Rapid changes in speed in a pipe generate significant pressures or depressions due to the inertia of the water. If these pressure variations are large enough, the water becomes a compressible fluid capable of propagating high-speed waves that can cause water hammer. To dampen the shock waves and prevent damage in the pipes, equilibrium chimneys are introduced. However, they create a new phenomenon of mass oscillation.
The water hammer and equilibrium stacker, EH170, allows the study of non-permanent flows in a stainless steel serpentine pipe with a length of eleven meters and having at each of its ends a Pressure sensor. The shock waves are caused either by the rapid closing of a pneumatic valve placed downstream of the pipe, or by the closure of the flow control valve placed upstream of the flowmeter. A bypass with stop and control valves leading to a vertical tube allows the influence of an equilibrium stack to be studied.