Publisher Summary This chapter presents some of the "rules of thumb" or heuristics related to chemical process equipments. In case of compressors and vacuum pumps, fans are used to raise the pressure about 3% (12 in. water), blowers raise to less than 40 psig, and compressors to higher pressures. In case of conveyors for particulate solids, screw conveyors are suited to transport of even sticky and abrasive solids up inclines of 20º or so and they are limited to distances of 150 ft or so because of shaft torque strength. Belt conveyors used are for high capacity and long distances up inclines of 30º maximum. Bucket elevators are suited to vertical transport of sticky and abrasive materials whereas drag-type conveyors (Redler) are suited to short distances in any direction and are completely enclosed. Pneumatic conveyors are used for high capacity, short distance (400 ft) transport simultaneously from several sources to several destinations. In case of cooling towers, water in contact with air under adiabatic conditions eventually cools to the wet bulb temperature. Tower fill is of a highly open structure so as to minimize pressure drop, which is in standard practice a maximum of 2 in. of water. Countercurrent induced draft towers are the most common in process industries and they are able to cool water within 2º F of the wet bulb.