US2207809A - Feed-water system - Google Patents

Description

y 1.940- W. G. LAUFFER' ET AL 2,207,809

FEED-WATER SYSTEM Filed April 2, 1938 4 Sheets-Sheet l ImJenkorS N/LLIRH GEOREF LHI/FFER Y HEN/Q) 8. Ken .51

Attorneys y 1940- -w. G. LAUFFER ET AL 2,207,809

1 FEED-WATER SYS/TEM Filed April 2, 1938 4 Sheets-Sheet 2 w m w 7 2 M. 1 A A k w i\ V M sin $2 bi /l E .4 w w r;

July 1 6, 1940- w. G. LAUFFER ET AL FEED-WATER SYSTEM 4 Sheets-Sheet 5 Filed April 2, 1938 f a l Inventors u/LL/mv Geoze: Lea/KER H N F E J y 16 19 0 wfe. LAUFFER Er AL 2,207,809

FEED-WATER SYSTEM Filed April 2, 193a 4 Sheets-Sheet 4 1NVENTOR5. h ILL /F7/1 GEOKG'ELA UFFE/E' BY Haw? Y A. KEssLER ATTORNEYS Patented July 16, 1940 UNITED STATES ArE-Nr orrica FEED-WATER SYSTEM Application April 2, 1938, serial No. 199,570

12 Claims.

This invention relates to pumping system and more particularly to high pressure systems employing a continuously driven pump.

In high pressure pumping systems employing a continuously running pump it has been found that when the demand for liquid is very low the pump overheats and may be burned out. In other words, it is necessary, to protect the pump, that a certain minimum flowof liquid be maintained therethrough regardless of the demand for liquid.

It is accordingly one of the objects of the present invention to provide a pumping system in which flow through the pump is'never allowed to fall below a predetermined minimum.

' Another object of the invention is to provide a pumping system in which a by-pass around the pump is automatically opened when the de- I mand falls below a predetermined minimum. According to one desirable arrangement the bypass is automatically re-closed if the demand rises to a predetermined value in excess of said minimum. In some cases where it is desired to call the operators attention to the reduced demand, for example so that he can cut out one or more of a plurality of parallel pumps, a valve may be employed which requires manual resetting.

Another object of the inventionis to provide a pumping system in which a by-pass around a continuously running pump is automatically controlled in accordance with a function of the fluid being pumped. Preferably the controlling function is rate of flow but temperature or some other function might be used Since a flowmeter is usually employed in connection with feedwater systems, it is a further object of the invention to provide a pump bypass which is controlled by the flowmeter.

Another object of the invention is to provide a pumping system in which suitable signals are provided to indicate the condition of the system.

The invention is applicable to a great many uses such as boiler feedwater pumps, scaling pumps in rolling mills and in fact in substantially all places where a constantly running high pressure pump is employed to supply a variable demand. Since it is particularly useful in connection with boiler feed-water systems, it has been described hereinafter in connection with such a system but it will be understood that this description is illustrative only and is not to be taken as a definition .of the limits of the invention.

other objects, advantages and novel features oi the invention will be apparent from the following description when read in connection with the accompanying drawings, in which:

Figure 1- is a diagram of a feed-water system embodying the invention;

Figure 2 is a wiring diagram of the system of Figure l witlparts in section;

Figure 3 is a view similar to Figure 2 of a slightly modified form;

fi'igure 4 is a section of a valve construction; 10 an Figure 5 is a wiring diagram of another system embodying the invention.

As shown in Figure 1, feed-water is pumped from a storage reservoir III by a low pressure 16 pump i2 into a low pressure heater 14 from which it passes to a de-aerator l5 and through an orifice 16 to a high pressure feed-water pump l8 having an outlet pipe 20 connected through suitable valves to the boiler. The high pressure 20 pump I8 is driven by a turbine 22 connected to 1 the boiler through a steam pipe 24.

Flow of water through the high pressure pump I8 is measured by a flow meter having a high pressure chamber 26 and a low pressure cham- 25 her 28 connected by a U-tube 30 adapted to be filled with mercury or the like. As best seen in Figure 2, thelow pressure chamber 28 carries a contactor 32 of the type more particularly described and claimed invthe patent to Spitz- 30 glass, No. 1,325,763, which creates a variable resistance to operate a pen 34 in a recorder 35. The recorder'may be of any conventional type, as illustrated for instance in the patent to Spitzglass, No. 2,076,100.

In normal operation the low pressure pump l2 draws water from the storage reservoir and ,forces it through the heater l4 into the high pressure pump l8. The pump l8 forces the .water at high pressure into the boiler in ac- 40 cordance with the demands thereof, the rated delivery being controlled in any desired manner, not shown. When the rate of flow of water through the pump l8 falls below a predetermined minimum, this pump heats up very rap- 45 idly and is apt to be burned out. We have found that for proper operation of the pump it is necessary that a flow of water therethrough equal to approximately one sixth to one fifteenth of its capacity be maintained.

According to the present invention, minimum flow of water through the high pressure pump is maintained by providing a by-pass connection 38 from a high pressure point posterior to the pump outlet to a low pressure point in the system anterior to the pump inlet and anterior to the orifi e I6. Flow through the by-pass 88 is contro led by a valve 40 more particularly illustrated in Figure 2 as including a valve stem 42 urged to open position by fluid pressure thereon preferably supplemented by a pair of springs 44 and adapted to be closed by a fluid pressure piston 46 in a cylinder 48. The upper end of cylinder 48 is connected to a pipe 80 leading from a source of compressed air or the like through a double ended valve 52 urged to exhaust position by a spring 54 and adapted to be opened by a solenoid 56. In the position shown in Figure 2 the solenoid is de-energized, valve 52 is in its exhaust position, and valve stem 42 is raised by springs 44 to open the by-pass.

The solenoid 56 is controlled from the flow meter through suitable control circuits including a low contact 58 in the high pressure chamber 26 and a high contact 68 in the low pressure chamber 28. The low contact 58 is connected to a coil 62 and ,to one side of a switch 64 which is operated by a core 66 in the coil 62. The core 68 also operates a switch 68'controllinga holding circuit from one side of a power line I to a second coil I2 which is also connected to the high contact 60. Both coils 62 and I2 are connected to the other side of the power line shown at 14. The coil I2 has amovable core I6 controlling a switch I8 in series with the switch 68 and a switch 80 in series with the switch 64. A third switch 82 is connected to the core I6 and controls power lines 84 leading to the solenoid 56.

' When the flow through the orifice I6 is relatively high, the mercury will be forced down in chamber 26 and up in chamber 28 to engage the high contact 60. This will complete a circuit through the coil 12, raising the core 16 to close switches I8 and 82. At this time the solenoid, 56 will be energized, the valve 52 will be raised to its open position, and fluid under pressure will be v admitted to the upper end of cylinder 48 to move the valve stem 42 down, thereby closing the bypass. This is the normal operating condition in which the boiler demand for feedwater is sufflcient to maintain a flow above the desired minimum through the high pressure pump.

As the flow decreases, the mercury will move away from the high contact 68, but the coil I2 will still be energized due to the holding circuit from line through switches 68 and I8 to the 0011. As the flow drops further to the minimum allowable value, mercury will rise in the chamber 26 to engage the contact 58, thereby completing a circuit through the coil 62 to raise core 66 to the position shown in Figure 2. This interrupts the holding circuit for coil 12 by opening switch 68, and the core I6 falls to the position shown, opening switches 18 and 82 and closing switch 86. At this time solenoid 56 is de-energized and valve 52 moves down under the influence of spring 54 to exhaust pressure from the cylinder 48 and to permit valve stem 42 to rise under the influence of springs 44. The by-pass 38 is then opened and water is recirculated from the pump outlet pipe 28 back to the pump inlet to maintain the desired minimum'flow through the pump regardless of boiler demand.

This operation will immediately effect an increase in flow through the orifice I6, causing mercury in the chamber 26 to move away from the contact 58. Coil 62, however, will remain energized due to the holding circuit from line I0 through switches 80 and 84, so that the by-pass valve 40 will remain open. The valve will be held open until the flow increases in response to increasing demand to a point suillcient to close the above described circuit through high contact 68. This will raise core 16, opening switch 88 and interrupting the holding circuit through the coil 62. It will be noted from the above that a substantial increase in flow is necessary before the valve 48 closes after once being opened. This insures that minimum flow will be maintained through the pump and eliminates possibility of fluttering of the valve due to small variations in demand. It. will be apparent that, if desired, the valve could be regulated tointermediate positions to control the flow through the by-pass.

Figure 3 illustrates a slightly modified control,

parts therein corresponding to like parts in Fig-.

ures 1 and 2 being indicated by the same reference numbers plus 100. Inthis construction the control circuits are substantially identicaL- but a somewhat different valve arrangement is provided to control flow of operating fluid to-the cylinder I48. As shown, the solenoid I56 has a movable core I51 connected to one 'end or a lever I6! which is pivoted at its opposite end to the valve desirable to provide a measurement of flow,

through the by-pass so that the total amount of water actually supplied to the boiler will be indicated. For this purpose the flow meter may be'provided with a second pen I86 controlled by a circuit I88 including a variable resistance I80 and a switch I92 which is operated by the valve stem I42. Since the by-pass is either fully opened or fully closed, the flow therethrough will either be zero or some predetermined quantity depending upon the size of the by-pass connection or of a suitable throttling orifice therein. The variable resistor I98 may therefore be set to a value which will cause the pen I86 to indicate flow through the by-pass so that whenever switch I82 is closed, pen I86 will record a substantially constant value, and whenever switch I92 is opened, it will record zero. Thus the flow through the by-pass is indicated and the amount of feedwater supplied to the boiler may be computed by deducting this flow from the total flow indicated by pen I34. It will be understood that if desired, this deduction could be made automatically so that the pen I84 would indicate at all times the amount of feed water actually being supplied to the boiler.

, It is sometimes desirable to provide a system in which the by-pass valve must be manually reset to call the operators attention forcibly to the reduced demand for feed water. This is particularly desirable where a plurality of feed water pumps operating in parallel are provided, so that the operator may cut out one or more pumps when they are not necessary to supply the demand. For this purpose a valve, as illustrated in Figure 4, may be employed, the illustrated valve including a body 286 and a sliding stem 282 moved upwardly to open the by-pass by a spring 288. The valve is normally held closed by a latch mechanism including a pivoted lever 286 engaging an abutment on the valve stem 202 and held down in the position shown by a pivoted latch 288. A solenoid 218 operates a plunger 2" urged in one direction by springs 2 so that when the solenoid is energized the plunger 2l2 will strike the latch 288 and disengage it from the lever 286 to permit the valve to open under the influence of spring 284. It will be understood that any suitable signal can be operated in parallel with the solenoid 218 to indicate to the operator when the by-pass is opened.

In orderto reset the valve, the latch 288 is mounted on a carriage 2| 6 which can be moved by a fixed screw 218 having a hand wheel 226. When the valve is open, the hand wheel may be turned to raise the carriage 216 far enough to permit engagement of latch 268 with the lever 206. Thereafter the carriage may be screwed down to the position shown with the valve closed.

In Figure 5 there is shown a modified circuit arrangement, parts therein corresponding to like parts in l igures 1' and 2 being indicated by the same reference numerals plus 200. As shown in this arrangement the contacts in the meter body are replaced by a rotating member 294 driven by or in synchronism with the meter mechanism and carrying a pair of contactors 286 and 288. The contactor 286 serves to connect the power lead 218 with a wire 868 leading to one side of the coil 262 and the contactor 288 connects lead 218 with a wire 882 leading to one side of the coil 212. The other sides of both coils are connected to the power lead 214. The contactors 286 and 288 are so spaced with relation to their corresponding contacts that only'one of the coils can be energized at any one time.

The coil 262 operates a core 266 carrying a switch member 268 connecting a wire 884 which is connected to the lead 218 to a fixed contact at one side of switch member 218 carried by the core 218. A fixed contact at the other side of switch 218 is connected by a wire 866 tothe wire 862 and the 0011212. The core 216 carries a second switch member 282 adapted to open and close a circuit in the power leads 284 through the solenoid 256.

In order to indicate the operation of the device a red. signal light 888 and a green signal light 816 are provided. Both lights are connected on one side to one of the leads 284 and the other side oi the green light 8H1 is connected to a fixed contact on one side of the switch 264 carried by core 266 and having a contact on its other side connected to the other lead 284. The other side of the red light is connected to the other lead 284 through a switch 8|2 which is operated by the valve 248 to be closed when the valve is open and open when the valve is closed.

The parts are shown in the position they will occupy when the flow is at or below the minimum permissible value with the contactor 286 closed to energize the coil 262 to open both switches 264 and 268. At this time the coil 212 is deenergized to open switches 218 and 282 thereby .interrupting the circuit to solenoid 256.

Switch 264 will close 'a' the red light will be extinguished. Thus only the green light is burning, indicating that the demand is greater than the minimum pump capacity.

If the demand should drop suillciently to cause contaetor 288 to open the coil 212 will remain energized due to the holding circuit through switches 268 and 218. This condition will continue until the demand drops below the minimum and closes contactor 286 to energize the coil 262 and raisecore 266 at which time switch 268 will be opened to interrupt the holding circuit.

While several embodiments of the invention have been shown and described in detail, it will be understood that various changes might'be made therein, and it is not intended to limit the scope of the invention to the forms shown nor otherwise than by the terms of the appended claims.

What is claimed is: l. A safety control system for a boiler feedwater pump having its inlet connected to a source of liquid supply and having a by-pass connection from its outlet to the source of supply comprising, a normally closed valve in the bypass, and means responsive to the flow of liquid through the pump to open the valve when the flow falls below a predeterminedminirhum, and

to close the valve when the flow reaches a value a predetermined amount greater than said minimum.

2. A safety control system for a boiler feedwater pump having its inlet connected to a source of liquid supply and having a by-pass connection from its outlet to the source of supply comprising, a flowmeter responsive to the flow of liquid through the pump, a normally closed valve in the by-pass, electrically controlled means to open the valve, and electric control circuits for said means including switch means operated by the flowmeter to open the valve when the flow falls below a predetermined minimum, said circuits including a holding circuit to hold the valve open until the flow reaches a value a predetermined amount in excess of said minimum.

3. A safety control system for a boiler teedwater pump having its inlet connected to a source of liquid supply and having a by-pass connection from its outlet to the source of supply compris ing, a normally closed valve in said by-pass, fluid pressure means to operate said valve, and electric control means responsive to the flow of liquid through the pump to control said fluid pressure means to open the valve when the flow falls below a predetermined minimum and to close the valve when the flow reaches a value a predetermined amount in excess of said minimum.

4. A safety control system for a boiler feedwater pump having its inlet connected to a source of liquid supply and having a-by-pass connection from its outlet to theis'ource of supply comprising, a normally closed valve in said by-pass, fluid pressure means to operate said valve, and electric control means responsive to the flow of liquid through the pump to exhaust fluid from said fluid pressure means to open the valve when the flow falls below a predeterminedminimum and to supply fluid to the fluid pressure means to close the valve when the flow reaches a value a predetermined amount in excess of said minimum.

5. A pumping system comprising a; pump having its inlet connected to a source of liquid supply, a by-pass connection from the pump outlet to the pump inlet, a valve in said by-pass, resilient means urging the valve to open position, a latch' normally holding the valve closed, and means responsive to the flow of liquid through the pump to release the latch when the flow falls below a predetermined minimum.

6. A pumping system comprising a pump having its inlet connected to a source of liquid supply, a by-pass connection from the pump outlet to the pump inlet, a valve in said by-pass, resilient means urging the valve to open position, a latch normally holding the valve closed, a flowmeter responsive to the fiow of liquid through the pump, and means controlled by the flowmeter to release the latch when the flow falls below a predetermined minimum.

7,. A pumping system comprising a pump having its inlet connected to a source of liquid supply, a by-pass connection from the pump outlet to the pump inlet, a valve in said by-pass, resilient means urging the valve to open position, a latch normally holding the valve closecha flowmeter responsive to the flow of liquid through the pump, a solenoid operably associated with the latch, and a control circuit operated by the flowmeter to energize the solenoid to release the latch when the flow falls below a predetermined minimum.

8. In a pumping system including a pump, safety control means comprising a by-pass connection from the pump inlet to the pump outlet, a valve in said by-pass, a flowmeter having means for indicating the flow through the pump, means operated by the flowmeter to open said valve when the flow falls below a predetermined minimum, and supplemental means on the flowmeter to indicate the rate of flow through the by-pass when the valve is open.

9. In a pumping system including a pump, safety control means comprising a by-pass connection from the pump inlet to the pump outlet, a valve in said by-pass, a flowmeter having means for indicating the flow through the pump, means operated by the flowmeter to open said valve when the flow falls below a predetermined "minimum, and supplemental means on the flowmeter operated by the valve to indicate the normal rate of flow through the by-pass when the valve is open.

10. In a pumping system including a pump, safety control means comprising a by-pass connection from the pump inlet to the pump outlet,

a valve in said by-pass, means responsive to the rate of flow through the pump, electrical means for operating said valve and including electrically operated switches controlled by said last named means, said means operating to open the valve when the flow falls below a predetermined minimum, and signal means operated by one of said switches and by opening and closing of the valve to indicate the condition of the system.

11. In a pumping system having a pump with a by-pass between its discharge line and its intake line and a valve in the by-pass, control means for the valve comprising a flowmeter responsive to the flow of fluid passing through the pump, means to operate the valve, and means controlled by the flowmeter for controlling said last named'means to open the valve fully when the flow falls below a predetermined minimum and to close the valve when the flow reaches a value a predetermined amount-above said minimum. l

12. In a pumping system having a pump with a by-pass between its discharge line and its intake line and a valve in the by-pass, control means for the valve comprising a flowmeter responsive to the flow of fluid passing through the pump, means to operate the valve, means con-

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