Figure: Schematic of Beacon Hill field-scale experimental facility

The field-scale experimental facility at Beacon Hill, Kowloon, HK, consists of a 250 m long pipeline network of 6-inch (NS180) HDPE pipes constructed along the periphery of the site (covering a footprint of around 65 m x 65 m). Above figure shows a schematic of this facility. The water supply is fed from the Beacon Hill reservoir at around 61 m of head; the flow is monitored by an electromagnetic flow meter, and the upstream pressure can be set with a pressure reducing valve (PRV). A ball valve designed for rapid closure is installed at the downstream end of the system. The system can accommodate single and multiple leaks as well as access monitoring points. Additionally, it can turn into a branched or looped system. The branched system is composed of four pipes with different lengths: L₁ = 64 m (upstream PRV to junction), L₂ = 72 m (junction to wave-generating valve BV1), L₃ = 69 m (junction to BV4) and L₄ = 50 m. The system is designed such that it can operate as a single line, a branched line with multiple pipes connections (depending on the test case) or as a looped system containing one inlet and two outlets.

This facility is instrumental in sensing the background pressure noise in a field-scale pipeline system with increasingly complex layout. The upstream PRV resembles the ones at entry lines to the Pressure Management Areas (PMAs) (around 2000 in HK). This hydraulically automated device together with several hydraulic devices produce internal vibrations that contributed to the background pressure fluctuations. The internal noise can be studied systematically in this facility.

Both lab and field-scale experimental facilities are built above ground. Hence, the pipe wall is accessible to sense background vibrations in the solid media too. Acceleration and displacement sensors can be easily mounted. Triaxial piezoelectric accelerometers with high sensitivities of 10 mV/g (IPC 352A60 PCB accelerometer) and 316 pC/ms^–2 (B&K 4326-A, charge accelerometer) with frequency ranging up to 60 kHz can be used. Displacements are captured with electrical resistive strain gauges.