Important equations for process design engineers for - mass balancing, pressure drop calculations as well as for design of process equipment and instruments.

* Frictional pressure drop in a line* - Equations for calculating pressure drop per unit length across a pipe are given. EnggCyclopedia's pressure drop calculators for single phase and two-phase flow are based on these equations.

* Key terms for understanding and designing pressure relief devices* - Meaning and significance of terms such as - design pressure, maximum operating pressure, maximum allowable working pressure (MAWP), set pressure, pressure accumulation, blowdown etc. are discussed.

* Mass Balance Equation* - The mass balance equation forms basis to a number of process engineering calculations. Mass balance equation simply states that total mass in any system is always conserved. That is,

Total mass in = Total mass out + Total mass accumulated in the system