A series of flow verification services are carried out for open channel flow meters at rest area (R&R) sewage treatment plant (STP) along the highways running through the west coast of Peninsular Malaysia.
Requirements
- Instrument: 6 open channel flow meters at 6 different STP
- Medium: STP effluent
- Installation configurations:
- 3” parshall flume
- 60° v-notch weir
- Non-standard sizing v-notch weir
- Services:
- To ensure the flowrates are accurate comparing against the 3” parshall flume discharge table
- To ensure the flowrates are accurate comparing against the 60° v-notch weir discharge table and the standard Kindsvater-Shen equation for non-standard sized v-notch
- To ensure the flow meters are calibrated and measuring accurately under optimal operating conditions and installation method
Solutions
- For the parshall flume installations, the throat width size, installation height and the water level is measured. The flow rate is calculated using the formula provided by the 3” parshall flume discharge table.
- For the 60° v-notch weir installations, the flow rate is calculated using the formula provided by the 60° v-notch discharge table.
- For non-standard sizing v-notch weir, the flow rate is calculated using the Kindsvater-Shen equation (Q = 4.28 Ce Tan(θ/2)(H + k)5/2), where Q = Discharge (cfs), H = Head (ft), θ = angle of the v notch, Ce is the effective discharge coefficient, and k is a head correction factor.
- Recommendations were suggested to improve the performance and accuracy of the flowrate:
- Position of parshall flume is too near the incoming flow causing fluctuations in measurement values. Installation of a stilling well – a cylinder-shaped chamber that is connected to, but isolated from, a channel’s main flow of water, is recommended. Capturing a portion of water inside of a stilling well helps to quiet the interfering turbulence found in the main channel.
- The expected flow rate does not match the correspond value in the parshall flume discharge table. A smaller parshall flume is recommended to achieve optimal flow measurement.
- This verification lasts for one (1) year.
