WO2003058098A1

WO2003058098A1 - An expeller device

Info

Publication number: WO2003058098A1
Application number: PCT/GB2003/000091
Authority: WO
Inventors: Alan Roddis
Original assignee: Aes Engineering Ltd
Priority date: 2002-01-14
Filing date: 2003-01-14
Publication date: 2003-07-17
Also published as: WO2003058098A9; AU2003202009A1; GB0200695D0

Abstract

A roating expeller ring (17) for use with a mechanical seal, comprises at least one spiral channel (26) and at least one convex, concave or tapered outer peripheral surface (25). It helps to protect the mechanical seal by preventing the slurry particles from entering the stuffing box or seal chamber adjacent to the seal.

Description

An Expelier device

Rotating equipment is used to process a variety of liquids in practically every industrial sector.

The present invention relates to an expelier ring, more particularly, an expelier ring which can be applied to the stuffing box or seal chamber of any centrifugal pump or piece of rotating equipment.

Often, rotating equipment is used to process slurries, or process media, which contains particles. Commonly, rotating equipment is sealed using mechanical seals. Often, in slurry applications, the slurry media can damage a mechanical seal, causing premature seal leakage.

A design, which helps to extend mechanical seal life in such applications, is considered particularly advantageous.

Preferably, although not essentially, the invention may be used in conjunction with a mechanical seal. The present invention helps to protect the mechanical seal by preventing the slurry particles from entering the stuffing box or seal chamber adjacent to the seal.

Mechanical seals are required to seal a variety of seal chamber pressures. Often, the lower the seal chamber pressure, the easier an application is to seal. Furthermore, in general, as the sealing pressure increases, the cost of the mechanical seal increases.

A further advantage of the invention is that it helps to reduce the operating pressure in the stuffing box or seal chamber, allowing the mechanical seal to work in a more pleasant environment. An expelier ring is a device used to throw back the slurries entering the seal chamber of a centrifugal pump or piece of rotating equipment. Such rotating pieces of rotating equipment are used in industries like chemical process, petrochemicals, fertilisers, refineries, alumina plants, ash handling plants and paper / pulp mills.

The general industry term which defines the area adjacent to the process media is "inboard". The industry term which defines the area adjacent to the atmospheric side is "outboard".

Figure 1, shows a cross sectional -view of a conventional prior art single cartridge mechanical seal fitted to a rotating piece of equipment.

Figure 2, shows a cross sectional view of an expelier ring and mechanical seal fitted on the rotating piece of equipment.

Figure 3, shows a cross sectional view of an alternative clamping arrangement of the expelier ring of the invention.

Figure 4, shows a cross sectional view of an alternative rotational drive arrangement of the expelier ring of the invention.

Figure 5, shows an end view of an expelier ring of the invention.

Figure 6, shows a cross sectional view of a series of expelier rings fitted on the rotating piece of equipment, without the mechanical seal.

Figure 7, shows a cross sectional view of at least one pair of expellers with counter spiral channels.

Figure 8, shows a cross sectional view of a mechanical seal with an integral expelier ring. Figure 9, shows an end view of an alternative expelier ring of the invention.

Figure 10, shows a cross sectional view of an alternative expelier ring of the invention, showing, by way of example only, a convex outer radial periphery

Figure 11, shows a cross sectional view of an alternative expelier ring of the invention, showing, by way of example only, a spiral channel with a channel depth which changes around the circumference of the spiral.

Figure 12, shows a cross sectional view of an alternative expelier ring of the invention, showing, by way of example only, a spiral channel with a channel base which is inclined relatively parallel to the periphery.

Figure 13, shows a cross sectional view of an alternative expelier ring of the invention, showing, by way of example only, a tandem expelier.

Figure 14, shows a cross sectional view of an inverse expelier ring mounted to a rotating housing which rotates around a stationary shaft.

From Figure-1, the rotary and axially floating mechanical seal face (1) is spring biased towards a static stationary seal face (2). The rotary seal face (1) is allowed to slide on the static seal face (2). The interface between the rotary seal face (1) and stationary seal face (2) forms sealing area (3). This sealing area (3) is the primary seal that prevents the process media (4) from escaping from the process chamber (5).

In addition to the sliding seal face (3), the process media (4) is sealed by a sleeve elastomer (6) in contact with the shaft (7) and sleeve (8). This has been termed the first secondary sealing area (9).

The second secondary sealing area (10) is formed between stationary seal face (2) and stationary gland (11) using elastomer (12).

The third secondary sealing area (13) is formed between the rotary seal face (1) and the sleeve (8) using elastomer (14).

The fourth secondary sealing area (15) is formed between the gland (11) and the process chamber (5) using gasket (16).

The four secondary sealing devices and ^"the primary sliding sealing interface prevent the process media (4) from escaping. The remaining parts of the mechanical seal will not be further explained.

It may be seen from Figure-1, that should the process media (4) contain solids, said solids could damage or break the seal area (3). This is a particular problem in some industrial applications.

Figure-2, corresponds to Figure-1, in that the mechanical seal and sealing elements remain unchanged.

From Figure 2, an expelier ring (17) is positioned between the mechanical seal (18) and rotating equipment impeller (19).

The expelier ring (17) is rotatably driven by the shaft (7) by a suitable means. Figure-2 shows the expelier ring (17) clamped between the shoulder (20) of the shaft (17) and the impeller (19). The outer most radial surface of the expelier ring (17) is in close proximity to the process chamber (5) inner radial surface. Said close proximity is not less radially than 0.001" (0.025mm) and preferably not more than 0.500" (12.7mm). The expelier ring (17) has at least one spiral channel (26) which is adjacent and preferably faces the process media (4) and rotating equipment's impeller (19). The base of the spiral channel (26) is relatively parallel to the axis of rotation of the rotating equipment.

Figure-3 shows an alternative rotating drive / clamping arrangement of the expelier ring (17) using at least one setscrew (21). Preferably more than one setscrew (21) is used. Said setscrews (21) are circumferential spaced on expelier (17) and radially engage to the shaft (7). This secures expelier (17) to shaft (7) in both an axial and rotational manner.

Figure-4 shows an alternative rotating ^"drive arrangement of the expelier ring (17) using key (22). Said Key (22) engages in slot (23) of the expelier (17) and slot (24) of the shaft (7). Said key (22) transmits rotational drive from the shaft (7) to the expelier (17).

It is considered self-explanatory that said expelier to shaft clamping and / or rotational transmission could be achieved by any suitable means including mechanical means, chemical means or thermal means. It will be further appreciated that the preferable clamping means will allow the component to be easily detached from the shaft for refurbishment or replacement.

From Figure 2, the expelier ring (17) has a tapered surface (25) on the outer radial periphery. On the circumference of the tapered surface lies a spiral channel (26) as shown in Figure-5. Said channel (26) spirals in either a clockwise or counter-clockwise direction depending on the direction of shaft rotation.

It has been found that when the shaft (7) rotates, the expelier (17) repels or expels the process media solids away from the mechanical sealing area (3). This helps to extend the mechanical seal life. It should be noted that the expelier (17) may be manufactured from a material that is compatible with pumping media. Furthermore, should it be appropriate, the expelier (17) could be offered in more than one material, either of which may be suitably surface treated to extend expelier (17) life.

Figure-6 illustrates a series of expelier rings (17) of the invention. In some applications the effect of the invention can be such that it is not necessary to seal the rotating piece of equipment with a mechanical seal. This has obvious benefits.

Furthermore, the placing of the expelier ring (17) in series has a similar effect to that of a multi-stage device, in that the pressure and / or fluid particles can be precisely controlled. This has obvious benefits when used with a mechanical seal.

It will be apparent to an experienced reader, that the modular nature of the expelier rings (17) allows a user to place them in any number of combination / orientations. For example only, Figure-7 illustrates one such combination. The inboard expelier ring (17) has a clockwise direction spiral channel (26) and the outboard expelier (27) has an counter clockwise direction spiral channel (28). This allows the invention to work irrespective of shaft (7) rotation.

Furthermore, it will be apparent that the invention can be an integral part of the mechanical seal. Figure-8 illustrates the spiral channel (29) in the end of the cartridge sleeve (30) of the mechanical seal (31).

By way of example only, Figure 9 illustrates an alternative spiral channel (32) of the invention.

It will be noted that the radial periphery of the expelier ring can be changed to suit a particular application. Preferably the outer radial surface is concave, however Figure-10 illustrates a convex (33) outer rad&l surface. Said convex (33) surface may have any suitable curve, ) or hybrid curve to suit a particular application.

Figure-11 illustrates an expelier ring with a concave (34) outer radial surface. Said concave (34) surface is designed to displace the process fluid in the most effective and efficient manner. Further shown is a spiral channel (35) with a larger channel depth (36) towards the inner most radial point and a smaller channel depth (37) towards the outer most radial point. .

From Figure-12, it will be noted that the channel depth may equally remain constant however the base (38) of the channel may be inclined, preferably relatively parallel to the outer periphery (39).

In certain restricted space applications, it may be necessary to offer more than one concave, convex or tapered outer peripheral in a hybrid expelier ring. By way of example only, this is shown in Figure- 13.

It is considered self evident to the experienced reader that the invention may be employed for rotating equipment whose shaft rotates and housing remains stationary, or where the housing rotates and the shaft remains stationary. This inverse expelier ring (40) is shown in Figure-14.

It is further considered self evident that the invention may be used in conjunction with a mechanical seal, or by itself. More than one expelier rings may be used in series or a tandem arrangement, or to that matter any combination of orientations.

The invention may be an individual unit with more than one expelling surface, or an integral unit part of a mechanical seal or other similar device.

A skilled person will note that the invention does not rely on a specific and complex profiled housing or seal chamber of a piece of rotating equipment. It therefore can be applied to seal chambers that are relatively parallel to the axis of rotation. This allows the invention to be applied to standard pieces of rotating equipment without modification. This has obvious commercial advantages.

A further commercial advantage is realised in certain applications as costly double mechanical seals can be replaced by the invention and a single seal. This is deemed to be particularly advantageous given the fact that double seals also require comprehensive and costly seal support systems.

Claims

Claims : An expelier ring, which comprises of at least one spiral channel which rotates with an item of rotating equipment.

An expelier ring according to claim 1, where the expelier ring has at least one convex, concave or tapered outer peripheral surface.

An expelier ring according to claim 1 or claim 2, where the expelier ring has a spiral channel base that is relatively parallel to the axis of rotation of the rotating equipment.

An expelier ring according to claim 1 or claim 2, where the expelier ring has a spiral channel base that is relatively parallel to the outer peripheral surface.

An expelier ring according to any preceding claims, where the expelier ring incorporates a suitable drive device to transmit rotational movement from the rotatable equipment.

An expelier ring according to any preceding claims, where the expelier ring is preferably positioned between a mechanical seal and impeller of a rotating piece of equipment.

An expelier ring according to any preceding claims, where the expelier ring incorporates a suitable axial positioning clamping device.

An expelier ring according to any preceding claims, where the expelier ring is may be infinitely positioned in a direction parallel to the axis of rotation of the rotating equipment. An expelier ring according to any preceding claims, where the expelier ring is positioned inside a process or seal chamber of an item of rotating equipment.

An expelier ring according to any preceding claims, where the expelier ring has a radial clearance between the outer most part of the expelier ring and inner most part of the process chamber, of no less than 0.001" (0.025mm) and preferably not more than 0.500" (12.7mm).

An expelier ring according to any preceding claims, where the expelier is manufactured from more than one material.

An expelier ring according to any preceding claims, where more than one expelier rings can be mounted in series, tandem, back to back, or any combination of orientations.

A mechanical seal according to any preceding claims, where the expelier ring features are an integral part of the mechanical seal.

A mechanical seal according to any of the preceding claims substantially as described here with reference to Figures 2 to 14 of the accompanying drawings.

A mechanical seal according to claim 1 and claim 2 and substantially as herein described.