This invention relates to a cyclone inlet unit, particularly to an inlet unit of a cyclone for use in separating oil and water mixtures e.g. the oil being in droplet form dispersed in water or vice versa.

When using a cyclone for separating oil from a mixture of oil and water containing relatively small quantities of oil e.g. up to 20% oil, the separating efficiency may be significantly dependent on the geometrical features thereof. One such important feature is the construction and arrangement of the inlet or inlets through which the mixture to be separated enters the cyclone so as to promote the formation of a vortex. For example, the shape and/or configuration of the inlet or inlets may limit the separating efficiency because of effects such as turbulence causing break-up of the oil droplets in the mixture being fed to the cyclone.

It is an object of the present invention to provide a cyclone inlet unit wherein the aforementioned disadvantages are reduced or overcome.

In accordance with the invention a cyclone inlet unit comprises three vanes between which are three inlet orifices, each orifice having a rectangular cross-sectional area and lying between two sidewalls, one on one vane and the other on another adjacent vane, each orifice being of gradually decreasing cross-sectional area towards the interior of the unit, at least one of the sidewall surfaces having a convex profile.

Both sidewall surfaces may have convex profiles or one may be convex and the other planar.

The rectangular orifices may be such that the length in an axial direction with respect to the cyclone is much greater than the length in a radial direction.

Each orifice may have a portion of unchanging cross-sectional area, said portion being directed along a tangent to the cyclone. The orifices are preferably equi-spaced around the near-cylindrically shaped interior of the unit.

The three vanes, may each be adjustable in position to vary the radial widths of the orifices and to change the rate of decreasing cross-sectional

area of each of the openings leading to the orifices.

Two embodiments of the invention will now be described by way of example only with respect to the accompanying drawings of which:-

Figure 1 shows a radial cross-section through an inlet unit in accordance with the first embodiment;

Figure 2 shows an axial cross-section on line ll-ll of Figure 1 ; and

Figure 3 shows a radial cross-section through an inlet unit in accordance with the second embodiment of the invention.

In general a cyclone separator comprises a tapered tube (not shown) into which a mixture of material e.g. oil and water, to be separated is fed tangentially through an inlet or inlets at or adjacent the wide end of the tube. A vortex is formed and the more dense material e.g water migrates to the outer parts of the tube and out through the narrow end of the tapered tube (known as the underflow outlet) and the less dense material e.g. oil migrates to the central core of the vortex in the tube, and out through an outlet on the axis, usually at the wide end (known as the overflow outlet). A separator tube is described in GB Patent No. 1583742.

The inlet unit of either embodiment is, in use, attached by bolts or other means to an end flange situated at the wide end of the tapered cyclone separator tube.

The unit 1 of the first embodiment shown in Figures 1 and 2 is made from a single piece of metal e.g. stainless steel, by suitable known techniques e.g. casting and machining, so as to have an end plate-like portion 2 which extends perpendicularly to the axis 0-0 of the cyclone and three vanes 3,4,5 extending in overlapping arrangement around the edge of the portion 2. A central circular bore 6 is formed in the plate-like portion and retains e.g. by force fitting, a cylindrical overflow outlet unit 7.

The three vanes define and separate three rectangular orifices 8,9, 10 through which material to be separated is introduced at an appropriate velocity into the cyclone to form a vortex. Typically the axial length of each orifice is 20 mm. The radially inner side 1 1 of each vane is smoothly

concavely curved from a very narrow portion 1 2, typically 1 mm wide, lying alongside the radially inner side of an orifice, and having a diameter D, of 60 mm (which matches the maximum diameter of the tapered separator tube) towards the radially outer side of the next orifice spaced apart therefrom by 120 ^° with respect to the axis of the separator. The diameter D ₂ of this radially inner surface at the next orifice is 67 mm, the increasing radius between one orifice and the next being directly proportional to the angular change. Thus, for example, the diameter D ₃ at a position 60 ^° from one orifice is 63.5mm.

The entrance 13 to each orifice 8 has a constant rectangular cross- sectional shape, the radial width being 2.5 mm for a tangential distance d of 3.0 mm. The radially outer surface 14 of a vane defining the inner surface of an orifice is convex, having a radius of curvature, beyond the initial 3.0 mm at the orifice entrance, of 144 mm. The radially inner surface 15 of a vane, defining the radially outer surface of an orifice is also convexly curved having a radius of curvature, beyond the initial 3.00 mm at the orifice entrance, of 13 mm decreasing to 2mm. The entrance to an orifice is therefore generally funnel-shaped, as can be seen in Figure 1 .

The radially outer surface of each vane may be provided with recesses such as 1 6 to allow space for external attachment means such as a bolt, which is used to hold the various components of the separator together.

The unit 20 of the second embodiment shown in Figure 3 also comprises three overlapping vanes 21 ,22,23 of metal e.g. stainless steel, but in this instance the vanes are not integrally formed with the plate-like end portion 35. The vanes define inlet orifices 31 , 32, 33. Each vane has a radially inner surface 24 having a curved profile which is the same as the radially inner surface of each vane of the first embodiment. However the radially outer surface 25 of each vane, defining the inner surface of an orifice entrance, is planar, in th s embodiment.

The three vanes are each provided with two bores 26,27, each parallel to the cyclone axis, one bore 26 being circular, and the other 27 being in the form of an elongated s t. This enables each vane to be bolted to the plate-

like portion 35 and the positions of each vane to be adjusted slightly to provide the optimum separating efficiency. Thus the narrow tips of each vane may remain positioned on an imaginary circle of 60mm diameter, while the position of the curved radially inner face defining the radially outer extremity of an orifice may be adjusted radially outwardly or inwardly so as to widen or narrow an orifice.

The use of a unit according to the invention having three inlet orifices provides reduced area wetted by the mixture inside the tapered tube compared to a unit having fewer inlets of the same radial width, larger surface areas causing greater frictional losses leading to reduced vortex velocities.