Process Flow Diagram, it's Types and it's Objectives

Process Flow Diagram

·       A diagram representing the entire process sequentially by means of equipment symbols and lines indicating all equipment and flow directions is called as “Process Flow Diagram ”.

·       The Process Engineering Department furnishes the piping analyst a Process Flow Diagram .

·       The Process Flow Diagram shows how the various items of process equipments are interconnected such as columns , heat exchanger , blowers and pumps, etc.

·       The Process Flow Diagram also indicate chemical & physical properties such as :-

         i) Flow rates, viscosity

        ii) Specific gravity, Bulk density

       iii) Molecular weights

       iv) General flowing materials

        v) Expansion factors

       vi) Temperatures

      vii) Pressures

·       It also shows the process requirements for fixed points in the process.

Objectives of PFDs :-

·       To indicate pictorially the inter-relationship among various unit operations and process units.

·       To provide material balance at all major steps.

·       To provide energy balance in the form of specific heat, temperature and state of material.(liquid,vapour or gas).

General Considerations while constructing PFDs :-

·       It is desirable to show all the equipments in their relative positions, for eg., pumps and compressors are at ground level.

·       Main process streams are always in bold, e.g., raw material to finished products.

·       The streams are numbered within a diamond.

·       Equipments are numbered generally based on function or area .

·       PFDs are also drawn for utilities , effluent treatment process.

·       While continuing PFD on other drawing sheet, one must indicate interconnection between various streams.