Honeywell F-BO-AFE70 Series Installation, Connection, Commissioning, Maintenance

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Honeywell F-BO-AFE70 Series Installation, Connection, Commissioning, Maintenance Manual pdf 14 page image

Chapter 4 • Pneumatic components – dimensioning User Manual Series F-BO-AFE704 Pneumatic components – dimensioning4.1 Purging unitThe geometry of the sampling pipe and the number and size of the aspiration holes depends on thesize and geometry of the room as well as the technical possibilities of the aspirating smoke detectorused. Thanks to the special construction of the Automatic Purging Unit F-BO-AFE70, it does notcause an additional air resistance in the piping that is worth mentioning, and therefore it does nothave to be taken into consideration when dimensioning the pipe system.Through intensive tests and experiments, the recommended values for dimensioning that are statedbelow, have been established. Please note that the specified values are only approximate valuesbecause a huge number of components (the length and the geometry of the pipe, the position of theaspiration holes along the piping, the opening pressure of a check valve that may exist, etc.) affectthe Purging process. Therefore you can only make sure that the Purging unit is working properly bycarrying out a final test on the individual system.First calculate the total aperture area of the aspiration holes that exist in the pipe network. In orderto keep the calculation simple, the table below shows the area of a circular hole, depending on itsdiameter.2.00 3.15 4.00 12.57 6.00 28.282.10 3.47 4.10 13.21 6.10 29.232.20 3.81 4.20 13.86 6.20 30.202.30 4.16 4.30 14.53 6.30 31.182.40 4.53 4.40 15.21 6.40 32.172.50 4.91 4.50 15.91 6.50 33.192.60 5.31 4.60 16.62 6.60 34.222.70 5.73 4.70 17.35 6.70 35.262.80 6.16 4.80 18.10 6.80 36.322.90 6.61 4.90 18.86 6.90 37.403.00 7.07 5.00 19.64 7.00 38.493.10 7.55 5.10 20.43 7.10 39.603.20 8.05 5.20 21.24 7.20 40.723.30 8.56 5.30 22.07 7.30 41.863.40 9.08 5.40 22.91 7.40 43.013.50 9.63 5.50 23.76 7.50 44.183.60 10.18 5.60 24.64 7.60 45.373.70 10.76 5.70 25.52 7.70 46.573.80 11.35 5.80 26.43 7.80 47.793.90 11.95 5.90 27.34 7.90 49.02Diameter[mm]Area[mm²]Diameter[mm]Area[mm²]Diameter[mm]Area[mm²]Table 3: Calculation aid for the determination of the total aperture area of the aspiration holes in thesampling pipework; add up the stated values for the holes in the piping that is to be connected tothe Purging unit. The diameters that have been marked in bold in the table are the predeterminedstandard values for the Series FAAST and VESDA.The tables below show the operation limits of the Automatic Purging Units F-BO-AFE70-2 andF-BO-AFE70-3, depending on the input overpressure during the Purging process and on the sum ofthe aperture area of the aspiration holes of the piping that is connected to the Purging unit.The data is based on a DN25 pipe network that has been realised as straight branch, and on acheck valve with an opening pressure of 25kPa (0.25bar) that has been installed at the end of thepipe network. A safety factor has been added to the data and therefore it can be regarded asapproximate value for normal system configurations, but the proper functioning of the respectivesystem must always be verified in a test!During the Purging process, the input overpressure decreases, depending on the quality of thecompressed-air supply and the air volume that is consumed. The input overpressure value listedin the table is the value when air is being consumed, i.e., the decreased value!I56-4252-010D200-104-0014