GB2190009A

GB2190009A - Centrifuge drum for an centrifuge drum

Info

Publication number: GB2190009A
Application number: GB08710243A
Authority: GB
Inventors: Heinz Houben
Original assignee: Fried Krupp AG
Current assignee: Fried Krupp AG
Priority date: 1986-05-02
Filing date: 1987-04-30
Publication date: 1987-11-11
Anticipated expiration: 2007-04-30
Also published as: SE500484C2; GB2190009B; GB8710243D0; FR2606295B1; SE8701101D0; SE8701101L; FR2606295A1; DE3614965A1

Abstract

The drum for an intermittently operating sugar centrifuge comprises a drum shell (3) having a bottom (4) and cover (5) attached thereto. The drum shell ends have welded-on rings (8, 9) to which the drum bottom (4) and cover (5) are screwed. The shell and rings are made of similar high quality steel, while the bottom and cover are of cheaper steel. <IMAGE>

Description

SPECIFICATION Centrifugedrum for an intermittently operating flat-bottom centrifuge The invention relates to a centrifuge drum for an intermittenly operating flat-bottom centrifuge, more particularly a sugar centrifuge, comprising a cylindrical drum shell of rust-resisting material which has bores and an attached drum bottom and cover.

For reasons of corrosion and strength the shells of centrifuge drums of the kind specified are made from high quality austenitic-ferritic materials, the drum bottoms and covers being made from ferritic materials,for reasons of cost. The bottom and cover are welded on to the drum shell.

In welding the construction it has in the past been found that the welded connection between the drum shell and its cover and bottom causes trouble as regards the change in the direction of the rolling fibre as between the shell and the cover and also the shell and the bottom. In the case of a mechanically processed bottom (produced, for example, from a sheet metal round) or a plastically deformed cover the rolling direction ofthe fibre of cover and bottom is radial. Following the welding operation, separations taking the form of hair cracks mainly extending peripherally of the shell may occur at the end surfaces of both the cover and the bottom. Such separations in the crystal line structure ofthe cover and bottom weaken the structure and are, for example, a cause for the rejection ofsugar centrifuges in manufacturing tests.See "Herstellungs- und Prüfgrundsätzen der Zuckerberufsgenossenschaft" vom Oktober 1986.

Afurther difficulty is that of making a welded joint between different materials.

The aforementioned Regulations prescribe for newly produced centrifuge drums the round seams betweenthe drum shell and coverandthe drum shell and bottom to be one hundred percent.

In the meantime, in-service testing underthe above-mentioned regulations have shown that after several years of operation the round seam on the side of the ferritic materiai -- i.e., on the cover or bottom side-- may be damaged by corrosion.

It is an object ofthe invention to obviate the difficulties concerning the manufacture,testing and durability of centrifuge drums with special steel shells and to provide an inexpensive centrifuge drum having a longer service life.

To this end according to the invention welded on to each ofthetwo ends ofthe drum shell is a ring of rust-resisting material to which the drum bottom and cover are screwed.

The cylindrical drum shell, which has a constant wall thickness throughout, has at each end a ring madefrom the same orsome similar material tothe shell.The partnermaterials ofthe drum shell and the rings are so designed that no corrosion can occur at the weld seam when the centrifuge is operated fill with massecuitThe ringsweldedto the drum shell andthe subsequent screwed connection of the drum bottom and cover results in the advantage that the bottom and cover can be made from a lower quality material withouttheoccurance of corrosion problems.

Another advantage ofthe centrifuge drum accord ing to the invention lies in the very simple mechanical after-machining ofthe weld seam from the inside, so that very simple tools and methods can be adopted.

The design according to the invention obviates the necessity of making the drum bottom and cover from a rust-resisting material, since the welded connection to be tested between the drum shell and the ring is no longer subjectto corrosion. A sealing element, for example, can be used to prevent gap corrosion between the rings and drum bottom and cover.

For reasons of strength and rigidity,with a centri fuge drum having a conical bottom, according to the invention the drum is constructed with an angle of inclination a to the horizontal of preferably 10 . In addition to the advantages regarding strength and rigidity, such an angle of inclination has a further advantage in the clearance ofthe centrifuged sugar filling from the centrifuge drum.

Otherfeatures ofthe invention are characterized in

the subclaims.

An embodiment ofthe invention will now be described in greater detail with reference to the drawings, wherein: Fig. lisa cross-section, and Fig. 2 shows a detail.

Fig. 1 shows only half of the embodiment of a centrifuge drum 1 with its axis 2. The drum comprises mainly a drum shell 3 and a bottom 4and cover 5.

According to the invention rings 8 and 9 are welded to the end surfaces 6 and 7 ofthe drum shell 3. The shell and rings are made ofthe same ora similar material, so thattheweld seams 16 and 17 make no particular demands. The rings 8 and 9 have screwthreaded bores 10 and 11, whilethe drum bottom 4 and cover 5 havethrough bores 13,sothatthedrum bottom4and cover 5 can be screwed tothe drum shell 3 by means of screws 14 and 15.

Seals 18 and 19 are inserted between the rings 8 and 9 and the drum bottom 4 and cover 5 respectively to avoid gap corrosion. Known bores 20 of such centrifuges are provided. The drum bottom 4 is formed with a recess 21 into which the ring 8 is let in, so that a smooth surface 23 is formed between the ring 8 and the drum bottom 4. As a result a scraper (not shown) can readily peel the drycentrifuged sugar off and remove it via inclined face 24 of the bottom 4. The face 24 ofthe drum bottom 4 is inclined by an angle oc in relation to the horizontal surface 23. The width ofthe rings 8 and 9 has the reference (b). The rings 8 and 9 are formed in the radial direction with a width (b) which is very small in comparison with the drum diameter. The rings need only be wide enough as to adequately guarantee the attachment of the drum bottom and cover.

The inner edge of the upper ring 9 has a chamfer25.

The corner in the upper part of the centrifuge drum 1 resulting from the ring 9 can readily be cleared by an appropriately shaped peeling blade of the scraper (not shown).

CLAIMS 1. Acentrifuge drum for an intermittently operat ing flat-bottom centrifuge, more particularly a sugar centrifuge, comprising a cylindrical drum shell of rust-resisting material which has bores and an

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Centrifugedrum for an intermittently operating flat-bottom centrifuge The invention relates to a centrifuge drum for an intermittenly operating flat-bottom centrifuge, more particularly a sugar centrifuge, comprising a cylindrical drum shell of rust-resisting material which has bores and an attached drum bottom and cover. For reasons of corrosion and strength the shells of centrifuge drums of the kind specified are made from high quality austenitic-ferritic materials, the drum bottoms and covers being made from ferritic materials,for reasons of cost. The bottom and cover are welded on to the drum shell. In welding the construction it has in the past been found that the welded connection between the drum shell and its cover and bottom causes trouble as regards the change in the direction of the rolling fibre as between the shell and the cover and also the shell and the bottom. In the case of a mechanically processed bottom (produced, for example, from a sheet metal round) or a plastically deformed cover the rolling direction ofthe fibre of cover and bottom is radial. Following the welding operation, separations taking the form of hair cracks mainly extending peripherally of the shell may occur at the end surfaces of both the cover and the bottom. Such separations in the crystal line structure ofthe cover and bottom weaken the structure and are, for example, a cause for the rejection ofsugar centrifuges in manufacturing tests.See "Herstellungs- und Prüfgrundsätzen der Zuckerberufsgenossenschaft" vom Oktober 1986. Afurther difficulty is that of making a welded joint between different materials. The aforementioned Regulations prescribe for newly produced centrifuge drums the round seams betweenthe drum shell and coverandthe drum shell and bottom to be one hundred percent. In the meantime, in-service testing underthe above-mentioned regulations have shown that after several years of operation the round seam on the side of the ferritic materiai -- i.e., on the cover or bottom side-- may be damaged by corrosion. It is an object ofthe invention to obviate the difficulties concerning the manufacture,testing and durability of centrifuge drums with special steel shells and to provide an inexpensive centrifuge drum having a longer service life. To this end according to the invention welded on to each ofthetwo ends ofthe drum shell is a ring of rust-resisting material to which the drum bottom and cover are screwed. The cylindrical drum shell, which has a constant wall thickness throughout, has at each end a ring madefrom the same orsome similar material tothe shell.The partnermaterials ofthe drum shell and the rings are so designed that no corrosion can occur at the weld seam when the centrifuge is operated fill with massecuitThe ringsweldedto the drum shell andthe subsequent screwed connection of the drum bottom and cover results in the advantage that the bottom and cover can be made from a lower quality material withouttheoccurance of corrosion problems. Another advantage ofthe centrifuge drum accord ing to the invention lies in the very simple mechanical after-machining ofthe weld seam from the inside, so that very simple tools and methods can be adopted. The design according to the invention obviates the necessity of making the drum bottom and cover from a rust-resisting material, since the welded connection to be tested between the drum shell and the ring is no longer subjectto corrosion. A sealing element, for example, can be used to prevent gap corrosion between the rings and drum bottom and cover. For reasons of strength and rigidity,with a centri fuge drum having a conical bottom, according to the invention the drum is constructed with an angle of inclination a to the horizontal of preferably 10 . In addition to the advantages regarding strength and rigidity, such an angle of inclination has a further advantage in the clearance ofthe centrifuged sugar filling from the centrifuge drum. Otherfeatures ofthe invention are characterized in the subclaims. An embodiment ofthe invention will now be described in greater detail with reference to the drawings, wherein: Fig. lisa cross-section, and Fig. 2 shows a detail. Fig. 1 shows only half of the embodiment of a centrifuge drum 1 with its axis 2. The drum comprises mainly a drum shell 3 and a bottom 4and cover 5. According to the invention rings 8 and 9 are welded to the end surfaces 6 and 7 ofthe drum shell 3. The shell and rings are made ofthe same ora similar material, so thattheweld seams 16 and 17 make no particular demands. The rings 8 and 9 have screwthreaded bores 10 and 11, whilethe drum bottom 4 and cover 5 havethrough bores 13,sothatthedrum bottom4and cover 5 can be screwed tothe drum shell 3 by means of screws 14 and 15. Seals 18 and 19 are inserted between the rings 8 and 9 and the drum bottom 4 and cover 5 respectively to avoid gap corrosion. Known bores 20 of such centrifuges are provided. The drum bottom 4 is formed with a recess 21 into which the ring 8 is let in, so that a smooth surface 23 is formed between the ring 8 and the drum bottom 4. As a result a scraper (not shown) can readily peel the drycentrifuged sugar off and remove it via inclined face 24 of the bottom 4. The face 24 ofthe drum bottom 4 is inclined by an angle oc in relation to the horizontal surface 23. The width ofthe rings 8 and 9 has the reference (b). The rings 8 and 9 are formed in the radial direction with a width (b) which is very small in comparison with the drum diameter. The rings need only be wide enough as to adequately guarantee the attachment of the drum bottom and cover. The inner edge of the upper ring 9 has a chamfer25. The corner in the upper part of the centrifuge drum 1 resulting from the ring 9 can readily be cleared by an appropriately shaped peeling blade of the scraper (not shown). CLAIMS

1. Acentrifuge drum for an intermittently operat ing flat-bottom centrifuge, more particularly a sugar centrifuge, comprising a cylindrical drum shell of rust-resisting material which has bores and an attached drum bottom and cover, in which a ring of rust-resisting material to which the drum bottom and coverarescrewed, is welded onto each ofthetwo ends ofthe drum shell.

2. A centrifuge drum according to Claim 1, in which the ratio ofthewidth ofthe rings to the thickness ofthe drum shell is from 3:1 to 1:6.

3. A centrifuge drum according to either of Claims 1 and 2 having a conical drum bottom, which is constructed with an angle of inclination to the horizontal of 5to 15 , preferably 10 .

4. A centrifuge drum according to any one of the preceding Claims, in which the drum bottom and cover are made from a ferritic material.

5. A centrifuge drum according to any one ofthe preceding Claims, in which the rings are forged from a forgeable material.

6. A centrifuge drum accordingto any one ofthe preceding Claims, in which the drum bottom and cover are each formed with a recess for receiving the rings.

7. A centrifuge drum according to Claim 6, in which the depth ofthe recess in the drum bottom is such thatthe surfaces of the ring and the drum bottom form a smooth face.

8. Acentrifuge drum according to anyone ofthe preceding Claims, in which a seal is inserted between the rings and the drum bottom and cover.

9. A centrifuge drum according to any one of the preceding Claims, in which the innerfree edge of the ring associated with the drum cover is chamfered.

10. A centrifuge drum according to any one of the preceding Claims, in which the rings are L-shaped, the minor arm being associated with the drum shell.

11.- A centrifuge drum according to Claim 1 substantially as hereinbefore described with reference to the drawings.