As noted above, water cleaning diverges significantly from steam or air cleaning in the core mechanism which facilitates the successful removal of deposits from the tube surface. The typical mechanism with conventional air or steam blowers is that of kinetic impact or using the brute force of the cleaning media impact to scour or scrape the deposits from the wall. Typical media speeds are close to Mach one, or about 300 meters per second.
All water cleaning devices (bar water cutting tools operating in the tens of thousands of pounds per square inch range) employ a two step process:

• The first step is for the cleaning device (lance, cannon, even fire hose) to deliver water droplets into the cracks or pores of the deposit on the tube surface. The water droplets must be delivered with sufficient residual momentum to penetrate the deposits
• The second step is the automatic and almost immediate expansion of the water into steam. It is this explosion taking place during the phase change of water to its vapor form that provides the necessary impetus for the cleaning effect.

Consideration of this process provides the reasons for the argument noted above that the impact angle determines the cleaning effect. This permits the quantity of water used for water cannon operations, which impact the water wall more directly, to typically be far less than equivalent water lances, which employ a more tangential impact on the wall. Cleaning effect can be modified and controlled according to local needs and requirements, by changing the system’s pressure and speeds. This process of optimization and “tuning” is key to achieving optimal system performance, and in balancing the two goals of minimizing thermal impact and effective cleaning.