Tearing water
In steam engines, water tearing is the undesired entry of water into the cylinder together with the steam . This must be avoided as the incompressible water in the cylinder can cause serious damage.
The water tearing is not to be confused with the water hammer , which is caused by condensation .
The problem is the rapid pressure drop in a boiler with a high output, whereby the water begins to form large bubbles - it begins to bubble - which when bursting can carry the water up into the steam space. If these water droplets are carried away with the steam and brought into the cylinders, damage is almost inevitable. In the meantime, this problem is no longer so common, as newer steam engines have a built-in superheater in which the water droplets can completely evaporate. Saturated steam machines are significantly more prone to water cracking than superheated steam machines. If, however, a surge of water gets into the steam supply due to a change in incline and a too high water level, the output of the superheater is no longer sufficient. This large amount of water ingress usually results in the affected cylinders suffering total write-offs, as the water fills the entire remaining space of the cylinder and cannot be compressed. Smaller amounts of water, however, impair the lubrication because they wash out the oil. This can lead to piston seizure .
While this problem is relatively easy to cope with with stationary steam engines (in that the steam is extracted high above the maximum water level), an anhydrous steam extraction from the boiler makes greater demands on a mobile steam boiler, for example steam locomotives , because these are usually only limited The height of the steam dome is possible and the installation of other components for water separation is difficult. Depending on the design of the steam locomotive boiler, some steam locomotive series tend to tear more than others.
One possibility for steam locomotives is to install a steam collecting pipe with slots on top of the long boiler. As a result, there is no great pressure difference in the boiler and the water droplets are not carried away. The other possibility with steam locomotives is that a spray plate is installed below in the steam dome, on which the water droplets bounce off. However, both options cannot prevent water from being carried away if the water level in the boiler is too high, due to the water rocking, a change in the incline of the boiler or a delay. The choice of slide and valve can also have a positive as well as a negative effect on water tearing.