Programs for the Calculation of SHEVS and Gas Extinguishing Systems

Assessment of SHEVS

With the VdS program, SHEVS (Smoke and Heat Exhaust Ventilation Systems), can be measured according to the regulations of VdS CEA 4020, DIN 18232-2 and DIN 18232-5. The program features simple data input and contains a management device that makes repeated registration of the system components used superfluous. Smoke compartments are calculated individually. Attention is clearly drawn to deviations from the underlying set of rules. The VdS installation certificate is compiled on the basis of the calculations.

VdS calculation software for gas extinguishing systems

The basis for an optimal application of gas fire extinguishing systems are the hydraulic equations combining the technical data of the installation components (pipe diameters, resistance coefficients of armatures, etc.) with the specific properties of the extinguishing agent and the physical conditions during the discharge (e.g. flow velocity, pressures in the pipes and at the nozzles).  Furthermore, conservation laws and balance equations must be fulfilled.  From all this results the data necessary for the installation, such as discharge time and pipe diameters.

The calculation programmes allow you to calculate gas extinguishing installations of very different construction. Your input of flooding zones, gas storage, and pipe system will be saved in project files which the programme accesses for any calculation. You can modify these parameters anytime and make a recalculation of any system with altered parameters, e.g. graded nozzle and restrictor orifices, to see the effects on the discharge time or on the distribution of the extinguishing agent amongst the nozzles.  The results can be printed or viewed on screen.

Inert gas extinguishing systems usually employ restrictor plates behind the manifold, reducing the pressure in the pipe system downstream the restrictor to a defined maximum value. Due to the necessarily strong pressure reduction a so-called over-critical flow through the restrictor appears.  Here the general relation (Bernoulli) between pressure drop and mass flow is no longer valid, so the calculation requires additional care.

Generally, the flow through the nozzles is also over-critical, so specific models are implemented for the nozzles, too.

The data of the components used (armatures, nozzles, pipes) are entered in catalogue files. This way you can easily manage and distribute component data within your company. The resistance coefficients can be determined by the VdS-laboratories, in case the manufacturer did not already receive them during the VdS approval process for the component.  The component data in the example catalogues (vds.*) comprises merely example values to allow for a calculation of example systems.  They have to be replaced with data of the specific components you are using.

In addition to the design of the installation a material list is generated stating the type, number/amount and dimension of the components needed as well as the atmospheric composition after the flooding and a recommendation for the pressure relief opening.

For the intended purpose of the calculation programs it is implied that the user of the calculation program possess the necessary knowledge of gas extinguishing systems and of the state of the art of the field of gas extinguishing systems and that the user creates system layouts which represent this knowledge.

Contact:

Dr. Florian Irrek
VdS Schadenverhütung GmbH
BS-EO
Amsterdamer Str. 172
50735 Köln
Germany

Tel. +49 (0)221 7766 - 294
Fax. +49 (0)221 7766 – 510
firrek(at)vds.de
www.vds.de

Functional range of the programme

Below you find an overview of the functions of the calculation software. In case a function is available only for certain extinguishing gases, these are stated in braces, using the following abbrevations:

  • IG Inert Gases (N2, Ar, IG?55, IG?541)
  • FC Per- and Hydrofluorocarbons (HFC?227ea, FK?5?1?12)

Quantity calculation according to the regulations

  • CO2:
    • VdS 2093
    • NFPA 12
    • ISO 6183
    • CEA 4007
    • free user-defined input
  • IG:
    • VdS 2380
    • NFPA 2001
    • ISO 14520-1
  • FC:
    • VdS 2381
    • NFPA 2001
    • ISO 14520-1

Dimensioning of a completely entered pipe system

  • Pipe diameter,
    grading according to pipe catalogue
  • Restrictor orifice diameter (IG only)
  • Nozzle orifice diameters
  • Listing of the required material:
    pipes, fittings, nozzles
  • graphic display of the pipe network
  • calculation of O2 and CO2 concentrations in the flooded zone after the discharge
  • calculation of a recommended value for the pressure relief opening
    Resistance coefficient ? = 2 (IG and FC), user-defined resistance coefficient (CO2)

Recalculation of a completely entered installation

  • System state in the Working point
    (CO2 and FC only)
  • Dynamic Flooding (CO2 and IG only)
  • Quantity per nozzle
  • Discharge time and maximum mass flow
  • recommended value for the pressure relief opening,
    Resistance coefficient ? = 2 (IG and FC), user-defined resistance coefficient (CO2)
  • calculation of O2 and CO2 concentrations in the flooded zone after the discharge
  • Jet/Mixing distance (FC only)
  • Evaporation distance of the extinguishing agent (FK-5-1-12 only)

Required Input

  • High or low pressure system (CO2 only)
  • Total flooding or local application
    (CO2 only)
  • Pipe layout
  • Discharge time
  • Storage containers:
    • Volume
    • Fill pressure at 15°C (IG only)
    • Pressure of the N2 (superpressurization, FC only)
    • Number of containers
    • Storage temperature
      CO2: <30.9
      IG: ?50°C
      FC: -10 to +65°C
  • Component, pipe, and nozzle data in the respective catalogue files:
    • resistance coefficients of combinations of valve, hose and check-valve
    • resistance coefficients of divertor valves
    • Nozzle coefficients
      according to the nozzle model in VdS 2380 (IG) / VdS 2381 (FC) / VdS 2093 (CO2)
    • Restrictor coefficients according to the restrictor model in VdS 2380 (IG)
  • Nozzles (up to 200 nozzles)
    • Nozzle type according to nozzle catalogue
    • Number of nozzle orifices for each nozzle
      (?9 for IG and CO2,  ?99 for FC)
  • Pipes (up to zu 450 pipe sections)
    • Pipe type (smooth/galvanized/hose/black)
    • Length (0.1 m to 20 m per pipe section)
  • Position of diverter valves
  • Fittings: Bends or Elbows

Optional Input

  • Fixed pipe diameters for some or for all pipe sections
  • Fixed number of storage containers
  • Fixed nozzle orifices
  • Fixed quantity per nozzle for some or for all nozzles
  • Fixed restrictor diameter (IG only)
  • Fixed filling ratio of the storage container (CO2 and FC only)
  • Partition the flooded volume into up to 21 calculation zones with individual quantity calculation for each zone (e.g. room/ceiling/double floor)

Checks done by the Program (violation will create warnings or error messages)

  • Maximum transport time difference to the nozzles < 21% discharge time (FC)
  • Icing during discharge time (CO2)
  • Minimum nozzle pressure:
    FC: 7 bar abs
    CO2 HP/LP: 14/10 bar abs
    IG: 2 bar abs
  • Minimum orifice diameter according to regulation
  • Maximum
    total orifice cross-sectional area < 80% feeding pipe cross-sectional area
  • Sufficient number of storage containers for the calculated quantity
  • Minimum filling ratio of 0.4 kg/Liter (FC)
  • Illegal vertical branches
    (FC at a gas fraction in the pipe of > 1%)
  • Maximum Flow Split at Branches
    12,5 : 1 (FC)
  • Maximum flow velocity in a pipe section (> 80% velocity of sound)
  • Minimum flow velocity in a pipe section (laminar flow)

The following conditions must be met to guarantee for a sufficient precision of the calculation results.  In the case of deviations please consult with VdS:

  • The installation must meet the requirements of the respective regulation.
  • The maximum pipe pressure must be reached within 10% of the discharge time.
    (IG and CO2)

Support

The customer is entitled to support at no charge.  This support comprises:

  • Fixing of reported bugs in the graphical user interface within a reasonable time.
  • Assistance with the first project of a customer is free of charge.
    For analysing a troublesome system it may be necessary to transfer project data and nozzle-/component catalogues to VdS.
  • Assistance with later projects is free of charge if it can be proven that a system layout conform with the selected regulation cannot be designed or checked up.
  • The availability of the support is 50%, averaged over a year and referring to workdays (Monday-Friday) between 8 a.m. and 5 p.m.  Inquiries during absence are registered and may be responded to with a delay.
  • Contact is possible by email and by telephone.
  • The duration of the right of use is not changed by claiming support.

With costs
(charged depending on effort)

  • Introduction to the software / software training
  • On-site assistance
  • Assistance with the layout of projects other than the first, if the project cannot be calculat­ed due to a essentially faulty design made by the user.
    In this case the user will be informed that continued assistance will be charged.
    The user of the calculation program should generally possess basic knowledge of gas extinguishing systems [GES] as provided in the training courses „Grundlagen Gaslöschanlagen“ (GES basics) and „Gaslöschanlagen­technik“ (GES technology) of the VdS Bildungszentrum.

The following items are explicitly
excluded from support by VdS:

  • Problem caused by faulty hardware of operating system components of the PC used.
  • Problems with firewalls, anti-virus-software and printer drivers (this includes drivers for output to a real printer as well as drivers for output to files, e.g. pdf-files)
  • Adaption of the software for newly-developed GES components or designs, to new operating systems or new PC hardware.
    Modifications like this as well as extensions of the graphical user interface or the addition of new functions to the calculation module require separate agreements.