US2441708A

US2441708A - Pump for corrosive fluids

Info

Publication number: US2441708A
Application number: US522696A
Authority: US
Inventors: Enrique L Luaces; Melvin A Crosby
Original assignee: CHEMICAL DEVELOPMENTS CORP
Current assignee: CHEMICAL DEVELOPMENTS Corp
Priority date: 1944-02-17
Filing date: 1944-02-17
Publication date: 1948-05-18
Anticipated expiration: 1965-05-18

Description

May 18, 1948. E. L. UACES mL 2,441,708

PUMP FOR CORROSIVE FLUIDS Filed Feb. 17, 1944 INV TORS ENR: uf fgluncfs MELV N A. Roy,

ATTORNEYS hama Mutis, 194s UNITED STATES N PATE-NT OFFICE l EnillclalmocltanlllolvlnA. CMMDQYcgI: poration. Dayton. Ohio, a corporation of Ohio Application Fcbtllll! 17, 1944, Selhl N0. 522,698

This invention relates to pumps, and more particularly deals with a process for pumping corrosive fluids and a rotary pump therefor.

Rotary pumps made of stainless, non-corrosive steels have been used before for corrosive liquids. However, there always was the drawback that after a short while, the packings lost their tllht fit because they had been attacked by the corrcsivo huid. Thus the pumping procedure had to be interrupted quite frequently in orderto change the packings. I

This drawback has been overcome by the present invention, according to which the packings of the pump are continuously bathed inor washed by non-corrosive liquid forming part of the fluid to be pumped and thus protected against the corrosive action of the uid.

In the usual type centrifugal pump there is a space behind the impeller and into which space the fluid being pumped canpass during operation.

. 2 Claims. (Cl. 10S-103) nected by pipe 2l and the passage 2l with the annular groove2'l.

Since the drive shaft for such a pump is most practically manufactured from a corrosive substance such as ordinary steel, it will be apparent that the corrosive fluid can reach the surface of the shaft under ordinary circumstances.

Astlll furtherv object of this invention is to prevent the corrosive uid from reaching the shaft by continuously bathing the said shaft when the-pump is in operation by a non-corro-j sive fluid.

The invention will be more fully understood from the following vdescription taken in connection with the accompanyingdrawings, in which,

Fig. 1 'is a cross-sectional view of the pump.

Fig. 2 is a diagrammatic viewof an installation showing one way of conjointly operating a m'ain pump and an auxiliary pump for washing the pump packing; and

Fig. 3 is a diagrammatic view of another modiiication of an installationl showing another way of conjointly operating a main pump and anauxillary pump for washing the pump packing.

Referring particularly to Fig. 1, l0 is the casingv of the pump with the inlet Il and the outlet i2 for the liquid to be pumped. I3 is a rotor which-lits the reduced part II of the shaft Il. The cover I1, which is screwed on the threaded part i8 of the shaft, holdsA the 'rotor' in position.

Il and i8 are gaskets, and 20 and12| are .portions of the packing material placed around the 'shaft Il. The packing 20, 2l is tightly pressed against the walls of the stuillng box 4and the shaft by a "

coil spring

22, 23. 24 is a pump which is con- It will belnoted in the drawings that the rotor i3 has a raised boss portion lia standing up from the back surface thereof which projects into the bore Ma .in the casing and through which the shaft Il extends.

The diameter or the boa nu n substantially equal to that of the shaft i4 and thus theshaft and boss together and with the bore Ila form a relatively thin passage connecting the groove 21 with the space between the casing and the back of the impeller.

It will be apparent that this passage of relatively small cross section will provide for adequate bathing of the shaft and the boss part of the impeller by fluid forced into the groove 21 under pressure and will accomplish this with an economy of bathing fluid.

Due to the fact that the shaft Il is necessarily machined to smooth finish and has other'ma- `corrosive to as marry fluids as possible,4 the said substance becomes very brittle and diillcult to machine and quite unsuitable for use as a drive shaft.

By way of example, the operation of the pump of this'inventlon will be described as applied to the pumping of a mixture of oil and sulfuric acid. The shaft I4 is connected with a motor (not shown in Fig. 1) which rotates the shaft and with it the rotormounted on the' shaft.V By the .rotation of the rotor, liquid is 'sucked into the pump through the inlet Il and continuously discharged through tlie outlet I2. According to the invention, the pump 24 delivers a non-corrosive substance such as. for example, the same oil as is contained in the mixture to be pumped,

through pipe 25 and passage 2l into the annular Y groov'e 21. The discharge pressure of this auxiliary pump 24 is slightly greater than that of the 'main pump I0 in order that only oil free from sulfuric acid fills the annular groove and none of' the corrosive mixture contacts the packing 20, 2|. By this, the service life of the packing i-s considerably increased, thus making possible a more continuous and less `costly process, since less interruptions are required for repacking the pump.

Fig. 2 shows, by way of example, how the two pumps may be coniointly operated by a single motor.

In Fig. 2, I again is the main pump with inlet Il and outlet I2, 24 is an auxiliary pump o! the constant delivery or positive displacement type, I4 is the shaft -of the main pump l0 connected with the motor 28, and 29 the shaft of the auxiliary pump 24 which also is connected with the motor 28. As in Fig. 1, the pipe 25 connects the auxiliary pump with the shaft end of the main pump I0.

Since the auxiliary pump is a constant delivery pump, and the main pump a centrifugal pump which only works at capacity after the rotor has been brought up to a sufficiently high speed, in the beginning of the operation of the motor 28, the pump 24 will immediately pump the non-corrosive liquid and deliver it to the shaft end of the main pump l0 while the pump I0 itself is still in the starting up period. Thus the noncorrosive liquid reaches the main pump before any of the corrosive fluid has a chance to enter the pump and by bathing the packing 20, 2l protects it from the action of the corrosive fluid being pumped.

Fig. 3 illustrates another embodiment of the invention. There again, I0 is the main pump and i4 the pump shaft. 30 is a switch on the main power line, 3l a motor, 20 a constant delivery pump driven by the motor 3|, 25 a pipe connecting the pump 24 with the shaft end ofthe pump l0, and 32 an inlet pipe for the non-corrosive fluid. 33 is a bellows connected with a pressure switch 34, and 35 is the motor having a shaft I4 connected with the pump I0 for driving the pump l0.

'I'he arrangement shown in Fig. 3 operates as follows: On starting the operation, the switch 30 is closed and the circuit of which the motor 3l is a part is energized. Consequently the motor 3| starts to run and drives the constant delivery pump 20, thus causing non-corrosive fluid to ow into the pump 24 through pipe 32 and to be delivered to the shaft end of the main pump l0 through pipe 25. As the pipe 25 is brought under pressure, the bellows 33 is expanded, and thereby the switch 34 is closed. Thus the circuit with the motor 35 is energized and the motor 35 starts to run and drives the main pump i9. Also in this modification the pump 24 delivering the noncorrosive fluid to the shaft end of the main pump I0 for protection of the packing is set to work before the corrosive fluid can enter the main pump I0.

The arrangement illustrated in Fig. 3, particularly the arrangement of the pressure switch 34 operated by the bellows 33 actuated by pressure from the auxiliary pump 24, insures protection of the packing by bathing it with non-corrosive fluid before pumping of the corrosive fluid starts.

Instead of a centrifugal pump as shown at I0, any other kind of pump suitable for handling corrosive fluids may be used.

It is also understood that instead of using a non-corrosive component of the fluid mixture being pumped, any other non-corrosive fluid may be used for bathing and thus protecting the packing according to the invention.

It will be understood that while there have been described certain specific embodiments of this 4 invention, it is not intended thereby to have this invention limited to or circumscribed by the specic details of procedure, arrangement of parts, materials. proportions or conditions set forth in the specification or illustrated in the drawing, in view of the fact that this invention may be modified according to individual preference and conditions without departing from the spirit of the disclosure and the scope of the appended claims. We claim:

1. In an apparatus for pumping corrosive fluids, a main centrifugal pump comprising a corrosion resistant casing and a corrosion resistant impeller rotatable therein, an opening in said casing for receiving a drive shaft, a boss on said impeller extending therefrom into said opening, a drive shaft passing through said opening and extend: ing into said boss, said boss and the portion of the drive shaft extending therefrom being of substantially the same diameter, alseal in said casing and around said shaft, an attenuated annular passage around said shaft between said seal and the interior of said casing and consisting in part of said boss and the part of said opening surrounding said boss, an auxiliary pump connected to deliver non-corrosive fluids to said annular passage and therethrough to the interior of said pump casing, means of driving said auxiliary pump to so supply said non-corrosive fluid, and means'responsive to a predetermined delivery pressure of said auxiliary pump brought about by the delivery thereby of fluid through said annular passageway to actuate said main pump.

2. In an apparatus for pumping corrosive fluids, a main pump having a corrosion resistant pumping element having a boss extending from the back thereof, a corrosion resistant casing for receiving said element and having an opening in one wall for receiving said boss, a drive shaft extending through said opening and into said boss to drive said pumping element, said boss and the part of said shaft extending' from the boss being substantially the same diameter, a packing gland between said casing and shaft, a reduced area annular passage way around said shaft between said packing and the interior of said casing and including the annular passageway between said boss and said opening, an auxiliary pump and a pressure connection between said auxiliary pump and said passageway whereby said auxiliary pump may supply non-corrosive fluid to said passageway, driving means for said main pump, and means controlling the actuation of said driving means whereby said auxiliary pump forces noncorrosive fluid through said passageway prior to the delivery of corrosive fluid by said main pump.

E. L. LUcEs. mmm A. CROSBY.

REFERENCES ci'ran The following references are of record in the ille of this patent:

UNITED STATES PATENTS Reeves et al May 2, 1944