Xtrails VESDA VLI Product Manual

Xtrails VESDA VLI Product Manual Manual pdf 37 page image

VESDA by Xtralis VESDA VLI Product Guidewww.xtralis.com 314 Pipe Network DesignThe Pipe Network should be designed by trained personnel, and verified using the ASPIRE2 software.4.1 Design ConsiderationsThe following points should be considered when designing a pipe network for the VLI detector:l At all times the detector requires a minimum total airflow of 40 liters per minute, and a minimum of 20 litersper minute per pipe. It is possible that over a period of time sampling holes may block due toenvironmental conditions which may result in reduced airflow, hence it is highly recommended thatdetector and pipe flows be set to 20% higher than required minimums i.e. set detector flow to minimum 50liters per minute and a minimum of 25 liters per minute pipe flow.l It is preferred to use at least two pipes in the design (use pipe inlets 2 and 3) with a flow rate of at least 25ltr/min per pipe, and detector flow rate at least 50 ltr/min. Verify the design using the ASPIRE2 software.If required, use higher aspirator speed setting to meet these limits.l Similarly, for single pipe installations, the pipe flow rate should be at least 50 liters per minute. Verify thedesign using the ASPIRE2 software. If required, use higher aspirator speed setting to meet this limit.l Avoid using exhaust pipes unless there is substantial pressure differential where exhaust pipe needs tobe go back to the sampling area, keep exhaust pipe length minimum. Refer to Section 4.4. for furtherinformation.l VESDA VLI is specifically designed to cater for industrial applications where high background levelsexist. It is recommended that minimum hole sizes of 3mm shall be used for these applications. Certainindustrial applications will require the facility to conveniently blow out (Back Flush) the pipe networkduring maintenance regimes. Refer to Xtralis document 20016, Pipe Network Back Flush.Refer to the VESDA Pipe Network Design Guide for best design practices.4.2 Installation ConsiderationsThe following points should be considered when installing sampling pipe:l Minimize flexing in sampling pipes by supporting the pipe every 1.5m (5ft) or less, or at a distancedescribed in local codes and standards.l Evenly arrange the sampling pipe network over return air grilles.l Sampling pipe fits firmly into the tapered detector port, DO NOT glue this connection.l Allow sufficient movement at the detector to permit pipe removal for maintenance.l Keep the exhaust pipe as short as possible to minimize airflow resistance in the pipe.l Pipe ends must be made smooth for bonding.l Sampling holes must be drilled in line and perpendicular to the pipe.l Sample holes must be clear of rough edges and debris.l Pipes are free of debris.l All joints must be bonded except the endcaps and pipes entering the detector.Notes:l Sampling holes should face into the direction of airflow, or point downwards in static airflow situations.l Keep the sampling holes evenly spaced.l Counter-sunk holes are recommended for harsh environments.l For code-specific information, see Codes and Standards Information for Air Sampling Smoke Detectionon page iii.Refer to the Pipe Network Installation Guide for best installation practices.4.3 Inlet PipesThe VLI detector supports up to four sampling pipes.The air inlet ports in the pipe inlet manifold are tapered such that they accommodate both 25 mm (1 in) or IPS¾ inch outer diameter pipes.