Setup of the Lab Pipe Rig

The Lab pipe rig is comprised of a number of components including the pump, PVC pipes with diameters of 100mm and 200 mm, steel pipes with a diameter of 100 mm, control valves, the honeycomb, transitions and a water tank containing a V-notch weir plate.

Centrifugal pump

A 250X200-315 Southern Cross Centrifugal Pump was selected to supply water for the Lab pipe rig. The pump is classified as low head and high flow, and was manufactured by Tyco Pumping Systems, Australia. It is driven by a 6 Pole 22 KW 415V 3 phase AC motor and has the capacity to provide a maximum mean velocity of 6 m/s for the clean test section of the Lab pipe rig. The

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To

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Flow Rate (L/s)

Curves of Pump Performance & Lab Pipe Rig

Pump performance curve Curve of the Lab Pipe Rig Operating

point

Havailable

efficiency of the pump was around 57% for a clean pipe at the operating point. For the fouled test section, the maximum mean velocity was set at around 4.5 m/s.

Figure 5.4 Southern Cross Centrifugal Pump type 250x200-315 in the Hydraulic laboratory.

The centrifugal pump was installed on the ground floor in the Hydraulics laboratory. The water used in the pipe rig was stored in a large pit located underneath the laboratory. When the system runs, the pump draws water from the pit through a PVC pipe with a diameter of 250 mm. The water is propelled into a black coloured PVC pipe with a diameter of 200mm. The photo of the Centrifugal pump is shown in Figure 5.4, and the pump’s performance curve is shown in Appendix C.4.

PVC pipes with diameters of 200mm and 100 mm

The discharge diameter of the pump is 200 mm. A black coloured PVC pipe was used to connect the inlet of the pump (see Figure 5.4). Black coloured PVC pipes including 90 degree turns (diameter of 200 mm) were used up to the transition from 200 mm to 100 mm in diameter. The aim of this setup was to reduce the total system head loss.

Motor of pump Outlet of pump

Inlet of pump

A 5.2 m long PVC pipe with a diameter of 100 mm was selected after the transition from 200 mm to 100 mm diameter, to ensure a fully developed steady turbulent flow in the test section.

200 mm diameter to 100 mm diameter transition

In order to achieve the transition from the 200 mm diameter black coloured PVC pipe to the 100 mm diameter white coloured PVC pipe, a transition was used. A photo of the transition is shown in Figure 5.5 a)

Honeycomb

A plastic honeycomb (6 mm in tube diameter and 60 mm in length) was fitted inside the last segment of the transition, located before the 100 mm diameter PVC pipe. The purpose of the honeycomb block was to straighten the flow by reducing the transverse velocity component and the turbulence in the adjacent test section (Sargison et al., 2009). As recommended by Mehta et al. (1979), the length of the honeycomb section was 60 mm, which is 10 times the cell diameter.

Figure 5.5 a) Diameter 200 mm -100 mm PVC transition part. b) Honeycomb.

The resistance provided by the honeycomb can improve the flow stability and reduce the fluctuation level of the fully developed turbulent flow in the pipe. However, the side effect of the honeycomb should be considered, due to the additional small scale turbulence generated by the honeycomb itself (Loehrke et al., 1976). A photo of the honeycomb is shown in Figure 5.5 b).

Steel pipes with a diameter of 100mm

The inside of the existing steel hydropower penstocks and pipelines were painted using coal tar enamel several decades ago by Hydro Tasmania. The purpose of the paint coating is to provide a smooth internal surface in the pipes, to slow down corrosion and to prevent the growth of

a) Honeycomb inside

Transition part b)

biofouling. Galvanized iron pipes with a diameter of 100 mm were selected to simulate penstocks and pipelines on site. For environmental reasons Hydro has started replacing the coal tar enamel coating. In this study, Interzone 954,without anti-fouling agent, was used for the coating inside the 100 mm diameter galvanized pipes.

The Lab pipe rig consists of three steel pipes with lengths of 3.5 m, 1.5 m and 1.0 m. The pipe 1.5 m in length was the test section pipe. In the upstream of the test section is the reference pipe 3.5 m long. It helps to maintain a stable fully developed turbulent flow in the test section, and also provides a reference for the measurements. The other pipe 1.0 m in length is located at the downstream of the test section to provide consistent conditions for the measurements.

Control valve

A Lug type butterfly valve was installed on the downstream end of the 1.0 m long steel pipe. The valve allows the rig to remain full to prevent the biofouling from drying out when the pump is off.A photo of the butterfly control valve is shown in Figure 5.6 a)

Figure 5.6 a) Lug type butterfly valve. b) Water tank with V-notch weir inside.

Water tank and water storage pit

As part of the Lab pipe rig, an existing water storage pit located in the underground of the Hydraulics laboratory was used to store the water in the system. The pipe discharges into an existing V-notch weir to provide an alternative indication of the flow rate in the Lab pipe rig. The V-notch weir with an angle of 900 is shown in Figure 5.6 b).