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Extend SIL proof test intervals with Liquiphant Level Switches and Heartbeat Technology 

Across the process industries, and especially in the chemical industry, safety is paramount because process failures and accidents can be both costly and can place both personnel and the environment at risk. Under normal circumstances, the Basic Process Control System (BPCS) receives inputs and generates appropriate output signals to keep process equipment operating safely and effectively. However, any equipment or instrumentation failure introduces the opportunity for a dangerous situation to develop.   

To reduce the risk and mitigate the impact of a failure event, a Safety Instrumented System (SIS) provides an additional layer of plant and personnel protection, operating separately from the BPCS. 

SIL proof test

While a SIS provides improved process safety, it also comes with increased operating costs, requiring regular Safety Integrity Level (SIL) proof testing. This is necessary to ensure the SIS continues to reduce risk as intended. Proof testing often requires the entire system under protection to be shut down.  Lost production in addition to necessary instrument removal and reinstallation results in additional operation expenses. 

However, plant process owners can ensure safety while minimizing downtime and expenses by selecting equipment with automated onboard testing and diagnostics, such as the Liquiphant line of point level switches

Heartbeat Technology in Liquiphant switches 

Liquiphant (tuning fork) level switches utilize Endress+Hauser’s Heartbeat Technology to provide online diagnostics, verification and monitoring. Tuning fork level switches use a vibrating metallic two-pronged sensor to detect process fluid. The vibration frequency and consequent fluid detection can be affected by corrosion or substance build-up on the sensor surface, reducing measurement reliability if left unaddressed.  

Liquiphant switches for rescued SIL proof test intervals

To identify these types of adverse conditions, Endress+Hauser’s Liquiphant switches, with Heartbeat Technology, internally monitor vibration frequency. They will then issue a diagnostic warning for operators if significant deviation occurs, indicating if sensor maintenance and potential replacement is required. 

With Heartbeat Technology, plant operators and maintenance personnel can monitor Heartbeat parameters to observe trends over time and identify issues in their early stages. Heartbeat verification can be initiated at any time, on-site or remotely, with no process interruption. Furthermore, verification reports are clear and detailed, making it simple to confirm and document sensor health. The steady flow of diagnostic information and on-demand verification capability provides earlier issue detection, while extending intervals for every comprehensive SIL proof test required. 

Extended SIL proof test intervals yield positive results in a chemical plant 

SIL proof test

In one chemical manufacturing facility, Liquiphant devices are used as part of a SIL3 application to ensure safe levels are not exceeded in thionyl chloride tanks. Prior to their installation, a comprehensive SIL proof test had to be performed every year, requiring personnel to enter hazardous areas in full protective gear to completely drain and clean the tanks. They would then remove the level switches for offline proof testing.  

After replacing these switches with Heartbeat-equipped Liquiphant level switches, the plant extended its requirement for intensive offline testing to once every three years. This resulted in reduced plant downtime, safety hazards and the risk of process measurement error resulting from instrument removal and reinstallation.

Digital connectivity for greater flexibility 

While Heartbeat diagnostics can be accessed directly via a wired connection to a Liquiphant instrument, its power and ease-of-use is amplified with wireless connectivity capabilities via Bluetooth and the SmartBlue app. Additionally, Heartbeat Technology can be fully integrated with process control, plant asset management and maintenance systems. 

Bluetooth for SIL proof test extension

Maintaining high safety standards while operating profitably can be a challenge, but Liquiphant level switches with Heartbeat Technology bolster both in SIS and other critical applications. These tools simplify maintenance tasks with automated instrument diagnostics and reporting. They can also reduce invasive SIL proof test intervals, increasing uptime and improving safety. 

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