Pump assembly for handling liquid materials

[57] ABSTRACT

Disclosed is a pump assembly of the vertical submerged type, which has a rotatable shaft with a hollow upper portion and a solid, tapered lower portion. The pump is mounted on a tank containing liquid to be pumped by supporting the upper part of the shaft in a bearing pedestal mounted on top of the tank. A housing encloses the lower part of the pump shaft and an impeller is connected to the tip of the shaft. The impeller is enclosed by a head casing which has an inlet port and two outlet ports therein. Liquid drawn into the head casing is discharged through two separate discharge lines which converge into a single discharge line. The pump shaft is rotated by a motor having a hollow drive shaft, which is coupled to the hollow upper part of the pump shaft. During operation, the pump shaft is cooled by passing air through the hollow motor shaft and into the hollow part of the pump shaft. The pump assembly is particularly suitable for handling corrosive liquids at high temperatures, such as molten caustic.

Claims, 2 Drawing Figures

Air in

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PATENTED WAY 15 1973

3,733,151

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3,733,151

PUMP ASSEMBLY FOR HANDLING LIQUID MATERIALS

BACKGROUND OF THE INVENTION

Broadly, the invention relates to a pump assembly for handling liquid materials. More specifically, the invention covers a pump of the vertical submerged type, which is particularly adapted for pumping high temperature, corrosive liquids.

A pump known as a vertical submerged pump is commonly used in the chemical industry to pump corrosive liquids at high temperatures from one point to another. In making caustic beads, for example, molten caustic is pumped from a holding tank up into a tower, which includes a spinner disk. As the molten caustic stream is fed into the tower, it drops onto the spinner disk. The disk breaks the stream into discrete particles (beads) which fall vertically downwardly and are collected at the bottom of the tower.

The vertical submerged pumps presently in use have certain disadvantages when used to pump molten caustic out of a tank. In these pumps, for example, one of the parts which must operate below the caustic level is a bearing which supports the lower end of the pump shaft at the pump head casing. Because of the extremely high heat of the caustic solution, the bearing will wear excessively in a short time. Another drawback of this type of pump is that it has only a single discharge line for carrying the pumped material away from the pump head casing. With only a single outlet from the head casing into the discharge line, a considerable amount of pressure is exerted against the revolving impeller, at the lower end of the pump shaft, which draws the caustic solution up into the pump head casing. As the bearing begins to wear, the excessive pressure exerted against the impeller will cause the pump shaft to wobble. The result is frequent repair and replacement of the pump parts which have to operate in the molten solution.

SUMMARY OF THE INVENTION

A broad object of the invention is to provide a pump assembly which will pump a variety of liquid materials.

A more specific object is to provide a vertical submerged pump assembly which is especially adapted for handling corrosive, high temperature liquids.

Another object is to provide a pump as described which has a double discharge line for carrying liquid discharge from the pump head.

Broadly, the invention is directed to a pump assembly for handling liquid materials. The pump assembly includes a rotatable pump shaft which has a hollow upper portion and a solid lower portion. The upper portion of the shaft is supported by bearing members mounted in a bearing pedestal. The lower end of the bearing pedestal is adapted for mounting the pump assembly on a vessel, such as a tank. A shaft housing encloses the lower portion of the pump shaft and an impeller is connected to the lower end of the pump shaft. The impeller is enclosed by a pump head casing, which is joined to the lower end of the shaft housing. Liquid is drawn into the head casing by the impeller through an inlet port in the casing.

The head casing includes at least one outlet port and one discharge line connected into the outlet port, for carrying liquid discharged from the head casing. The pump shaft is rotated by a suitable drive means, prefer25 ably a motor. The drive means has a hollow shaft which is coupled to the upper end of the pump shaft. A suitable means is connected into the hollow drive shaft for directing the cooling fluid through the drive shaft and into the hollow upper portion of the pump shaft. The cooling fluid is exhausted through outlet ports positioned in the hollow upper portion of the pump shaft.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevation view, mostly in section, of one embodiment of the pump assembly of this invention. As shown in FIG. 1, the pump assembly is mounted m a typical operating position on a vessel containing a liquid material.

FIG. 2 is a fragmentary view of the lower portion of the pump assembly of FIG. 1. FIG. 2 illustrates the apparatus as it would appear looking in the direction of the arrow A in FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT

In the drawing, referring particularly to FIG. 1, the pump assembly is indicated generally by numeral 10. As shown in FIG. 1, the pump 10 is mounted on a holding tank 11, which contains a liquid material 12. Pump 10 includes a rotatable pump shaft 13 and an impeller 14, which is connected to the lower end of the shaft. As indicated by numeral 15, the upper portion of shaft 13 is hollow. The lower portion of shaft 13, which is that portion of the shaft below the hollow portion 15, is preferably solid. Also, the lower portion of shaft 13 preferably tapers downwardly toward the impeller 14.

The upper portion of shaft 13 is supported in a bearing pedestal, indicated generally by numeral 16. Pedestal 16 is defined generally by spaced apart upstanding leg members 17 and 18, which are joined to a centrallypositioned circular hub 19. Any desired number of leg members may be used in constructing the pedestal. The actual number of leg members used will depend primarily on the type of support required for a given pump unit. In the embodiment shown in FIG. 1, the pedestal 16 actually has three leg members, which are equally spaced, in tripod fashion, around hub 19. To simplify the illustration, however, only two leg members are shown.

The upper end of pedestal 16 is formed by a ringshaped plate 20, which is fastened to the top edge of leg members 17 and 18. A similar ring-shaped plate 21, which fastens to the bottom of leg members 17 and 18, forms the lower end of pedestal 16. The upper portion of shaft 13 is journaled in a single radial bearing 22 and tandem-mounted thrust bearings 23 and 24, which are mounted in hub 19 of pedestal 16. A bearing retainer 25 is mounted in hub 19 above the thrust bearings 23 and 24, to hold the thrust bearings in place in the hub. A similar bearing retainer 26 is mounted in hub 19 below the radial bearing 22.

The pump shaft 13 may be rotated by any suitable drive means. A preferred drive means for the pump shaft is provided by a motor 27, which has a hollow shaft 28. The lower end of the hollow motor shaft 28 is connected to the upper end of pump shaft 13 by a coupling 29. The upper portion of pump shaft 13 is cooled by directing a cooling fluid through the hollow shaft 28 and into the hollow space 15 in the pump shaft. In a preferred embodiment, the pump shaft is cooled by air. As shown in FIG. 1, one end of a line 30 is fitted into the upper end of the hollow motor shaft 28 and the

3,733,151 opposite end of the line is connected into a source of air (not shown).

The cooling fluid is exhausted through several outlet ports which are positioned in pump shaft 13 near the bottom of the hollow portion 15. In FIG. 1, two of the outlet ports are indicated by numerals 31 and 32. A tubular ring 33 is fitted around the periphery of pump shaft 13 slightly below the radial bearing 22 and bearing retainer 26. Positioned around the top part of ring 33 are small spaced-apart openings 34. A line 35 is connected into one side of ring 33, and the opposite end of this line is connected into a source of air (not shown). Air which passes into ring 33 from line 35 is thus directed upwardly through the holes 34, to cool the shaft at the bearing surface 22.

At the lower end of pedestal 16, ring plate 21 is fastened to a mounting plate 36, which is preferably circular. The diameter of plate 36 is slightly larger than an opening in the top wall of holding tank 11, so that the plate will fit across the opening. The pump assembly 10 20 is mounted on tank 11 by fastening the outer edge of plate 36 to the top wall of the tank. The upper portion of pump shaft 13 fits into an opening 37 at the left center of mounting plate 36.

A shaft housing 38, which is a tubular structure with large, closely-spaced openings 39 therein, encloses the lower portion of pump shaft 13. The purpose of the openings 39 is to reduce the weight of the housing. The upper end of shaft housing 38 is defined by a flange 40, which is fastened to the underside of mounting plate 36. The upper portion of pump shaft 13 fits within a central opening 41 in flange 40.

A flange 42 defines the lower end of housing 38. The lower end of pump shaft 13 extends down through a central opening 43 in flange 42. A pump head casing 44, which encloses the impeller 14, is defined by a cupshaped member which is fastened to the underside of flange 42. In the bottom wall of casing 44 is a central opening 45. Opening 45 provides an inlet port through which the liquid 12 in tank 11 is drawn up into the head casing by impeller 14.

As shown in FIG. 2, there are two openings 46 and 47 in flange 42, which are positioned directly opposite to each other near the outer edge of the flange. Openings 46 and 47 are outlet ports through which the liquid 12 is discharged from the pump head casing 44. Connected into outlet port 46 is a discharge line 48. A similar discharge line 49 is connected into outlet port 47.

At a point above pump head 44, the separate discharge lines 48 and 49 converge into a single main discharge line 50. Main discharge line 50 extends up through an opening (not shown) in mounting plate 36. Liquid drawn up into pump head 44 is pumped up through outlet ports 46 and 47, through the discharge lines 48 and 49 and into the main discharge line 50. In the usual practice of the invention, the upper end of discharge line 50 is connected into another line (not shown), which carries the liquid to some desired disposal point.

According to the invention, the pump assembly described herein may be used to pump various types of liquid materials. Such materials include hot or cold liquids, corrosive or non-corrosive liquids, and liquids having a wide range of viscosity. In a specific application, the pump assembly is particularly suited for ' pumping a high temperature, corrosive liquid, such as molten caustic.

The pump assembly described herein has certain features which give it a distinct advantage over the prior pumps, particularly in handling corrosive liquids at high temperatures. One feature is the tapered lower portion of the pump shaft 13, which helps to reduce heat transfer. Another feature is cooling of the pump shaft by directing a cooling fluid into the hollow space 15 of the shaft. Another feature is additional cooling of the pump shaft, as accomplished by directing a cooling fluid through tubular ring 33 and onto the shaft at bearing surface 22. Tapering the pump shaft and cooling it during operation prolongs the life of the shaft considerably.

The double discharge line 48 and 49 provide another desirable feature not found on the prior pumps. The advantage of the double line is that the liquid in pump head 44 is discharged through both lines simultaneously, so that the pressure on impeller 14 is equalized. By equalizing the pressure on the impeller, the pump shaft is held in vertical alignment during operation. This avoids shaft wobble and excessive wear at the lower end of the shaft. Another desirable feature is that the lower portion of the pump shaft, which must operate in a molten solution, does not require any bearings for supporting the shaft. When the pump assembly is used to pump corrosive liquids, the parts which must operate below the liquid level should be constructed of materials compatible with the liquid being pumped.