Shell And Tube Heat Exchanger
A shell-and-tube heat exchanger is a high-pressure static equipment class consisting of a cylindrical shell containing a tube bundle; one fluid flows through the tubes while a second fluid flows over them inside the shell to transfer heat via the tube walls, typically in counterflow.
In shop-floor maintenance, shell-and-tube heat exchangers are tracked as critical pressure boundaries where tube-side fluid is usually the corrosive, high-pressure, or fouling stream, while shell-side fluid handles lower pressure or cleaner media. Maintenance focuses on monitoring thermal performance (ΔT, ΔP) to detect fouling, executing bundle pulls for Eddy Current Testing (ECT) or ultrasonic thickness checks, and performing hydrostatic testing to verify joint integrity.
What is the primary Non-Destructive Examination (NDE) method for assessing non-ferrous tube wall condition?
Eddy Current Testing (ECT) is the primary technique for non-ferrous and austenitic stainless tubes, while ultrasonic thickness measurement is used for ferrous tubes.
What defines the retirement criteria for a tube bundle during inspection?
Retirement is mandated when the number of plugged tubes exceeds the maximum allowable percentage (defined by the integrity program) or when tubes exhibit uncharacterizable pitting/cracking that cannot be mitigated by NDE.
How does thermal cycling specifically impact shell-and-tube geometry?
Significant temperature differences between hot tubes and a cold shell generate thermal stress; in fixed tubesheet designs, this can cause buckling or joint failure unless expansion joints or floating bundles are employed.