Komatsu PC78US-6 Operation & Maintenance Manual page 202

MAINTENANCE PROCEDURE MAINTENANCE PROCEDURE
NOTICE
The inner element must not be used again even after its cleaning. When
replacing the outer element, replace the outer element at the same time.
NOTICE
When cleaning the element, do not hit or beat it against anything.
Do not use an element whose folds, gasket or seal are damaged.
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MAINTENANCE MAINTENANCE