US2292023A - Control system - Google Patents

Description

P. S. DICKEY CONTROL SYSTEM Aug. 4, 1942.

Filed July 2A, 1940 5 Sheets-Sheet l www .www

Slweutor Gforncg VPAUL S. DICKEY WMM/ NON zwNozouw P. S. DICKEY CONTROL SYSTEM Aug. 4, 1942.

Filed July 24, 1940 3 Sheets-Sheet 2 N mi ISnventor Cttorneg MIMI Iotaw #summum Stmme :@z

P. s. DICKEY CONTROL SYSTEM Aug. 4, 1942.

Filed July 24, 1940 3 Sheets-Sheet 5 Patented Aug. 4, 1942 CONTROL SYSTEM raul s. pieken-shaker neiging, omo, minor te Bailey Meter Company, a corporation of Delaapplication .my 24, 19in, serai No. 341,191 s claims. (ci. itz-504) This invention relates to method and means for operating and controlling the operation of vapor generators; particularly vapor generators of the drumless, forced ilow type, having a iiuid flow path including one or more long small-bore tubes, in which the flow in the path is initiated by the entrance of liquid under pressure at one end, and the exit of vapor only at the other end; characterized by an inilow of liquid normally greater than the outilow of vapor, the diierence being diverted from the path intermediate the ends thereof.

Such a vapor generator having small liquid storage and operated with wide range combustion devices forms a combination rendering practical extremely high heat release rates with the consequent ability to economically handle practically instantaneous -load changes from 'minlmum to maximum, and vice versa, without heavy standby expense, and is particularly suitable for operating conditions such as marine service, where load variations are of a wide range and are required to be met substantially instantaneously.

The generator has a minimum liquid storage capacitywith a maximum heat absorbing surface so disposed and arranged as to be substantially instantaneously responsive to rapid changes and wide diversities in heat release rate in the furnace. The heat absorbingsurface is arranged in relation to the path of the products of combustion and radiant heating so that the entering liquid is received at the cooler end of the Further, the vapor generator insofar as the passage of combustion gases is concerned has a continuously increasing resistance to gas ilow throughout the length of the passageway.

The heat absorbing surface, or ilow path for the working medium, is comprised of one or more long small-bore tubes with an enlargement, preferably at the end of the generating section, which acts as a separator to divide liquid and vapor. per-heater, through the while the excess liquid carried tubes for the Ipurpose of wetness The vapor is then passed through a su.

path.

. brought together at suitable headers.

and preventing scale deposit, is diverted out of the separator under regulated conditions, as will be hereinafter set forth. From the separator there is a normal continuous and an additional regulated spillover or diversion of a part of the liquid entering the economizer under pressure, so

that there is always being fed to and through the s economizer and vapor generating sections more liquid than can be converted into vapor in a single passage therethrough, although the propor-I only suiiicient to yinsure tion of such excess liquid may represent but a small part of the total volume of fluid passing through the vapor generator and is at most times tube wetness and to carry off scale'forming materials.

In vapor generators of the character mentioned having small liquid and heat storage with high heat release capabilities. the liquid inflow must of necessity be continuous and at all times proportioned to the vapor outilow, at the same time taking into account the desired diversion of excess liquid from the flow path. Furthermorel to accomplish the wide range in heat release with substantially instantaneous response, and to perform the combustion process efficiently, a method and means for operating such a vapor generator in accordance with varying conditions must be provided.

Still another object is to provide a sequence and protective system/ for maximum safety of operation.

Further objects will become evident from a study of the speciilcation and of the drawings, in which:

Fig, 1 diagrammatically illustrates a drumless forced ilow vapor generator, combined with the requisite apparatus to control the functioning thereof, and shown in partially diagrammatic fashion. l

Fig. 2 illustrates protective apparatus and circuits.

4 Fig. 3 shows a protective arrangement similar to Fig. 2.

In the various drawings; identical parts bear the same reference numerals.

The drumless forced ilow vapor generator of the type to which the present invention may preferably be applied is diagrammatically illustrated in Fig. l.

The ilow path for the working medium is comprised of a plurality of long small-bore tubes The generator includes an economizer 202 at the cooler end of the gas passage and which `receives liquid lfrom a pump `288. A

These parallel flow circuits comprising the vapor generating surface in the fluid now path, which is in the formo! a separating chamber 232 for dividing the iluid f into liquid and vapor; the vapor .passing to a superheater 242, and the excess liquid being diverted from the iluid flow path through a pipe I to the hot well or to waste. This excess liquid may pass through heat exchangers, if desired.

A normal continuous spiliover' occurs' through tangentially enter a bulge certain variables are adapted the restriction 2, whileak variable spillover occurs through the regulatingwalye 3.

The "heat source includes \an\ oil burner 4 supplied by a pipe 5 and an air chamber 6 supplied by a conduit 1. Initial ignition ofgthe oil firing means is accomplished through the agency ignition means is also disclosed and claimed in. said copending application.

Referring now in particular to Fig. 1, I illustrate the fluid ow path as a single sinuous tube, to the economlzer section 202 of which, liquid is supplied under pressure through a conduit II from a pump 289, which may be of any suitable type, and which I have therefore illustrated merely diagrammatically From the economizer section the fluid passes to and. through the generating section discharging into the separator 232. From the separator, vapor passes to and through the superheater 242, leaving by the conduit 244 to a main turbine I2 illustrative of a vapor consuming device. Products of combustion pass successively through the generating section comprising the furnace wall, superheater, and economizer and may contact a part or all of the separator. l

An auxiliary turbine 281 drives the liquid feed pump 289, the air blower 288, and the fuel supply pump 290. While I have illustrated these devices diagrammatically and as though all are located to be driven by the same shaft and at the same speed, it will be understood that the necessary gear reduction, or driving connections f betweenthe several devices, are'known and would be properly designed as to relative speed, power, etc., and that I merely intend to indicate that the auxiliary turbine 281 drives the devices 289, 288 and 290 simultaneously and in unison.

The rate of supply of fuel oil to the burner 4A is primarily controlled by thev speed4 of the oil pump 290, but the supply of oil is further regulated by the throttling of a regulatingy valve I3 located in the pipe ySi; and the rate of ow is continuously measured by a meter I4.

The rate of supply of air to support combustion is primarily determined by the speed of the blower 288, but is further under the control of a damper I5 positioned in the conduit 1, preferably a't `the inlet to the blower 288. of supply of air is continually measured by a ilow meter I6.

The rate of supply of liquid under pressure through the conduit I I is primarily controlled by the speed of the pump 289, but is further influenced 'through the positioning of the regulating valve I1 at the suction side of the pump and by a regulating valve'I8 in a by-pass around the Dump j In the operation of such a vapor generator measured, indicated, and utilized as the basis for automatically controlling the supply of liquid thereto and the supply of the elements of combustion to the heating furnace;

I indicate at I8 a pressure responsive device, such as a Bourdon tube connected to the conduit 244 and having an indicator pointer to cooperate with an index 2I for advising the instantaneous value of the vapor out- The rate ow pressure. At 22 is indicated a temperature responsive device, such as a Bourdon tube, form.

thev vapor outow temperature.

kAs an indicator of generator output, or load upon the vapor generator, I provide means actually measuring the vapor outflow through the pipe 244 leading to the turbine I2 or other uti- -lizer. vTo this end I provide a flow meter 18, similar to the ow meter I4, and connected to the pipe 244 across an orifice or other restriction 19, The flow meter, is adapted to vertically posi'- tion a pilot stem 42 relative to a pilot casing 43 to vary an air loading pressure effective upon the relay 41 proportional to -the rate of vapor outflow. The ow meter 18 furthermore positions a pointer relative to an index to continually advise the weight rate of vapor flowing through the conduit 244 as a guide to manual operation, and furthermore the meter 'I8 may, if desired, make a continuous record and/or integration of the weight rate of vapor outflow from the vapor generator.

29 represents means responsive to liquid level within the separator 232 and constitutes a pres-v The flow vmeter indicated in general at I4 for,

providing a measure of the rate of supply of fuel to the furnace is of a known type, such as is disclosed in the patent to Ledoux No. 1,064,748.

vSuch a meter is a differential pressure responsive device adapted to correct for non-lineal relation between differential pressure and rate of ow, to the end that angular positioning of a pointer 32 relative to the index 33 is by increments directly proportional to increments of rate of now. I illustrate by dotted lines within the flow meter I4 the outline of the internal construction wherein is a liquid sealed bell having walls of material thickness and shaped as described and claimed in the above mentioned Ledoux patent.

The flow meter I6 formeasuring the rate of supply of air for combustion is similar to the meter I4 and positions a pointer 36 relative to an index 31 to provide a continuous indication of the instantaneous rate of flow of air supplied to the furnace.

I preferably primarily control the supply of liquid to the fluid flow path vand the elements of combustion to the furnace, through variation in speed of the auxiliary turbine, utilizing the liquid inflow asI e basis for such control. Realizing, however,l the possible difference in characteristics of the pumps and blower, as well as variations in conditions of operation, I provide readjusting means to supplement the primary control of the elements of combustion. For the air, such readjustingmeans comprises the damper I5 positioned .at the inlet to the blower 288 by a pneumatic actuator 38. For the fuel, the readjusting means comprises a regulating valve I3 positioned in the pipe 5 responsive to departure from desired relation of the measure of fuel flow and the measure of air ow.

'Ihe speed of the auxiliary turbine 281. is regthe actuator' 40.

ystructionand operation of the standardizing relay of the actuator 40 .will not necessarily be directly ulated through varying the opening of governor valves 33 adapted to admit relatively low pressure steam to the turbine, and at certain rates of p- 'eration to supplement this by additionally supplying relatively high pressure steam. For example, the low pressure steam may be the exhaust from the main turbine I2 or extraction steam therefrom, while the high pressure steam may be direct from the vapor generator. actuator 40 positions the valves 39 under the iniiuence of an air loading pressure established by a standardizing relay 4I. Such a standardizing relay is disclosed and claimed in the patent to Harvard H. Gorrie No. 2,098,914. 1n order tol regulate the liquid inflow (through variation in. speed of the water pump) I preferably accomplish the regulation responsive to liquid iniiow rate, vapor outflow rate, and level of liquid in the separator.

As previously mentioned, the vapor outflow meter 18 is adapted to vertically position a pilot stem 42 relative to a pilot casing 43 to which a supplyofcompressed air may be available as indicated by the small arrow. Such a pilot valve forms the subject matter of a patent to Clarence Johnson No. 2,054,464, and in general is adapted to establish an air loading pressure directly representative of weight rate of vapor outilow passing the orifice 18.

I indicate pipes or tubes for transmitting such air loadingv pressures, throughout the drawings, by dotted lines to distinguish from electrical con'L nections or other pipes or conduits. Such a connection is illustrated at 46 for transmitting an air loading pressure bearing a known relation to rate of vapor outfiow'to a differential relay device 41. Certain features of the differential relay 4.1 are disclosed and claimed in myPatent No. 2,098,- 913.

In similar manner the liquid level indicator 29 `vertically positions a pilot stem 48 to establish 4 at the relay 41, through the connection 4,9, an air loading pressure representative of liquid level.

The loading pressures transmitted through the pipes 46 and 49 are effective in separate chambers within the air relay 41 to establish an air loading pressure the pipe 62 representative of the algebraic sum of said pressures. Such re- ;.sultant air loading pressure'is effective through the pipe 62 for positioning the valvel I1.

construction serves to allow an initial major correction with a tapering follow-up, and such regulation is effective through a pipe 68 to position Certain features of the con- A pneumatic with the positioning of the valve I1.

In general, thevalve I1 is positioned responsive to vapor outflow and to liquid level within the separator and forms a variable oriilce in the suction line to the water pump. The device 4I receiving the diierential pressure across the valve I1 positions the actuator 40 and the turbine valves 39 Vto control the speed of the water pump in such manner that. the differential pressure across the valve I1Jwill be held constant regardless of the opening of the valve I1, and thus the liquid ow to the water pump is controlled proportional to vapor-outflow and to liquid level within the separator.

If vapor outflow increases, then the pilot stem 42 is lowered proportionally, thine proportionally increasing the loading pressure eillective through the connection 46, resulting in an increasing of the air loading pressure through the connection 62. The resulting change in opening of the valve I1. varies the pressure differential eiective upon the relay 4I, changing the loading pressuregeffective through the actuatorA 40 to position the turbine throttle valves 38, and results in an increased flow 'of water through the conduit II commensurate with the increase in vapor outilow from the vapor generator.

Should the liquid level within the separator 232 tend to fall, the pilot stem 48 will be raised, thus increasing the loading pressure in the proper chamber of the relay 41, and in like manner further opening the valve I1 to result in an increase in lthe supply of liquid to the vapor generator.

It will then be observed that the valve I1 is po-v sitioned responsive tovapor outiiow from the generator and to liquid level in the separator, while the speed of the water pump is not only responsive to these two variables but additionally to the rate of flow cf water to and through the Dump The liquid level responsive vdevice 23 further controls, through the pilot stem 48, the positioning of the variable spillover valve 3 in such manner that upon a rise in liquid level within the separator 232 above a predetermined elevation there will be a regulated opening of the valve 3 to supplement the normal continuous spillover 2 tothe pipe I.

Certain features directed to the control of the auxiliary turbine are disclosed and claimed in my Patents 2,163,592 and 2,170,348. Certain features relating to multiple and sequential control from n liquid level within the separator are disclosed and I acting upon the Bourdon tubeIS, I provide a pi- 4I -are disclosed and claimed in the patenttol Harvard Hf Gorrie No. 2,098,914.

In this instance the function of the controllable control 'of the same or different magnitude as a rfollow-up or supplemental action to prevent overtravel or hunting, and wherein the positioning lot valve 63 for establishing an air loading pressure through the connection 18 to position the bypass valve I8 and the damper I5. Upon a fall in vapor pressure from predetermined value the valve I8 and the damper I5 bothtend to open, each from a predetermined position. This action is particularly desirable upon sudden material increase in load upon ,the unit as a whole, thus causing a marked decrease invapoi' pressure.l When such sudden and material increases in va' por outflow occur, thereby lowering the` vapor pressure, the auxiliary turbine speed is increased and the vdamper I5 is opened. At such time it is desired to increase the supply of fuel and air' vwithout an immediate increasel in the supply of flow rates.

and valve I1 and causes the auxiliary turbine 281 to speed up to restore the original liquid ow, and in so speeding up increases the air flow and fuel Without the by-pass I8, not only would this advantage be lost, but the momentary increase in liquid inflow when the auxiliary turbine speed is increased, would be more than would be desired to utilize the available heat storage of the unit. The adjustment of the actuator 38 and of the actuator of the valve I8 is preferably such that they will be responsive only to predetermined variations in vapor pressure and corresponding air loading pressure in the connection 10. For example, the damper I5 may be regulated as to position upon any departure of vapor pressure from predetermined value in either, direction, while the valve I8 may be completely closed until vapor pressure has fallen a predetermined amount below the desired standard. Beyond that point the valve I8 would begin to open and the damper I5 may, or may not, be completely open while thcopening of the valve I8 is being regulated.

I preferably primarily control the supply of the elements of combustion through varying the speed of the auxiliary turbine, and thereby the speed of the blower and the oil pump in unison with the liquid inflow rate. Having readjusted the air supply through a positioning of the damper I5, and provided a measure of the air flow by the meter I6, I then utilize the regulating valve I3 in the oil supply line to properly proportion fuel to air. To this end the meters I4, I 6 are interconnected with linkage 1I for positioning a pilot stem 12 to establish an air loading pressure through the connection 13 to a standardizing relay 14 in general construction similar to that i1- lustrated at 4I. The air loading pressure resultant from operation of the relay 'Il is effective through a connection 15 for positioning the regulating valve I3 upon `departure of air flowfuel flow relation from predetermined value.

A method and apparatus of electrical protection of such a power system is disclosed and claimed in my Patent No. 2,170,346, as well as being disclosed and claimed in part in the copending application of Jack F. Shannon, Serial No. 55,028, filed December 18, 1935.

Figs. 2 and 3 in general show the lprotective arrangement and circuit for the vapor generator, in which a series electric circuit is arranged to normally hold open the solenoid valve supply-A ing control air to the fuel shutoff valve |08 and to pilot valve 68. Upon loss of electrical power at the solenoid valve the valve closes, shutting off the air pressure from the fuel supply valve and thus cutting off fuel supply to the furnace. The normally energized solenoid of the valve is in a series circuit including normally closed contacts which are arranged to open the solenoid circuit upon excessively high pressure at the separator drum, low water in the separator drum, low pump lubricating oil pressure, flame failure, or from excessively high 'temperature experienced in any of the individual furnace circuits. 'I'hus any one of tlje/ mentioned emergency conditions will be effective in tripping the re through shutting off the fuel supply 'valve |08 tothe furnace.

extreme magnitude and rapidity of load changes.

A, It is, for example, not uncommon to have such a. vapor generator operating at an overload and almost instantaneously drop the load to say 1%. This sudden substantially complete loss of load may cause the steam pressure to rise very rapidly. The high pressure trip of Figs. 2 and 3 will shut off the ilre, but the stored heat inthe furnace causes the pressure to go on up in spite of that and to blow the safety valve. Itis, of course,

not desirable to frequently blow the safety valve on a vapor generator operating at pressures in the order of twelve hundred pounds and greater.

pen before the normal drum level control can y drain the separator drum down to a safe operating level.

Both of these conditions indicate the desirability of opening the spillover valve v3y Widely In addition to the protective circuits menunder emergency high pressure conditionsi The arrangements of Figs. 2 and 3 preferablytdump the separator drum byopening the spillover valve immediately and completely when an excessive vapor pressure is experienced.

Such an opening of the spillover valve relieves the pressure (thus saving the safety valves from blowing) and may'blow the separator empty. discharging hot water and saturated steam to the hot well. vThis does no harm however as the heat exchangers or hot well will utilize the heat of the water and steam. In the meantime the incoming water from the feed pump continues and cools the circuit. Furthermore, by blowing the separator drum through the, spillover v alve immediately after a loss of load, and having a minimum water storage in the unit, minimizes the danger of carry-over due toswell upon a cessively high steam pressure is experienced,

either from sudden loss of load or for other cause, the re will be tripped off through a closing of the fuel supply valve |08 and the spillover valve 3 will be opened widely to blow down the separator drum. It is preferable that as the pressure increases it rst causes a tripping of the fire and immediately thereafter (or at 'a slightly higher pressurek value) causes an opening of the spillover valve. This is so that the separator will not be empty with the fire lighted and to avoid the danger ,of burning the separator. It is therefore essential alwaysto trip there before blowing down the separator drum.

In Fig. 2, in addition to the protective circuits previously described, the air loading pressure developed by the pilot 89 is led to one chamber of a standardizing relay |09 from which a control loading pressure leads to a differential relay I I0. The latter also receives a second loading pressure developed by the level controller pilot '49, which loading pressure in Fig. 1 goes directly to the spillover valve 3. In Fig. 2 the spillover valve 3 is controlled by they loading pressure from the relay III), resultant between that established by the/pilot B9 and that established by thefpilot 49.

The construction and biasing of the relay H is such that the emergency loading pressure from the pilot 69 is normally ineffective upon the relay H0 until a certain predetermined high steam pressure is obtained, whereafter this loading pressure comes into effect on the averaging relay -relay H0 is normally under control of a loading pressure from the level control pilot 49 for positioning of the spillover valve 3, there occurs under an emergency condition an opening of a solenoid valve lllin an air supply line to a second chamber of the relay H0 to immediately open the spillover valve wide. In this arrangement the solenoid valve III will be actuated in parallel with the solenoid valve which causes the shutting olf of the fuel supply valve |08 and from any one of the emergency trips previously described.

It will be appreciated that there may be many modifications and arrangements possible of the illustrative example given herein, without departing from the spirit of my invention, and that I have illustrated and described only preferred embodiments without intending them to be limiting,

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

l. 'I'he method of operating a vapor generator of the forced flow type receiving liquid under pressure at one end of the flow path and delivering superheated vapor at the other end, which includes, supplying liquid in predetermined excess over vapor outflow, discharging the liquidvapor mixture to a separator between the generating and superheating portions of the path, utilizing the liquid level in the separator to so control the discharge therefrom as to maintain a .predetermined level therein under normal load `conditions and increasing the rate of blowing down of the separator when a predetermined low load condition on the generator and a corresponding low firing rate of the generator is experienced.

control the discharge therefrom as to maintain a predetermined level therein under normal load conditions and increasing the rate of blowingdown of the separator when a predetermined high pressure in the generator is experienced following a low ring rate of the generator;

3. The method of operating a vapor generator of the forced flow type receiving liquid under pressure at one end of the flow path and delivering superheated vapor at the other end, which includes, supplying liquid in predetermined excess over vapor outow, discharging the liquidvapor mixture to a separator between the generating and superheating portions of the path, utilizing the liquid level in the separator to so control the discharge therefrom as to maintain a predetermined level therein under normal load conditions and increasing the rate of Ablowing down of the separator when there is no load on the generator and the firing rate of the generator ceases.

4. The combination of a vapor generator of the forced ow typemmeans supplying liquid under pressure to one *end of the forced flow path in excessy over vapor generated, a liquidvapor separator in the `ilowpath between the generating and superheating portions of the path, a meter continuously determining liquid level in said separator, a valve controlled by said meter and variably discharging liquid from the separator, and means responsive to a predetermined low load condition and corresponding low ilring rate of the generator adapted to increase the rate of blowing down of the separator through additional opening of said valve.

' 5. The combination of a vapor generator of the forced flow type, means supplying liquidA under pressure to one end of the forced flow path in excess over vapor generated, a liquidvapor. separator in the flow path between the generating and superheating portions of the path, a metercontinuously determining liquid level in said separatoi; a valve controlled by said meter and variably discharging liquid from the separator, and means responsive to a predetermined high pressure condition in the generator following a low firing rate of the gen'- erator adapted to increase the rate of blowing down of the separator through additional opening of said valve.

6. The combination ofv a vapor generator of the forced ow type, means supplying liquid under pressure to one end of the forced flow pathv in excess over vapor generated, a liquidvapor separator in the ow path between the generating and superheating portions of the path, a meter continuously determining liquid level in saidseparator, a valve controlled by said meter and variably discharging liquid from the separator, and means responsive to the shutting off of the fire following loss of load on the generator adapted to increase the rate of blowing down of the separator through additional opening of said valve.

PAUL S. DICKEY.

Images