Centrifuge with a self-evacuating drum

Details Centrifuge with a self-evacuating drum Centrifuge with a self-evacuating drum

1992-08-12

1993-12-07

Jenkins, Robert W.

Imperforate bowl: centrifugal separators

Rotatable bowl

Including discharge-related structure in nature of static...

494 61, B04B 1102

Patent

active

052679373

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention concerns a centrifuge with a self-evacuating drum, with a line for feeding the drum with the stock to be centrifuged, with at least one outlet line with an elastic section for extracting a liquid phase from the drum under pressure, and with a mechanism for expelling solids from the drum at prescribed intervals.
Such centrifuges are generally known. The solids can be expelled in what are called fractional evacuations, whereby only a small fraction of the drum's contents is removed. This procedure suddenly reduces the pressure in the drum and accordingly in the outlet line, which can be detrimental to downstream equipment.
In skimming milk as described in German C 3 539 485 for example, the skimmed milk is forwarded to a heater, and heat is also transferred to the starting milk. Regulations require that the pressure at the pasteurized skim-milk end must always be higher than the pressure at the starting-milk end. This condition cannot for the aforesaid reasons be satisfied during the evacuation procedure.
A centrifuge is known from FR A 1 481 803 with a volume limiter that stretches to a certain extent in the feed line and another in at least one outlet line. The volume limiter is intended to prevent variations in the ratio between the volumes in two outlet lines when the pressure changes. These mechanisms cannot, however, compensate for a sudden reduction in pressure in an outlet line as occurs in conjunction with centrifuge drums with solids-expulsion mechanisms during the expulsion procedure. The elastic deformation of the outlet line and the associated variation in volume are so slight in relation to the materials generally employed that no effect on the pressure reduction is to be expected.
German A 2 151 475 describes a valve with a tubular diaphragm that can be subjected to external compressed air in order to vary the valve's channel and hence the rate of the fluid flowing through it. Valves of this type are also appropriate for maintaining a constant pressure in a line with a fluid flowing continuously through it. When the flow is interrupted as occurs while solids are being expelled from the drum and into the outlet lines in a centrifuge, however, such a reduction in pressure cannot be prevented.


SUMMARY OF THE INVENTION

The object of the present invention is to improve the known centrifuge such as to prevent reductions in pressure in the outlet line even while the centrifuge is being fractionally evacuated.
This object is attained in accordance with the invention in that the elastic section is accommodated in an air-tight housing, the housing communicates with a compressor through a line, and the line accommodates a valve that opens prior to every solids expulsion and subjects the elastic section to pressure from outside, compressing it in response to the reduction in pressure accompanying the solids expulsion and forcing as much product from the elastic section as solids are expelled from the drum.
The valve opens prior to fractional evacuation, subjecting the elastic section of the outlet line to pressure. When the pressure is reduced in the outlet line during the fractional evacuation, the external pressure will compress the elastic section and force out a certain volume of the product therein. The volume will equal the volume of solids expelled. These procedures will compensate for the drop in pressure.
The elastic section in one advantageous embodiment of the invention is part of a bypass line. In this event the rest of the line can be rigid, as is conventional.
Another advantageous embodiment has valves accommodated in the outlet line and the bypass line that make it possible to remove material from the centrifuge through only one of the lines. This system is of particular advantage when flushing the lines by recirculation.
When the centrifuge has another outlet line it is of advantage for the centrifuge's feed line to communicate with the second outlet line through another bypass line that accommodates a valve. In this event the valve is opened d

REFERENCES:
patent: 4631048 (1986-12-01), Titus

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