Filtration apparatus with means for preventing peeling off of a pre-coat layer

A filtration apparatus comprising:

• at least one upright tubular filter element mounted in a housing, and having an outer surface on which a pre-coat layer of a filter aid is to be formed such that a liquid to be filtered is passed through said pre-coat layer and through said filter element from said outer surface toward an inner surface thereof;
• means for feeding a liquid suspension including a liquid carrying a pre-coat material into said housing and to said at least one tubular filter element for forming said pre-coat layer on said surface of said at least tubular filter element;
• means for feeding a liquid to be filtered into said housing such that said liquid to be filtered passes through said at least one precoated filter element;
• means for discharging filtrate from said at least one filter element and from said housing;
• means for feeding a purging gas into said tubular housing for pressurizing the interior of said housing for removing said liquid carrying said pre-coat material from said tubular filter element;
• means coupled to said housing for discharging said liquid suspension from said housing;
• and
• liquid drain means including a liquid drain tube coupled to an opening on a lower part of said at least one tubular filter element for draining at least said liquid carrying the inner part of said pre-coat material from the inner part of said at least one tubular filter element and from the filter apparatus prior to input of the liquid to be filtered.