Deposit is the occurrence of clumping substance in the boiler water which is caused by suspended solid such as copper oxide, iron oxide and others. Deposit is also caused by steam which is contaminated in the production process. Sources of deposit in the feedwater are dissolved salts and suspended solid which can affect particles that can make lower solubility are deposited. There is different definition between crust and sludge. The crust is a form of deposits that remain on the metal surface of boiler, while sludge is a form of deposits that are not settled or can be called soft deposits.
In the high pressure boiler, silica can settles with steam so can make deposit on the turbine blade and potential to damage occur. Prevention actions can be done as following below:
- Minimize the entry of minerals in the feedwater that can lead to deposits such as iron oxide, copper oxide and the others on the water treatment plant.
- Prevent corrosion by doing neutralization process such as adjust PH 8.2 to 9.2 and can be also performed by the occurrence of air leakage in the condensate system.
- Prevention contaminated steam can be performed by using chemical to disperse the minerals that causing deposits.
- Reduction of existing deposits can be done by acid cleaning, online cleaning and mechanical cleaning.