WO1986003424A1

WO1986003424A1 - Separator drain boxes

Info

Publication number: WO1986003424A1
Application number: PCT/GB1985/000570
Authority: WO
Inventors: Stratos Mavros
Original assignee: Parmatic Filter Corporation; Hooper, John, Peter, Lindesay
Priority date: 1984-12-12
Filing date: 1985-12-11
Publication date: 1986-06-19
Also published as: GB8431361D0; EP0205525A1; CA1283059C; GB2168264A; GB8530462D0

Abstract

It is common for engines of the gas turbine variety to have filters at their air intakes. An example of a system employing such a filter takes the form of a tube or duct into which is drawn the air to be filtered, which tube contains a number of filtering components inlcuding pads of knitted mesh and a series of zig-zag vanes. These vanes remove any entrained water droplets, and the "condensed" water runs down the vanes (under gravity) into what is known as a "drain box", from which it is led away and disposed of. The present invention proposes a novel design of drain box; instead of having the vanes bottom on a ledge in the drain box, above the drain box floor, leaving a gap between the bottom of the vanes and the floor of the drain box, and so allowing re-entrainment of the moisture, the present invention proposes that the vanes be extended to the floor of the drain box in intimate contact with the drain enclosure bottom surface. In addition to preventing re-entrainment, extending the vanes in this way provides additional structural vane support, and results in a stronger, more rigid filter system.

Description

-1- Separator Drain Boxes

The present invention relates to separator drain boxes, and concerns more particularly, but not exclusively, drain boxesfor separator assemblies used with gas turbines for landborne or marine applications.

It is common for engines of the gas turbine variety to have filters at their air intakes. These filters not only get rid of potentially damaging solid particulate matter, they can also remove excess water (even in vapour orm) from the air. An example of a system employing such a filter is described in the Specification of our European Patent Application No. 83/300,521.8 (Publication No. 0,087,229), one embodiment of which takes the form of a tube or duct into which is drawn the air to be filtered, which tube contains a number of filtering components including pads of knitted mesh and a series of zig-zag vanes. These vanes remove any entrained water droplets that have got this far, and the "condensed" water runs down the vanes (under gravity) into what is known as a "drain box", from which it is led away and disposed of. The present invention proposes a novel design of drain box that quite significantly improves the performance of moisture separating devices by incorporating a more efficient system of drain water and solids removal, and by providing for a more efficient air flow through the filter assembly.

Moisture separators can carry a very high water loading. However, the upper limit of water-carrying capacity is normally defined by the re-entrainment of large drops of spray from the drain box at the bottom of the moisture separator. This re-entrainment is more marked at higher velocities, thereby considerably reducing the water-handling capability of the separator assembly. It is, therefore, very important to design the drain box in such a way as to reduce,or even eliminate, re-entrainment over the range of operating velocities, in addition to improving the draining of water and solids from the drain box. In one classic design of currently-available three- stage separator assembly system (like that of the aforementioned European Application, for instance), the vanes bottom on a ledge in the drain box, above the drain box floor, leaving a gap between the bottom of the vanes and the floor of the drain box. Re-entrainment is reduced by having moisture and solids drain from the vanes into the drain box for disposal through a draining means at the bottom of the drain box. However, unfor¬ tunately the gap formed in the space between the bottom of the vanes and the floor of the drain box does not offer significant resistance to the air> flow, and as a result the gap becomes a major source of re-entrainment of moisture laden air into the filter air flow, thereby diluting the filtering effect of the separation assembly. I^{n one} proposal to correct this re-entrainment problem, the drain box is packed with a knitted mesh material (made of type 9035 "HIT" polypropylene, for example) . However, this packing "solution" introduces a new, and more significant, problem in that a drain box with packing collects and retains the corrosive solids draining from the vanes, causing a loading of dirt and salt solids in the packing material and drain box trough, and inhibiting the efficient draining of the drain box. In turn, the lack of proper draining forces frequent cleaning and maintenance of the drain box, which is a difficult task due to the inefficient design of the box. These factors lead inevitably to extensive corrosion of the drain box, and ultimately to possible structural failure. This problem - what to do to stop air passing through the gap between the vane bottom and drain box floor - has beset separator assembly designers for some years, and as yet no "solution" (such as the knitted packing one mentioned above) has proved satisfactory. The present invention, though, does provide such a satisfactory solution - and, moreover, by what seems at first sight to be a minor change in the design of the vane/drain box portion of the assembly, yet which turns out to be of major significance. It is amazingly simple: in the present invention, the vanes utilized in the separator assembly to remove airborne water vapour or droplets are extended to the floor of the drain box in intimate contact with the drain enclosure bottom surface. Extending the vanes of the drain box floor in this way provides additional structural vane support, and results in a stronger, more rigid filter system. All need for knitted mesh or other packing materials is eliminated, providing for no retention of corrosive solids, for ease of flushing and maintenance, and for the virtual elimination of corrosion leading to structural failure.

In one aspect, therefore, this invention provides, in a separator of the kind described, the use of vanes which extend all the way to the floor of the drain box.

Appart from the extension of the vanes into contact with the drain box floor, the assembly may be of any type, conventional or otherwise. Specifically, the draining means (the actual draining vents via which collected moisture/dirt is removed from the drain box) may be directly under the vanes. However, in a particularly preferred embodiment the matter is arranged slightly differently, and there is provided, in a direction downstream of the vanes/drain box combination proper, an extension of the box (rather like a boot/trunk of a motor car) which is not part of the passageway by which the filtered air is -fed on and out of the assembly. This extension, or drain chamber, is open to the box proper, but closed to the rest of the assembly, and the draining means, or vents, are positioned within the chamber - thus, downstream of the vanes rather than directly beneath the vanes themselves.

The efficiency of the flow of air through the filter of a system incorporating the present invention is not negatively affected as in the previously-described three-stage system utilizing a drain box with an air gap below the vanes. In the present invention, air flow through the bottom of the vanes and the drain box will take a longer flow path having greater resistance to flow than the flow of air through the filter. Consequently, the flow of air will be contained within the filter with a resultant greater efficiency due to the elimination of re-entrainment. The most significant factor, however, is the ability of a separator fabricated with the present invention to perform consistently, as described herein,over the entire operating range of the moisture separator.

A particularly beneficial advantage of this drain chamber idea is that an integral drain box washdown system may be incorporated to provide, for example, a multiplicity of flushing ports, a removable drain box trough, or a combination of both. The washdown system provides a means of flushing the drain chamber of debris and corrosive particles normally retained by systems having drain boxes with packing, and by systems not incorporating the drain box features of the present invention. The described flushing feature of this invention prevents excessive corrosion in the area most prone to galvanic and chemical erosion.

The improved separator assembly of the invention allows a free, unimpeded flow of drain water and suspended solids to the drain ports in the drain box extension. The drain ports may be amply proportioned to accept the full drainage flow regardless of the relative position of the system with respect to the horizontal plane. By way of example, when the system is installed in a sea-going vessel, the ship's pitch or roll does not affect the operation of the drain connections or impede their flow capabilities.

The drain chamber in the preferred embodiments of the invention is located downstream of the vane bank, and in this way is capable of providing a full, unobstructed, area for the free flow of the drain water. This drain chamber also provides an excellent means of preventing particle re-entrainment, as can occur in other moisture separation devices, by having a large unimpeded flow area for full drop off and capture of particles.

The design of the drain box of this invention can also provides a supplementary means of structural integrity by enclosing the moisture separation system in a semi-monocoque enclosure to enhance the shock and vibration capabilities of the complete system.

The separator assembly of the present invention provides for greater flexibility in the manner of flushing the drain box, utilizing (at least in its preferred embodiments) :- a multiplicity of flushing ports located in one or more locations in the top, ends and/or sides of the drain box or drain box extension; a flushing of the drain box with fresh water, saturated steam or fresh water and saturated steam in combination; a manual flushing of the drain box through flushing ports using: i) hand-held flexible hoses or pipes, and/or ii) hand-held rigid lances inserted through ports; an automatic flushing of the drain box with flexible or rigid lines temporarily or permanently attached to selected flushing ports, operated by any of a variety of manual or automatic timing devices; any combination of flushing ports, manual operation, automatic operation, fresh water flushing, saturated steam flushing, through permanent or temporary connections to any of the flushing ports, to accomplish the desired elimination of unwanted debris of salt and solid particles from the drain box or drain box extension.

The described preferred flushing system of the present invention will eliminate unwanted debris by dissolving the salt particles and utilizing the washdown flow velocity to dislodge the remaining undissolved debris. The movement of this flushing flow of water and debris is channeled, into the existing drain connections of the drain box or drains box extension. This flush and drain feature is unique in that it is not available in any other moisture separation system, but is exclusively available in that of the present invention.

The present invention provides a separator assembly having an improved, more efficient air flow through the vane bank; an improved, more efficient system for dissolving and/or flushing solids and salts from the drain box; and an improved, more efficient drain water and solids removal system for draining such water and solids from the drain canal of the drain box and drain box extension. One embodiment of the invention is now described, though by way of illustration only, with reference to the accompanying Drawings, in whichϊ-

Figure 1 shows a diagramatic vertical cross-section through the final stage (the vane/drain box section) of a separator assembly of the invention; and

Figure 2 shows a diagramatic top plan view (partly in section) of the assembly of Figure 1.

The vane/drain box section of the separator assembly of Figures 1 and 2 comprises a duct (only the duct floor 11 - the lower edge/surface - is shown) at or near the downstream end of which is an array of vertical vanes (12) . The vanes extend below the bottom of the duct floor il and into a "closed" drain box (13) that is sealingly mounted on the underside of the duct floor; the vojes extend into actual contact (at 14) with the bottom of the drain box. The drain box 13 has a rearward extension (15) into which flows the water (not shown) draining off the vanes 12, and at the bottom of this extension is a series of drain pipes (as 16; only two are here shown) through which the water may be lead off and disposed of. The box's rear extension 15 also has, in its upper and side surfaces, a series of plugged flushing ports (as 17) through which water, steam and so on may be forced in to help clear the box of any solids (dirt or scale) lodged therein.

Claims

1. For use in a separator of the kind described, a drain box having vanes which extend all the way to the floor of the drain box.

2. A separator drain box as claimed in Claim 1, wherein there is provided, in a direction down¬ stream of the vanes/drain box combination proper, an extension of the box which is not part of the passageway by which the filtered air is fed on and out of the assembly.

3. A separator drain box as claimed in either of the preceding Claims, wherein the drain box is underneath the duct.

4. A separator drain box as claimed in any of the preceding Claims, wherein the drain box is provided with a multiplicity of flushing ports.

5. A separator drain box as claimed in any of the preceding Claims and substantially as described hereinbefore.

6. A separator assembly having a drain box as claimed in any of the preceding Claims.