The Liquiphant FTL51B, FTL62 and FTL64 tuning fork level switches, equipped with Hart electronics, enable remote Heartbeat Verification and Sil tests.
While many process transmitters today have advanced features such as diagnostics, function tests, modern communications, etc., there are still a few types of sensor, such as level switches, that do not benefit from all these features.
This imposes constraints, sometimes onerous and costly, on technicians and operators in the field when they have to check the correct operation of a level switch mounted on a large tank and liable to have a problem, for example.
Endress+Hauser now offers 8/16 mA electronics with digital Hart protocol for its Liquiphant FTL51B, FTL62 and FTL64 vibrating level switches for liquids, the successors to the Liquiphant FTL50/51, FTL51C and FTL70/71, respectively, two years ago. "The new electronics unlock new functionalities. Customers can choose between two operating modes: a switching mode (8/16mA) for conventional level detection, and a 4/20mA mode proportional to blade vibration frequency."says Andréa Logos, Chemicals Market Manager at Endress+Hauser France.
The Liquiphant FTL51B, FTL62 and FTL64 level switches are now true standard 4-20 mA sensors, capable of feeding a primary value (in this case, the frequency of the tuning fork) back to a PLC. One application now possible is to differentiate between two products with very different vibration frequencies. "In addition to the level detection information itself, in the case of a two-phase medium, the customer can find out whether the sensor is located in the tank's gas head, in the first phase of the mixture or in the second phase."explains Andréa Logos.
Heartbeat Technology's association with the Hart protocol also makes it possible to define thresholds for level detection and signal frequency change over time. "When customized thresholds are exceeded, alerts are triggered, which may be due to contamination or corrosion of the tuning fork, or a drop in resistance in the current loop. This is the role of Heartbeat Monitoring: continuous monitoring of certain parameters to quickly identify a possible problem, before the device goes into fault."explains Aurélia Genet, Process Industries Team Leader at Endress+Hauser France.
Another benefit of the new electronics is the ability for operators to perform Heartbeat Verification and SIL tests remotely, in accordance with IEC 61508 and IEC61511. "With Liquiphant FTL51B, FTL62 and FTL64 detectors, it was already possible to trigger tests locally, via the Bluetooth interface and a tablet or smartphone equipped with the SmartBlue iOS/Android app. But it is now possible to do so via the Hart signal, from a supervisor for example.says Andréa Logos.
This gives users the tools they need to get a true picture of the health of their level switches, and ultimately, to know what's going on inside their tanks and processes. They no longer have to wait for a faulty device to intervene, and can plan the most appropriate action based on the information provided by the device. As they no longer need to dismantle the device to carry out these tests, operators are no longer obliged to climb to the top of a tank, to provide a ladder or even a gondola, or to drain a tank. This means significant time savings for maintenance teams.
The three tuning fork level switches for liquids are each designed for a specific type of application:
- Liquiphant FTL51B standard model: process temperature from -50 to +150°C (PN 64 or 100 bar version optional)
- Liquiphant FTL62 model with highly corrosion-resistant coating (ECTFE, PFA or enamel): process temperature from -50 to +150 °C and process pressure from -1 to 25 or 40 bar (depending on coating).
- Liquiphant FTL64 high-temperature model: process temperature from -60 to +230°C and maximum pressure up to 100 bar