Pressure surges or shock waves - caused by the sudden, rapid acceleration or deceleration of a liquid - can cause steam or water hammer. The resulting pressure surges have been measured at levels up to 20,000 psi, which is high enough to rupture or collapse the tubing in a heat exchanger (figure 1).įIGURE 1. Pressure surges or shock waves caused by the sudden and rapid acceleration or deceleration of a liquid can cause steam or water hammer. Where density is in pound-mass per cubic foot (lbm/ft3) and velocity is the shell nozzle velocity in feet per second (ft/sec). Typical shell-side nozzle-velocity limits to prevent impingement erosion on the outside of tubes can be established with the following: Wet-gas impingement is controlled by oversizing inlet nozzles, or by placing impingement baffles in the inlet nozzle. The maximum recommended velocities in heat exchanger tubes and entrance nozzles are shown for materials such as steel, stainless steel and copper-nickel.Įrosion problems on the outside of the tubes can occur with impingement of wet, high velocity gases such as steam.
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