Book - School of Science and Technology

System arrangements 617It is the use of a series of such empirical assumptions, in parallel with more reasonedconsideration of diversity of use, that has led to the reappraisal, previously mentioned, ofthe roles of the traditional `flows and returns'.Air venting of high level storesIt is essential that each vessel be provided with a separate open vent pipe taken up to asuitable height and it should be noted that an automatic air release valve is not anacceptable substitute. This provision is necessary to provide against collapse (implosion)of the vessel when water is drawn from it.Tall buildingsBearing in mind the comments made earlier regarding problems of excess pressure atdraw-off points, the case of very tall buildings is worth consideration. The preferredCisternCirculationCold feedHead tankHead tankR191817161514131211Calorifier 10H.W. PointsCalorifierPumpP987654321GPumpPrimariesBFigure 21.11 Intermediate plant rooms in tall buildings