommended by API520 for rigorous multiphase flow calculations).

The DIERS model integrates the thermodynamic path for the fluid across the relief valve orifice, and uses the inbuilt property simulator for the physical properties & vapour / liquid composition at each step. The DIERS Homogeneous Frozen model is also implemented (where the quantity & composition of liquid & vapour do not change, but the physical properties of each phase are calculated). By definition, DIERS methods are applicable for rigorous solution of flow for all inlet conditions, not just 2-phase, but are generally not used for single phase fluids due to the complexity of the calculations. There are, however, conditions which benefit from this more rigorous approach as described below, and thus the Flaretot solution allows simultaneous use of simple methods, DIERS HEM and DIERS Frozen for all inlet conditions.

Advantages for relief valve inlet as Vapour / Steam
  • The API vapour sizing equations are based on ideal gas and will give answers that are likely to be further from the real situation than DIERS.
  • The DIERS HEM model will reveal and take into account retrograde condensation over the orifice
  • The DIERS frozen model results can be used where retrograde condensation is indicated, but the kinetics are likely to result in droplets forming only after exiting the orifice.

Advantages for relief valve inlet as Liquid
  • The DIERS HEM model will indicate if vaporisation of the liquid will occur over the orifice.
  • The DIERS Frozen model can be used where vaporisation of the liquid is indicated, but the kinetics are likely to result in bubbles forming after the orifice.

The relief valve sizing can thus simulate all situations with phase change, two-phase relief, vaporising liquid relief and vapour retrograde condensation relief.

Detailed Flare Radiation Calculations with Contour Plots
The radiation calculations are linked directly to the flare network data, so that it is easy to prepare design and turndown case studies without transcribing data from other programs, thus minimising man-hours and potential transcription errors.

The module supports radiation from multiple flares simultaneously to calculate cumulative radiation.

Radiation can be calculated at any number of target points as well as plotted on contour charts, both in the vertical and horizontal planes. Radiation contour plots include the flame profile. These are in real coordinates and so can be exported & overlaid on actual plot plans. Standard exposure time contour radiation levels are provided, but any number of user values can be used.

The flame profiles as the basis for up to 100 radiating points are calculated using the API or Brzustowski methods and flame transparency is user selectable.

Typical industry values are provided for the heat fraction radiated (F) from the flames to aid in rapid conceptual design. Estimated values are provided for both low velocity stack flares or high velocity / sonic type flares and can be corrected for steam injection. Estimated F values for high pressure / sonic flares are corrected for flare tip velocity, and thus form a useful basis for turn-down even for detailed design. (Turndown calculations for sonic flares is essential since they experience much higher radiated heat fraction at flowrates lower than design).

Flare stack height sizing is available to meet required maximum radiation at any of the target points.

Detailed Pollutant Dispersion Calculations with Contour Plots
As with other modules, the pollutant dispersion calculations are linked to the flare network data to ensure rapid and accurate preparation of calculations. User industry standard calculations are used and the module is designed to be flexible but without an excess of confusing options so maximising user output and minimising training required. Calculation steps are reported clearly in the output to aid in checking and so that engineers inexperienced in dispersion can gain an insight into the procedures.

A gaussian dispersion model is used, standard for most non-complex dispersion problems.

The module supports dispersion from multiple flares simultaneously to calculate cumulative pollutant concentration. Both flared and flameout conditions are supported for each flare and any combination of these for multiple flares. Components classified as pollutants are specified by the user.

Maximum pollutant concentration is calculated as wells as actual values at any number of target points. Actual values can be plotted on contour charts. Dispersion contour charts can be created in the vertical and horizontal planes and include the flame and plume profile. These are in real coordinates and so can be exported & overlaid on actual plot plans. Automatic or custom contours values may be specified. Automatic selection of the contour plot area is provided, since measurable concentrations may lie some distance from the flare, and initial manually entered values may indicate no concentration in that area.

The calculation is treated in detail, but requires very little user input for intermediate values as these are derived from standard values for rural and urban areas, atmospheric stability conditions and typical flare flame operation.
  • Flame length for the flared condition is calculated from the radiation module flame specification.
  • Composition for the burnt gas (flared condition) is calculated automatically using combustion equations and taking into account steam injection and excess entrained air.
  • Flame temperature (flared condition) is calculated automatically taking into account heat fraction radiated from the flame.
  • The wind speed is corrected from user values at the measurement height to required heights for rural or urban areas.
  • Maximum dispersion plume rise is calculated either from the end of the flame (flared) or flare stack (flameout) using the briggs formulas and Pasquill atmospheric stability class.
  • Dispersion coefficients for the dispersion equations are derived from the Pasquill atmospheric stability class for either rural or urban conditions.
  • Calculated pollutant values are corrected for time averaged measurements.

Produced Noise Modules
This module covers three basic noise calculations for noise produced by flares, control valves and piping. Data has to be manually entered but implementation of links to network data are planned.

Advanced Vessel and System Blowdown Modules
The blowdown module uses a rigorous time dependent model of depressurisation of a vessel and the surrounding system and incorporates simulation of a pool fire beneath the vessel for fire situations.

The model
  • determines minimum vessel wall temperatures to ensure they remain above metal lower limits during blowdown (risk of wall fracture due to crystallisation)
  • determines system pressure as a function of time to ensure code guidelines for blowdown such as API521 are met
  • determines maximum wall temperatures and pressures, from which vessel wall stress is derived as a function of time and overlaid on the allowable stress chart. This determines the probability of vessel wall failure during the blowdown and if the blowdown rate therefore needs to increased.
  • determines the blowdown rate versus time for a specified blowdown device size. This allows for blowdown device sizing.
  • determines the possibility of liquid droplets in the blowdown vapour by entrainment at all times during the blowdown.
  • determines the liquid level in the vessel during blowdown and final composition for assessment of risk (for example flammable light hydrocarbons).
The key features of the model to ensure accurate and reliable results are as follows:
  • The model uses a component based model to determine phase split and physical properties, enthalpy and inventory calculations.
  • Unsteady state heat conduction is modelled in the insulation (if present) and metal wall.
  • Heat transfer coefficients are calculated separately for the wetted and vapour regions of the vessel, and the heat transferred is calculated.
  • Detailed blowdown device rating is used rather than using generic flowrate formulas (currently only square edge orifice). This means the blowdown device does not have to be sized separately and eliminates potentially incorrect bias on the pressure curve which especially impacts on multiphase compositions and thus the overall blowdown time.
  • Calculating vessel stress during blowdown to determine allowable blowdown time is considerably more realistic than code guidelines such as API521. While these codes are useful for hand calculations, they have been based on behaviour of a specific design & material in a fire (consult these codes for more details), and extrapolation to the actual design may lead to unrealistic or unsafe blowdown rates.
The user interface is intuitive so as to minimise user training.
  • Vertical, horizontal and spherical vessels are supported.
  • Fire extent for fire cases can limited to a specific height as per codes and API521 heat input by fire can be used if required.
  • A library of typical insulation and metal properties is provided for lookup.
  • A library of typical material allowable stresses is provided for lookup.
  • Extensive output is given in chart form to assist the user in understanding the system behaviour and thus reach a viable solution with the appropriate blowdown device size. Comprehensive output is also given in text & tabular form.
  • Multiple blowdown calculations are easily managed in a single flare network file.

Knock Out Drum Sizing with Horizontal Drum Size Optimisation
Knockout drum calculations are provided for vertical drums and 3 types of horizontal drums (standard, inlet at centre & inlets at either end).

Stand-alone calculations and calculations associated with network KO drums can be created.

KO drum physical property data can be copied from a solved network, and is retained as this will be the design or sizing case.

Shell wall thickness is calculated from design pressure and allowable stress, which can easily be obtained from the design temperature and the lookup library of design codes provided. This allows for horizontal knockout drum weight optimisation by tabulating various feasible configurations with associated calculated wall thickness and vessel weights.

Data entry is primarily on the vessel sketch for clarity, and feedback by colour coding on each entry field is given if the value is in error.

Calculation of Structural Steel Temperature Rise
This module predicts the temperature rise with time of a tubular structural steel element resulting from flare radiation. A detailed four quadrant model is used to calculate all aspects of heat transfer namely, radiant, conductive and convective (forced and natural convection), both inside and outside the tubular element.

All required heat transfer coefficients and related air physical properties required are calculated internally so a minimum of user input is required.

Results are presented in both chart and comprehensive tabular form for clarity.

Full control over coefficient calculation choices is also provided to give maximum flexibility in meeting project or company standards of calculation

Calculation of Flare System Purge Rate Requirement
The purge rate module allows required flare network purge rates to be calculated using 3 methods (Husa, Tan and alternative modified methods).

Unit Conversion Module
Aside from the ability to select custom units for all flare network calculations, Flaretot also offers a unit conversion module covering conversion from a wide range of other units.








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