US3111904A

US3111904A - Turbine pump

Info

Publication number: US3111904A
Application number: US160085A
Authority: US
Inventors: William C Burns
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1961-12-18
Filing date: 1961-12-18
Publication date: 1963-11-26
Anticipated expiration: 1980-11-26

Description

Nov. 26, 1963 w, c, U N 3,111,904

TURBINE PUMP Filed Dec. 18, 1961 I s 2 l5 s lo a 4 22 v w a v 9 23 FI G.|

I 2l l2 I l9 I l4 FIG. 3

I INVENTOR:

WILLIAM C.. BURNS HIS ATTORNEY United States Patent 3,111,904 TURBINE PUMP William C. Burns, Pleasant Hill, Calif assignor to Shell Oil Company, New York, N.Y., a corporatien of Dela- Filcd Dec. 18, 1961, Ser. No. 160,085 2 Claims. (Cl. 1103-96) This invention relates to a special type of pump known as a turbine pump and is more particularly concerned with an improved pump construction whereby greater reliability is obtained. A characteristic of the turbine or turbine vane pump is that the power required to drive the pump increases as the differential pressure increases, but the capacity decreases at the same time.

In the turbine vane pump liquid enters a suction inlet located close to the periphery of the pump, passes through suction ports in the casing and is picked up by a single multivaned disc impeller. The centrifugal force imparted by the vanes throws the liquid into a channel in the casing which the vane section of the impeller partially fills. The liquid is deflected into succeeding vanes of the impeller. This action is called the regenerative action and it continues around the channel continually building up pressure until the liquid reaches a stop or stripper which deflects the liquid into the discharge opening.

The pressure head and capacity characteristics of these pumps are dependent upon the various factors such as diameter of impeller, the width and depth of the vanes on the impeller, the area of the channel carrying liquid around the pump case, the speed of impeller rotation, and the clearance between the impeller and the side plates of the casing. In view of the close fitting of the impeller sides on the casing and cover, required to obtain efficient pumping, these pumps are not suitable for pumping liquids containing solids such as crystals in suspension but are highly effective for pumping clean liquids such as water, light hydrocarbons and other light or vaporous liquids such as ammonia, propane and butane. These pumps are also most useful in pilot plants and chemical plants where relatively small quantities of liquids are pumped at high pressure heads. One difficulty encountered is that the pumps must be operated at a fairly constant temperature to avoid possible severe damage. An appreciable temperature rise in either the liquid being pumped or an incorrect setting of the bearings or packing glands will bring very rapid and disastrous results in the form of a badly galled impeller and cover and case contact surfaces especially in the case of nickel and alloys of nickel. Considerable skill of the assembly mechanic is required to provide the necessary clearance between the impeller and stationary liners at a close clearance of .0015 to .002" which are needed at either side of the impeller for high performance and efiiciency.

While some improvement in case of assembly has been obtained by the use of an impeller which is keyed to its shaft but is free to move axially thereon within defined limits, seizures due to temperature change often occur.

It is therefore an object of this invention to supply a means by which damaging seizure of turbine vane pumps is avoided.

Another object of this invention is to provide a pump which will automatically and safely stop upon a sufficient rise in temperature occurring due to increased friction following loss of suction.

A further object of the invention is to provide a means of protecting turbine vane pumps from damage due to the presence of solid particles in the liquid.

The further objects of the invention will be more clearly understood from the following detailed description of a specific embodiment. Throughout the descripddllfifid Patented Nov. 26, 1963 tion, reference is made to the accompanying drawing of which:

FIG. 1 is a side elevation, mainly in section, of the turbine pump.

FIG. 2 is an end elevation taken along the line 2-2 of FIG. 1.

FIG. 3 is an enlarged partial sectional detail of the pump cover.

Referring to the drawing, the pump has a case 1 pro vided with a cover 2. An impeller 3 mounted on shaft 4 is located centrally in the cover and case. A key 5 holds the impeller on the shaft against rotation independent of the shaft. A mechanical seal unit 6 encircles the shaft 4 and with associated seal housing 7 serves to separate the interior of the pump from the exterior while permitting the shaft to be rotated by an external power source (not shown). The shaft 4 is mounted on two spaced ball bearings 8 and 9 both located on one side of the impeller 3. A grease seal ll) is provided ahead of bearing to prevent dust or other contaminants from reaching the hearing.

The case i and cover 2 are provided with split passageways 11 and 12 connected to the suction nozzle 13. These passageways are spiral in configuration and each terminates in ports connected to the channel 14 surrounding the vane portion 15 of the impeller 3. The channel 14- is diverted at one end by a stripper 21 into the outlet port in the casing which terminates in the pump discharge 16.

As will be seen from FIG. 1, the clearance between the impeller and the casing and cover in the disc section 17 of the impeller 3 is very slight; in some situations being ess than two thousandths of an inch. To obtain this clearance the impeller is floated on the shaft 4 so that it can move slightly in a direction parallel to the shaft axis. By this means and the use of a shim between the case 1 and cover 2 a desired clearance is obtainable.

In some operations it has been found advantageous to re-circulate part of the liquid from the discharge side of the pump into the area surrounding the hub of the impeller. This internal cavity is divided into two isolated parts 22 and 23 by the impeller 3. Usually vapor or some liquid will exist in this cavity.

By means of a bypass return line from the discharge side, a flushing stream of liquid can be continuously led by way of pipe fittings tapped into the walls of the cavity on either side of the impeller. The pressured stream from the discharge side of the pump can be cooled by heat exchange if desired.

Such a return stream provides a cooling means for the mechanical seal faces as well as a continuous radial flush to the impeller and the associated area of the cover and casing. Besides allowing transfer of heat due to driver energy in the fluid at throttled flow conditions, the possible lodging of extraneous solid particles between the impeller and the close casing and cover areas is prevented.

On each side of the impeller and located opposite the disc area 17 of the impeller, annular plastic inserts l8 and 19 are provided in the case and in the cover. These inserts, as will be seen from FIGS. 1 and 3, are preferably of rectangular cross-section and are fitted into channels cut in the casing and cover, respectively.

The material I have found suitable for these inserts in petroleum chemical pilot plant work is tetrafiuoroethylene polymer marketed under the trademark Teflon and manufactured by E. I. du Pont de Nemours and Company.- For other applications other hard or semi-hard plastic such as polypropylene or epoxy resin may be satisfactory. The Teflon rings are machined to provide an overhang of a few thousandths of an inch at the metal face of the casing and cover. The rings of plastic are thus so located that upon a reduction in the clearance of the disc portion 17 of the impeller from the casing and cover a metal to non-metal contact will be made. By the above action the braking of the impeller will be effected so that a stalling of the impeller results.

If the motor driving the pump is fitted with a sensitive overload cut out a complete stalling of the impeller may not be necessary.

The following examples further illustrate the invention:

Example I A standard turbine pump, having required close running clearance in the disc area, was modified by the provision of Teflon rings so as to provide metal to non-metal surfaces between the impeller and fixed cover and case. This was done by machining the cover and casing to allow the insertion of a wide rectangular sectioned Teflon ring of 2 /2 inside diameter at the critical areas. Each ring was machined to provide a .005" overhang at the metal face. The pump was assembled with a running clearance of approximately .001" on either side of the impeller. The unit was installed on a test stand and its suction inlet connected to a 2" diameter pipe from an atmospheric tank about 20 ft. away which held 250 gallons of hexane. The liquid level in the tank was 8 above the center line or" the pump suction. A nitrogen purge was maintained above the liquid in the tank. The pump shaft was directly coupled to a 2 horsepower, 3600 rpm. electric motor. The motor was started up and the pump differential pressure rose from to 140 p.s.i.g. at shutoff.

The motor and pump stalled after about 1% minutes running time at the shutoff condition. An ammeter in the line showed the electric motor was operating at 200% overload at stall. The pump was stalled 13 times in successive runs and was then disassembled. Inspection showed no wear or grooving on the contacting surfaces. A slight discoloration of the turbine impeller contact surfaces indicated considerable heat had been generated.

Example 11 In another test with a similar pump which was constructed of a nickel alloy and not fitted with the plastic rings on each side of the disc area of the impeller and operated under the same conditions as in Example I, the motor stalled. Upon disassembly it was found that the casing, cover and impeller sides were severely galled and scored and necessitated replacement of the pump parts.

Example III In another test, using the pump of Example I, all fluid was drained from the pump. The pump was started and run entirely dry. After a run of only a few seconds the pump stalled. The unit was disassembled and the impeller and plastic ring surfaces examined. No evidence of wear, scoring or galling was present. The unit was then reassembled, liquid admitted and the motor started. Discharge head pressure at shutoff conditions showed the same reading as before the dry operation test. The pump was thereafter run continuously in service operation at 110 p.s.i.g. head.

It will be appreciated by those acquainted with the art that the installation of plastic liner rings provides a solution to a problem that has long plagued the turbine pump user. By the above means an automatic acting brake within the pump case which acts to stop the pump when loss of suction occurs has been provided. Loss of suction prior hereto resulted in the pump continuing to run until it ruined its shaft sealing device as well as destroyed the impeller and surfaces in the casing and cover. By the provision of the Teflon rings in the casing and cover advantage is obtained from the low friction properties of the material coupled with its high rate of expansion at a relatively low temperature level. These two properties are helpful in obtaining a fast-acting automatic internal brake.

The above braking system has been used in pumps constructed of special iron alloys, nickel alloys and of stainless steel and can be used in pumps manufactured of other metals. Another advantage of the described pump is that the pump can be overhauled without removing the pump from the foundation or disconnecting the piping. When the insert rings eventually become worn they can be removed with standard packing tools and new rings installed and seated.

A further advantage of the invention is that an additional safety feature is provided in installations where motor overload cut outs are relied upon to prevent damage to the pump.

I claim as my invention:

1. Normally disengaged temperature responsive braking means for a vane turbine pump comprising: a casing, a cover fitted thereto, a disc impeller provided with fluid impeller means, said impeller means being mounted on a shaft in said casing and freely rotatable with respect to said casing and cover, annular expansible plastic brake rings mounted in said casing and cover and extending axially toward said disc impeller on opposite sides thereof and normally out of engagement therewith, said plastic rings being so arranged that upon an abnormal rise in temperature in the pump they will expand axially and be brought into rapid braking contact with said disc timpeller so as to stall the impeller.

2. The combination as defined in claim 1 in which said plastic rings are tetrnfluoroethylene polymer.

References Cited in the file of this patent UNITED STATES PATENTS 2,007,954 Carlson July 16, 1935 2,090,162 Tighe Aug. 17, 1937 2,364,168 Shallenberg Dec. 4, 1944 2,396,319 Edwards et a1 Mar. 12, 1946 2,587,222 Riester Feb. 26, 1952 2,717,025 Jel-inek Sept. 6, 1955 2,768,849 Riesing Oct. 30, 1956 2,775,208 Mueller Dec. 25, 1956 2,880,676 Succop Apr. 7, 1959 2,906,208 White Sept. 29, 1959 2,954,739 Lung Oct. 4, 1960 2,960,280 Connelly et al. Nov. 15, 1960 3,000,591 Backlin Sept. 1, 1961 3,037,458 Olmstead et a1. June 5, 1962 OTHER REFERENCES Publication: Product Engineering, November 1947, High Heat and Corrosion Resistant Plastic, by Everett B. Yelton (Plastic Dept, E. I. du Pont de Nemours & Co.), pp. 154-158.

Claims

1. NORMALLY DISENGAGED TEMPERATURE RESPONSIVE BRAKING MEANS FOR A VANE TURBINE PUMP COMPRISING: A CASING, A COVER FITTED THERETO, A DISC IMPELLER PROVIDED WITH FLUID IMPELLER MEANS, SAID IMPELLER MEANS BEING MOUNTED ON A SHAFT IN SAID CASING AND FREELY ROTATABLE WITH RESPECT TO SAID CASING AND COVER, ANNULAR EXPANSIBLE PLASTIC BRAKE RINGS MOUNTED IN SAID CASING AND COVER AND EXTENDING AXIALLY TOWARD SAID DISC IMPELLER ON OPPOSITE SIDES THEREOF AND NORMALLY OUT OF ENGAGEMENT THEREWITH, SAID PLASTIC RINGS BEING SO ARRANGED THAT UPON AN ABNORMAL RISE IN TEMPERATURE IN THE PUMP THEY WILL EXPAND AXIALLY AND BE BROUGHT INTO RAPID BRAKING CONTACT WITH SAID DISC IMPELLER SO AS TO STALL THE IMPELLER.