Proof testing of safety instrumented systems can be compared to checking the roadworthiness of a car. The tests take place at intervals that depend on the plants and devices involved and are essential for safe operation. Thanks to modern safety systems and the “digitization” of field device information, test procedures can now be automated to a large extent. In practice, this means substantial simplifications and opens up savings potential.
IEC 61511 requires testing before commissioning and after modifications of a plant. This involves verifying the functions and components, checking the documentation, and performing visual inspections. All these tasks are performed within a predefined, recurring schedule and always under tight deadlines to minimize the negative impact on earnings caused by production downtimes. The scope of proof testing is broad and includes a wide variety of activities: Are the right devices installed with the appropriate hardware and software versions? Have the parameter settings of field devices and the safety application remained unchanged? Do all components work reliably? Are measuring points labeled and the labels legible? Is there any sign of wear or leaks? Is replacement, calibration, or overhaul of field devices required?
Optimizing test procedures
A significant portion of the tests can be automated and their sequence digitally synchronized with unavoidable manual activities to allow the teams in the control room and in the field to coordinate with one another. Using test procedures stored in SILworX, the software programming tool for all HIMA safety controllers, the prescribed tests of field devices can be performed automatically in full or in part at predefined times, and the results can be recorded in documents suitable for approval by a certification body such as TÜV. Depending on the plant status, partial tests can also be performed during operation.
Which periodic tests can be automated?
A wide range of test tasks – in particular in conjunction with HART-enabled field devices – can be automated, and includes identification of field devices, monitoring of the configuration, and evaluation of the diagnostics. For comparative measurements, runtime measurements, or leak tests, for example, it is also possible to specify values, control actuators, and thus check their feedback signals. Integrated device diagnostics of HART-enabled field devices can also be triggered and evaluated automatically. In this way, additional meaningful diagnostic, verification and monitoring data is evaluated, which provides information about the condition of the field devices in use.