US2425958A - Fluid-driven pump control - Google Patents

Description

1947- c. A. SCHELLENS ET AL FLUID DRIVEN PUMP CONTROL Filed Dec. 2, 1943 4 Sheets-Sheet 1 Q QM u o @K N o s IflvereTors.

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g- 1947- c. A. SVCHELLENS ET AL 2,425,958

FLUID DRIVEN PUMP CONTROL Filed Dec. 2, 1945 4 Sheets-Sheet 2 19, 1947- c. A. SCHELLENS El AL FLUID DRIVEN PUMP CONTROL 4 Sheets-Sheet 3 Filed Dec. 2, 1943 ll v11 c. A. SCHELLENS El AL 7 2,425,958

FLUID DRIVEN PUMP CONTROL Aug. 19, 194-7.

Filed Dec. 2, 1945 4 Sheets-Sheet 4 a WAW/P N Q Irleniors fizzw Patented Aug. 19, 1947 ,425,958 FLUID-DRIVEN PUMP CONTROL Christopher A. Schellens, Tenants Harbor, Maine, and Arthur L. Sherman, Englewood, N. J.

Application December 2, 1943, Serial No. 512,584

(Cl. 1i)319) 23 Claims.

This invention relates to improvements in control mechanism for high speed turbine-driven centrifugal pumps suitable for supplying feed water to boilers, and more particularly to such mechanisms designed to prevent over-speeding of the turbine-pump unit when the load on the turbine becomes insufficient to keep the speed down within safe limits, as when there may be a failure or throttling of the water supply to the pump, or when the water supplied to the pump becomes heated to such a high temperature that its suction head is insufficient to supply the demands of the pump without flashing to steam.

A primary diificulty encountered in connection with mechanisms for preventing over-speeding of turbine-driven pumps results from the tendency of control valves and operating parts to become stuck and rendered inoperative by formation of .scale thereon, corrosion, etc. Such over-speed protective mechanisms may not be called upon to operate for long periods of time, and hence there is ample opportunity for scale to form and oxidization to occur unless effective measures are taken to prevent it. This tendency of control devices to become stuck and inoperative is particularly prevalent when the control is of a turbine-pump unit supplying feed water to boilers where hard or unclean Water has to be used, and the pump unit may not be given requisite attention.

In Patent No. 1,725,? 22, granted August 20, 1929, to Christopher A. Schellens, one of the present joint applicants, there is disclosed an over-speed protective control which avoids much of the difficulty resulting from scaling and corroding of operating parts and which operates on the principle of effecting such control by inter-action of turbine steam pressure and pump-discharge pressure on the control valve, whereby the occurrence of a condition favorable to over-speeding of the pump unit results in a slowing down of the unit to a safe speed without an actual stopping of the unit, and the speed automatically is restored to normal when the faulty condition has been corrected.

Our present invention utilizes the same principle of automatic control of a turbine-driven pump against over-speeding by the opposed action of turbine steam pressure and pump delivery pressure on a control valve unit, and has among its objects to provide an improved control valve unit and. improved means for effecting the control. In the illustrated embodiment of the in- Vention, we provide a double-disc valve unit having an integral piston on which the turbine steam pressure acts in direction to close the valve disc's against passage of steam to the turbine and on which the pump discharge pressure acts in the opposite direction tending to maintain the valve discs open. The water pressure may act through a lever, and an adjustable spring may act with the water pressure in opposition to th steam nozzle pressure and may be adjusted to hold the valve slightly open, even though the water pressure fails completely, so that the turbine can operate at a suitably low and safe speed until the Water pressure is restored.

Another and important object of our present invention is to provide means for controlling the main control valve unit by controlling a relatively small flow of fluid whose pressure is effective on the main control valve unit. In some cases, this relatively small flow of fluid which is to be controlled may be steam which escapes past a steam piston on the control valve unit and which is con-' ducted through a relatively small pipe to the exhaust side of the turbine, the control of which can maintain a constant or nearly constant pump discharge pressure at the pump outlet notwithstanding variations in the volume of liquid discharged; or, as herein shown, the control may be of a small flow of liquid in a relatively small pipe which leads from the discharge side of the pump to the under side of a water piston acting in opposition to the steam nozzle pressure on the control valve unit; or under some conditions, it may be desirable to effect the control by controlling a relatively small flow of liquid which has leaked past the water piston into a conduit leading to the suction side of the pump. Furthermore, the valve or other means for controlling the small flow can be small and, if desired, may be placed at a remote location where it can provide sensitive and inexpensive control by hand or automatically, such as by a float operating in the feed tank which supplies the pump, or other well known control devices which respond to water level, pressure, temperature, or other characteristics which it is desired to control.

A further object is to combine with the above mentioned control of over-speeding by the relation of steam pressure to water pressure, a pen.- trifugal acting trip control for stopping pump op:- eration in the event of over-speeding of the turbine-pump unit. Associated with a lever through which the water pressure acts on the piston of the control valve unit, we provide trip mechanism operative in response to speeding up of the pump shaft, for removing the force due to the upward pressure on the piston of the valve unit so that steam pressure can completely close the Valves against admission of steam to the turbine. The

provision for this emergency shut-down control and the structure for causing its action through the same valve unit that controls normal operation and emergency slow-down operation of the turbine-pump unit constitute additional objects of our invention.

Another object resides in provision for conducting steam leaking past the steam pressure control piston to' theexhaust side of the turbine, and for conducting water leaking past the water pressure control piston to the suction side of the pump, thereby providin conduit connections whereby pump inlet pressure and turbine exhaust pressure are constantly acting on the control valve which responds to variations in these pressures to compensate'therefor and ensure a proper positioning of the valve unit under all conditions of operation.

Still another object of the invention is to provide means for maintaining a proper equilibrium ofthe control valves in the event of a drop in steam pressure. It has been customary heretoore to provide a valved conduit whereby one or more auxiliary nozzles might be thrown into communication with the normally operating nozzle belt of the turbine when the steam supply pressure drops; thereby to prevent a drop in pump delivery pressure and volume under conditions of nearly full load. With our improved control valve unit, such a cutting-in of one or more extra or auxiliary nozzles would disturb the equilibrium relations between bowl pressure and delivery pressure acting respectively on the steam and water pistons unless means were provided for correcting this effect. the form of a conduitconnecting the auxiliary nozzle belt to a chamber in the control valve casing whereby the auxiliary nozzle pressure acts with and in addition to the normally operating nozzle pressure when the said valved conduit of the auxiliary nozzle or nozzles is open.

It is, moreover, our purpose and object generally to improve the structure and operation of over-speed controls for turbine-driven centrifugal um In the "accomp anyin g drawings Figurel is a diagrammatic view showing a turbine-,fdriven pump and control system, mbodying featuresofour invention, for supplying feed water toi'a boiler, the control unit being shown separated and turned around relative to the turbine-pump unit, and the centrifugal trip mechanism being m t d- Figure 2 is a vertical cross-sectional view showing our improved control mechanism in its relationto the shaft of the turbine-pump unit;

Figure 3'is, a View looking from the left in Figure 2 the upper portion being in vertical crosssection on line 3- 3 of Figure 2;

Figure 4 is a cross-sectional view on line l-4 of Figure 2; v

Figure. 5 is a perspective of the centrifugal trip mechanism shown in elevation in Figures 2 and 3; Figure 6 is a detail cross-sectional view approximately on line 6-5 of Figure 5, showing a 'meansfor adjusting the latch; and v Figure? is a fragmentary elevation showing the hand valve, conduit, and connections for applying the steam pressure of the auxiliar nozzles to'the upper endof the valve unit. 7 Referring to the drawings, and more particularly to Fig ,'1 the present invention is shown applied to a feed-waterpump l0 which draws feedwaterthrough'pipe 12 from asuitable source, 'such as the tank It, and delivers it through a Such means is provided in combined check and regulating valve [6 to the boiler l3 after first passing the water through a heater 20 connected in the delivery pipe 22. A shut-oil valve 26 is provided in the suction pipe I2 and the delivery pipe 22 has a check-valve 26 located between the pump and heater 26, and has a pressure relief valve 28 between the pump and check-valve 26, with relief conduit 33 opening into the tank I i, I

Pump I9 is a turbine-driven high speed centrifugal pump whose turbine 32 is supplied with steam through pipe 3 leading from any suitable source of steam, the exhaust from the turbine eing conducted through pipe 35, having the usual shut off valve 38, to any convenient exhaust steam conduit or chamber.

Control mechanism embodying features of the invention is arranged in the steam line 34 between the steam source and the turbine. As illustrated in the drawings, the control mechanism is mounted on the turbine casing, as best seen in Fig. 3, and comprises a valve casing 42 secured to the top of the turbine casing as by the screws 45. An entrance chamber 46 within valve casing 62 has the steam pipe 3 1 deliverin thereto, and a discharge chamber l8 of the valve casing opens directly into the turbine.

The amount of steam admitted to the turbine i controlled within the valve casing 42 by a double-disc valve unit whose discs 50, 52 respectively control the ports 56, 56 in the walls 58, 6B which constitute partition walls between the entrance and discharge chambers 46, 48 of the valve casing 42. .Ihe disc are mounted in fixed spaced relation on a valve stem 62 whose upper end is slidably mounted as at 64 and whose lower end is formed as a piston or plug 66 which is slidable in the cylindrical passage 68 in wall 73. Passage 88 leads between discharge chamber 68 and a shallow chamber 12 but i continually closed by the slidable piston or plug 66 excepting as slight leakage of steam past the piston into chamber F2 may occur and be conducted through pipe 74 to the turbine exhaust pipe 36, or exhaust chamber of the turbine casing.

From the foregoing description, it will be obvious that the pressure in discharge chamber 48 of valve casing 5-2 corresponds to the turbine nozzle bowl pressure and continually acts on the piston 65 tending to force it downward to a valveclosing position. According to the invention, however, any downward movement of the piston is resisted by mechanism which is responsive to the water pressure at the delivery side of the pump, so that the positions of valve discs 50, 52 at any time during operation of the pump is determined 'by the existing turbine nozzle bowl pressure and the water pressure on the delivery sideof the pump. Figs. 2, '3 and 4 show mechanism for thu controlling valve discs 50,'52. In Figs. 2 and 3, a bracket '56 is mounted on the under side of valve casing 32 at the part thereof which projects from the turbine casing, as best seen in Fig. 3. Operable in the bracket 76 is a lever '53 whose one end is pivoted at 80 to the upper end of a link "82 of centrifugal trip mechanism later to be described, and whose other end has a knife-blade bearing on a vertical rod 86 which extends slidably entirely through bracket '16 with a'coil spring 83 surrounding the upper part of the rod and under compression between the bracktfili and a discfifi which-is adjustable to vary the sprin tension by means of nut 92 on thethreaded upper end of rod'flfi. 'As shown in Fig. 2, the knife-blade bearing of lever '18'on 2,4.- is rod 86 is attained by having the rod extend through a relatively large hole 92 in the end of the lever, within which hole is fixedly mounted a bushing 9 having V-notches on opposite sides of rod 86 which engage knife-edges on a loose bushing 96 which in turn has a similar knifeedge bearing at B l on a collar its fixed on rod 86. Hence spring 83 constantly tends to raise or lift rod 86 and the end of lever it through which the rod extends.

This lifting tendency of spring 88 is resisted by the steam pressure acting on piston 68 and through a rod I92 on the lever l8. Rod I632 extends vertically through a relatively large hole I04 at a mid-location along lever 13 and through the upper wall of bracket IE and the under wall of valve casing 62 into the shallow chamber I2, with the upper end of rod Hi2 engaging the lower end of piston 65. Rod N32 has a knife-blade bearing on the lever It, the rod having a fixed collar I06 with knife-edges and the lever having a rigid sleeve IIIB with V-notches in which the knife-edges of collar I66 engage as at lot in Fig. 2. A shield III) on rod I92 covers the hole I04 through the lever against foreign matter and drip getting into the knife-edge bearing. The lower end of rod IIlZ extends into a dash pot H2 and is equipped with a disc-like piston Il for braking and preventing flutterin of rod Hence spring 88 continually acts to maintain the upper end of rod IIIZ pressed tightly against the lower end of piston 66.

Referring to Fig. 2, the rod St at the end or e ver I8 has its lower end projecting into a casing I I8 secured on the under wall of bracket This casing IIB interiorly is divided by wall Ii-3 into upper and lower chambers I'Zt, I22, and a piston or plug I24 is vertically slidable in a short cylinder I26 in wall H3 with its upper end arranged in position to engage the lower end of rod 85. Upper chamber 52d of easing Iii; is connected through pipe I28 to the suction side of the pump, and lower chamber I22 is connected by the relatively small diameter pipe I39 to the pressure or discharge side of the pump. Hence the lower end of piston I24 which is in chamber I22 is subjected to pump discharge pressure which acts upward on the piston tending to raise rod 35 and the end of lever I8. However, the turbine nozzle bowl steam pressure is acting downward on the steam piston 6t and through rod hi2 resists upward movement of lever IS by the water pressure, so that the position of steam piston 56 and thus of valve discs 5e, 52 is determined by the relation of steam pressure to the water pressure. So lon as the water pressure in conjunction with spring 88 can overcome the steam pressure acting downward on piston 63, the valve discs 58, 5?. will remain open more or less depending upon the relation of the opposing pressures. However, if tank It should run dry, or the water suppl to the pump fail or become inadequate for some other reason, the resulting sudden drop in pump charge pressure is communicated through pipe I30 to the under side of water piston I24 and the steam pressure then can force this water piston I24 downward until the valve discs 55, 52 become closed or nearly closed, to stop or slow down the turbine. Preferably the spring 88 will be adjusted initially so that the turbine will continue operation at an idling speed even though the water supply to the pump fails, this turbine idling speed being such that no harm can result even though the supply water for the pump be com pletely cut off. Then when the water pressure one 7 to th'eturbine. This results in a reduced debuilds up again, as by replenishing the supply intank III, or by correcting some other faulty condition, the water piston I24 will be forced upwardto open valve discs 56, 52 gradually until they are again open and a normal operating condition is restored.

It is a feature of importance that operation of valve discs 55, 52 can be controlled by controlling the water flow in the small pipe I30. In thisconnection it is notable that flow in pipe ISO is limited to the leakage past the water piston I24 and is relatively small. Piston I24 is slightly less in diameter than the interior diameter of its cylinder I23 so that this slight leakage past the piston can occur from lower chamber I22 to upper chamber IZEI, whence the leakage water passes through pipe I28 to the inlet or suction side of pump Ill. We have found that by controlling the small flow in pipe I39 the water pressure on water piston I26 can be modulated to control the valve discs Bil, 52. For this purpose, we show in Figs. 2 and 4 automatic valve mechanism associated with casing I I5 although the control might be by ma-nual or automatic means anywhere in the extent of pipe IEG which, because of its small size, can extend, if desired, to a location remote from the pump and the control means be'located at the remote point. A mere hand operated valve in pipe I33 can accomplish this control, or a well known type of float controlled valve operated by a float in the tank is could be employed for controlling now in pipe I36. As represented in the drawings, an automatic valve responsive to and holding substantially constant the pump delivery pressure accomplishes the said control of flow in I38. Valve spindle I32 is Vertically movable in a fixed valve sleeve I35 which has ports I38 through its walls opening into the lower chamber I22 of casing H 5 and ports I opening into the upper chamber I23. The lower end of sleeve I35 has the oppositely disposed V-notches I42 in its walls through which water from pipe I36 can pass into sleeve I38 and thence through ports I33 to chamber I22 when the valve spindle is in its lowermost position of Fig. 2, the valve spindle I32 having a reduced part I33 for this purpose. The upper end of valve spindle I32 is connected as at M4 to an inverted flanged cup member I48 in the cylindrical part Hi8 integral with casing IIB, the member I irl being yieldably held in its lowermost position of Fig. 2 by a coil spring I56 which is under compression between the flange of member ieii and the flange of an upright flanged cup member I52 which is adjustable to vary the compression of the spring, as by the adjusting screw I55 threaded in a depending part of a removable cover plate I55 on cylinder Hi8.

When valve spindle I32 is in its lowermost position of Fig. 2, water from pipe I3II enters lower chamber I2 as previously described and pump outlet or delivery pressure is thereby communicated to the under side of water piston I26. However, this water pressure in the small chamber I58 below the valve spindle I32 acts on the lower end of the valve spindle as a piston and, under normal operating conditions, will force the valve spindle upward against the pressure of spring I53, with gradual reduction of the flow passages through the V-notches I IZ.

The throttling of the flow through .the said V-notches results in the reduction of the pressure on the under side of piston I24 to a point where the steam piston 56 starts to close the steam valve discs 59, I52 and thereby reduces the input en a es:

force isin. equilibrium. with. the; spring; force.

Consequently whatever the volume-v of water.

pumped. the above describeimechanism: will operate to maintain that delivery pressure which-is= predetermined by. the. adjustment of the tension on spring I50:

In-.many pumping. systems. and in particular in the feeding. of boilers; there-is a constantly fluctuating demand-for waterrwhich necessitates some operative controlimeans forsthe steam input. This meansis constantly'inmotion asrthe load-fluctuates.v The control may. be-manual or automatic, responsive to water. level, speed, .pres' sure, temperature or otheivphysical qualities, and.

if, as iscontemplated in our invention, .this, con:- trol acts throughthe throttling. of" the flow through pipe I 36," it. will be. seenthat the. steam valve spindle -2 will bekeptrimconstant fiuctuae tion, and never; canbecome scaledor stuckand', since this same structure acts for the emergency.

controls, it is constantly. in-readinessto :function'. effectively and efficiently inanyemergency; In.

contrast, the prior controls..which require sep arate valves in the-steamiline to..the-turbine-re.-. spectively for normal operating control andJfor emergency control, are not: satisfactory because the emergency control may notzbe calledinto action for long periods of time and the emergency control valve and operating-mechanismissubject to scaling and corrosion so thatathey:caImot'function in emergencies and serious damageyfrequent ly results. Such a-failure cannot occur with our present control system and, if the steam valve discs 59, 52: should become scaled'and stuck: due to some very bad-water, the condition would'be. detected immediately at the control location by a departure from its normalvalue of whatever physical quantity is being held constant-such as pressure, for example, and'thez operator or attendant could correct the condition by manually activating lever l8 to free valve discs 50; 52:

Associated with automatic valve*I32 is a'hand:

controlled shut-off valve I34 (Fig. 4) which-normally is closed when the system is operating under the control of automatic valve I32: The-hand valve I 34 controls flowin a by-pass I6I'I -which extends betweenthe small chamber I58 below valve I32and through the ports I 38 andreduced' part I33 of valve I32 into chamber I22. As previously stated,i hand valve I34- normallyis closed so that the water fiowinto chamber I22-is through the V-notches I42. When it is desired to render automatic valvel32 inoperative, hand valve: I34 is opened to by-passthe-waterfiow. The. result-. ing increased flow acting'onwater.piston-.I24'pro-- duces increase of the-pump. delivery. pressure which. acting on-the lower end of valve. I32;

forces the valveupward'ato close the V-notches:

I42. Control of the system-.then-must-be -accom:-

plished by other means, suchzas; by the-"hand.

wheel I62.

To start the pump in operation;.the;hand.:wheelL I62 is turned to back its'stem I 64away .from the:

quate iiow ofwater to the pump, the pump will-- j.-bine which hastens the rise in water pressure andiultimate normal opening of valve discs 50, 52; Spring 58 initially is adjusted so that in absence of any water pressure on piston I24, it will maintain valve discs 58', 52open a slight amount so that the turbine can operate at a safe starting or idling speed. Each individual pump unit has adefinite bowl pressure at which it will idle safely and, by setting the spring tension to equilibrate the lever system when piston 56 is subjected to this particular pressure with no pressure on the water piston, discs 58, 52 wil1automatically be brought-to such a position of throttling as to securethis bowl pressure. If, as is preferred, the spring has a flat characteristic this idling bowl pressure will not vary substantially even though thepressure of'the steam supply varies greatly. Once spring 58has been thusproperly adjusted, it needs no further attention. Hence, so long as steam line-34 is open, steam can enter the turbine and'cause its operation at a speed slow enough to be safe even though-no water is being delivered by the pump. Our invention therefor provides the important advantage that a water supply failure for any cause does not result in-shutdown of the turbine and pump but only slows the turbine to a safe idling speed from which it can gradually build up normal speed when-the pump again receives and delivers water in a normal mannerwithout the attention of an attendant.

' The prior controls acting to shut down the pump have the disadvantage that the whole plant may have to be shut down until a water failure situation is corrected and the control mechanism manually reset. Our present mechanism acts -in an emergency to prevent over-speeding and, when the emergency condition is corrected, restores the system to normal without attention.

The mentioned of the eed of the turbine and pump due to awater in .16 ordinarilyis to a safe speed which cannot build up toan over-speeding condition capable of'harrnful efiects. It may happen, however, under unusual conditionswhere the sa e speed margin is small, that a slight over-speeding might occur. I-ience, we provide a further safety control actuated by a centrifugal trip mechanism associated with the pump shaft A collar or sleeve I68 is-slidably keyed on shaft in association with any suitable centriiugally acting means for actuating it in axial direction, such as the centrifugal-mechanism disclosedin Patent No. 2,124,339, granted July it 1938, to Christopher A. Schellens, one of is present joint applicants. An arm I i is fixed on the inner end of a short shaft 72 suitably mounted for free rotation in the side wall of the turbine-pump casing. As. illustrated in Fig. 2, an opening lid is pro vided inthe casing wall and is closed by a cover plate HEEL-in whichshaft i'iE'is journalled as at H85. On the outer end of shaft H2 is. fixed a latch member i8? whose depending part I82 has a projecting lug E8 3. Mounted on cover plate H6 isa pairof brackets iii-Ea, in which is pivotaily mounted) at 48?. the lever arm. it having a forked. upper endpivotally connected at IQD'to the. lower end of'the link 3-2-to whose other end is pivotally connected at 89 the steam valve operating lever lili- Pref'erabiy'lever arm I88= has a" depending tailpart ISQ-for engaging" a- -.slrock-absorbing mechanismor buffer I92 when" the centrifugal trip operates. Rigid with lever arm M8, or mounted to move in unison therewith, is a member E95. having a pin i535 normally engaging under projecting lug its of latch member use. A, coil spring 6533 is connected at one end to the upstanding part it! of latch member E86, as at 2353, and has its other end connected to member l by means of a pin l-Ience spring constantly biases member i9 5 in counterclockwise direction as viewed in 2, and latch lug i813 normally restrains such movement. However, if the turbine shaft 15$ should speed up to an unsafe speed for pump operation, the centrifugal acting mechanism (not shown) on shaft E56 moves collar Hi8 into contact with arm HE and rocks the latch member let counter-clockwise in Fig. 5, thereby releasing the latch and permitting spring let to rotate member 58 5 and lever arm H58 counter-clockwise in Fig. 2, thereby to pull down on lever l8 which leaves the control valve discs 52 free to be completely closed by the steam pressure, to stop the turbine and pump. Preferably a cam ass is provided on member M l to hold out of engagement with sleeve its to avoid undue wear of the point of engagewhen the trip mechanism operates.

Provision is made for adjustment of the setting of latch member as shown in Fig. 6. By mounting latch member 5% on the enlarged cylindrical part it] on shaft lit, the heads of the bolts lee, i815 can seat in notches it?) on opposite sides of cylinder l5? so that, by loosening one bolt and tightening the other, needed adjustment of latch member conveniently may be effected.

A further feature of our invention resides in provision of means for cutting in one or more auxiliary steam. nozzles and simultaneously increasing the effective area upon which the steam pressure acts tending to drive steam piston 55 downward. if the steam pressure inthe turbine supply line By this e can maintain the turbine power 'roxim cly it was prior to the pressure drop without changing the equilibrium of the control system, so that the pump continues normal operation during the adverse steam condition without its safety against over-speeding being reduced. Referring to Fig. '7, a hand valv controls steam conduit for cutting in the auxiliary nozsle or nozzles in the auxiliary nozzle belt 29?, 'l a conduit 285 leads between conduit and l in bonnet 21%} of the main valve casing upper end of valve stem 23 is t chamber so that when the con 36 i is backed away as in Fig. 2, the top of stem 52 is subjected solely to whatever pressure exists in chamber and added to t ec of piston 56 upon which ressure downward on the valve up Hence, at times of reduced steam pressure, opening of valve 2% opens chamber to the pressure at the an?) auxiliary nozzle bowls which acts downward on the end of v"lve stem thereby to permit the reduced ste. pressure to equilibrium of the valve unit because acting on a larger area. When hand valve is closed, the top of valve stem 52 similarly is subjected to exhaust pressure. i

The relative sizes of steam piston 65 and water piston I24 are proportioned to suit the rated steam and water pressures and are such that at full rated delivery volume there is a slight excess upward force on the water piston tending to hold the valve open, assuming that the regulator I32 is at its extreme lower position or the valve I34 is wide open. This upward bias increases if the delivery volume is decreased as by hand manipulation of the hand wheel I62 and its stem I64, the amount of increase depending upon the pump characteristics. Under these circumstances the opening of discs 55, 52 is determined by the position of stem ltd. When the system is controlled by the throttling of the water supply to the under side of water piston I24, as by the operation of regulator I32, and the hand wheel stem IE4 is in its upper position, the upward bias disappears since the forces acting on the lever it are in equilibrium at all delivery volumes. In the event of a failure of the water supply to the pump, however, the regulator I32 will call for more pressure and will open wide. Consequently from the standpoint of safety from over-speeding, the full delivery pressure may be regarded as acting on the under ide of water piston I24. If the piston is made too large, the excessive upward bias at lighter delivery volumes would prevent the rapid closing of the valve to prevent over-speedin Assuming that valve [34 is open, an unsafe upward bias would be produced by an excessive throttling of the discharge line, as at valve it, except for the opening of relief valve 28 which relieves the discharge pressure and limits it to a safe value. This relief valve is therefore an important part of the system.

In the above analysis it has been assumed that the pump inlet and turbine exhaust pressures were nearly atmospheric as is the case in many installations, but a large departure from atmospheric of either of these pressures has a bearing on the operation of the valve. If, for example, the steam and water pistons were designed for a machine having a high exhaust pressure, the exhaust pressure may be considerably lower than its rated value at times. Under these conditions, at a given delivery volume and pressure, a lowered turbine bowl pressure would exist which would increase the upward bias on the valve system and render it unsafe for rapid closure in the event of water supply failure. This efiect is compensated for if the chamber 12 i piped to the exhaust chamber of the turbine by lowering the pressure on the under side of the steam piston 6t and thereby restoring the bias to its safe value. A like efiect results if the suction pressure is raised and compensation is secured by piping the upper chamber lZll to the suction side of the pump as heretofore described.

From the foregoing description, it will be apparent that we have provided mechanism which effectively controls a turbine-driven centrifugal pump, ensuring against over-speeding and against scaling and sticking of the control valves. Also it provides for preventing over-speeding without shutting down the pump but merely by slowing its operation to a speed which is safe even through nowater is entering the pump; and the speed is automatically restored to normal when the pump again receives an adequate supply of water. However, a centrifugal trip control stands everready to stop the pump if over-speeding should, for any reason, occur.

The control of the main steam valves by con- 11 zin'operationthan any previous system-.of which We have-knowledge.

v It will: be apparent to Y those :skilled in :the art that the structure: described herein .is illustrative of but-:one-of-several -methods which -might 'be accomplishment :of the necessary :results :as set forth, .and it :is :intended that the *patentshall ..cover, by suitable expression in the appended claims, the broad aspects of the invention :inccluding whatever features of patentable :novelty exist .in'the'invention disclosed. Weclaim as "our: invention: 1.-.Control -mechanism for 1a turbine-driven ipump -'comprising a valve unit :controlling the :supply :line to the turbine, means -for applying toitheuvalve'unit the turbineinozzle bowl pressure in direction :tending v to close rthe i, turbine supply 2- line ia ndtthe pump delivery :pressure in 1 direction ztending to :open the turbine supply :line, and meansjfor :controlling: the "eifect :of-z the pump :de-

-iiv ery pressure .as rappliedito the valve .unit, .said

:vaive :unit .lcomprising a ,pair :of :discs :fixed ,in spacedzrelation onaavalve. stem andapistonrigid ion one:end;of.the stem the unit as. a wholeibeing .movable :between .a position in which said discs iclose'i the: supply: line i to the turbine: and. positions in.which'thavalves are openmore or less: depend- -ing upon :the relation of :the opposing :pressures .acting on the valve unit and said means for: con- --trolling "the effect of the pump delivery pressure =comprising a :member movable in response to :pressure applied thereto and arranged to act on -the;piston o'f the valve unit, a:re1atively small 'condui-t leading from the delivery side of the pump and applying the pump delivery pressure :to said ':member. indirection tending to open said discs,-and:means'for controlling fiow in said rela- J tively small conduit.

2. :Control mechanism ifor .a turbine-driven pump .comprising a valve unit controlling the supply iline Ito :the 'turbine, means including a piston rigid on wthe'valve unit for applying'toithe valve unit the :turbine nozzle bowl pressure in 1 direction tending to close the supply :line to the Iturbine, "means including aipiston for applying :to-the valve unit-the pump delivery :pressure in direction tending toopen the supp1y line=to:the turbine, and conduits 1 respectively forconducting ffluid leakin past the first said piston to-the exlhaust' side of the turbine and'forconducting water 'leakingpast the second said piStonLtothe suction side of :the :pump.

:3.-i'Control mechanism .for :a turbine-driven pump comprising a valve unit controlling the supply line 130 .the :turbine, :means for applying itoithetvalve:unittthezturbinemozzleibowl pressure .in .idirection ztending .tozclose :the turbine supply :line and :therpump delivery pressure in direction *ten'dingzto open the turbine supply line,.means acting with and intaddition do the:pump-:delivery pressure on :said valve unitforqmaintaining the valve. unit against complete closing by the-turbine vnozzle bowl pressure in absence-0f pump delivery pressure, thereby to reduce turbine operation to a safe idling speed Without stoppage of the-turbine-and automatic trip mechanism responsive to over-speedingof the turbine and operative to permit complete closing of said valve unit thereby to stop turbine operation.

4. Control mechanism for a turbine-driven pump comprising a valve unit controlling the supplyline to'the turbine, means for'applying to the valve unit the turbine nozzle bowl pressure in direction tending to close the turbine supply line andthe pump delivery pressurein direction tendingtoopen the turbine supply line, said means for applying the pump delivery pressure to the valve .unit including -a lever arranged toacton said valve unitat a locationintermediate'of the ends of the lever, tripmechanism normally supporting one end of the leverand responsive to over-speding of the turbine for releasing-said end whereby the turbine nozzle .bowl pressure can close said valveunit and stop the turbine, arelatively small conduit leading from .the delivery side of the pump and applying the pump delivery pressure to the other endof said lever in direction tending to open the valve unit, and means acting on said other end of the lever.with. and in addition to the pump deliverypressure for preventing total closing of the valve unit in vabsence of pump delivery pressure and solong as said trip mechanism. is in non-tripped condition.

-5.'Control mechanism for a turbine-driven pump comprising a valve .unit controlling the supply line to the turbine, means for applying to the valve unit the turbine nozzle bowl pressure indirection tending to close the turbine supply line and the pump delivery pressure in direction tending to open the turbine supply line, said means for applying the pump delivery pressure :to .the valve unit including a lever pivotally mounted at one end, a rod flexibly-connected to its other end with an adjustable spring acting on said rod and. biasing it and its end of the lever in :one direction,.a, relatively small conduit leading 'from the delivery side ofthe-pump and applying pump delivery pressure to said rodin the direction of its spring bias, and means intermediate of the ends of'thelever and-carried by the lever engaging said valve unit and held thereagainst by the bias of said spring and by the pump delivery pressure, said spring bias being sufficient in absence of pump delivery pressure to maintain the valve unit slightly open against the turbine nozzle bowl pressure acting in direction-to close it.

-6. Control mechanism for a turbine-driven pump comprising a valve unit controlling the supply'linetothe turbine, means for applying to the valve unit the turbine nozzle bowl pressure in direction tending to close the turbine supply line and the pump delivery pressure in direction tending to open the turbine supply line, said means for applying the pump delivery pressure to the valve unit including a lever engaging the valve unit intermediate of the ends of the lever and in opposition to the turbine nozzle bowl pressure.

'7. A turbine-driven pump and control mechanism therefor comprising a turbine having a normally operative nozzle belt and an auxiliary nozzle belt, a valved conduit for cutting in said auxiliary nozzle belt, a control valve unit controlling the supply line to the turbine, means for applying to the control. valve unit the turbine nozzle bowl pressure in direction tending to close the turbine supply line and the pump delivery pressure in direction tending to open the turbine supply line, means for maintaining equilibrium of the valve unit when pressure in the turbine supply line drops and the valved conduit is opened comprising a conduit leading from said valved conduit on the exhaust side of the valve therein, and applying the auxiliary nozzle bowl pressure to the control Valve unit in direction tending to close the turbine supply line and over an area of said control valve unit additional to the area on which the pressure of the normally operative turbine nozzles act on said control valve unit.

8. Control mechanism for a turbine-driven pump comprising a valve unit controlling the supply line to the turbine, means for applying to the valve unit the turbine nozzle bowl pressure in direction tending to close the valve unit, means for applying the pump delivery pressure to the valve unit in direction to open the valve unit, and adjustable means acting With and in addition to the pump delivery pressure on said valve unit in opposition to said turbine nozzle bowl pressure, said adjustable means being constructed, arranged and adjustable to maintain said valv unit slightly open even though the pump discharge pressure drops to zero, trip mechanism associated with said means for applying the pump delivery pressure to the valve unit, and centrifug-ally responsive means on the turbine shaft for tripping said trip mechanism upon over-speeding of the turbine thereby to stop the turbine.

9. Control mechanism for a turbine-driven pump comprising a valve-carrying piston having a pair of discs arranged and operative to control the supply line to the turbine, the turbine nozzle bowl pressure acting on said piston in direction to close the supply line to the turbine, a member operable on said piston in opposition to said turbine nozzle bowl pressure, a second piston for actuating said member, and means for applying the pump delivery pressure to the second said piston and through said member to the first mentioned piston in opposition to said turbine nozzle bowl pressure.

10. Control mechanism for a turbine-driven pump comprising a valve-carrying piston having a pair of discs arranged and operative to control the supply line to the turbine, the turbine nozzle bowl pressure acting on said piston in direction to close the supply line to the turbine, a lever having a paru intermediate its ends operable on said piston in opposition to said turbine nozzle bowl pressure, trip mechanism normally supporting one end of the lever, means for applying the pump delivery pressure to the other end of the lever in direction urging said intermediate part of the lever toward said piston, means for varying the effect of the pump delivery pressure as applied to said lever thereby to alter the relation of turbine nozzle bowl pressure and pump delivery pressure in their cumulative effect on the positions of said discs, and means for tripping said trip mechanism in response to an over-speeding condition of the turbine, thereby to remove from the piston the pressure in opposition to the turbine nozzle bowl pressure, whereby the latter pressure can close the discs and stop the turbine.

11. Control mechanism for a steam-turbinedriven pump comprising a source of steam and a conduit thence to the turbine, a source of water and a conduit thence to the pump, a valve unit in the steam conduit controlling the amount of steam delivered to the turbine, a pump delivery conduit having a pressure relief valve therein, means for applying turbine nozzle bowl pressure to said valve unit in direction tending to close the steam supply conduit, means for applying pump delivery pressure to the valve unit in opposition to the turbine nozzle bowl pressure, a, spring acting with and in addition to the pump delivery pressure and adjustable to a tension capable of preventing total closing of the steam supply conduit by the turbine nozzle bowl pressure in absence of pump delivery pressure, whereby a failure of pump delivery pressure results in slowing down of the turbine, and means responsive to over-speeding of the turbine for stopping the turbine.

12. In a fluid driven pump, a valve unit controlling the supply of fluid for driving the pump, means for applying to the valve unit the pressure of the fluid leaving the valve unit in direction tending to close the valve unit, means for applying to the valve unit the pump delivery pressure in direction tending to open the valve unit, and mechanism in actuating relation to the valve unit and constantly engaging the valve unit, said mechanism including a spring biasing the mechanism into engagement with the valve unit in direction tending to open the valve unit, whereby said mechanism acts with and in addition to the pump delivery pressure to maintain said valve unit slightly open even though the pump delivery pressure drops to zero.

13. In a fluid driven pump, a valve unit controlling the supply of fluid for driving the pump, means responsive to increased pressure of the fluid leaving the valve unit to bias said unit to- Wards closed position, means responsive to decreased exhaust pressure of the driving fluid to bias said unit towards closed position, means responsive to increased pump delivery pressure to bias the unit towards open position, means responsive to decreased pump inlet pressure to bias the unit towards open position, and means for regulating the pressure biasing one of said means, thereby to control the valve unit.

14. In a fluid driven pump, a valve unit controlling the supply of fluid for driving the pump, means for applying to the valve unit the pressure of the fluid leaving the valve unit, in direction tending to close the valve unit, means for applying to the valve unit the pump delivery pressure indirection and manner tending to open the valve unit, the latter pressure tendency being stronger than the former pressure tendency, whereby the valve tends towards Wide open position when the said pump is operating normally and tends towards closed position when the pump delivery pressure is excessively reduced, and means for varying the opening tendency of said delivery pressure on said valve unit to effect positioning of the valve unit at such intermediate positions between fully open and fully closed positions as may be required to suit the load demands on said pump.

15. Control mechanism for a pump driven by a turbine having an auxiliary nozzle belt, comprising a valve unit controlling the supply line to the turbine, a conduit connecting the auxiliary nozzlejbelt withttheidischarge side of the valve .unitifor supplying theauxiliary nozzle belt with driving flui'd'from the "discharge'side of said valve unit, :a valvein isaid conduit.io-rcontrolling the flow therethrough, means for applying to the valve unitithe pressure of the driving fluid leaving said valve unit indirection tending to close the supply line, means acting with and in addition .to the'first said means for applying to the valve unit the auxiliary nozzle belt pressure in direction tending 'to close the supply line, and means for applying to the valve unit the pump dischargerpressure in direction tending to open said supplyfline.

16. Control mechanism for a turbine-driven pump comprising a valve unit controlling the supply ,line .tothe turbine, means for applying to the valve unit the turbine nozzle bowl pressure in direction tending to close the valve unit, means for-applying to the valve unit the pump delivery pressure in direction tending to open the valve'unit, thelatter said means including a chamber, and a relatively small conduit leading 'thereto from the discharge side of the pump, and lmeans'for reducing the said valve opening tendency including means permitting leakage from said chamben and'throttling means in said conduit.

17. Control mechanism for a turbine-driven pump including a valve casing for supplying driving'fiuidto the turbine, a'valve unit including a disc movable in'the casing and coacting there with to control the amount of said driving fluid supplied'to the-turbine, means responsive to and increasing with "the discharge pressure of said pump actinglon said valve unit and tending to 'move said disc to open position,means within the valve casing responsive to the turbine bowl pressure acting on said valve unit and tending to move said disc to closed position, and adjustable means acting on the valve unit in opposition to said bowl pressure and adjustable to hold said disc inequilibrium when said discharge pressure islzero and when said bowl pressure is relatively small.

18. Control mechanism for a turbine-driven pump-including a valve casing for supplying driving'fiuid'to the turbine, a valve unit including a :disctmovable in the casing and coacting there- 'withto control the amount of said driving fluid supplied to the-turbine, and means for controlling the movement of said disc including means responsive tothe speed'of rotation of said'turbine, means having conduit connection to the discharge side of the pump, responsive'to the pump discharge pressure and acting on said valve unit in opposition to the driving fluidpressure thereon, the latte said means including adjustable resilient means for varying the amount of opposition offered by said pump discharge pressure :responsive means on said valve unit under any particular pump discharge pressure thereby to control the position of said disc in the valve casing.

:19. Control "mechanism for a turbine-driven pump, comprising a valve unit controlling the supply line to the turbine, means for applying to the valve unit the pressure prevailing on the delivery-side 'of'the valve unit in direction tending to closethe supply line, means including a relatively small diameter conduit leading from the "delivery sideof an impeller of the pump to the region of the valve unit for applying to the valve unit the pressure prevailing at the delivery side 'oi-saidimpellerindirection tending to open the 16 supply line, and means in said relativelysmall conduit for varying the magnitude of the said supply-line-opening-tendency of the said delivery pressure as applied to said valve unit.

20. Control mechanism for a turbine-driven pump, comprising a valveunit in and controlling the supply line to the turbine, said valve unit including an inlet chamber in free communication with the suppl line, and an outlet chamber in free communication with the turbine nozzle bowls, and including also valve means between said chambers for controlling flow therebetween, means in said valve unit for applying to said valve means the turbine nozzle bowl pressure indirection tending to close the supply-line, means operatively associated with said valve means for applying the pressure of liquid on the delivery side of an impeller of the pump to the valve means in direction tending to open the supplyline, and adjustable means acting with and in addition to the said pressureof liquid on said valve means in opposition to said turbine nozzle bowl pressure and having a normal condition of adjustmentfor maintaining said valve means slightly "open even though the said pressure of liquid dropsto'zero.

21. Control mechanism for a turbine driven pump comprising a valve unit-having throttling means therein for controlling the supply line to the turbine, means for applying to the throttling means the turbine nozzlebowl pressure'in direction tending to close the turbine supply line and for applying the pump delivery pressureto the throttling means in direction tending to open the turbine supply line, leverage mechanism in actuating relation to said throttling meansand responsive to the pump delivery pressure for urging the throttling means in direction to'open 'the supply line, and a spring associated with theleverage mechanism and acting on said throttling means through said leverage mechanism in the same direction as and in addition to the pump delivery pressure, said spring being adjustable to vary its efifect on the throttling means,

22. Control mechanism for a turbine-driven pump comprising a valve unit having throttling means therein for controlling the supply line to the turbine, means for applying to the throttling means the turbine nozzle bowl pressure in direction tending to close the turbine-supply'line and for applying the pump delivery pressure'to the throttling means in direction tending to open the turbine supply line, leverage mechanism in actuating relation tothe throttling means and responsive to the pump delivery pressure for urging the throttling means in direction'to open'the supply line, said means for applying the pump delivery pressure to the throttling means including a relatively small conduit leading fromthe delivery side of the pump and applying the pump delivery pressure to said leverage mechanism, and valve means in said relatively small conduit for controlling said throttling means by controlling the relatively small flow of water under pump delivery pressure in said relatively small conduit.

23. Control mechanism for a turbine-driven pump comprising a valve unit having throttling means therein for controlling thesupply line-to the turbine, means on the throttling meansand open to the turbine nozzle bowl pressure for applying to the throttling means the turbine'nozzle bowl pressure in direction tending to close'the turbine supply line, means operatively associated with the throttling means for applying the pump delivery pressure to the throttling-means in direction tending to open the turbine supply line, said CHRISTOPHER A. SCHELLENS. ARTHUR L. SHERMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 624,779 Ford May 9, 1899 822,184 Chamberlain et a1. May 29, 1906 10 1,399,280 Venschoten Dec. 6, 1921 1,564,686 Kimball Dec. 8, 1925 1,725,722 Schellens Aug. 20, 1929

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