Process Control System

Basic Guidelines for Process Control System Validation

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The system integrator or system supplier often has to provide sufficient documentary records to ensure that the user accepts and validates the system. Use of integrator or supplier document can simplify the overall validation process. For example, the supplier’s own inspection procedures and documentation may meet the requirements of the normal installation qualification (IQ) activities if the user reviews and approves them.

Correspondingly, the supplier’s development methods, quality procedures and documents may supplement or replace some normal operational qualification (OQ) activities. The essential part of IQ and OQ is testing procedure. The system integrator or supplier shall provide two IQ testing documents named IQ1: FAT and IQ2: SAT. In IQ1 test, all hardware I/Os get tested on a signal simulator; software I/Os should undergo verification and testing simultaneously.


The IQ Test: Put your Hardware to the Test

IQ2 shall proceed once all site instruments have been calibrated and loop-checked with all electrical components ready. The software OQ is the systematic and formally documented verification that customer built application control software performs its proper function as specified in the functional specification (FS). For the control system, this means supplying evidence that all functions individually and as a whole are operating in accordance with the specification. The OQ test can also be separated into OQ1: FAT and OQ2: SAT.

Of these, OQ1 happens where the target process is simulated. It happens in a structured approach from cell to unit, to process area, module by module, or function block by function block. OQ2 takes place in an operational environment and software OQ is always the essential subset of the overall system OQ.

Mandatory Documentation for GMP Compliance

To develop PLC software, three documents must be in place namely, control system design standard (CSDS), which is basically detailed SOPs for control system design; user requirement specification (URS) and FS. The URS is critical and the end-user should take responsibility for its contents by reviewing and approving the document. In practice, the system integrator’s engineer may write most part of the URS with assistance from end-user, but final acceptance by the user is essential and mandatory. The FS should describe what the system should perform under given conditions, but not how.