Designing a safe process is a key idea that Is written throughout the article and describes that by spending both time and money to create the guideline, It can prevent a much more expensive and costly consequence that can happen with poor process safety In place. In the article entitled "Designing for a Safe Process" by Phil Licker It points out two Incidents one In Dalton, Ga and one In Texas City, Tex where poor guidelines and poor process designs caused explosions and leaks that injured and killed workers on site.
When working on a commercial scale chemical reaction it is essential to promote safe process design so incidents can be avoided. The two flow diagrams that are talked about in the article are block flow diagram (BED) and the process flow diagram (PDF). Bed's show he overall picture of the process, showing only the major process steps. Pod's shows both major and minor equipment with symbols, usually alphanumeric designation. PDF not only shows equipment but major and minor process streams like utility streams, which Include team, condensate, and cooling media.
Because both flow diagrams have there own strengths BFD and PDF should be included Into the basic design package. Also, a process definition drawing (POD) Is needed for the process design engineer to avoid accidents. The PAD provides the operating and design conditions for each equipment item, each control valve station and relief devices. By implementing this the process engineer can recognize inconsistent operating and design conditions. This can give rethought to the safety efficiency and what the operations need to conduct safe reactions.
This document is usually constructed using rudimentary drawing software instead of CAD, so that it is simple to construct and maintain. After the basic design package is made the preliminary safety review (USSR) is done to gather documentation with process safety. These documents include MASS for each substance used, project scope definitions, process design basis, and the process description. The documents are gathered and filled Into a formal report to be strutted to all members of the design team.
Since designs and substances are changed throughout the lifespan of the design process the USSR is a living document and is subject to change. After the USSR is completed the document is reviewed and changes to the design process is done to ensure that the pressure relief valves and rupture disk are located, the hazardous location classification (HAL) is defined for specific equipment safety, fire and gas detector placement, and evaluating layout with respect to minimizing hazards.
By doing this the devices used in the process can be fully defined and evaluated if modifications are necessary for a safer system. When all equipment is chosen for the process design a preliminary hazard analysis (Para) Is needed to visualize ways that a process design can malfunction or operate Incorrectly. Finally all documents related to safety Including the USSR, HAL, and Para are compiled Into a design package, which will be used In the detailed process-engineering phase.