Download White Paper: It is often perceived that the continuous and batch process industries are different manufacturing worlds. Certainly there are notable differences, but on many levels they are the same. But one element that is often perceived as being the same is functional safety requirements. Frequently however, in this instance, there are key differences.
In continuous processes, typically the general operating parameters are fixed for long periods of time. The functional safety parameters (setpoints and the active or disabled state of safety functions or initiators) also stay the same for long periods. But in batch processing operations, functional safety conditions can vary significantly from one product type, or family, to another when the plant is capable of making a range of products. And the larger the diversity of products, the more likely the functional safety parameters will need to be changed with the production recipe to safely manufacture the products.
Understanding Functional Safety Requirements is Key
Too frequently, when a Functional Requirements Specification (FRS) for a Safety Instrumented System (SIS) is created, there is a simplifying assumption made that trip conditions for Safety Instrumented Functions (SIFs) will be set once and rarely changed. This may be a valid assumption in many single product continuous processes, but often one that is improper in batch processing when different product
recipes are executed.
It is not uncommon for batch processes to have requirements that dictate changing SIF parameters when a production cell is tasked to manufacture a product different from the last. Too often an engineer must intervene to make the changes to SIF parameters. This can lead to process delays if the engineer is not immediately available when the production change occurs.