GB2353571A

GB2353571A - Mechanical seal for a pump

Info

Publication number: GB2353571A
Application number: GB0014229A
Authority: GB
Inventors: Christopher Rea; Alan Roddis
Original assignee: AES Engineering Ltd
Current assignee: AES Engineering Ltd
Priority date: 1999-06-11
Filing date: 2000-06-12
Publication date: 2001-02-28
Also published as: GB9913579D0; GB0014229D0

Abstract

A mechanical seal between a shaft 6 and the casing 3 of a pump is positioned such that components of the seal can be replaced from the front of the pump, without the casing having to be removed. Bolts connecting a gland 7 to the casing may also be accessible from the front (Fig. 6). The seal may be a double instead of a single seal.

Description

2353571 Mechanical Seals This invention relates to mechanical seals and

especially mechanical seals fitted on mechanical equipment such as pumps or mixers.

A mechanical seal comprises a "floating" component which is mounted axially movably around the rotary shaft of, for example, a pump and a "static" component which is axially fixed, typically being secured to a housing. The floating component has a flat annular end face, ie its seal face, directed towards a complementary seal face of tile static component. The floating component is urged towards the static component to close the seal faces together to form a sliding face seal, usually by means of one or more springs. In use, one of the floating and static components rotates; this component is therefore referred to as the rotary component. The other of the floating and'static components does not rotate and is referred to as the stationary component.

those seals whose floating component is rotary are described as rotary seals. If the floating component is stationary, the seal is referred to as a stationary seal.

If the sliding seal between the rotary and stationary components are assembled and pre-set prior to despatch from the mechanical seat manufacturing premises, the industry terminology for this is "cartridge seal". If the rotary and stationary components are despatched individually (unassembled) from the mechanical seal manufacturing premises, the industry terminology for this is "component seal".

Mechanical seals are commonly fitted to process equipment such as pumps, however, on certain types of machinery their installation can often be difficult and time consuming, due to the prevalent equipment design.

1 The design of a mechanical seal which eliminates/simplifies the number of components which are required for fitting or dis-assembling of such equipment is therefore thought to be advantageous, due to the respective time and cost savings.

By way of example only, a prior art seal/equipment design which could be suggested to be difficult and time consuming to disassemble is illustrated, in Figure 1.

Figure I illustrates a partial section of a rotary lobe pump and seal arrangement.

Briefly outlined, the following actions are typically required in order to replace, or remove a mechanical seal; Removal of cover plate (1) and retaining ring (2), then outer casing (3). This allows the seal (4) to be removed, once released from the shaft (5). The industry terminology for this type of seal arrangement is "rear mounted", as the seal (4) can only be removed once the outer casing (3) is removed.

Frequently, the outer casing (3) is large and cumbersome to remove/replace therefore the elimination of this procedure, offers a wide range of benefits including reduced equipment/process downtime, reduced labour costs and more reliable seal installation.

The present invention is described by way of example only wit reference to the accompanying drawings in which:- Figure 2 is a longitudinal cross section through a single rotary cartridge mechanical seal of the invention, in situ on an item of mechanical equipment.

Figure 3 is a longitudinal cross section through a double rotary cartridge mechanical seal of the invention, in situ on an item of mechanical equipment.

2 Figure 4 corresponds to figure 2 and is a partial longitudinal cross section through single rotary cartridge mechanical seal with a back bolted gland arrangement, of the invention.

Figure 5 is a partial longitudinal cross section through single rotary component mechanical seal of the invention.

It is considered self evident to the experienced reader that the invention may be employed for both rotary seals and stationary seals, and/or, for single mechanical seals and triple mechanical seals as well as double/tandem mechanical seals, whether designed in a cartridge or component seal format. It is also consider self evident that the invention may be used with metallic components as well as non-metallic components.

Figure 6 corresponds to figure 4, and illustrates a single rotary cartridge mechanical seal with a front bolted gland arrangement, of the invention.

Figure 4 therefore shows a single rotary cartridge mechanical seal according to the invention. The seal is a cartridge seal and comprises of a stationary component (1) and a rotary component (2) which defines a seal face (3) which in turn forms a sliding seal with the stationary component (1).

The rotary component (2) is disposed radially outwardly of rotary member (5), which is a sleeve fixed for rotation with a rotary shaft (6) of an item of mechanical equipment.

The stationary component (1) is sealed to stationary, radially outwardly disposed gland (7) using stationary elastomer (8). The gland is secured to the equipment outer casing (10) using bolts (9).

3 It is considered self evident that the gland (7) may be shaped in any form so that it facilitates seal installation, and/or it optimises the seal face (3) environment.

Increasing the volume of processed product around the seal faces is thought to be 5 advantageous as this facilitates seal face cooling and heat distribution, hence helps to pro-long seal survival.

By way of example, Figure 7 illustrates a mechanical seal gland, of the invention, with integral flow breakers.

As a shaft (6) rotates, solids present in the sealed product are subjected to centrifugal forces and therefore can rapidly wear stationary and/or rotary components. A gland (7) with flow breakers machined or affixed, help to disrupt the said centrifugal action hence help to prolong seal survival.

The seal design shown in Figure 4 to front mounted, and therefore may be removed from the equipment shaft (6), without the need for removing the equipment outer casing (10).

Thus in use the stationary component is adjacent the gland whilst the rotary component is adjacent the drive end of the rotary shafL In the prior art the stationary component is adjacent the drive end of the rotary shaft and the rotary component is distal. of the drive end.

30P15565 1 4

Claims

1. A mechanical seal design which is adapted to be front mounted.

2. A mechanical seal according to claim 1 characterised in that the seal comprises a floating component and a stationary component.

3. A mechanical seal according to claim 1 characterised in that in use, the seal is retained in position by a seal gland.

4. A mechanical seal according to claim 3 characterised in that the seal gland is adapted to engage the stationary component.

5. A mechanical seal according to claim 1 characterised in that the gland is 15 provided with at least one integral flow breaker.

6. A mechanical seal according to claim 1, characterised in that the seal is provided with an integral wear plate.

7. A mechanical seal, according to claim 1 characterised in that the integral wear plate is secured to the seal gland.

8. A mechanical seal according to claim 7 characterised in that integral wear plate is secured between the gland and the stationary component.

9. A mechanical seal according to claim 8 characterised in that the integral wear plate comprises an elastomer.

10. A mechanical seal according to claim 1 characterised in that it is a component 30 seal, 4 4.

11. A mechanical seal according to claim 1 characterised in that it is a cartridge seal.

12. A seal gland which is adapted to be front mounted for use with a mechanical seal.

13. A seal gland according to claim 11 characterised in that the gland is provided with at least one integral flow breaker.

14. A seal gland according to claim 1 characterised in that the seal is provided with an integral wear plate.

15. A method of sealing a rotary shaft which comprises the use of a seal according to claim 1.

16. A mechanical seal substantially as described with reference to the accompanying drawings. 20 30 35P15565 6