representing the separator tube inlet 16 b 16 c 16 d and 16 e representing intermediate segments of the tube 16 and 16 f representing the underflow outlet end having an underflow outlet orifice or bore 17 the separator tube 16 is mounted in a correspondingly shaped bore 18 within the housing 1 which includes an inwardly disposed shoulder region 19 in the lower half 3 to which abuts a shoulder region 20 of the cyclone separator tube segment 16 f at the other end of the housing 1 in the upper half 2 is a corresponding shoulder 21 which ensures that the cyclone separator tube 16 and all its respective component segments 16 a to 16 f are captured within this part of the bore 18 immediately below the inlet chamber 9 as will be appreciated manufacturing tolerances for the various segments 16 a to 16 f can mean that they may be collectively a tight fit or a loose fit within the limits imposed by the shoulder regions 19 21 and in accordance with another aspect of the invention this potential problem is resolved through the use of an annular hollow shim 22 made of e g metal tubing and including apertures therein so that as the clamp 4 is tightened to move the upper and lower halves 2 3 together the shim 22 deforms to ensure that there is no play in the system at the lower.