Automated partial prooftesting
Partial proof testing in general offers great opportunities to increase overall plant safety and the reduction of proof test efforts. Besides the partial proof testing of automated industrial valve assemblies, it is now also possible to partially proof test sensing elements, such as flowmeters, pressure meters, etc.
However, the test methods are now possibly also fully automated. For this purpose, the safety system (SSPS) first reads out the entire configuration of the measuring device while in SIL mode. Then the safety control system (SSPS) transfers the measuring device from SIL mode to simulation mode in order to perform the specified partial proof tests:
Conducting a complete self-test
First, the SSPS causes the device to perform a complete self-test. In doing so, the device can test memory areas, among others, that it could not be tested in normal operation. Depending on the measuring method, this self-test can reach a test depth (PTC - Partial Proof Test Coverage) of up to 40%.
Easy testing of current loops
Secondly, the current loops can now be easily tested without disconnecting the cabling. Via simulation, the SSPS instructs the measuring device to apply different current values to the output, which are measured directly by the input modules of the SSPS. This makes it easy to check whether the setpoint and actual values still match. Depending on the device type, the PTC here is approx. 30%.
Aligning the configuration
At the end of the automated partial proof test, the measuring device is set back to SIL mode and the previously read configuration is compared with the current configuration. This is done to ensure that the device is 100% in the same configuration state as before the test.
Important: The plant operator must be aware that during the partial proof test, manually performed or automated, the safety function is not available for the duration of the test!
It is essential to ensure that the safety of the plant operation is guaranteed during the partial proof test. This is usually regulated by organizational measures: If, for example, there is a risk of overfilling a container, which could result in persons in the immediate vicinity being burned, the corresponding area must be closed off to persons for the duration of the partial test.
Partial proof tests bring a test coverage of up to 80% of all undetected failures by self-diagnosis. They ensure the safe operation of any safety-relevant function and can be carried out under process conditions – no need to remove the device from the process.
Electromagnetic flowmeter for safety instrumented systems (SIS) and high-accuracy requirements