The basis for an optimum design of gas extinguishing systems are the fluid mechanics equations which describe the relationships between the technical data of the components of the system (e.g. pipe diameter, resistance coefficients of the fittings) and the specific material values of the extinguishing agent as well as the physical conditions occurring during flooding (e.g. flow velocity, pressure in the pipes and at the nozzles). Furthermore, the balance equations must of course be fulfilled. This results in the data required for the construction of the plant, such as flooding time and pipe diameter.
The calculation programs are able to calculate the most diverse gas extinguishing systems according to your specifications. Your specifications for the flooding areas, the gas supply and the pipeline networks are saved in a project file which the program uses for the calculation. You can change these parameters at any time and perform a new calculation with modified parameters. The results can be printed or displayed on the screen.
In inert gas extinguishing systems, orifices are installed, usually directly behind the collector pipe. Orifices are used to reduce the pressure of the gas flowing through to a defined maximum value, allowing the subsequent pipe network to be designed for lower pressure levels. Due to the required strong pressure reduction, a so-called supercritical flow occurs in the area of the orifice plate. Since the usual relationships (Bernoulli) between pressure drop and mass flow no longer apply to this supercritical flow, the calculation requires special care.
The supercritical flow occurring at nozzles and orifices, which is difficult to treat in terms of flow technology, is taken into account in the VdS calculation program.
The characteristic values of the plant components used, such as fittings, nozzles and pipe types, are stored in special catalogue files and can thus be adapted and managed to meet company-specific requirements. The determination of the resistance coefficients of nozzles and fittings can be carried out by the VdS laboratories on request. The values stored in the sample component catalogues (vds.*) after the initial installation of the program are only exemplary. They have no relation to real plants. Before the first design of an actual system, they must be replaced with the data of the components you are using.
In addition to the actual plant design, the program provides you with lists of the dimensions and number of components used, guide values for the required pressure relief opening and the extinguishing gas and oxygen concentrations in the flooding area after flooding.
For the intended use of the calculation programs and the reliability of the calculation results it is assumed that the user has sufficient knowledge of the relevant regulations, that he is familiar with the state of the art in the field of gas extinguishing systems and that he designs the systems accordingly.
The following is an overview of the functions of the calculation program. If a function is only available for certain quenching gases, these are listed in brackets, using the following abbreviations:
- IG: Inert gases (N2, Ar, IG?55, IG?541)
- HFC: Per- and partly fluorinated hydrocarbons (HFC?227ea, FK?5?1?12)
Quantity calculation according to the following guidelines
- VdS 2093
- NFPA 12
- ISO 6183
- CEA 4007
- Free input
- VdS 2380
- NFPA 2001
- ISO 14520-1
- VdS 2381
- NFPA 2001
- ISO 14520-1
Dimensioning of a completely entered pipeline network
- Pipe diameter, gradations according to catalogue
- Aperture diameter (IG)
- Nozzle openings
- Output of a material list: pipes, fittings, nozzles
- Graphical representation of the pipe network
- Calculation of reference values for the oxygen and CO2 concentrations that occur in the flooding area after flooding
- Determination of a guide value for the required pressure relief opening
Recalculation of a completely entered pipe network
- System status at operating point (CO2 and HFC)
- Dynamic flooding (CO2 and IG)
- Discharge per nozzle
- Flood time and maximum mass flow
- Recommended free opening area of the pressure relief opening for a resistance coefficient ? = 2 (IG and FKW) or user-defined resistance coefficient (CO2)
- Composition of the atmosphere in the flooding area after flooding
- Beam length/mixing length (FKW)
- Evaporation length (FK-5-1-12)
- High or low pressure system (CO2)
- Object protection or room protection (CO2))
- Course of the pipeline network
- Flooding time
- Filling pressure at 15°C (IG)
- Pressure of the nitrogen cushion (FKW)
- Number of containers
- Storage temperature
- CO2: <30,9°C
- IG: ?50°C
- PFC: -10 to +65°C
Specification of component, pipe and nozzle data in the corresponding catalog files:
- Resistance coefficients of valve and hose combinations
- Resistance coefficients of range valves
- Nozzle coefficients according to the nozzle model from VdS 2380 (IG) / VdS 2381 (FKW) / VdS 2093 (CO2)
- Aperture coefficients according to the aperture model from VdS 2380 (IG)
Nozzles (up to 200 nozzles)
- Nozzle type (according to nozzle catalogue)
- Number of nozzle holes for each nozzle (?9 for IG and CO2, ?99 for FKW)
Tubes (up to 450 tube sections)
- Pipe type (smooth/galvanised/hose/black)
- Length (0.1 m to 20 m per pipe section)
Position of range valves
Fittings: bends or elbows
- Specification of pipe diameters for individual or all pipe sections
- Specification of the number of storage tanks
- Specification of the diameter of the nozzle openings
- Specification of the gas output per nozzle for individual or all nozzles
- Specification of the aperture diameter (IG)
- Specification of the filling factor of the storage tanks (CO2, FKW)
- Division of the flooding area into up to 21 calculation areas with separate quantity calculation, allocation of nozzles to calculation areas
Tests by the program (Exceeding it generates warnings or error messages)
- Maximum difference of transport times to the nozzles < 21% Flooding time (FKW)
- Icing within the flooding period (CO2)
- Minimum nozzle pressure:
- FKW: 7 bar abs
- CO2 HD/ND: 14/10 bar abs
- IG: 2 bar abs
- Minimum nozzle hole diameter according to guideline
- Maximum nozzle hole opening area < 80% Connection pipe cross-sectional area
- Sufficient number of cylinders for calculated application quantity
- Minimum filling factor of 0.4 kg/litre (FKW)
- Forbidden vertical branches (HFCs for gas content in the pipe > 1%)
- Maximum distribution at junctions 12.5 : 1 (HFC)
- Maximum flow velocity in the pipe network (> 80% sound velocity)
- Minimum flow velocity in the pipe network (laminar flow)
The following conditions must be met to ensure that the calculation is sufficiently accurate. VdS must be consulted in case of deviations:
- The design of the system must meet the requirements of the relevant guidelines.
- The maximum pressure in the pipe network must be reached within 10% of the flooding time (IG, CO2).
The customer is entitled to free support for the duration of the license. This includes:
- Correction of reported errors in the user interface within a reasonable period of time.
- For a customer's first project, assistance in designing the system is free of charge. In order to analyse a problematic system it may be necessary to send project files and nozzle/component catalogues to VdS.
- Support for later projects is free of charge if it turns out that a system that complies with the guidelines cannot be dimensioned or calculated.
- The time availability of the support, averaged over the year, is 50%, based on working days between 8 and 17 o'clock. Inquiries in absence are registered and could be answered with a delay.
- Contact is possible by e-mail and by telephone.
- The duration of the license remains unchanged when using the support.
Chargeable services (invoicing according to time and effort)
- Introduction to the software/software training
- On-site assistance
- Assistance with the design of projects, except the first one, if it turns out that a system cannot be dimensioned or calculated because it has been constructed by the user in an inappropriate way.
- In this case the customer is informed that further support is subject to a charge. The user of the program should generally have a basic knowledge of gas extinguishing systems [GLA], as taught, for example, in the "GLA Basics" and "GLA Technology" courses of the VdS Training center.
The following points are excluded from VdS support:
- Problems caused by faulty hardware or operating system components of the computer used.
- Problems with firewalls, antivirus software and printer drivers (both for output to a printer and output to a file, e.g. Pdf generation)
- Adaptation of the software to new GLA technical conditions, to new operating systems or to new PC hardware. Such adaptations, as well as extensions of the user interface or the calculation section with new functions, require separate agreements.