A new smartphone app, coupled with tried-and-tested cable glands from process and chemical technology, is helping overcome some oft-encountered problems when taking hydrostatic filling-level measurements
Filling tanks on ships to a constant level is no easy task. Tanks are often of different size, shape and structure and the filling level must be monitored continuously. In addition to the various products –fuel, ballast water, potable and process water, lubricants and coolants – which vary greatly with regards to their chemical and physical properties, the type of tank and monitoring system often differ.
Because the measuring range of the filling-level transmitter depends on the tank height and the density of the contents, either the corresponding values are parameterised in the control (which requires a 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 approach are longer delivery times – due to the sensor being bespoke – and complex warehousing, when replacement parts for various installations must be available at a central location.
Parameterising via smartphone
More expensive transmitters can be configured via a PC; Trafag’s solution is a standard filling-level transmitter that can be configured via an Android app. For this purpose, a special Trafag interface tool is required, as well as a voltage source in the form of a "powerbank". With these in place, the measuring instruments can be parameterised quickly via mobile. The parameter sets can be saved as files and in the case of replacement parts, the original parameter set can be loaded onto the replacement device in just a few seconds.
This opens up new options for manufacturers of tank and pump control systems. It is now possible to use a simple, standard control (which does not require a programming interface) to input the tank and fluid parameters. The filling-level sensor can then be parameterised with a smartphone on site during installation; the data can then be saved in the project documentation. This results in a streamlined, cost-effective solution to realise simple tank control and monitoring systems.
Overcoming installation problems
To prevent openings at the tank, and therefore potential leakage, 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 often stem from two notable areas: due to flows in the tank, the transmitter can be driven away from its original position and thus measure a level other than that intended; or the cable sheath may be damaged during installation or operation, allowing fluid to penetrate the transmitter between the sheath and cable wires, resulting in electronic failure. Penetration of fluid into the pressure transmitter is the most frequent cause of failure in immersed-level probes.
As such, 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 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 adapter included in delivery. This solution is more expensive than a bare cable, but it offers a wide range of advantages:
The adapter system has been thoroughly 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.