A new smartphone app, coupled with tried-and-tested cable glands, helps overcome problems when taking hydrostatic filling-level measurements.
Filling tanks to a constant level is a broad field: Tanks can have different sizes, shapes and structures and the filling level must be monitored continuously. In addition to the various media, which vary greatly regarding their chemical and physical properties, the tanks and their monitoring systems also differ.
Because the measuring range of the filling level transmitter depends on the tank height and the density of the medium, either the corresponding values are parameterised in the control – which requires a somewhat more complex control and an input option – or the filling level sensors are calibrated for the required pressure measurement range individually. The main disadvantages of the individual calibration are the longer delivery times, due to the sensor being specially made, and complex warehousing, when replacement parts for various installations must be kept available at a central location.
Parameterising via smartphone
More expensive transmitters can be configured via a special tool on a PC. Trafag’s innovative solution is a standard filling-level transmitter, configured via an Android app. Only a Trafag interface tool is required, and a voltage source in the form of a “powerbank”. With these in place, the measuring instruments can be parameterised quickly via mobile. This opens up new options for manufacturers of tank and pump control systems: One can take a simple, standardized control (which does not require a programming interface) to input the tank and fluid parameters. The filling level sensor can then be parametrised with a smartphone on site during installation. This results in a, cost-effective solution to realise simple tank control and monitoring systems.
Overcoming installation issues
To prevent openings at the tank, and therefore potential leaks, the pressure transmitters are usually introduced into the tank suspended by a cable through special openings and immersed in the medium to be measured. Because both the measuring probe and the cable are in the tank and hang freely, problems can arise from two notable areas: the sensor can be pulled along by the flow in the tank and thus measure a level other than that intended; or the cable may be damaged during installation or operation allowing fluid to penetrate the transmitter between the sheath and cable wires, resulting in electronic failure, the most frequent cause of failure in immersed level sensors.
The transmitters are often provided with an additional weight to prevent them from being pulled along with the flow or are fastened to the tank wall. Special cable protection is rarely used.
Trafag’s especially clever solution uses an interface on the pressure transmitter for a special Serto® screw joint. With this metallic-sealing screw joint, a simple metal pipe can be pushed over the cable and screwed bluntly with the supplied adapter. This solution is more expensive than a bare cable, but offers a wide range of advantages:
1 The stainless-steel pipe protects the cable from damage, including the cable sheath.
2 The steel pipe is firmly mounted to the upper part of the tank and fixes the immersed transmitter in its position, independent of any flows.
3 The entire upper part of the transmitter, including the cable, is insulated from the medium with the stainless-steel pipe and leak-tight screw joint. This removes the need for an expensive cable to protect against aggressive media, the user can select a more cost-effective cable material.
4 In the case of very deep tanks, the pipe can be welded in the lower area of the tank, saving a lot of cable length and wiring work (from the upper section of the tank).
5 Optimal equipotential bonding is ensured by the metallic connection of the sensor housing with the tank, which protects the transmitter with regards to EMC and electrochemical corrosion.
The adapter system has been tried and tested over many years and is safe and easy to install. It is also corrosion – and ageing – resistant thanks to the metallic seal. All necessary parts, except for the steel pipe and the assembly tools, are included with the Trafag pressure transmitter.