Pressure transient suppression and alleviation in drainage systems of tall buildings

The suppression of pressure transients in building drainage systems is now much better understood due to the 17 years of work following the invention of the first drainage specific positive pressure transient attenuation device (P.A.P.ATM) in 2000. This device dealt with low-amplitude, yet significant, positive air pressure transients (typically 100 mm water gauge). This research deals with the attenuation of much larger problematic air pressure transients found particularly in tall buildings. This research describes the development of a new device which can attenuate a positive air pressure transient of approximately 2000 mm wg (20kPa), a pressure transient of such magnitude which is not uncommon in tall buildings and for which there is currently no means to alleviate. The performance of the new device was validated by numerical simulation and laboratory testing. The laboratory test rig represented a 50 storey building drainage stack with a main stack diameter of 150 mm. The pressure wave generator used to apply the 2000 mm wg pressure transient consisted of a large accumulator compressor capable of delivering 270 litres of air at 10bar pressure. This resulted in a capacity of 2700 litres of air at atmospheric pressure delivered into the system within 0.2 s. The pressure waves were delivered via an automatic computer controlled valve. Results show that the new device is capable of reducing the applied pressure transient by 88%, , rendering it harmless and returning the system to normal operation in a matter of seconds.