Temperature of saturated steam
Steam and its influence on hoses
Water can occur in three different states: solid, liquid or gaseous. In the gaseous states (steam) there are also three different forms determined by the pressure and temperature.
These 3 forms are:
- wet saturated steam or “Wet Steam”
- dry saturated steam
- overheated steam or “Dry Steam”.
For an explanation see the steam diagram. The thick black line shows the boiling point of water at different pressures. Each point on this line represents saturated steam. Saturated steam may or may not be fully free of unevaporated water particles. In other words saturated steam can be “dry” or “wet”. Each point below line (zone A) represents hot water - each point above line (zone B) represents overheated steam. The dotted line in zone B shows the process of saturated steam converted into overheated steam. If a steam hose is under a pressure of 150 psi (10.5 bar) at a temperature of 366°F (186°C) this hose contains saturated steam. When the pressure is reduced by the expansion of the steam (e.g. when suddenly opening a stop valve or when the steam arrives in a wider pipe or hose), the state of the steam follows the dotted line to a point “X” in the zone of the overheated steam.
This state will not last very long but the overheated steam displays the inclination to harden or soften the inside wall of an ordinary steam hose intended for use with saturated steam. When the inside wall becomes hard or soft this usually means the hose will become defective. How to choose the correct steam hose
- Establish the required hose inside diameter. The required hose inside diameter is usually determined by the sizes of the couplings or the pipe to which the hose must be connected. It is important to not choose an inside diameter larger than the diameter of the supply pipe.
- Determine the working pressure and temperature.Record the pressure and temperature data just before the hose connection.
- Determine the state of the steam (saturated or overheated). Compare working pressure and temperature with the steam diagram. Each point on the thick Iine is saturated steam; each point in zone B is overheated steam.
- Choose the correct hose. Choose the correct hose that complies with the requirements set, taking account of both the state of the steam and the working pressure.
- Determine the required length. The required length is nearly always determined by the application. (Avoid tight bends!)