Avoidance of systematic errors

In functional safety, a distinction is made between random and systematic errors. The random faults are usually due to the failure of hardware. The systematic faults, on the other hand, are mostly due to errors in planning, commissioning or operation.

Statistically, the systematic faults are responsible for more than 90% of all malfunctions of safety loops. These faults are also referred to as "preventable" faults, since the plant operator can largely ensure that they do not occur through careful planning and operation.

Planning:

Here it must be ensured that the measuring device can really cope with the requirements of the measuring operation. Are the wetted parts designed accordingly? Are process parameters such as temperature and operating pressure correct? Are the right approvals available? Have e.g. the thermowells been calculated correctly for a temperature measurement?

Commissioning:

Is the measuring device correctly installed? If, for example, the temperature sensor does not touch the end of the thermowell, a too low temperature would be measured permanently. In the case of a high temperature shutdown, it would then trigger the safety function too late.

Operation:

Is it ensured that the process conditions assumed during the planning phase are actually maintained in practice? Does the maintenance of all components of the safety circuit correspond exactly to the manufacturer's specifications?

The sources of errors that can lead to the failure of safety functions are very diverse. Careful planning, operation and documentation of all measures within the framework of a safety management system are the best prerequisites for trouble-free plant operation.