API Plan 21, 23 Cooler is indicated to be used for high temperature applications and for non polymerizing hot fluids. It is required for recirculation of discharge via control orifice & exchanger within a sealed chamber. Execution of this plan is said to assure proper flow rate, improve pressure margin, & to reduce coking. It is placed after flow control orifice and serves as self venting plan. API Plan 21, 23 Cooler comprises temperature indicator, flush, and quenching & draining system. It is said to have hassle-free installation and assures long service life.