US2005429A

US2005429A - Centrifugal pump and the like

Info

Publication number: US2005429A
Application number: US600085A
Authority: US
Inventors: Lichtenstein Joseph
Original assignee: Foster Wheeler Inc
Current assignee: Foster Wheeler Inc
Priority date: 1932-03-21
Filing date: 1932-03-21
Publication date: 1935-06-18
Anticipated expiration: 1952-06-18

Description

Be E8, 1935,- J. LICHTENSTEIN 2,005,429

CENTRIFUGAL PUMP AND THE LIKE Filed March 21, 1932 2 Sheets-Sheet l 4, ATTORNEY June 18, 1935. J. LICHTENSTEIN 2,005,429,

CENTRIFUG'AL PUMP AND THE LIKE Mia-444M2 5;

1 ATTORNEY Patented June 18, 1935 UNITED STATES PATENT OFFICE OENTRIIFUGAL PUMP AND THE LIKE Joseph Lichtenstein, Brooklyn, N. Y., assignor to Foster Wheeler Corporation, New York, N. Y., a corporation of New .York

Application March 21, 1932, Serial No. 600,085 I 16 Claims. (01. 103-112) This invention relates to centrifugal pumps and like devices and more particularly to sealing means therefor adapted to handle liquid at high temperatures and high pressures and to balanc ing means therefor.

The invention is particularly applicable to feed water pumps for supplying water at high temperatures and pressures to a steam boiler. In pumps operating at high temperatures and pressures, as, for example above 500 F. and 1000 lbs. per sq. in., difficulties have been encountered in maintaining leakage through the stufling boxes at a minimum and in reducing the pressure and temperature at the stufling boxes to values such trouble therewith is not likely to occur.

It is an object of the present invention to 'pro- 4 vide means for reducing. both the temperature and pressure of the water before it is applied to the stuffing box, to a value such that injurious effects are avoided and leakage is reduced to a minimum.

A further object is to reduce the temperature of the water without substantial loss of heat from the system.

A still further object is to provide a sealing means that occupies a minimum amount of axial space in the pump.

Still another and important object of themvention is'to eliminate the usual separate balancing disc or device in multi-stage pumps and the accompanying leakage loss due to the flow of water past the balancing disc and back to the suction side of the pump. This I accomplish by my novel construction of sealing means which at the same time serves as a balancing disc.

According. to a preferred form of the inven-- pressure; for example, by a connection to a low pressure operating element of the system in which the pump is used such as a low pressure, feed water heater or a condenser. ,As the pressure of the water is reduced, a portion of the water 55 vaporized. The heat required-to supply the that cutting 'of the packing material or otherv latent heat of vaporization is extracted from the water itself which is cooled in accordance with established factors of thermodynamics.

The vapor, or steam, is preferably drawn off to a low pressure heater or condenser and the a water, which is now at a low temperature and pressure, can be readily handled by a standard stuffing box. The heat of the steam is recovered in the low pressure heater or condenser.

In the preferred form two radial labyrinth 10 discs are employed which are respectively subjected to suction and discharge pressure and which are'so dimensioned that the difference in pressure on the two discs balances the unbalanced end thrust due to the pressures on the 15 impellers. so that theoretically there is no end thrust in'the pump.

Various other features of the invention will I be apparent from the following description and accompanying drawings in which a preferred 20 form of the invention is disclosed.

In the drawings:

Fig. 1 is a brokenlongitudinal sectional view' of a centrifugal pump constructed in accordance with the invention;

Fig. 2 is a transverse section taken on the line 2-2 of Fig. 1;

Fig. 3 is a section taken on the line 3-3 of Fig. l; and

Fig. 4 is a section taken on the line 4-4 of Fig. 2.

Referring more particularly to the drawings, the invention is shown as applied to a centrifugal pump comprising a housing It! containing a low pressure chamber ll having an inlet port l2. A shaft I3 is journalled for rotation in said housin and carries a series of impellers M which may be of known construction. Guide members l5 and casing parts ll form channels [8, which direct the liquid from the discharge side of one impeller to the inlet side of the next impeller. Each impeller It may be provided with a ring projection H! which cooperates with a stationary circular groove 20 formed in a section of said housingto restrict flow around 'theimpeller. It is to be understood that the pump may be formed of any number of stages comprising-any number of impellers which may be required to build up the desired discharge pressure. The first impeller receives liquid from the low pressure chamber I I. From the last impeller the liq-p uid is discharged into a high pressure chamber 2| formed in housing l0 and communicating with a discharge port 22.

On the outside of the last impeller is an in- A radially extending labyrinth disc 45 having annular projecting rings 8| thereon is secured to shaft I3 and cooperates with the radial portion of a. stationary labyrinth member 46 having annular projecting rings 82 thereon and which is secured to housing 10, to provide a tortuous channel between the interfitting projections 8| and 82 extending in a general radial direction in which the flow of liquid is generally toward the axis of shaft l3. Adjacent labyrinth disc 45is a sleeve 32 secured on the shaft and'having radial projecting rings 33 interfitting between rings 34' on the axially extending portion of member 46 whereby an axial labyrinth is formed as a com .tinuation of the radial labyrinth. The interfitting projections are closely spaced so that the channel between them is narrow. The radial portions of the channels are wider than the axial portions toprovide a series of expansion spaces in the labyrinth passage for development of steam. The discharge end 36 of the labyrinth channel communicates with a separation chamber 41 formed in housing Ill. Said separation chamber is provided with an outlet port 48 which is connected, as by pipe 49, to alow pressure point such as a feed water heater of the system or a condenser indicated at '80.

The water within flash chamber 41 is held back by a stufling box comprising a plurality of packing rings 50 of compressible packing material which are held between a projection 5| oi housing I 0 and a sleeve 52 which is mounted on shaft l3. A gland 53 maybe secured to projection 5| in any desired manner 'forapplying longi- 'tudinal. pressure against said packing rings 50 and maintaining them in operating position. The stufiing box may also be provided with a. rigid metallic spacing ring 54 which is located centrally of rings 50. If chamber 41 is operated at a pressure below atmospheric, water under pressure may be supplied through a pipe 56 to the space adjacent ring 54 to form an air seal for preventing air from being drawn into chamber The sealing means for the low pressure side of the pump is similar to that described above and, although the following description thereof ls less detailed, it is to be understood that the various parts correspond in construction and function. Low pressure chamber ll communicates by means of a passage 59 with a circular passage Git-containing a plurality of radially extending stationary baiiles or ribs 64 which are formedsimilar to the. baiiles 44 at the high pressure end of the pump. A radiallabyrinth seal comprising a rotating radial labyrinth disc 66 and an axial labyrinth sleeve 60 mounted on shaft l3 and stationary labyrinth member 61 secured in housing It] is located between circular passage 63 and a. separation chamber 65. These parts have intermeshing projections and form a tortuous .pass'age having a radial inwardly extending portion and an axial portion similar to that at the high pressure end." Said chamber 65 is provided with an outlet port 31 which may be connectedas by pipe 81 to a suitable low pressure point 0. Chamber 65 issealed by a stufling box compris g a plurality of packing rings 68 held between projection 69 of housing I and a sleeve 10 carried on shaft,l3. Said packing rings are held in position by gland H in any well known manner. A metallic spacing ring" may be located cen'tr'ally of rings 68 and a. connection 14 may be provided for applying water for sealing againstvacuum.

v The operation of the above described sealing means is assfollows, referring to the'sealing means at the high pressure end: a

The leakage -.water at high temperature and high pressure passes between the right hand impeller l4 and wall 35' and thence through circular passage 43 wherein ribs 44 substantially prevent the water from rotating. From passage 43 the water passes through the radial labyrinth passage formed by disc 45 and the radial portion of member 46 and is caused to ravel toward the axis of shaft [3. The moveme t of rotating disc 45 causes the water flowing through the tortuous passage to rotate and to thereby set up outwardly directed centrifugal force which opposes the inward passage of the water therethrough. This centrifugal force introduces a resistance to the flow of water equivalent to' the resistance of a considerable number of labyrinth turns. There radial portion of the labyrinth passage, the fluid then being a mixture of water and steam, passes through the generally axial portion'of the labyrinth passage between member 32 and projection 34. The steam and water mixture after passing through: the labyrinth passage entersseparation chamber 41 which is maintained at suitable .low pressure such as atmospheric or somewhat above or. below atmospheric, depending upon the low pressure point to which pipe 49 is connected. In passing through the labyrinth passage, the hot wateris reduced in pressure and some of itis flashed into steam, the latent heat of vaporization being taken from the. liquid. The temperature of the leakage liquid is thus reduced corresponding to the reduction in pressure" Cham-v ber 41 accordingly receives a mixture of water and steam, preferably at,a temperature notmaterially exceeding 212 F. The steam is withdrawn to the low pressure point through pipe 49 and the water .which is now at low pressure and temperatln'e is readily'held back by-the stuning box and the temperature and pressure is such that the stufling box can stand up.

The above described method of flashing for sealing purposes has the further advantage of reducing the amount of leakage considerably. As soon as the pressure drop'in the first labyrinth turns has been sufiicient to reduce the pressure of the hot water below the corresponding tem-' perature of the water, flashing starts'and the mixture of steam and water flows through the succeeding turns while more steam is flashed. It can readly be seen that the'lower the pressure becomes the bigger the volume-of .the steam becomes as compared to the initial volume of the water entering the labyrinth system. Since at the same time the cross-sectional area of the passage becomes smaller in the radial portion of the labyrinth and at least does not incrme in the axial portion, the velocity of the 'balanced thrust of the impellers.

must increase enormously, or the amount of the mixture for a given pressure drop is correspondingly decreased.

If chamber 41 is maintained at a pressure below atmospheric, access of air thereto may be prevented by applying water under pressure to pipes 56 and 14.

The operation of the low pressure end sealing means is the same as that at the high pressure end.

Besides serving to provide a radial flow labyrinth, the member 45 serves also as a balancing disc. The pump has an end thrust due to the impellers toward the low pressure end. This is ofiset because the pressure differential on the two sides of disc 45 is greater than the pressure differential on the two sides of disc 66. Consequenily there is an unbalanced 'thrust on the labyrinth discs which acts oppositely to the un- The labyrinth discs can be designed with respect to area so as to equalize the thrust of theimpellers. Therefore it may be said that the labyrinth disc permits the omission of the usual balance disc and connection from the high pressure end to the low pressure end, with corresponding saving of leakage flow between these two points.

I have shown a combined radial flow and axial flow labyrinth because the pump shown was designed for service in which the placing of the entire labyrinth passage radially would have necessitated a disc of such radial extent as to give rise to undesirable rotational strains. It will be appreciated nevertheless that there are great advantages in the radial flow labyrinth whether or not combined with an axial labyrinth. The equivalent entire axial labyrinth passage to what is shown in Fig. 1 would make a much longer pump. The effects of centrifugal flow opposition and balancing are not present in an axial labyrinth.

By the use of radially extending labyrinth segls inwhich centrifugal force is utilized to impede the flow of the leakage water, any desired number of labyrinths may be employed to obtain the necessary pressure drop without materially increasing the axial length of the pump. It will be understood that a number of radial flow labyrinth channels in accordancewith the invention can be connected in series. It is obviously a matter of design whether to use one or several radial labyrinths or whether to combine an axial labyrinth with one or more radial labyrlnths.

By converting a portion of the leakage water .into steam and using the latent heat of vaporization thereof for cooling purposes, a comparatively great cooling effect is obtained and at the same time loss of heat in the system is avoided, since the heat value may be recovered therefrom in the feed water heaters or other devices. The system is accordingly particularly efficient from the standpoint of heat loss and may be so designed that the temperature and pressure of the leakage water may be reduced to any des red value before the water is applied to the stufling box. This permits the stuffing boxes to be used for considerable periods of time without injury and materially reduces both the cost ofinstalls. tion and the maintenance charges of the pump.

Although a preferred form of the invention has been shown and described for purposes of illustration, it is obvious that various modifications and changes may be made therein. For example, the packing herein described may be applied to various other utilities wherein high'pressures special liquid pumps and in turbines. It will be appreciated that the novel balancing feature is applicable to pumps with different kinds of. sealing means or different paths of flow of liquid. Various specific terms have been used in the present description for convenience and not by way of limitation. The invention is only to be limited in accordance with the following claims when interpreted in view of the prior art.

What I claim is:

1. In a device adapted to operate with liquids at high pressure, a rotor and a housing, a stufiing box carried by said housing and cooperating with said rotor, a passage having radial baflles therein and adapted to have radial flow of liquid therein toward the periphery thereof, fixed and rotatable members forming a radiallabyrinth seal communicating at its outer end. with said passage and adapted to have radial flow of said liquid through said labyrinth toward the axis of said rotor and causing rotational flow of said liquid about said axis whereby centrifugal force is developed to oppose said flow, and a chamber for receiving the liquid after passage through said radial labyrinth seal and in communication with said stuffing box.

2. In a device adapted to operate with liquids at high pressure, a rotor and a housing, a stufiing box carried by said housing and cooperating with said rotor, and means to reduce the temperature and pressure of the liquid within said housing before applying the same to said stuifing box comprising a circular passage formed in said housin to receive leakage liquid,-stationary baflles in said ,passage to substantially prevent'rotation of liquid therein, a radial flow tortuous labyrinth passage having its outer end communicating with the periphery of said passage, and means for causing passage of said liquid through said labyrinth passage toward the axis of said rotor while rotating about said axis whereby centrifugal force is produced for opposing the flow of liquid compris'ng a low pressure separation chamber connected to receive liquid from said labyrinth at a point near the axis of said rotor, whereby to vaporize a portion of said liquid and to reduce the temperature of the remaining liquid.

- 3. A centrifugal pump compris'ng a housing, a rotor. a passage in the housing adapted to receive leakage liquid, a rotating disc one side of which forms a wall of the passage, and means in the passage to reduce the rotation of the liquid leaking thereinto, the other side of the disc having projections forming, with a cooperating member, a labyrinth seal.

4. A centrifugal pump comprising a housing, a rotor, a passage in the housing adapted to receive leakage liquid, a rotating disc one side of which forms a wall of the passage, means in the passage to reduce the rotation of the liquid leaking thereinto, the other side of the disc having projections forming, with a cooperating member, a radially extending labyrinth seal, and an axially extending labyrinth seal communicating with the radially extending labyrinth seal.

5. A centrifugal pump comprising a housing, a rotor, a passage in the housing adapted to receive leakage liquid, a rotating disc one side of which forms a wall of the passage, means in the passage to reduce the rotation of the liqu'd leaking thereinto, the other side of the disc having projections forming, with a cooperating member, a radially extending labyrinth seal, an axially extending labyrinth seal communicating and high temperatures are involved, such as in 'liquid in said chamber to cool the remaining liquid and thereby cool the stuffing box.

6. Apparatus for pumping liquids comprising stationary and movable members, a stuffing box between said members, means causing leakage liquid to flow into contact with the stuifing box, and means including a source of pressure outside the stationary member for subjecting the leakage liquid to a pressure lower than the pressure at which the liquid will vaporize at the temperature thereof, whereby the ensuing vaporization will cool the remaining leakage liquid and the stufling box.

7. Apparatus for pumping relatively high temperature liquids comprising stationary andmovable members, a stufiing box between said members, means causing leakage liquid to flow into contact with the stumng box, and means including a source of pressure outside the stationary member for subjecting the leakage liquid to a pressure substantially lower than the pressure at which the liquid will vaporize at the temperature thereof, whereby the ensuing vaporization will cool the remaining leakage liquid and the stuffing box.

8. Apparatus for pumping liquids comprising stationary and movable members, a stufling box between said members, means causing leakage liquid to flow into contact with the stufling box, and means including a source of pressure outside the stationary member for subjecting the leakage liquid to a pressure lower than the pressure at which the liquid will vaporize at the temperature thereof, whereby the ensuing vaporization will cool the remaining leakage liquid and the stufling box, said last mentioned means serving to conduct the vapor evolved from the appa ratus. Y

9. Apparatus for pumping liquids comprising stationary and movable members, a stuffing box between said members, means including a restricted passageway for causing leakage liquid to flow into contact with the stufling box, and means including a source of pressure outside the stationary member for subjecting the. leakage liquid to a pressure lower than the pressure at which the liquid will vaporize at the temperature thereof, whereby the ensuring vaporization will cool the remaining leakage liquid and the stufling box. I

10. Apparatus for pumping liquids comprising stationary and movable members, a stufling box between said members, a chamber in communication with the stufling box, means causing leakage liquid to flow into the chamber and into contact with the stufling box, and means including a source of pressure outside the stationary member for subjecting the leakage liquid flowing into the chamber to a pressure lower than the .pressure at which the liquid will vaporize at the temperature thereof, whereby the ensuing Va porization will cool the remaining leakage liquid and the stufling box.

11. Apparatus for pumping liquids comprising stationary and movable members, .a stuffing box between said members, a chamber in-communication with the stufling box, means causing leakage liquid to flow through a restricted passage into the chamber and into contact with the stufling box, and means including a source of pressure outside the stationary member for subjecting the leakage liquid flowing into the chamber to a pressure lower than the pressure at which the liquid will vaporize at the temperature thereof, whereby the ensuing vaporization will cool the remaining leakage liquid and the stufling box.

12. Apparatus for pumping liquids comprising stationary and movable members, a stufling box between said members, a chamber in communication with the stufiing box, means causing leakage liquid to flow through a restricted passage into the chamber and into contact with the stufiing box, and means including a source of pressure outside the stationary member for subjecting. the leakage liquid flowing into the chamber to a pressure lower than the pressure at which the liquid will vaporize at the'temperature thereof,r whereby the ensuing vaporization will cool the remaining-leakage liquid and the stufling box, said last mentioned means serving to conduct the evolved vapor to the source of the lower pressure.

13. A centrifugal pump comprising a rotor and a housing, a stufling box carried by the housing and cooperating with the rotor, means causing leakage liquid to flow into contact with the stuffing box, and means including asource of pressure outside said housing for subjecting the leakage liquid to a pressure lower than the pressure at which the liquid will vaporize at the temperature thereof, whereby the ensuing vaporization will coolthe remaining leakage liquid and the stumng box. P

14. A centrifugal pump comprising a rotor and a housing, a stuffing box carried by the housing and cooperating with the rotor, means causing leakage liquid to flow through a restricted pas sage into contact with the stufiing box, and means including a source of pressure outside said housing for subjecting the leakage liquid to a" and into contact with the stufflng box, and means I including a source of pressure outside said housing for subjecting the leakage liquid flowing into the chamber to a pressure lower than the pressure at which the liquid will vaporize at the temperature thereof, whereby the ensuing vaporization will cool the remaining leakage liquid and the stufling box.

16. A centrifugal pump comprising a rotor and a housing, a stufiing box carried by the housing and cooperating with the rotor, a chamber in communication with the stuffing box means causing leakage liquid to flow thro h. a restricted passage into the chamber and/into contact withothe stufling box, and means including a source of pressure outsidesaid housing for subjecting the leakage liquid flowing into the cham-