A boiler fired in its dry state may lead to hazardous results. Hence, it is very crucial to maintain appropriate water levels in a boiler system. In case of hydronic boilers, the system must be entirely filled with water whereas in steam boilers, the level of water should not touch the mains otherwise the system will not work properly. In steam boilers, a control at the water supply must always be maintained to limit the water levels.
A gate or ball valve is usually employed to stop the supply of water in periods of maintenance or water leaks. When the water supply is put to a halt, the power and fuel source supply should also be cut from the boiler system. “After the shut off valve there should be a back flow preventer, however there may be some older systems that do not have back flow preventer’s. Current local and national codes require back flow preventer’s to keep the supply water from being contaminated by back flow water from the hot water loop.”
Subsequent to the back flow preventer, a pressure reduction valve should always be mounted for the purpose of bringing down the supply water pressure upto 12 P.S.I. “After the pressure reducer, the source supply water should be fed into the return or supply loop depending on the application and type of system.”
The boiler feed water must undergo various treatment and conditioning processes before entering the boiler system due to following major reasons:
- Water treatment helps in maintaining continuous heat exchange within the system.
- It provides resistance against corrosion.
- It helps in generation of high grade steam output.
Two major ways via which the boiler water supply can be purified include: External water treatment & Internal water treatment methods.
In this method, the boiler feed water is treated and purified outside the boiler system. This method of water treatment is normally chosen when the levels of impurities present in feedwater reaches so high that they can damage the inside structure of the boiler system in use. Hence, the impurities must be removed from feed water before water enters inside the boiler via external method.
Various kinds of external water treatment techniques are available such as water softening, evaporation process, deaeration technique and membrane contractors etc. Any of these techniques can be utilized depending upon the requirements of a specific boiler system.
In this method, the treatment & conditioning of water impurities is carried out inside the boiler only. The necessary reactions tend to take place either in the water feed lines or exactly in the boiler. This method of water treatment can be employed either alone or in combination with external water purification techniques. Internal water treatment method basically fights with following feed water problems:
- Water hardness
- Sludge formation
- Oxygen feed
- Water foaming etc.