Pharmaceutical & medical
monitoring module – must be considered and assessed separately from one another. They each operate independently and the measuring instrument and the monitoring module both have their own signal output. The DMSU21SA is different: it is designed as an integrated system and has EHEDG, 3A and IEC Ex approval in this form. In addition to process pressure data or the sensor temperature and status, its process transmitter now also supplies information on the diaphragm status. It monitors the switch contact of the diaphragm monitoring system and outputs an alarm signal via the HART protocol if a failure is detected. The setpoint must previously have been reached for a minimum of 1.5 seconds. This setting prevents unwanted alarms due to shocks or vibration. The emphasis on digitisation means the new diaphragm seal system only communicates via one output. It can be got up and running fast thanks to the 'plug & play' principle. It is a simple matter to integrate it into an existing HART environment. There is no need to lay a second cable as there is for the first system generation’s monitoring function. The plant reassessment that is sometimes stipulated when an additional, independent measuring component is built in can likewise be dispensed with. The capital costs for users and the human resources for planning or converting the measuring point are substantially lower as a result. The DMSU21A is also potentially suitable for analogue brown field plants for this reason. The transmitter’s electronics generally work with a 4 ... 20 mA signal, which is simultaneously the basis for HART. In the version without the communication protocol, status information in case of anomalies is output via a residual current, diaphragm monitoring included. The current is defined as 3.5 or 21.5 mA. If an error message appears, the user can determine the concrete cause on site after stopping the process, safe in the knowledge that its integrity was maintained up until the moment it was interrupted.
Self-monitoring instruments make processes more reliable and mitigate the consequences of failures to an acceptable level. The diaphragm monitoring module tells users the exact second when a process-side measuring element was damaged, so that appropriate counteraction can be taken.
Delayed detection of a ruptured diaphragm can quickly lead to significant economic damage. For instance, a UHT plant operating 24/7 processes up to 30,000 litres of milk per hour. An enormous amount of waste will be produced in a relatively short time in the event of contamination. Diaphragm seal systems with diaphragm monitoring rule out loss on this kind of scale. Furthermore, they avoid the need for risk assessments and eliminate the associated time and costs. From the point of view of operating expenses (OPEX), the bottom line here is as follows: the higher the throughput in a production process, the more economical it is to use self-monitoring instruments.
SUMMARY
When electronic measuring instruments have to be connected to sterile processes, diaphragm seals are practically without alternative. Diaphragm seal systems with built-in diaphragm monitoring maintain process integrity and product purity if a measuring element is damaged. A new, integrated system based on this principle with a process transmitter and the HART protocol now also permits self-monitoring in digitised processes.
WIKA Instrumentation Monthly June 2024
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