The strainer has at least two strainer sections (2) spaced from each other and disposed axially in series along the tubular strainer.

A first tubular screen means (6) has outside itself a first screen chamber (7) with an outer defining surface (8).

Described herein is a direct-heating column assembly for chromatography, in which a capillary column is enveloped in a tubular mesh formed by a plurality of woven filaments.

The screening structure may be a flat screen (11) usually of disc configuration, or a tubular screen (25) within which a material conveying auger screw rotates.

An apparatus for separating a mixture of gaseous and liquid phases comprising a tubular screen (3) containing a helical vane (4) which defines, with the screen, a helical passage.

The filtering and purging system includes one outer transparent tube (6) containing an inner tubular sieve (8).

The spray means has at least one row of spray nozzles (7) extending axially along the tubular strainer and adapted to spray the suspension onto the strainer sections from above the strainer.

An apparatus for fractionating suspensions includes a tubular strainer (1) turnable about a horizontal axis, and spray means (5, 7) arranged to spray the suspension against the strainer.