CA1248070A

CA1248070A - Sealing ring for a centrifugal separator

Info

Publication number: CA1248070A
Application number: CA000454247A
Authority: CA
Inventors: Jan Munde
Original assignee: ALFA-LAVAL Ltd
Current assignee: ALFA-LAVAL Ltd
Priority date: 1984-05-14
Filing date: 1984-05-14
Publication date: 1989-01-03

Abstract

ABSTRACT OF THE DISCLOSURE
A sealing ring for sealing between two axially relatively movable parts of the rotor of a centrifugal separator, and which has edges bevelled such that is can be impressed in its sealing surface only when the recesses formed by the bevelling have been filled up by material from the sealing ring as a result of plastic deformation of the latter by compression between the rotor parts.

Description

The present invention relates to a sealing ring for place-ment in an axially open groove in a first rotor part of a centri-fugal separator of the type having a second rotor part, which is axially movable relative to the first rotor part and arranged to be moved into and out of abutment against said sealing ring placed in the groove via an annular projection, which is narrower than said groove in the first rotor part.
A sealing ring of this type is subjected to heavy compres-sion between the two rotor parts, which are axially movable rela-tive to each other. As a result of this the sealing ring is rather quickly impressed, i.e. plastically deformed by the annular pro-jection of the second rotor part. After some operation time, dur-ing which the rotor parts have been axially moved a number of times relative to each other into and out of sealing engagement via the sealing ring, the impression of the sealing ring has become so extensive that the sealing ring has to be replaced.
The present invention provides an arrangement by means of which the problem of impression of sealing rings of the above desc-ribed kind is considerably reduced.
According to the present invention there is provided a sealing ring for placement in an axially open groove in a first rotor part of a centrifugal separator of the type having a second rotor part which is axially movable relative to the first rotor part into and out of abutment against said sealing ring placed in said groove via an annular projection, which is narrower than said groove, the edges of the sealing riny on each side of the surface with which the sealing ring abuts the projection of the second rotor part, are bevelled to such a degree that the annular surface of the projection, adjacent the sealing ring, has a radial extension at least as large as that of the sealing ring surface between the bevels.

Thus, according to the invention, by only a minor change Q~

~2~

of the design of the sealing ring, namely such than the edges of the sealing ring on each side of the surface, by which the sealing ring abuts the projection of the second rotor part, are bevelled .o such a degree that the annular surface of the projection, loca-ted nearest the sealing ring, has a radial extension which is at least as large as that of the sealing ring surface between the bevels. The bevel is preferably such that the annular surface of the projection has a larger radial extension than the sealing ring surface remaining between the bevels.
By designing sealing rings in this way an essentially d^uble life-time has been verified by tests for the sealing rings.
In one case, for instance, it has been possible to prolong the operational time of a centrifugal separator from 1000 to 2000 hours before replacement of the sealing ring has been necessary.
The present invention will be further described more in detail below with reference to the accompanying drawing, in which:-Figure 1 is a section through part of a centrifugalseparator with a sealing ring;
Figure 2 are sections through a sealing ring designed in a conventional manner, before and after impression; and Figure 3 is a section of a sealing ring according to one embodiment of the present invention.
Figure 1 shows a part of a centrifugal separator compris-ing a lower rotor part 1 and an upper rotor par$ 2, which are axially joined by a lock ring 3. The axis of the rotor is denoted by a dash-dot line 4. In a downwardly open annular groove in the upper rotor part 2 there is disposed a sealing ring 5. Abutting sealing rings is an annular projection 6 o~ a slide member 7, which is axially mQvable relative to the ro~or parts 1 and 2. Bet~een the slide member 7 and the upper rotor part 2 there is a separation chamber 8, in which a set of conical separation plates 9 is arranged. The separation chamber 8 has an inlet 10 for a mixture of liquid and 7~

sludge to be separated. ~etween the slide member 7 and the lower rotor part 1 there is a chamber 11, which during operation of the rotor is charged and kept filled with liquia, usually water. By the rotation of the rotor a liquid pressure is created in the chamber 11, which forces the slide member 7 into sealing contact wi~h the sealing ring 5 against the pressure from the mixture of sludge and liquid present in the separation chamber 8. Sludge 12 is separated in the separation chamber 8.
Liquid freed from sludge 12 leaves the separation chamber 8 through an outlet (not shown) radially inside the set of plates 9. I~hen desired, the supply of liquid to the chamber 11 is tempor-arily cut off, the chamber 11 being drained via a plurality of throttled peripheral outlets 13. The slide member 7, thereby, will be forced downwards by the pressure of the contents of the separation chamber 8, and the separated sludge will be thrown out through a plurality of peripheral outlets 14. Dependi ng on the length of the time period, during which the supply of liquid to the chamber 11 is cut off, more or less of the contents of the separation chamber 8 will be thrown out through the outlets 14.
In Figure 2 at a there is shown a sealing ring 5 of con-ventional design as it appears in a newly manufactured condition.
After some operation time of a centrifuge rotor according to Figure 1 a sealing ring of this kind has assumed a shape as that illustra-ted at b. This is because it has been impressed, i.e. plastically deformed, by the projection 6 of the slide member 7, lips 15 having been formed therein. If such an impression is allowed to proceed too far, the sealing ability of the sealing ring 5 may be los-t by a piece of a lip 15 being bent inwardly and being squeezed between the sealing surfaces of the ring 5 and the projection 6, respect-ively, in connection with sludge discharge through the outlets 14.
There is also a risk -than an insufficient gap would be provided between the sealing ring 5 and the projection 6 for separated sludge ~2~1307~
to leave the separation chamber 8.
To avoid this and to ~rolong the life-time of the sealing ring the sealing ring may be as shown in Figure 3. ~ere a seal-ing ring 5a is disposed in the aforesaid groove in the rotor part

2. The size of the flat surface 16 of the sealing ring facing away from the groove has, in this embodiment, been reduced by bevelling of the sealing ring edges at 17. The bevels 17 are such that the flat surface 16 has a somewhat smaller radial extension than the flat surface 18 of the projection 6 facing the sealing ring 5a. As shown, the surface 16 of the sealing ring 5a is loca-ted at a level somewhat axially outside the groove in the rotor part 2, so that a sufficient gap can be created for unobstructed passage of sludge between the rotor part 2 and the projection 6 even after a certain plastic deformation of the sealing ring 5a has occurred.
After some operation time a sealing ring 5a according to Figure 3, has assumed substantially the same form as a sealing ring 5 of conventional design according to Figure 2a. After some fur-ther time the sealing ring 5a will have the same form as illustrated in Figure 2b. The total time of operation, during which a sealing ring 5a according to the invention can be used, is approximately twice as long as the corresponding time of operation for a sealing ring of conventional design.
The present invention has been defined to mean bevelling of the sealing ring edges on each side of the surface 16, with which the sealing ring abuts the projection 6. By the expression bevell-ing in this connection it shall be understood any recessing action giving as a result that the recess i.s filled up with material from the sealing ring, when the sealing ring is plastically deformed by compression between the rotor parts 2 and 7 during the operation of the centrifugal separator.

Claims

THE EMBODIMENT OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A sealing ring for placement in an axially open groove in a first rotor part of a centrifugal separator of the type having a second rotor part which is axially movable relative to the first rotor part into and out of abutment against said sealing ring placed in said groove via an annular projection, which is narrower than said groove, the edges of the sealing ring on each side of the surface with which the sealing ring abuts the projec-tion of the second rotor part, are bevelled to such a degree that the annular surface of the projection, adjacent the sealing ring, has a radial extension at least as large as that of the sealing ring surface between the bevels.

2. A sealing ring according to claim 1, in which the annular surface of the projection has a larger radial extension than the sealing ring surface between the bevels.

3. In a centrifugal separator of the type having an axially open groove and a first rotor part having a sealing ring disposed therein and a second rotor part axially movable relative to the first rotor part, into and out of abutment with said seal-ing ring via an annular projection which is narrower than said groove the improvement in which the sealing ring is as in claim 1 or 2.