The CIP of the decanter is carried out in two steps:
First a High-speed CIP at full bowl speed, which is followed by a Low-speed CIP at speeds corresponding to just under 1*g (50 - 150 rpm).
While the high-speed CIP is performed, the pipings, the inlet parts, and the outside of bowl and decanter casing are cleaned. The sludge remaining in the bowl after completion of the high-speed is cleaned out during the low-speed CIP.
When terminating the separation performance, the decantershould be prerinse with water until all visible solids and process material have been removed before using a liquid with cleaning detergent.
In most cases water alone cannot remove the dirt and deposits, its removing power being insufficient.
Chemicals such as sodium hydroxide, also known as caustic soda, must be added in order to achieve a satisfactory result. Caustic Solution: 1-1.5% NaOH, to ensure a pH value of 12 to 13. A detergent compound of NaOH with an admixture of complexing agent such as sodium-polyphosphates, EDTA, or should be used.
An acid cleaning could be carried out as a supplement to thecaustic cleaning. Nitric acid (HNO), concentration 0.5%, is suitable.