US2998017A - Emergency governor exerciser - Google Patents

Description

Aug. 29, 1961 A. CAVALIERI 2,998,017

EMERGENCY GOVERNOR EXERCISER Filed March 28, 1960 l /6`./. EMERGENCY sEcoNoARY 1/f /5' Govt-:RNoR @overwon l RELAYS T0 OTHER RELAYS 20 /N VEA/Tof? ,maaar L. cAI/AL/ER/ H/S ATTORNEY tte This invention relates to an improved governing system for a prime mover such as a steam turbine, and more particularly it relates -to an exerciser for the emergency governing mechanism which permits testing of all the emergency governing components while the turbine is operating without shutting down the turbine, including special means to automatically place the emergency governor back intoV an operative condition if the turbine overspeeds while the emergency governor is in a testing position.

A conventional steam turbine powerplant often includes both a control valve unit which is actuated by a main governor to control the flow of motive fluid to the turbine in accordance with the varying load demands, and also a stop valve which is actuated by an emergency governor to completely shut olf the ilow of motive iluid in case the turbine overspeeds. This invention is concerned Withan exerciser mechanism for testing the emergency governing mechanism, since, although the emergency governing mechanism would rarely be called upon to function in actual service, reliability of its components is absolutely necessary. inasmuch as' the emergency governor has to be removed from operation for a short time in order to test it without shutting down the turbine, some guarding means must be provided to protect the turbine against overspeeding while the emergency governor is not operating. The eventuality of an overspeed condition while the emergency governing mechanism is being tested is quite serious' and extensive damage could result to the powerplant if complete protection were not provided.

Patent 2,926,680, issued March 1, 1960, to Markus A. Eggenberger, and assigned to the assignee of the present application, describes a mechanism for testing the emergency governor without shutting down the turbine and includes an additional pre-emergency governor as a guarding means for shutting down the turbine in the event the turbine overspeeds during the period that the emergency overspeed governor is rendered inetfective. ln that system, alternate control over the stop valve vests in either the main emergency governor or a pre-emergency governor; however, the pre-emergency governor or guarding means cannot be tested during operation.

The present invention overcomes the foregoing difficulties and provides an improved exerciscr for an emergency governing mechanism in which every component can be tested while the turbine is operating.

Accordingly, one object of the present invention is to provide an improved emergency governing mechanism exerciser which permits testing of the emergency governor while the turbine is operating.

Another object is to provide a simpliiied arrangement for utilizing a speed responsive arrangement to guard the powerplant while the overspeed governor is being tested. A more specific object is to provide means for exercising all of the components of the emergency governing system, including the components' of the guarding means itself, while the turbine is operating, while providing full overspeed protection at all times.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawings in which:

FIG. l is a simplied schematic diagram illustrating the disposition of the emergency governor and the governor exerciser in relation to the overall powerplant;

' 2,998,017 Patented Aug. 29, 1.96111 FIG. 2 is a more detailed schematic diagram illustrating the various components of the emergency governor exerciser in the rst phase of operation; and

FIG. 3 illustrates the emergency governor exerciser of FIG. 2 as it appears in the second phase of operation.

The invention, in one form, is practiced by providing a spill valve serving the hydraulically-operated valves, which is actuated by the emergency governor to shut down the powerplant. A special three-way valve is placed in the hydraulic line intermediate to the spill valve and the devices which it controls. The three-way valve normally resides in a run position and affords free communication between the spill valve and these devices, but when the emergency governor is to be exercised, the three-way valve is moved to a test position and bypasses the emergency governor-actuated spill valve. A secondary governor returns the three-way valve to its previous run position in the event that the turbine overspeeds while testing is taking place.

Referring now to FIG. 1- of the drawing, the emergency governor exerciser is shown in greatly simplified diagrammatic form so as to indicate its relationship with the powerplant and in order to illustrate the basic principle of operation. A prime mover such as a steam turbine 1 is furnished with motive iluid from the steam generating coils 2. A main governing mechanism 3 includes a ilyball governor 4, a steam control valve 5, and an operating lever 6. The governing mechanism 3 regulates the speed of the turbine under varying load conditions in the conventional manner and the details are not pertinent to the present invention;

A stop valve 7 operated by hydraulic relay 8 is shown as a diagrammatic representation of typical equipment controlled by the emergency governor. A centrifugal pump 9 driven by turbine 1 furnishes hydraulic fluid under pressure to relay 8 through conduit 10. Hydraulic relay 8 is so constructed that the relay must be under hydraulic pressure furnished by the conduit 10, in order for it to hold stop valve 7 open. Loss of pressure in hydraulic line 10 will cause relay 8 to completely close stop valve 7 and shut off the ow of steam from the steam generator 2. Stop valve 7 is merely representative and it will be understood that many other devices may also be shut down or turned on by the emergency governor upon loss of pressure in line 10. Two examples would be the interstage valve in an extraction turbine or the reheat stop valve between two turbines where the motive iluid is reheated.

An emergency governor 11 is set to trip a spill valve 12 at a predetermined overspeed condition, for example, of rated speed, discharging hydraulic fluid through drain conduit 13. A three-way valve 14 which is normally positioned to aiford communication between spill valve 12 and hydraulic relay i8 is controlled by a speed responsive secondary governor 15. On desiring to test or exercise the system, a test signal from device 16 moves three-way valve 14 to bypass hydraulic iiuid around spill valve 12 through the bypass line 17. Thus the emergency governor 11 can be tested and spill valve 12 actuated without losing pressure in line 10. The seeondary governor 15, however, overrides the commands from test signal device 16 in the event that the turbine exceeds a predetermined speed while the emergency governor is being tested. Secondary governor 15 is a guarding device which returns three-way valve 14 to its previons running position when this speed is exceeded, to again put the emergency governor 11 in control. lThus the secondary governor 15 controls the ability yof the emergency governor 11 to carry out its intended function.

With the above simplified explanation in mind, reference'to FIG. 2 will show the actual emergency governor exerciser in more detail. Corresponding members in FIGS. l, 2 and 3 bear the same numeralk designations.

Y the top land and thehousing. Y

The emergency governor` 11, which is of the off-center bolt type is geared to the turbine shaft in a suitable manner so as to turn therewith and includes an oli-center member 11a held in retracted position by spring 11b to actuate a trip lever 20 at a predetermined speed in the conventional manner. Au oil trip nozzle 21 vset to discharge into the central portion 11e` of emergency governor 11 is controlled by a valve 22. Thus the overspeed condition can be simulated by an opening valve 22 and discharging oil into the emergency governor 11 to trip lever 20 by creating an added eccentric load, even though governor 11 is turning at a speed less than the normal trip speed.

The foregoing overspeed simulating 'arrangement for testing the emergency governor 11 is disclosed in the aforementioned Eggenberger patent.

The spill valve shown generally at 12 comprises a pilot piston 12a biased downward by spring 12b and includes means for resetting piston 12a against the biasing of spring 12b by a lever 12e, link 12d, and a handle 12e in a manner which will be obvious from the drawing. Pilot piston 12a is held upward against the bias of spring 12b by a cam surface 20a on lever 20. In its se position, spill valve 12 alfords a free flow of oil from a source of hydraulic pressure (not shown) by means of the conduit 23, ports 123, 12g and conduit 24 to the three-way valve 14.

Three-way valve 14 is a fluid pressure actuated Ytwoland piston-type valve which includes a housing 14a and a pressure actuated piston 14h. Hydraulic fluid from the same pressure source supplies three-way valve 14 through port 14C in the side of the housing via conduit 25 and port 14d in the end of the housing 14a via conduit 26. Surface 14e of the right-hand land defines a pressure chamber 14f with the valve housing 14a which biases the piston 14h to the left. A stop 14g prevents movement of the piston 14b to the left beyond a predetermined point. The surface 14h of the left-hand land delines with the casing 14a a pressure chamber 144' which is supplied with fluid by port 14j in the end of the housing. It will be observed that the area of surface 14h exposed to the pressure in chamber 141' is larger than that of surface 14e exposed to the pressure in chamber 14f. Therefore, if equal pressures exist in chambers 14, 14j, piston 14b will be biased to the right.

Ports 14k, 14m in the side of housing 14a both communicate with a chamber 14n between the lands of the pilot piston when it is in its left-hand position, as shown in FIG. 2. Conduit connects port 14k with the various devices controlled by the emergency governor mechanism and represented diagrammatically by the relay 8. Thus when the piston 1411 is to the left (run position),'relay 8 willbe furnished with hydraulic fluid by way of conduit 23, spill valve 12, conduit24, chamber 14n and conduit tion, relay 8 will be supplied with fluid by way of con- 'duit 25, chamber 14n, conduit 10. Thus Whenpiston 14b is to its right-handyposition (test position), FIG. 3, spill valve 12 will be bypassed in order that goyernor'll may be tested. Y

The secondary governor controls Ythe positioning of three-way valve 14. iA two-land piston 15a is slidable in a housing 15b which defines por-ts 15C, 15d in the side of the housing. The top and bottom lands of pilot piston 154 define control orifices 15e,.15f with ports 15C, 15d respectively. Another port 15g between thelands communicates with port 14]' of theVthree-way v alvef14 by means of conduit 27.` Hydraulic lluid is supplied to the secondary governor 15 through orifice 15e by way of conduit 2S. A port 15h in the top of housing 15b Vand a branch conduit, V29V connected` to conduit S also allow entry of hydraulic fluidrto a chamber 151' defined between lt will be apparent ,that the full topsurface top land of piston 15a is exposed to the pressure in line 28'.

Piston 15a is biased upward against the pressure in chamber 15i by a spring 151 disposed in a recess 15k in the bottom of housing 15b. A chamber 15m, defined between the lower side of the bottom land and the housing aids spring 15]' in biasing piston 15a upward. A oonstri-cted passageway 15p in the bottom land provides a pressure in chamber 15m which is equal to the pressure between lands. Thus a pressure reduction between lands (caused by closing orifice 15e and opening orifice 15) is transmitted by port 15p to chamber 15m. This improves the speed of response of piston 15a. A valve 30, having an elective area greater than that of port 15p, provides means to evacuate chamber 15m.

It will be apparent that piston 15a may be caused to move downward in two different ways. First, by increasing the pressure in chamber 151', the piston will begin to move, closing orifice 15e and opening orifice 15f. This causes the pressure between lands to drop oi rapidly, and this loss of pressure is communicated to 15m to further unstabilize piston 15a, causing it to move downward.

The second way to cause piston 15a to move downward is to open valve 30. The restricted opening 15p in the bottom land will not allow a rapid enough ow of hydraulic fluid to restore the full pressure in chamber 15m, since the opening furnished by valve 30 is designed to be much greater than the restricted opening 15p.

The ow of hydraulic fluid to secondary governor 15 is controlled by a pilot valve 31 from a speed responsive variable pressure source (not shown). This source may, for instance, be the centrifugal pump 9 shown in FIG. 1 whose outlet pressure varies as a function of turbine speed. The fluid enters lthrough conduits 32, 33 and ports 31a, 31b respectively in valve housing 31C. A twoland piston 31d is slidable in housing 31C, and a port 31e in the side of the housing communicates with a chamber 317c defined between the two lands and the housing. A port 31g leads to an exhaust conduit 31k and an additional port 31h leads to a chamber 311' defined beneath the bottom land and the housing. A source of hydraulic fluid under pressure (not shown) supplies fluid to port 31h. and chamber 311 through a valve 34, and a connecting conduit 35. A restricted bleed orifice 36 is located in communication ywith conduit 35 intermediate valve 34 and pilot valve 31. The upward pressure on the bottom land surface of piston 31d resulting from pressure in chamber Sli is opposed by pressure in an upper chamber 31j acting on the surface of the top land. It will be observed that the land surface area exposed to the pressure in chamber 31]' is much smaller than the land surface area exposed to the pressure in chamber 311' so that the position of piston 31d is lat the top when the pressures in chambers 31j, 31i are equal. Chamber 31j is continuously exposed to the pressure in source conduit 33, whereas chamber 31i is exposed to the full hydraulic pressure only when valve 34 is opened. When valve 34 is closed, bleed orice 36 slowly drains chamber 31:' so that pilot valve piston 31d moves downward.

The top land of piston 31d of the pilot valve 31 defines an orice 31m with port 31a and the bottom land delines an orifice 31u with port 31g. As will be apparent from FIG. 2 of the drawing, when piston 31d is in its upward position, iluid is supplied from conduit 32 through orifice 31m, chamber 313, port 31e, and conduit 2S to the secondary governor 15. Conversely, when pilot valve piston 31d is in its bottom position, orifice 31m is closed and fluid can discharge from line 28 through port31e, chamber 31], orice 31u, and out exhaust conduit 31k.

The hydraulic fluid supplying conduits 23, 25, 26, 35, 32, 33 may conveniently be from the same source. If the pressure of the fluid varies, orilices (not shown) may be used in conduits 23, 25, 26, 35 to obtain substantially constant pressure. However, it is necessary for the successful operation of exerciser governor 15 that thepressure of the hydraulic fluid furnished to conduits 32, 33

(hence to chamber 151') vary as a function of the turbine speed. Since the main hydraulic oil pump 9 (see FIG. l) is a centrifugal pump, the turbine hydraulic oil pressure will vary as the square of the turbine speed. Thus it is Ithat the spring biased piston valve is termed a secondary governor, since it functions as a governor to trip the piston 15a when oil pressure is increased in chamber 151'. The greater the turbine speed, the greater the pressure in chamber 151' and the lower the p iston 1511 will move in its housing. The spring constant of spring 15j is selected to hold orifice 15f in a closed position when the turbine is at normal rated speed. When the speed of the turbine has increased to a predetermined amount, however, for example to 105% of rated speed, the pressure in chamber 151- supplied by the centrifugal turbine-driven pump has also increased to such an extent that orifice 15)c starts to open. Thereafter, a rapid movement of piston 1511 takes place.

The operation of my improved emergency governor exerciser will now be described. Referring to FIG. 2 of the drawing, the rst phase of the governor exercising procedure is illustrated. Valve 34 is `opened causing piston 31d of pilot valve 31 to rise to its top position as shown. Oil ows from conduit 32 through orice 31m, chamber 31f, port 31e, conduit 28, and conduit 29 to chamber 151` on the top of the secondary governor piston 1511. Assuming that the turbine is not exceeding lthe calibrated overspeed setting of secondary governor 15 when testing is commenced, secondary governor piston 1511 will remain close to the top of the housing and orifice 15e will remain open (shown closed in the drawing). The fluid entering through orifice 15e leaves the secondary governor 15 via port 15g, conduit 27, and enters chamber 141' of the three-way valve 14 biasing three-way valve piston 14h to the right or test position. In FIG. 2 of `the drawing, the piston is shown to the left in its normal or operating position since it will be immediately returned to this position during the irst phase of testing in the following manner.

Valve 30 is opened and uid discharges from chamber 15m allowing piston 15a to move downward, opening orice 15j". When this occurs, piston `14b of lthe threeway valve immediately returns -to its run position as shown in FIG. 2, since the pressure in chamber `141 is relieved. Also, the secondary governor 15 has been simultaneously exercised by virtue of the movement of piston 1511. This gives the assurance that the piston 1511 is not stuck or jammed and is free to operate smoothly.

4It will be observed that a positive check of the speed calibration of secondary governor 15 is not obtained by thus exercising it by opening valve 30, but the only probable malfunction of secondary governor 15 would be due to plugged ports or sticking of `the piston 1511 in the housing. Thus merely causing the piston to move downward as though in an overspeed situation is a suicient safety precaution.

It should be apparent that, during this first phase of testing, pilot valve 31, secondary governor 15, and threeway valve 14 have all been actuated thus insuring their reliable operation in case of an emergency. At the same time, it will be observed that the turbine has constantly been under surveillance by either the secondary governor 15 or by the emergency governor 11 during the foregoing. It is to be particularly noted that secondary governor 15 does not act to close any valves controlling motive uid to the turbine, but that on the other hand it controls the ability of emergency governor 11 to function by means of its control over the three-way bypass valve 14.

Reference to FIG. 3 of the drawing will aid in an understanding of the operation of my emergency governor exerciser during the second phase of testing. Valves 30, 34 supplying the secondary governor 15 and the pilot valve 31 respectively are now closed. The bleed orice 36 permits fluid to escape from the lower part of pilot valve 31 emptying chamber 311 and the pressure on the 6, top of the' pilot piston: 31d forcesl ity downward. When this occurs, orifice 31m closes and orifice 3111 opens allowing fluid to drain from the pressure chamber .151' at the top of the exerciser governor 15.

This resetting ofthe pilot valve 31 and the secondary governor 15 takes only a few seconds. Thereafter, valve 34 leading to pilot valve 31 is again opened and the piston 31d again rises to its uppermost position re-admitting hydraulic iluid to the chamber 151 of secondary governor 15. Fluid is also admitted through orifice 15e of the secondary governor to enter chamber 141' of the three-way valve and force the piston 14b of the three-way valve 14 tok the right as shown in FIG. 3. This ow of fluidfis a test signal since it sets valve 14 in its test position. Since the three-way valve 14 is in its test position, hydraulic Huid is bypassed from conduit 23 to the relays, and the emergency governor 11 may now be exercised` without shutting down the turbine.

It is to be noted that while the subsequent testing takes place, the turbine is under constant surveillance by secondary governor 15 and if the turbine overspeeds, the pressure in chamber 151' will increase, tripping piston 15a and discharging lluid from chamber 14iof three-way valve 14, thus returning it to its run position. In the run position, of course, the emergency governor 11 has control and will shut off motive uid to the turbine if its speed setting is exceeded.

The valve 22 supplying oil trip nozzle 21 is now opened and oil is admitted to the interior 11C of the governor 11. Its added weight moves the olf-center member 1111 outward to strike lever 20. When this occurs, cam surface 2011 is rotated to allow the spring 12b of the spill valve 12 to force the spill valve piston 1211 downward discharging the uid in conduit 24. Note that the port 127C is also closed by the spill Valve piston thus preventing loss of excessive iiuid from the line 23. Valve 22 is then closed to stop oil from being admitted to 11C, which then resets 1111.

The operating capability of emergency governor 11 and spill Avalve 12 having been thus assured by exercising the components, spill valve 12 is reset by moving lever 12e to the left and the spring on lever 20 will re-establish the position of spill valve piston 12a on the cam surface 20a.

It only remains to close the valve 34 which permits pilot valve piston 31d to return to its bottom position. When this occurs, the three-way valve 14 isv reset to its run position, with valve piston 14b moving to the left, the fluid in chamber '14i escaping via conduit 27, orifice 15e, conduit 28, orilice 3111, and discharge conduit 31k.

It will be understood that the explanation of the operation of the system referred to Valves 22, 30, 34 as though they were manually operated. In actual practice, it is more convenient to employ electrical solenoid valves operated in accordance with a predetermined switching sequence. The use of an electrically controlled sequence of operations with limit switches to determine the position of the various members assures that the proper sequence of valve openings and closings is carried out, since the exercising of the emergency governing system must be a routine periodic inspection forming part of the safety plan of the power station. Also, a suitable time delay can be introduced between the switching events. The design of the circuitry to accomplish the proper sequence of events lies within the scope of one skilled in the art, and is not included in the drawing since it would only tend to obscure the invention.

It also lies within the scope of the invention to use some other speed responsive means for a secondary governor, such as a yball governor to position the threeway Valve 14'. The use of a hydraulic line pressure which Varies as a function` of turbine speed, however, is a convenient way to incorporate the speed responsive means into the system at a minimum cost and the reliability of the pressure Variation with speed is accurate enough for guarding the turbine while the emergency governor is' being exercised, since absolute accuracy of speed sensing is not necessary for this application. Hence, FIG. l of the drawing shows a general representation of the secondary governor indicating that other types of speed responsive means can be used to operate the three-Way valve 14. i Y

In conclusion, it will be seen that all components of the emergency exercising system are testable during operation without shutting down the powerplant. At the same time, full protection against the possibility of overspeed while the testing procedure is being carried out is provided by means of the arrangement described.

The importance of complete protection at all times cannot be overemphasized, since overspeed will 'cause seriousrdamage to the powerplant. If the emergency governor were not periodically tested, long periods of idleness couldrpossibly cause' the valve pistons to stick in their housings. A routine exercising of all componentswill greatly reduce this possibility. The foregoing emergency governor exerciser provides a valuable adjunct to a safe, reliable Powerplant and allows routine testing ofthe emergency governor without danger of overspeed possibility during testing.

lt is, of course, intended to cover by the appended claims all such modiiications as fall Within the tru spirit and scope of the invention.

What I claim las new and desire to secure by Letters Patent of the United States is: Y

l. In combination a turbine having inlet valve means controlling the flow of motive fluid to the turbine, uid pressure actuated motor means connecte-d to operate the inlet valve means, a source of V.actuating fluid under pressure supplying said motor means, emergency governor means responsive to a rst turbine overspeed condition, means to artificially trip said emergency governor means at a speed below said first turbine overspeed, an emergency governor exerciser for said turbine comprising rst means operated by the emergency governor means controlling the ilow of actuating fluid to the motor means, second means havingV a run position bypassing fluid between said tirst means 'and said motor means and a test position controlling the ow of actuating fluid to the motor means independently of said iirst means, whereby the emergency governor and the rst means may b'etested/without shutting down the turbine, third'means to placeV said second means'in the Vtest position, and secondary governor means responsive to a second turbine overspeed condition adapted to inactivate said third means by Yreturning said second means to the' run position when the second turbine overspeed is exceeded, whereby primary control over theV motor means will 1b.f"r`et-ur'11ed to the yrst means. l f 'i 2.. 1 The combination according to claim l and including means to artificially actuate the secondary governor means at a speed below the second turbine overspeed,V whereby it will also inactivate said third means.

3. In combinati-on a turbine having inlet valve means controlling the flow of motive uid to the turbine, uid pressure actuated motor means connected to operate the inlet valve means, a source of actuating iluid under pressure supplying said motor means, spill valve means connected to discharge actuating fluid from said motor means, emergency governor means responsive to a rst turbine overspeed condition to actuate said spill valve means, means to artificially trip said emergency governor means below said iirstturbine overspeed, an emergency governor exerciser for said turbine comprising three-way valve means having a iirst position connecting the spill valve means directly with the motor means and a second position connecting the actuating fluid source with the motor means and bypassing thespillvalve means, whereby the emergency governor means may be arti'cially tripped below Ythe Viirst turbine overspeed when'the three-way valve means is in the secondposition vvithoutVV shutting down the turbine, and secondary governor means responsive to a second turbine overspeed condition connected to returnfthe three-way valve means to its rst position in the event that the second turbine overspeed is exceeded while the emergency governor is being tested.

4. In combination a turbine having inlet valve means controlling the flow of motive iluid to the turbine, uid pressure yactuated motor means connected to operate the inlet valve means, a tirst source of actuating uid under pressure supplying said motor means, spill valve means connected to discharge actuating uid from said motor means, emergency governor means responsive to a iirst turbine overspeed condition to actuate said spill valve means, means to articially trip said emergency governor means below said first turbine overspeed, an emergency governor exerciser for said turbine comprising three-way valve means having a iirst position connecting the spill valve means directly with the motor means and a second position connecting the actuating fluid source with the motor means and bypassing the spill valve means, whereby the emergency governor means may be articially tripped below the iirst turbine overspeed when the threeway valve means is in the second position without shutting down the turbine, secondary governor means responsive to a second turbine overspeed condition connected to return the three-way valve means to its rst position in the event that the second turbine overspeed is exceeded, and means to artificially actuate said secondary Agovernor means below the'second turbine overspeed, whereby it will simultaneously move the three-way valve means from its second position to its iirst position while said secondary governor is being actuated.

5. In combination a turbine having inlet valve means controlling the ow of motive uid to the turbine, uid pressure actuated motor means connected to operate the inlet valve means, a source of actuating uid under pressure supplying said motor means, spill valve means connected to discharge actuating uid from said motor means, emergency governormeaus responsive to a rst turbine overspeed condition to actuate said spill valve means, means to articially trip said emergency governor means below said rst turbine overspeed, an emergency governor exerciser for said turbine comprising three-way valve means having a rst position connecting the spill valve means `directly with lche motor means and a second position connecting the actuating fluid source with the motorV means and bypassing the spill valve means, whereby the emergency governor meansV may be artiiicially tripped belowrthe tirst turbine overspeed when the threeway valve means is in the second position without shutting down the turbine, a second source of `actuating uid having a pressure varying as a function of turbine speed, secondary governor means including a housing having biased piston means: therein -with a surface exposed to said second actuating iluid pressure source and connected to return the three-way valve means to its rst position in the event that .the second turbine overspeed is exceeded while `the emergency governor is being tested.

6. In combination a turbine having inlet valve'means controlling'the ilow of motive uid to the turbine, irst fluid pressure actuated motor Vmeans connected to operate the inlet valve means, a first source'of actuating luid under pressure supplying said motor means, spill Vvalve means connected to discharge actuating Huid from said tirst motor means, emergency governor means responsiveto a iirst turbine overspeed condition to Yactuate saidV spill valve means, meansY to artiiicially trip said emergency governor means below said iirstturbine overspeed, an emergency' governor exerciser for saidv turbine comprisingwthree-way valve' means including a housing having slidable piston means therein exposing a first pair otports in a'rst position connecting the spill valve means with the motorV means and exposing a second pair of ports in aV second positionk connecting the first actuating fluid source with the first motor.means, second` uid pressure actuated motor means arranged to move the three-way valve piston toward the second position, means to bias the piston toward its iirst position, a second source of actuating fluid under pressure supplying said second motor means, and secondary governor means responsive to a second turbine overspeed condition and connected to discharge uid from said second motor means when the turbine exceeds said second turbine overspeed, whereby the three-way valve piston will be returned to its first position in the event that the second turbine overspeed is exceeded While the emergency governor is being tested.

7. In combination a turbine having inlet valve means controlling the flow of motive uid to the turbine, fluid pressure actuated motor means connected to operate the inlet valve means, a first source of actuating uid under pressure supplying said motor means, spill valve means connected to discharge actuating fluid from said motor means, emergency Ygovernor means responsive to a first turbine overspeed condition to actuate said spill valve means, means to artificially trip said emergency governor means below said rst turbine overspeed, an emergency governor exeroiser for said turbine comprising three-way valve means including a housing having slidable piston means therein exposing a first pair of ports in a first position connecting the spill valve means with the motor means and a second pair of ports in a second position connecting the first actuating uid source with the motor means and bypassing the spill valve means, whereby the emergency governor means may be tripped when the three-Way valve is in the second position Without shutting down the turbine, said three-way valve means housing also defining together with the piston a first pressure chamber to move the piston toward its second position,

means to bias the three-Way valve piston toward its first position, a second source of actuating fluid having a pressure varying `as a function of turbine speed, pilot valve means connected to control the flow from said second pressure source, secondary governor means including a housing having slidable piston means therein, exposing a third pair of ports in a third position connecting said pilot valve means with said three-way valve first pressure chamber and a fourth pair of ports in a fourth position arranged to discharge uid from the first pressure chamber, resilient means biasing the secondary governor piston toward its third position, the eXerciser governor piston also defining together with its housing a second pressure chamber opposing said resilient means and connected to said pilot valve means, whereby increase in pressure of the second source of actuating fluid beyond that corresponding to a predetermined second turbine overspeed condition will move the secondary governor piston from its third positionto its fourth position to discharge fluid from the rst pressure chamber of the three-way valve means inthe event the second turbine overspeed is exceeded while the emergency governor means is being tested.

8. The combination according to claim 7 and including means to articially actuate the secondary governor means below the second turbine overspeed, whereby it will simultaneously move the threewvay valve means from its second position to its first position While the secondary governor means is being actuated.

References Cited in the file of this patent UNITED STATES PATENTS 2,926,680 Eggenberger Mar. 1, 1960

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