Imperforate bowl: centrifugal separators – Rotatable bowl – Having structural provision for facilitating cleaning
Patent
1986-01-15
1987-12-01
Jenkins, Robert W.
Imperforate bowl: centrifugal separators
Rotatable bowl
Having structural provision for facilitating cleaning
B04B 1506
Patent
active
047101601
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a centrifugal separator comprising a first and a second rotor part, which together surround a separation chamber, a flange portion of the first rotor part being axially inserted into a sleeve formed end portion of the second rotor part and connected thereto by means of a locking joint. The locking joint comprises at least one locking member, which from a position radially inside said sleeve formed end portion and axially outside said annular flange portion has been moved radially outwards, so that part of the locking member is located in an internal recess in the sleeve formed end portion, while the remaining part of the locking member is located radially inside the periphery of said flange portion, whereby the locking member is arranged to transmit to said second rotor part axial forces arising during operation of the rotor and acting against the inside of said first rotor part.
For interconnecting the rotor main parts of high speed centrifugal separators there are used screw joints or shear-ring joints. Among the screw joints there are principally, on the one hand, joints with a threaded locking ring and, on the other hand, joints with threaded bolts. Joints with a threaded locking ring are clearly dominating in the large group of centrifuges having no movable sludge conveyor, fo which group a conical separation chamber contour--resulting in a relatively large radius of the rotor body--is necessary for the transport of sludge to peripheral sludge outlets or nozzle openings. In a common design there is formed at the largest radius of the rotor body an internally threaded cylindrical sleeve portion, into which there is inserted a rotor cover that is locked by means of a locking ring threaded into said sleeve portion. During operation the liquid pressure in the separator will create a separating axial force on the rotor cover and the rotor body, which force has be be taken up by the thread-engagement between the locking ring and said sleeve portion, if the locking ring should not be pressed out of the sleeve portion. As said sleeve portion is also subjected to large centrifugal forces in the radial direction, which forces try to separate the sleeve portion from the locking ring, it is realized that there are extraordinary demands on correct dimensioning and on construction material for both the locking ring and the rotor body.
In the group of centrifuges named decanters, having a relatively elongated rotor body and a sludge conveyor for ter transport of sludge normally to one end of the rotor body, bolt joints are dominating for the connection of the rotor end walls to the rotor body or drum. In a conventional decanter the rotor is provided with radially outwards extending flanges at the ends, at which flanges the rotor end walls are fixed by means of a large number of bolts. The largest stress in a rotating flange joint of this kind occurs at the threaded holes in the flange, and even if the drum is made of a special casting material the flange joint itself limits the peripheral speed that can be allowed. Further, assembling and the disassembling of the rotor are time consuming operations owing to the large number of bolts and owing to security measures, for instance for the obtainment of correct tightening moments. The high load on the bolt joint in the axial as well as the radial direction leads to complicated calculations concerning tightening moment, wear of the threads, and endurance. The difficulty is highly increased with increasing peripheral speed. Besides, projecting bolts or holes for socket head cap screws at a large radius result in an annoying noise generation.
One example of a centrifugal separator, in which the rotor main parts are interconnected by means of a shear-ring joint, is shown in the U.S. specification No. 2,668,658. The shear-ring disclosed is expanded from a position radially inside of the sleeve formed end portion of the rotor body itself outwards into an internal groove therein, and is pressing the rotor cover axially against an internal shoulder
REFERENCES:
patent: 2668658 (1954-02-01), Peltzer
patent: 3408000 (1968-10-01), Nilson
patent: 4026462 (1977-05-01), Tenthoff
patent: 4067494 (1978-01-01), Willus
patent: 4464163 (1984-08-01), Heckmann
Foldhazy Zoltan
Forsberg Bjorn
Klintenstedt Kjell
Alfa-Laval AB
Hapgood Cyrus S.
Jenkins Robert W.
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