US2842149A

US2842149A - Suction-trip shut-off valves provided with manual resetting means, for turbine driven boiler feed pumps

Info

Publication number: US2842149A
Application number: US452077A
Authority: US
Inventors: Robert R Donaldson
Original assignee: Hagan Chemicals and Controls Inc
Current assignee: Hagan Chemicals and Controls Inc
Priority date: 1954-08-25
Filing date: 1954-08-25
Publication date: 1958-07-08
Anticipated expiration: 1975-07-08

Description

y 1958 R. R. DONALDSON ,8 9

SUCTION-TRIP SHUT-OFF VALVES PROVIDED WITH MANUAL RESETTING MEANS, FOR TURBINE DRIVEN BOILER FEED PUMPS Filed Aug. 25, 1954 DISCHARGE PRESSURE v 7 r STEAM TURBINE n WATER PUMP SUPPLY DR'VE PUMP DISCHARGE:

LINE

'o/L OPERATED w PUMP 6 eovsmvon I 3. ,53 PUMP [48 V 60 SLiCHTVIgN 52 A A I 4.9 VALVE 22 ml 0/ 4- 5 zj Jw/ zy 43 2g? 3 F 0/4 0mm 60 6g 50 3 46 57 I 54156 44 /0 3/ I T 26 22 El 1 23 3/ 27 36 I 40 64 29 lgfl. -33 V 35 3 3 INVENTOR.

7 7 L ROBERT R. DONALDSON BY Q 67 68 Afys.

United States Patent SUCTION-TRIP SHUT-OFF VALVES PROVIDED WITH MANUAL RESETTING MEANS, FOR TUR- BINE DRIVEN BOILER FEED PUMPS Robert R. Donaldson, Forest Hills, Pa., assignor to Hagan Chemicals 85 Controls, Inc., a corporation of Pennsylvania Application August 25, 1354, Serial No. 452,077. 6 Claims. (Cl. 137-87) This invention relates to turbine driven boiler'feed water pumps, and more particularly to safety valves that operate upon the turbine governor to shut the turbine down in the event the temperature-pressure relationshipv the pump loses its load causing the turbine to overspeed.

It is therefore essential to safety to provide a valve for shutting the turbine clown automatically when the pump suction approaches a point where the feed water is likely to flash into steam.

An object of this invention is to provide a valve which is so constructed that a fluid such as oil is supplied to the turbine governor so long as the feed water atthe suction of the feed pump is above the pressure temperature relationship at which flashing of steam would occur but which, when the pump suction approaches the flashing condition, the valve automatically shuts off the governor oil supply and stopsthe turbine.

A further object of the invention is .to provide a valve as above set forth that will remain in the turbine-off position once it has ben operated to shut off the oil supply to the turbine governor, but which valve is provided with means for resetting the valve to turbine-on position when a condition causing the excessive pump suction has been corrected.

Other objects of the invention will be apparent to those of ordinary skill in the art to which the invention pertains from the following description taken in conjunction with the accompanying drawings.

In the drawings: I

Figure 1 is a more or less diagrammatic view of a boiler feed Water pump driven by a steam turbine, the turbine being provided with an oil operated governor and a valve which is responsive to the suction at the intake of the pump to shut the turbine down in the event that the ump suction approaches. a condition where flashing of the feed water into steam is about to occur; and

Fig. 2 is a view in longitudinal section of a valve shown schematically in Fig. 1, which is arranged and constructed in accordance with an embodiment of the invention.

In Fig. 1 is illustrated a boiler feed water pump 1 driven by a steam turbine 2. The feed water pump 1 is connected to a feed water supply line 3 which leads to the suction or intake of the pump. The feed water is discharged by the pump into a line 4 which leads to a steam boiler (not shown). The turbine is supplied with steam from a steam line 6 in which is a valve 7 operated by a governor 8 of the oil operated pump type. Governor 8 is connected to the discharge pipe 4 so that the steam admitted to the turbine is regulated by and in accordance with the pressure in the discharge line 4. If the pres sure decreases, the governor opens valve 7 to supply more steam to the turbine and thereby increase the pump discharge pressure. The governor 8 therefore controls valve 7 in such manner that the pressure in the pump discharge line 4 is maintained at the proper value with reference to the boiler pressure to be overcome.

The governor 8 is supplied with operating oil through a valve 10 which is connected to an oil supply line 11. The valve is provided with an outlet port that is connected to a pipe 12 leading to the governor 8. The valve is also provided with a drain line 13 which is connected to a drain port on the valve, as will be described infra.

If the suction at the intake of pump 1 is at the proper value in the sense that the feed water at the intake will not flash into steam, the turbine will drive the water pump in a normal manner. However, if the suction in the intake of the pump increases to a point which is dangerously close to the flashing point of the feed water, a suction pressure responsive means 10 responds to that suction and actuates valve 10 in a direction to shut ofi the oil supply to line 12 leading to the governor, causing the governor to close the steam valve 7 thereby shutting down the turbine. Valve 10 is so constructed that it will remain in a turbine-off position until it is reset. The valve, of course, would be reset to turbine-on position after the condition has been corrected which caused the pump suction to increase to approximately the flashing pressure.

The details of construction of valve 10 are illustrated in Fig. 2. Valve 10 comprises a valve body 15 having in one end thereof a cylinder 16 which is closed by a cylinder head 17. The body is provided with a cylindrical bore 18 that is coaxial of the longitudinal axis of cylinder 16. The cylinder 16 is provided with a piston 19 having a piston ring 20 and a piston rod 21 operating in the bore 18.

The body 15 is provided with an inlet or supply port 22 which would be connected to the oil supply line 11 of Fig. 1, an outlet port 23 which, in Fig. 1 is connected to line 12, and a drain port 24, which in Fig. 1 is connected to drain line 13.

The rod 21 is provided with spaced annular grooves 26 and 27. When the piston 19 and the rod 21 are in the position shown in Fig. 2, the annular groove 26 places the supply port 22 and the outlet port 23 in communication so that oil can be supplied to the governor 8.

The piston 19 and the rod 21 are provided with an axial'bore 29. The rod 21 is provided with a trip port 30 that provides communication between the space in the cylinder above the piston and the bore 29.

A pilot valve 31 having lands 32 and 33 is disposed in the bore 29. One end of the bore 29 terminates in an orifice 35 leading to the space within the cylinder head 17. That space is connected by communicating ports which form a passageway 36 leading to the drain port 24. The piston 13 and its rod 21 are urged upwardly by a relatively strong compression spring 37 disposed in the cylinder head 17 and bearing on the piston 19, the spring being compressed between the piston 19 and the cylinder head as shown.

In the order that the piston 19 and its rod 21 may be urged to the position shown in Fig. 2, that position being theturbine-on position of the valve, the valve body is provided with a passageway 39 leading from theinlet port 22 to the cylinder 16. The passageway 39 terminates in a restricted passageway or oriflce 41 When the valve is in the turbine-on position, the pilot valve 31 is in the position shown in Fig. 2, namely, in the position where the land 33 closesthe trip 30. Under those conditions, thejsupply port. is directly connected to the outlet port 23. Oil under pressure is supplied to the passageway 39 and the orifice 40 into the cylinder 16, that pressure being sufiicient to hold the valve in the turbine-on position against the force of spring 37.

Pilot valve 31 is operated by the pump suction responsive means 10. The means 16' comprises a housing 43 which is supported by a tubular support 44 on the valve body 15. Within the housing 43 is a bellows or other pressure deflectable member 45. The bellows 45 has the characteristics of a spring in resisting elongation. The lower end of the bellows is provided with a bearing plate 46 to which it is soldered or brazed. The housing 43 is closed by a cap 48 which is bolted to the housing 43. The upper end of the bellows 45 is secured by brazing or other suitable means to a ring flange 49 which is clamped between the cap 48 and the body 43, as shown.

Within the bellows 45 is a compression spring 50. The spring is retained under compression by means of a nut 51 screwed into the cap 48 as shown. By adjusting the nut 51 and locking it in position by means of a set screw 52, the initial tension on spring 50 may be adjusted to set the trip point of valve 10. The nut 51 is provided with a bore 53 by means of which atmospheric pressure is maintained within the bellows 45.

The bearing plate 46 is connected by a stem 54 to valve 31. As shown, the valve 31 extends through a washer 55 of fibrous material, for example, to provide a wiping seal at the end of the bore 29. The stem 54 passes out of housing 43 through an aperture 56. That aperture is sealed by means of a sealing bellows 57, one end of which is welded or otherwise secured to the housing at the margin of the aperture 56 and the other of which is welded or otherwise secured to the bearing plate 46, as at 58. Thus, the chamber within the housing 43 and about the bellows 45 is pressure tight. The housing 43 is provided with a port 60 to which the suction line 3 (see Fig. 1) is connected to subject the interior of the housing 43 to the condition to which it is to respond.

So long as the suction at the intake of the pump 1 is above the point where flashing would occur, the pilot valve 31 will be in the position shown in Fig. 2, namely, in a position where trip port 30 is closed by the land 33. As the suction increases and approaches the point where the feed water is about to flash into steam, the bellows 45 expands, moving pilot valve 31 downwardly to the position where land 33 uncovers the trip port 39. As soon as the trip port 30 is uncovered, oil flows from the cylinder 16 through port 30, a passageway 63 in the piston, the orifice 35, thence into the cylinder head 17, from which it discharges through passage 36 to the drain port 24. When the oil flows through the passageway 63, the orifice 35 and the passageway 36 to the drain port 24, the pressure drop across orifice 40 increases, whereby the pressure of the upper side of piston 16 is decreased. The reduction in pressure is such that the force of spring 37 will overcome the force of the oil acting in opposition to it and move the piston and its rod upwardly until the piston strikes the upper end 64 of the cylinder 16 at which point the piston and its rod come to rest. When the piston 19 and the rod 21 have reached the position 64, the annular groove 26 is out of registry with the

ports

22 and 23 thereby shutting off the flow of oil to the governor. At the same time port 23 is connected to the annular groove 27 whereby the governor supply line 12 is connected to the drain port 24. The turbine is thereby shut down and will remain so until the valve is reset to its turbine-on position. The resetting, of course, would be done after the condition which caused the shut-down condition has been corrected.

In order to provide for resetting the valve to turbin-on position, resetting means 65 are provided for closing the orifice 35. The means 65 comprises a stem 66 having a cone point valve 67, which, when stem 66 is pushed inwardly, seats in the orifice 35 and closes it. The stem 66 is urged out of engagement with the orifice 35 by means of a compression spring 68 disposed between the cylinder head 17 and a push button 69 at the end of the stem 66.

When the orifice 35 is closed by the valve 67 the pressure in the cylinder 16 in the space above the Piston 19 builds up and forces the piston 19 and its rod 21 downwardly. The piston travels downwardly until it strikes an annular shoulder 70 on the cylinder head which is the limit of its stroke in that direction and corresponds to the turbine-on position, the

ports

22 and 23 being then in communication through the annular groove 26. When the piston 19 and the rod 21 have reached the turbineon position, the land 33 of the trip pilot valve 31 will be in the position where the trip port 36 is closed.

As shown in Fig. 2, the upper end of the rod 21 is provided with inclined passageways 72 that communicate with a passageway 73 leading to the drain port 24, to provide drainage for oil leaking past annular groove Having thus described the invention, it will be apparent to those of ordinary skill in the art to which the pump in response to the pump suction increasing to a value at which flashing of the feed water into steam is about to occur, said valve comprising a body having a cylinder therein, a bore of smaller diameter coaxial therewith, the body having a supply port, an outlet port and a drain port, a piston in said cylinder and having a rod provided with spaced annular valve grooves, one of which provides communication between the supply and outlet portions when the piston and red are in on position and another of said annular grooves providing communication between the outlet and drain ports when the valve is in oil position, said valve body having a restricted passageway leading from the supply port to one side of said piston to normally hold the piston in the on position, means urging said piston and rod to off position, said piston and rod having a longitudinal bore, the rod having a trip port providing communication between said passageway and the cylinder, a pilot valve in said longitudinal bore for controlling said trip port, means adapted to respond to the difference between atmosphen'c pressure and sub-atmospheric pressure for actuating said pilot valve in a direction to uncover said trip port, said longitudinal bore having a restricted outlet leading to the opposite side of the piston, a drain passage connected to the opposite side of the piston whereby when the sub-atmospheric reaches a predetermined value the pilot valve uncovers said trip port and provides communication between the supply port and the opposite side of said piston to drain thereby decreasing the supply pressure on said piston so that the urging means can actuate the piston and rod to the off position, in which position the supply port is closed and the outlet port is connected to the drain port, and means for closing the outlet of said pilot valve bore to restore the supply pressure to one side of the piston and return it to the normal on position.

2. A valve having an on position for connecting, and an ofi position for shutting ofl, the oil supply to the governor of a steam turbine driving a boiler feed water pump, in response to the pump suction increasing to a value at which flashing of the water into steam is about to occur, said valve comprising a body having at one end a cylinder, a piston in said cylinder, a bore of smaller diameter than the cylinder which is coaxial with the longitudinal axis of the cylinder and having a supply port, an outlet port and a drain port, a supply passageway in said body leading to one end of said cylinder, the body having a drain passage for the opposite end of the cylinder, said supply passageway having an orifice therein and supplying pressure from the body supply port to one side of the piston to actuate it to the on position, said piston in said cylinder having a rod slidable in said coaxial bore, said rod having spaced annular valve grooves one of which connects the supply and outlet ports when the valve is in on position, and the other of which connects the outlet and drain ports when the valve is in off position, means urging the piston and rod to ofi position, said rod and piston having a longitudinal pilot valve bore, the rod having a valve trip port providing communication between said cylinder and said longitudinal bore, said longitudinal bore terrninating in a discharge orifice leading to the opposite side of the piston, a pilot valve in said longitudinal bore for controlling said trip port, the piston being held in on position when the trip port is closed, means responsive to sub-atmospheric pressure for normally biasing and holding the pilot valve in a position to close the trip port, but actuating the pilot valve to a position where the trip port is uncovered when said sub-atmospheric pressure increases to a predetermined value, the trip port, when uncovered, admitting oil to said port and bore into the opposite end of the cylinder to drain whereby the supply pressure to the piston is decreased and the urging means actuate the piston rod to the off position, and means for closing said bore to return the valve to on position.

3. A turbine governor shut-off valve for a turbine driving a boiler feed water pump, said valve comprising a body having a cylinder a cylinder head, a piston in the cylinder, said piston having valve on and off positions and a bore coaxial with the axis of the cylinder, the piston having a rod operating in said coaxial bore, the body having supply, outlet and drain ports, the rod having spaced annular grooves, one of which provides communication between the supply and outlet ports when the piston is in the on position, and another of which provides communication between the outlet and drain ports when the piston is in off position, the body having a restricted passage leading from the supply port to the cylinder for urging the piston and rod to valve on position, the cylinder head having means therein for urging the piston and rod to off position, the rod and piston having a longitudinally extending pilot valve bore which is provided with a trip port providing communication between the space in the cylinder supplied by said restricted passageway and the pilot valve bore, a pilot valve in said bore for controlling the trip port; means adapted for response to sub-atmospheric pressure for holding the pilot valve in trip port closed position when the said sub-atmospheric pressure is at substantially a predetermined value, and opening said trip port when said sub-atmospheric pressure is approximately at another value of pressure, said trip port when open connecting the cylinder to drain thereby reducing the pressure on the piston, as applied through said restricted passageway, to a value at which the urging means aetuates the piston and rod to off position, and means for closing the outlet of the pilot valve bore to shut-oft flow into the cylinder head thereby building up pressure on the piston to return it and the piston rod to turbine-on position.

4. A valve as in claim 3, in which the sub-atmospheric pressure responsive means for actuating the pilot valve comprises a housing having therein a pressure deflectable member dividing the housing into opposed chambers one of which is in communication with the atmosphere and the other of which is adapted to be subjected to said sub-atmospheric pressure, and means operatively connected to the pressure defiectable member for adjustably pre-setting the pressure at which the pilot valve uncovers the trip port.

5. A valve as in claim 1, in which the sub-atmospheric pressure responsive means for actuating the pilot valve comprises a housing having therein a pressure deflectable member dividing the housing into opposed chambers one of which is in communication with the atmosphere and the other of which is adapted to be subjected to said sub-atmospheric pressure, and means operatively connected to the pressure deflectable member for adjustably pro-setting the pressure at which the pilot valve uncovers the trip port.

6. A valve as in claim 2, in which the sub-atmospheric pressure responsive means for actuating the pilot valve comprises a housing having therein a pressure de iectable References Cited in the file of this patent UNITED STATES PATENTS 1,517,490 Bayles et al. Dec. 2, 1924 1,567,184 Conrader Dec. 29, 1925 2,384,227

Albert' n Sept. 4, 1945