US1951049A - Fluid-pressure system - Google Patents

Description

' March 13, 1934. c GRAESSER 1,951,049

FLUID PRESSURE SYSTEM Filed June 15. 1931 3 Sheets-Sheet 1 l Q QIIQ up"! March 13, 1934. I c. a; GRAESSER I 1,951,049

rwwrnnssuna SYSTEM Filed June 15. 1931 3 Sheets-Sheet 2 Mi i,- 13, 1934. 'c H RAESSER 1,951,049

FLUID PRESSURE SYSTEM Filed June 15, 1931 3 Sheets-Sheet 3 Jar/baton" ('arZ J'Y. 'raesser; @i 2 Patented Mar. 13, 1934 UNITED STATES PATENT OFFHCE FLUID-PRESSURE SYSTEM Application June 15, 1931, Serial No. 544,299

9 Claims.

This invention pertains to fluid pressure systems and relates more particularly to a novel method of and apparatus for regulating and controlling the pressure in a steam power plant, for

example, although in its broader aspects it is of utility in the regulation or control of fluid pressure in any container, receptacle, or system.

In earlier times, when steam boilers were operated at moderate pressures, it was practicable to employ safety valves having a relatively high blow-down (that is to say, a relatively large pressure range between the blowing and the closing pressures), but under modern conditions, where very high pressures are often used, a high blow-down means serious loss of energy. Practical difiiculties have been experienced in designing spring-actuated safety valves having less than 4% blow-down, but even at 4% the blowing of a high pressure boiler represents a very substantial waste. Moreover, under the old conditions it was possible to set the safety valve to blow at a pressure well above the working pressure so that it remained tight under all ordinary circumstances and only opened in response to emergency rise in pressure. In order to keep the valve tight and to avoid leakage and chatter, the gap between normal working pressure and the blowing pressure should be as great as possible, and with a blow-down of 4% this gap must be at least 4% of the boiler pressure, and preferably 5% to 6%. However, to obtain the greatest economy in original cost, it is common to use the lowest pressure boiler which will deliver the required working pressure and this necessitates operating the boiler at a high rating, in consequence of which the gap between working pressure and valve blowing pressure may be very small, and thus the valve tends to blow frequently.

The standard rating of a boiler is upon the basis of capacity to evaporate water at the rate of 30 lbs. per horse power hour, but with modern methods of firing, etc., it is possible to increase this rate of evaporation so that some boilers evaporate at from 500% to 600% of the normal rating. Assuming the use of a superheater designed for the normal boiler. rating, this increased rating-results in an extremely high steam velocity through the superheater with conse- 50 quent substantial frictional loss, so that the steam delivered by the superheater is at a considerably lower pressure than that in the boiler drum.

The superheater tubes are usually located at the hottest part of the furnace where the temnance, together with other advantages hereinperature may approach 1000 F., and unless constantly cooled by the flowing steam the superheater tubes quickly soften, sag, and blister. It is thus essential to maintain the flow of steam through the superheater substantially unintere1 rupted even though the demand for steam by the turbine, engine, or other steam consuming apparatus'should suddenly lessen or cease. Accordingly it is usual to place a safety valve upon the superheater so that if steam delivery 6! is suddenly stopped, as, for example, upon breakdown of the-turbine, the resultant increase in pressure will cause this valve to pop, thus allowing steam to continue to flow through the superheater tubes. 7'1

However, as above noted, the pressure in the delivery of the superheater is less than the maximum working pressure of the boiler drum so that a superheater valve must be set to blow before the drum valve, as otherwise the It drum valve would blow first and the flow through the superheater would not be assured. Moreover, the superheater valve is necessarily located at a point where it is subjected to great heat, and it is thus especially difficult to keep 81 it in working condition even at a 4% blow-down, while, on the other hand, excessive blow-down at this point, where the steam has been given added heat energy, is even more wasteful than prolonged blow-down from the boiler itself.

In accordance with the present invention the above difficulties are largely overcome, with consequent greater efiic'iency in boiler operation as well as a substantial saving in valve mainte- 9 after more fully explained. To this effect the present invention provides for the employment of what may be termed a working valve usually in conjunction with one or more usual safety valves. This working valve is so designed as to have a very low blow-down; for example, 1%, which is readily obtainable in a valve apparatus of the type hereinafter described and which is capable of caring for such frequent slight rises of the pressure as occur during normal working conditions, thereby relieving the true determines the" opening and closing of this working valve may be located at any desired and convenient position, remote if preferred from the heat and gases of the furnace. Under certain conditions, temperature is of more immediate importance than pressure as a controlling factor '(although pressure and temperature are usually interdependent), and it is thus proposed to arrange the working valve to respond to temperature changes, although for some purposes it may be desirable to have it respond to pressure conditions, or to both pressure and temperature.

In the accompanying drawings one embodiment of the invention is illustrated by way of example, and in such drawings:

Fig. 1 is a diagrammatic elevation showing the invention as applied to 'a steam generating system;

Fig. 2 is a diagrammatic view illustrating one suitable arrangement of electrical connections;

Fig. 3 is a view generally similar to Fig. 2, but showing the apparatus as designed for temperature control only;

Fig. 4 is 'a front elevation of a temperature control appliance useful for the purpose referred to;

Fig. 5 is, a fragmentary view illustrating certain details of a desirable form of working valve;

Fig.6 is a diagrammatic view similar to Fig. 1 illustrating a modified construction; and

Fig. 7 is another diagrammatic view similar to Fig. 6 but illustrating a further modification.

Referring to the drawings, the numeral 1 designates the drum of a steam generating boiler provided with a header 2 from which the delivery pipe 3 extends to a superheater 4. A header 5 receives the superheated steam from the superheater and delivers it to the steam main 6 leading to the turbine or other steam consuming apparatus, indicated at 7. The parts thus far described may be of any usual and standard construction, and while the system has been referred to as a steam generating system, it is to be understood that this is merely for illustrative purposes and that the invention herein described is applicable to other pressure fiuid systems, for

example, oil refining apparatus or the like.

' As here illustrated the boiler drum 1 is furnished with a series of safety valves 8 which, in accordance with one well known practice, may be so adjusted as to blow at progressively increasing pressures and with progressively increasing blow-downs. These valves may be of the usual spring-loaded type or such other kind as may be desired. The header 5 leading from the superheater is also furnished, if desired, with one or more usual safety valves 9, and in accordance with the present invention is further provided with a valve 10, hereinafter referred as the working valve, and which preferably is of the pressure-loaded type. Such a valve is particularly suitable for use in this location, since its exposure to high temperatures does not cause it to deteriorate nearly so rapidly as is the case when a spring-loaded valve is employed for the purpose, and while spring-loaded valves such as the valves 9 maybe useful'in this location, if not called upon to operate too frequently, such spring-loaded valves are not well suited to be used as working valves insuch a position. This working valve 10 may be of the type disclosed in the copending application of Philip G. Darling, Serial No. 507,094, filed January 7, 1931, such valve having a pilot which is electrically actuated by means of a solenoid, or the valve may be of the kind shown, for-example, in the patent to Darling No. 1,500,674, dated July 8, 1924, but with its pilot valve arranged to actuation by a solenoid instead of by'fluid pressure, for example, as shown in Figs. 2 and 5.

In Fig. 2 this actuating solenoid is indicated at 17, the solenoid having a movable core which operates a lever arm 18,, thereby controlling the pilot valve 19 which in turn determines the operation of the working valve 10. The solenoid 17 is connected by a conductor or conductors 11 (Fig. 1) with a remote control device 12 conveniently consisting of a panel having mounted thereon the various controlling elements. As shown in Fig. 2, these controlling elements comprise a temperature responsive mechanism 13, a pressure responsive mechanism 15, and a manually actuable switch 71. The temperature responsive device is of the remote reading type and is connected-to the superheater by means of a flexible or other suitable capillary tube 14, while the pressure responsive device preferably is connected by a tube 16 to the boiler drum so as to respond to the pressure therein. While the arrangement just described is preferred, it is within the scope of the invention, as illustrated in Fig. 6, to connect temperature responsive device 13 to the drum'by means of a capillary tube 14 or equivalent device so as to be subject to the temperature of the fluid therein, or alternatively, as illustrated in Fig. 7, to connect a pressure responsive device l5 to the superheater by means of a tube 16 so as to respond to the pressure ofthe fluid in the latter. The temperature responsive device 13 is indicated in Fig. 4 as comprising an outer casing enclosing suitable actuating mechanism of a well known type and having a graduated dial 20 with which cooperates a manually adjustable pointer 22 adapted to be set by means of a handle or other suitable device shown at 23 The mechanism also comprises a movable pointer 24 which moves over the scale in response to variations in temperature at the selected point.

In the instrument shown a bulb 25 or other suitable container for mercury or other expansive fluid is connected by means of a capillary tube, enclosed if desired in a suitable outer casing 14, to a pressure sensitive device inside of the casing 13, so that as the temperature varies at the bulb 25, the expansion or contraction of the pressure'fluid will cause the index needle 24 to move along the scale 20. The needle 24 has associated therewith suitable electrical'contact devices, diagrammatically indicated in Fig. 2, wherein the arm 24 'may be assumed to move with the pointer 24 between a fixed contact 26 and a contact 22 adjustable with the hand 22. Since remote reading temperature control- 'lers of this type are well known to the art, it

device comprises a Bourdon tube 27 whose expansion and contraction causes a movable contact 21 to move between a pair of cooperating contacts 54 and 55 respectively.

If it be desired to blow .the working valve 10 manually, for example, in case of emergency or for testing or other purpose, it is merely necessary to close the switch '71, bringing it into the position shown in dotted lines in Fig. 2. (It may be noted that such manually actuable switches may, if desired, be located at a plurality of convenient points about the plant so that in case of accident, the working valve 10 may be opened to relieve the pressure in the system with little loss of time.) Assuming that the switch '71 has been set in the dotted line position, electrical current received from any siutable source passes from the main 18", the switch 71, the wire 72, and the wire 11, the solenoid 17, the wire 11*, the switch '71, and back to the other main 18 The solenoid is thus energized, causing the pilot valve 19 to operate, whereupon the workingvalve 10 opens in response to unbalanced pressure and the pressure in the system is relieved, the valve continuing to blow until the switch '71 is moved to open position.

On the other hand, assuming that the apparatus is set for automatic operation, the switch '71 is moved to the full line position of Fig. 2. In this case, if for any reason the temperature at the superheater should rise abnormally, the movable contact arm 24. will swing to the right, eventually engaging the contact 22*. This completes a circuit through the contacts 22 and 24, the wires 62 and 62, the battery B, the solenoid coil '77, and the wire 61, thus causing the core 94 to move downwardly and closing circuits at the bridge-pieces and 89. As soon as the bridge-piece 80 completes its circuit, current flows from the main 18 through the switch 71, the wire '74, the bridge 80, the holding winding 81 of the solenoid, the bridgepiece 83, the wire 85, the wire 11, the solenoid 17, the wire 11, the wire '75, the switch '71, and the main 18 The solenoid 17 is thus actuated to open the valve 10 and the blowing of this valve continues even after the temperature drops and the contact 24 separates from the contact 22 This blowing of the valve will continue until the contact 24 has returned to make engagement with the contact 26, whereupon a circuit is completed through the wires 60, and 60, the breaking winding '78, the bridge 89, the battery B, the wires 62 and 62, and the contact 24 This breaks the circuit at the bridge 83, thus causing the bridge members 80 and 89 to rise, thereby breaking the circuit through the solenoid 1'7 so that the valve 10 closes.

A similar operation takes place if the pressure rises abnormally in the system through the operation of the device 15. It is thus evident that whether the temperature or the pressure first reaches the desired blowing point, the valve 10 will be automatically opened and will remain open for so long a period as may be determined by the setting of the control devices 13 or 15.

In the arrangement shown in Fig. 3 the device 13 corresponds to the device 13 of Fig. 2, but in this instance this temperature responsive device is used alone as the means for controlling the solenoid 1'7 and thus for determining the blowing of the valve 10. Since the connections are substantially the same as those above described, it is unnecessary to repeat the detailed construction or mode of operation.

In setting the several valves above described the controllers 13 and 15 are so adjusted that the working valve 10 will always blow before any of the valves 8 or 9, but, on the other hand, the working valve 10 must be so set as to blow above the maximum operating drum pressure, since otherwise it would blow constantly. The best setting is substantially half way between the maximum operating drum pressure and the lowest drum valve popping point. The valves 9 should then be set to blow substantially half-way between the popping point of the lowest drum valve and the pressure at which the working valve actually blows. For example, the pressure control device 15 may be set to operate at a drum pressure of 453 lbs. which may, for example, open the valve 10 at a superheater pressure of 426 lbs., and in such case the superheater valves should be set to blow at approximately 443 lbs.

In some cases when the gap between the drum pressure and the lowest set valve 8 is necessarily so small that it is impractical to set the working valve between such pressures, then the connection 16 may lead to the superheater outlet header 5. This connection may also be desirable if the load in the plant varies so greatly as to cause overheating at the superheater without blowing the working valve if the latter were connected for operation by the drum pressures. Even when connected for operation by superheater pressure, the arrangement has certain advantages, for example, although it may blow at the same pressure as it is usual to set the superheater valve for, it may readily be caused to close with .a much smaller blow-down than the usual valve, with a resulting saving in energy. In this connection it is to be noted that with the small blow-down possible with this arrangement, for example 1%, it is never necessary to reduce the line pressure, in the pipe 6 for example, by checking the fires in order to cause the valve 10 to close. Moreover, the capacity of this working valve 10 may readily be made large enough so that the regular safety valves 8 and 9 are never called upon to blow except in some unusual emergency, thus reducing valve maintenance to a minimum. Since by this arrangement it is possible to use a pressure-loaded valve as the working valve, it is not subject to leak or simmer, while at the same time its working parts are not so subject to the efiects of high temperature as is the case with a spring-loaded valve. The arrangement permits control of the system from a remote point where the sensitive controlling devices are not subject to high temperature or furnace gases,' and by the use of a temperature sensitive controlling devicecsuch as hereinabove described, it is possible to ensure the necessary flow of fluid through the superheater or other conduit or receptacle irrespective of any factors which may aifect the pressure without regard to temperature and thus avoiding dangers which are sometimes incident to dependence wholly upon pressure-actuated devices for determining the opening of the working valve.

While I have herein disclosed one desirable embodiment of the invention by way of example, I wish it to be understood that other and equivalent arrangements may be used and that other combinations of parts andthe substitution of other specific types of control instrument are regarded as within the scope of the invention.

I claim: I

1. That method of controlling pressure in a fluid pressure system, including a generator having a relief valve, and a receiver to which pressure fluid is delivered by the generator and in which the pressure difiers from that in the generator, the receiver also having a relief valve,

which comprises as steps controlling the blowing of the relief valve upon the receiver in direct response to variations in an energy characteristic of the pressure fluid which is still within the generator.

2. That method of regulating and controlling the pressure in a fluid pressure system including a pressure generator having a safety valve, a superheater provided with a remote controlled working valve at a point adjacent to the delivery end of said superheater, and a delivery conduit leading from the superheater, which comprises as steps setting the generator safety valve to pop at a predetermined pressure above that of the working pressure in the generator, and setting the remote controlled superheater working valve to pop in response to rise in pressure in the generator to a point above the working pressure therein but below the popping pressure of the safety valve thereon.

3. That method of regulating and controlling the pressure in a steam generating system including a steam generator having at least one emergency safety valve, a superheater through which flows steam delivered from the generator, said superheater having adjacent to its delivery end an emergency safety valve and a working safety valve, the latter having control means which responds directly to variations in pressure in the generator, and a steam delivery conduit leading from the superheater and through which the steam flows at a pressure below the normal working pressure of the generator, which comprises as steps setting the generator emergency safety valve to pop at a predetermined pressure above the normal working pressure in the generator, setting the control means of said working valve to respond directly to a rise in pressure in the generator to a point intermediate the working pressure and the poping pressure of the emergency safety valve on the generator but at a point above the pressure at the delivery end of the superheater, and setting the emergency valve on the superheater to pop at a superheater pressure higher than that at which the working valve pops.

4. Apparatus of the class described comprisinga steam generator having a safety valve set to pop at a predetermined pressure above the working pressure in the generator, a superheater which receives steam from the generator and which delivers the steam at increased temperature but decreased pressure, a working valve adjacent to the delivery end of the superhearter, said latter valve having a small blow-down as compared with that of the safety valve on the generator, and remote control means for the working valve disposed out of range of the heat of the superheater, said control means being sensitively responsive to variations in pressure in the generator and being constructed and arranged to cause the working valve to open at a generator pressure intermediate the working pressure and the pressure at which the generator safety valve is set to pop.

5. Apparatus of the class described comprising a steam generator, a superheater which receives steam from the generator and delivers for the working valve disposed out range of the heat of the superheater and set to cause said working valve to pop at a pressure intermediate the popping pressure of the boiler valve, and the normal working pressure of the boiler, the safety valve on the superheater being set to pop at a pressure intermediate the working pressure of the boiler valve and the superheater pressure at which the working valve pops.

6. Apparatus of the class described comprising a generator for pressure fluid provided with an emergency safety valve set to pop at a pressure above the working pressure in the generator, a superheater which receives fluid "from the generator and delivers it at an increased temperature and at a pressure below the working pressure in the generator, an emergency safety valve on the superheater, said emergency safety valve on the superheater being set to blow at a superheater pressure intermediate the working pressure in the generator and the pressure at which the generator emergency safety valve will pop, a working valve arranged at the delivery end of the superheater, said working valve being of the pressure loaded type and having a blow-down of the order of one per cent, and control means disposed out of range of the heat of the superheater but which is sensitively responsive to abnormal temperature rise in the superheater, said control means being set to respond to a superheater temperature above that of pressure fluid at a pressure which would cause the emergency safety valve on the superheater to blow, said control means acting to unbalance the pressure at said working valve thereby to permit the valve to open.

7. A fluid pressure system comprising a generator having an emergency safety valve set to pop at a pressure above the working pressure in the generator, a receiver for fluid delivered by the generator, a working valve arranged adjacent to the delivery end of the receiver, control means for said working valve disposed remotely from said valve and from the generator and from the receiver, said control means comprising electromagnetic devices for determining the opening and closing of the working valve and including an electrical circuit and a switch therein, said control means being responsive to a predetermined deflnite temperature in the receiver and/or to a predetermined pressure in the genrator thereby to actuate said switch and cause the working valve to open, said control means being set to operate at a generator pressure intermediate the working pressure in the generator and the pressure which will cause the emergency safety valve to pop.

8. Apparatus of the class described comprising a pressure fluid generator provided with a safety valve, a superheater which receives pressure fluid from the generator and delivers the fluid at an increased temperature but decreased pressure, a relief valve upon the superheater, said relief valve being of the pressure loaded type, a pilot valve for controlling the blowing of the relief valve, and means including a temperature-responsive element, exposed to the temperature in the generator, operative to control the pilot valve, said temperature-responsive element being arranged to respond to a predetermined temperature of the pressure fluid in the generator.

' 9. A fluid pressure system comprising a supply drum and a receiver to which pressure fluid is delivered from the supply drum, a relief valve control means with its sensitive elements being so constructed and arranged that the relief valve will open in response to the occurrence of either of two diflerent energy conditions within the system.

CARL H. GRAESSER.

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