- Hot search：
BS 8490-2007 pdf free download
BS 8490-2007 pdf free download.Guide to siphonic roof drainage systems.
recommendations given in Clause 6 for minimum pressure, minimum velocity, degree of balancing between outlets, and speed of priming are met.
8.4.2 Values of pressure and velocity in the ipes should be calculated at all changes of direction or diameter in a system in order to ensure that the lowest values of these parameters are i(lentified and are within the allowable limits. Particular attention should be given to the pipework at or near the top of the downpipe because the lowest pressures normally occur near this point.
8.4.3 The head losses in straight lengths of pipe should be calculated using an established hydraulic equation or a corresponding set of flow tables or charts. In case of dispute, the Colebrook—White equation 12] should be used (see Annex A and cf. BS EN 12056-3:2000, 6.3.1).
8.4.4 When calculating the flow capacity of a system, the value of pipe roiighnes.s used should take account of the effects of )ipc joints, ageing and possible deposition of line sediment washed through the outlets. For the Colebrook—White equation 121, the minimum value of pipe roughness used for design should be k = 0. 1 5 mm.
8.4.5 Head loss coefficients for the types of pipe fitting used In the system (e.g. bends, reducers. increasers, junctions, etc.) should be determined from tests or obtained from appropriate published data 13, 4]. Loss coefficients for a given geometry of pipe junction caim vary according to the relative flow rates in the branches. The loss coefficient for the siphonic outlets should be determined by test using the procedure given in Annex B.
8.4.6 Pressures In a siphonic system should be calculated starling at its downstream end and working upstream (see Annex A). Unless a suitably designed siphon break is installed (see 8.10.4 to 8.10.6). account should be takemi of possible surcharging in the downstream site drainage system when determining the flow capacity of the siphonic drainage system. If the first downstream manhole or chamber has a suitable vented cover (see 8. 10.1), it may be assumed that the positive pressure head acting at the point of discharge from the siptionic system will not be greater than the height of the vented cover above the end of the last pipe. If a siphon break is used above ground level, atmospheric pressure may be asswned to apply at the siphon break provided that it is fully ventilated and that no surcharging to that level can occur from the downstream site drainage system.BS 8490-2007 pdf free download.
All resources on this website are from the Internet. It is only for personal study and research. No one is allowed to use it for any commercial purpose. If you need, please buy the genuine standard. If there is any infringement of your copyright, please contact the webmaster in time, and I will correct it immediately.
- Maybe you like
- Latest Updates
- ISO 287-2009 pdf free download
- ISO 527-5-2009 pdf free download
- ISO 659-2009 pdf free download
- ISO 660-2009 pdf free download
- ISO 712-2009 pdf free download
- ISO 725-2009 pdf free download
- ISO 730-2009 pdf free download
- ISO 927-2009 pdf free download
- ISO 2041-2009 pdf free download
- ISO 3040-2009 pdf free download
- ISO 3506-2-2009 pdf free download
- ISO 3506-3-2009 pdf free download