Area-Velocity Flowmeter Installations in Denmark - Case Study
Area-Velocity Flow Meters are designed to monitor flow rates in partially filled pipes and open channels without flumes or weirs. A sealed ultrasonic sensor is mounted on the bottom of the pipe or channel and connected to electronics through a watertight cable. The sensor measures both level and velocity and when calibrated with the pipe diameter or channel dimensions, the Greyline AVFM computes flow.
Greyline AVFM 5.0 Flowmeter
Teletronic Denmark ApS specializes in collecting data from measurement systems, including Greyline Area-Velocity Flow Meters, installed in sewers, channels and streams. Instruments are powered by batteries and recharged with photovoltaic solar panels. Measurement data is transmitted wirelessly through GSM modems or closed UHF radio systems. Teletronic's service includes rental, sales, installation and operation of complete monitoring systems. Web based software allows customers the access and monitor measurement data through the Internet.
A busy day's work is ahead for Teletronic Denmark as flowmeters and ultrasonic sensors are set out for deployment in municipal sewer applications.
Greyline AVFM flowmeters can monitor flow in channels of any shape but most municipal applications in Denmark are installed in manhole pipe entries ranging in size from 150 mm to 1 m diameter (6' to 40').
Electronics are exposed to high humidity, condensate and rainwater in manhole installations.
Teletronic Denmark provides customers with repackaged systems including Greyline AVFM Area-Velocity Flow Meter electronics and Teletronic modems in sealed polycarbonate housings. Cable entries to the electronics are made through watertight glands so that the systems can operate reliably and without damage in wet conditions and during periods of accidental submersion.
Municipal staff have easy access to electronics just below the manhole cover and the whole assembly can be raised and removed from the manhole to allow access to personnel.
Using stainless steel mounting hardware Teletronic Denmark installs a Greyline ultrasonic sensor on the invert of a concrete pipe. Stainless steel banding is formed to the pipe shape and screwed to the pipe. Sensor cable is tie-wrapped to the banding and then connected to AVFM flow meter electronics installed at the top of the access manhole.
Sewage influent to this manhole is from 100 mm (4') and 150 mm (6') pipes. The municipality of Stevns needed to monitor flow from both sources so separate Greyline AVFM ultrasonic sensors are installed in both pipes.
An extension has been added to the 100 mm pipe to enable mounting of the flow sensor. It discharges to the 150 mm pipe below after influent to the 150 mm pipe has been measured separately.
Greyline AVFM flowmeter electronics and battery are protected under a temporary rain tight cover and powered by a solar photovoltaic charging system. After baseline flow data has been collected, the system is removed for deployment at another location.
Teletronic Denmark use Greyline's AVFM 'level offset' calibration feature and raise the ultrasonic sensor above the invert of the pipe by mounting on an adapted stainless steel mounting bracket. Periodic flushing of the channel is still required but by installing the sensor above the sediment layer, the flowmeter continues to function reliably.