Cause and Effect

Cause and Effect

Some project categorizes Cause and effect is part of process document and some other projects consider Cause and effect is part of instrument deliverables. Literally, “cause” means something that makes something else happen and “effect” is what happens as a result of the cause.

The interaction between cause and effect could simple to complex. For a simple example in process control: cause could be a tank high liquid level alarm and effect could be open the tank outlet valve. The complex example could be like this: If minimum two flame detectors detect fire in area 1 and coincide with one flame detector detect fire in area 2, then it should close valve A, close valve B, open valve C, de-energize the power outlet, etc.

Cause and effect is presented as a form of matrix. The causes are listed in left section while the effects are listed on top section, both are described in form of tag number with their descriptions (other additional information such as P&ID may supplement). The marked intersection between both means that they are related as cause-effect. Marks could be in form of letter “X” which mean effect will be activated, “T” which mean effect will be activated with time delay, “P” which mean cause will give permissive to an effect.

There are two category of Cause and Effect Diagram:

ESD C&E Diagram
Fire and Gas C&E Diagram

Reference document: SAFE Chart, ESD Logic Diagram, Philosophy

SAFE Chart presents the required safety devices for each process equipment. SAFE Chart shall ensure all safety requirements have been fulfilled and what executive actions the safety devices take.

Philosophy provide the narration and engineer shall translate it to cause and effect interaction so that the plant operates as the intended philosophy.

ESD Logic Diagram shows the plant shutdown hierarchy and describes input that initiate the shutdown and output as the results upon shutdown.

The purpose of Cause and Effect document

Cause and effect document will be translated to program language by control system engineer and implemented in control system as logic. These logic will always monitor plant during operation and works if pre-determined condition attained.

You can download an example of Cause and Effect Chart document pushing the buttom here.