Finding the best suited solution for unique applications

A custom instrument bracket designed for polemounted installations

WRP offers the ideal water level monitoring solution: a Technolog data logger and VEGA sensor.

ABy Kirsten Raw data is centrally Kelly stored and backed up specialist – and can be intelligently engineering queried from anywhere, via consultancy in the web, using any recent water resource engineering, internet browser.” water conservation and water demand management, WRP Consulting has Data logger started to supply various products to the One of the products that WRP has sourced water industry. and supplied to the South African industry

“As part of our consulting service, we for the past 20 years is the Technolog Cello have to measure and monitor pressures, 4s GSM data logger – a remote monitoring flows and water levels. This has evolved to solution that is both scalable and versatile. where we now source and supply these “We chose this type of data logger because products to the industry,” says Boeta Swart, it is rugged, portable, waterproof and associate at WRP Consulting. very reliable. It is a unique, integral data

Swart adds that they have also logger that has an internal battery and developed a web-based platform called GSM modem, which allows you to install Zednet that manages infrastructure. “It the device in remote locations where you supplies management information about do not need external power to operate the both the water resource itself and the device. It also powers the attached sensors monitoring hardware installed in a water from the data logger, so no external distribution system. Because the service is power sources are needed to run the hosted, no software needs to be installed instrumentation,” adds Swart. on-site and the system can optionally Equipped with the ideal data logger, be fully managed on behalf of a client. WRP started to source a sensor.

TYPES OF SENSORS

1)Traditionally, the monitoring of water levels was done by a chart recorder. This monitoring device is actuated mechanically by a float that follows the water level.

The graphic recorder provides a continuous pen and ink trace of the water level on a chart, which is graduated to record both water level and time. 2)A shaft encoder has a similar setup to the chart recorder, but it provides a digital recording of values instead of a pen line on a chart. 3)Submersible level transmitters are submerged in water and reference the head of the water above the sensor location. 4)Ultrasonic sensors fire ultrasonic pulses at the surface of the water. Return time calculations are used to determine the depth of the water.

According to Swart, submersible sensors are unsuitable for certain applications: “In rivers with a lot of siltation, a build-up of silt and sand occurs around the sensor. This requires a lot more maintenance on the site, which is difficult in remote locations. In these circumstances, you need a noncontact sensor. The VEGAPULS C11 fills in the gap in our product and service offer.”

Introducing the VEGAPULS C11

This is a sensor that is ideal for non-contact level measurement in simple applications where a high degree of protection is required.

Technical specifications

Measuring range (distance) Process temperatures Process pressure Accuracy Frequency Beam angle Materials, wetted parts Threaded connection Seal material Protection rating Output Ambient temperature 8 m -40˚C to 60˚C -1 to 3 bar ±5 mm 80 GHz 8 degrees PVDF G1½/G1, 1½ NPT/1 NPT, R1½/R1 FKM IP66/IP68 (3 bar), Type 6P 4 mA to 20 mA -40˚C to 60˚C

Boeta Swart, associate at WRP Consulting

Ultrasonic vs radar sensors

The VEGAPULS C11 is a radar sensor, which Swart prefers, as they can be used in more locations: “Traditional ultrasonic level sensors have a wide beam angle and are typically installed above the water, hanging off a ledge or vertical wall. The projection of the sensor beam on to the water surface is virtually round, so the diameter of this projection on to the water surface increases as the distance from the water level increases. Their readings can be affected by debris floating on the water surface or obstructions that protrude into the beam area. The VEGA radar sensor has a smaller beam angle, so it does not have to be installed in positions that require a large, unobstructed water surface area.

We have even installed these VEGA radar sensors in pipes and small stilling wells.”

The VEGAPULS C11 has a versatile threaded mounting position, and is easily installed on a lid of a well

Different locations, different brackets

Installations

WRP deployed the VEGAPULS C11 sensor and the Technolog data logger at an irrigation board in the Northern Cape near Douglas. The Orange-Vaal Water Users Association needed an instrument to measure the water levels of a balancing dam on the irrigation scheme.

This solution was also used in Namibia for water-level monitoring of flood plains and will replace all the traditional chart and shaft encoders that were there were beforehand. “The VEGAPULS C11 is well suited for riverbeds that are seasonally dry. A submersible sensor would be exposed on the sand or mud of the riverbed or basin for extended periods of time. This would pose a problem for the sensor itself and its offset calibration, as it needs to be constantly submerged in order to work as expected. The offset calibration of the sensor is compromised once it is exposed for months and then submerged again.

“The VEGAPULS C11 is not affected by these site conditions. It is a non-contact sensor so the riverbed can be dry for a year and then during the rainy season it will perform optimally,” states Swart.

Instead of using the standard VEGA brackets, WRP manufactured its own brackets because the locations where the company installs sensors are different to where the industry normally installs them. “We use the VEGAPULS C11 in open-channel flow applications, so the installation of the sensor is quite unique. WRP therefore designed brackets where one can adjust the angle of the arms. “Many types of sensors are available in the water industry, and knowledge about the application type and basic operating condition requirements can create a more informed and accurate sensor selection choice. That is why WRP – with our consulting and project experience – is best placed to make that decision,” The VEGAPULS C11 measuring in a concludes Swart.

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