US2660378A

US2660378A - Boiler control apparatus

Info

Publication number: US2660378A
Application number: US172701A
Authority: US
Inventors: William S Smoot
Original assignee: Republic Flow Meters Co
Current assignee: Republic Flow Meters Co
Priority date: 1950-07-08
Filing date: 1950-07-08
Publication date: 1953-11-24
Anticipated expiration: 1970-11-24

Description

NOV- 24, 1953 w, s s o 2,660,378

BOILER CONTROL APPARATUS I Filed July 8, 1950 2 Sheets-Sheet l 32- I Q J7 man/5141775 TRANS MITTER INVENTOR.

AT T ORNE Y5,

Nov. 24, 1953 w. s. SMOOT 2,660,378

BOILER CONTROL APPARATUS Filed July 8, 1950 2 Sheets- Sheet 2 TRANSMITTER- TRANSMITTER ATTORNEYS.

Patented Nov. 24, 1953 UNITED RATE-NT goFFI-CE M -2;660,378 I e I BOILEKGDMROLARBABAT S William- ES. Smofot', EHighlanii Park; Ill., assignor ---t'o Republic Flow Meters "Gompany; 'Ghioa'go, -..-.:ill zarcorporation oflllinois lappllcafionluli.8,;1950, seri t yo. 172,701

This 'inventionrelates .to control apparatus for interrelated conditions and particularly to apparatus for controlling one condition or factor in response to a plurality of interrelated conditions affected by the first. Specifically the invention relates'to control of'the air supply to'a'st'eam generator in response to 'functions'of steam'pressure and flow.

"The invention is particularly'usefulin' the control of one element or factor which affects "other interrelated conditions responding indifferent manner to changes 'in'the first factor or to external conditions. This type of control is highy desirable in many "industrial processes in. addition to steam generators. "Thereforefwhile'theinvention will be particularly described for control ling the supply of 'combustionair'to asteamggenerator it is not intended to The limited toj'this purpose, this example beingselect'ed only for convenience of description or one application in which the invention has'pajrticularadvantages.

It is one'object of the invention to .providea control apparatus in which onejof several interrelated conditions is controlled "rapidly, in response to a change in a second condition and more slowly'in 'response'to a change in a jthird condition. As applied'to *a steam generatorjjthe airflow is controlled rapidly inresponsetojsteam pressure and slowly in response'ltosteam flow.

.Another object is'to provide. control-apparatus in which a rapid control effect in 'res'ponsejto one condition is cancelled out gradually at the same time that another control efiect'responsive to'another conditionfcomes into efiect.

sun another object is toprovide'a control 'apler; and

Figure 3 is a view 'similarto Figure '1 showing an alternativecontrol.

As shown in "Figure '1, the control "apparatus I Figure 2 is an enlarged sectionof-t'he controlb'oiler indicated generally at I'll.

olgth'eipre'sent inventionis applied to the control of ,airJfor combustionto .a steam generator for Combustion air -is supplied by atfoirced draft blower ll and is controlledby avalve 12 in a. conduit [3 .connecting the blower to the boiler. 'Fuelissupplied Lthrougha conduit, M to mix'withthe air in aycombustible mixture, and the combustion products vare exhausted through a ffiue T5 controlled in any .desire'd manner 'by a valve Ilfi. Steam; .igenerated in thefboiler flows to any desired points of -ilseathrough a main outlet pipe 1;! andasteamtheader ,ilii. ZIheairyalvelZ is (20ntrolled hyaailiegulator, 19 which may be of the type moremarticularly described :and claimed in the patent to OGonnor; No.-;2;039,924; andwhich is controlled through a balance :beam -2l by two diaphr-agms 122 :and 2.3. The diaphragm 22 :is

. connected across an orifice 24 in theconduit 4L3 to -measure the airflow, and the diaphragm 23 is supplied-withfluidfunderpressure from a con-- troll'er to be described more fully hereinafter. With this construction the regulator will controlthe valve "I-'2 to maintain flow through-the conduit' la whichis proportional to the pressure applied on the diaphragm-2 3.

The -"supp'ly-offuel is similarly controlled "by a regulator 25 connectedtoa valve '26 in theful line. '"Ihe -regulator 25 is controlled by a 'differeritial diaphragm -21 1 connected across an oriflee in the fuel --'supply conduit "I 4 and 'a' diaphragm '28 to which a "controlling pressurefis supplied 'as described hereinafter. V

According to the present invention it is desiredto maintain the air flow. to the generator proportional-tosteam flow' therefrom and to provide "an initial correction of the air 'flow -in response to"changes-in'the-steam pressure. This is because thefuel supply to the boiler will be controlled-in response tosteam :pressure and it is desired initially-to correlate changes in airflow with changes in fuel flow,- both functions being responsive tosteamv pressure, -so that upon an increase ;in steam demand the fuel supply and air flow will both increase proportionately in response'to-steam pressure. liatenwhen the steam demand has settled-at a-'umform value, the control ofair-flow will respond to steam flow only.

As -shown, the header I8 is connected to -a transmitter 29 which may be of the type more particularly-described and claimed in the patent to Rosenberger, No. 2 ,431,200. This-transmitter produces an air 'pressure in'its outlet conduit '3 I which =is=proportional to the-"existing steam pres- 3 sure. The conduit 3| is connected to the diaphragm 23 so that the fuel supply will be controlled in response to steam pressure and is also connected to the control indicated generally at 32 and more fully shown in Figure 2,

As illustrated in Figure 2 the controller comprises a balance beam 33 pivoted at its center and having a valve member 34 thereon which is moved toward and away from a bleed nozzle 35 as the beam moves. The bleed nozzle is supplied with air through a restriction 36 and is connected by a line 31 to the diaphragm 23 to supply a regulated air pressure thereto. The nozzle is also connected to a diaphragm 38 acting on a block 39 connected to the balance beam to urge the beam in one direction.

The beam is urged in the opposite direction I by a similar diaphragm 41 which is connected to the line 3 I to receive a pressure from thetransmitter 29 which is proportional to the steam pressure. The diaphragm 4| acts on a block 42 on the opposite side of the beam pivot from the block 33 so that it tends to turn the beam in the opposite direction from the diaphragm 38.

The line 3| is also connected to a time delay pressure responsive device 43 acting on the beam 42 in opposition to the diaphragm 4|. The device 43, as shown, comprises a vertical cylindrical casing 44 closed at its bottom by a diaphragm 45 acting on the block 42. An intermediate partition 46 in the casing 44 separates it into an upper chamber 47 and a lower chamber 48, one side of which is closed by the diaphragm 45. The lower parts of the chambers 41 and 48 are connected by a tube 49 which is variably restricted by a valve member 5i adjustably threaded in the top of the casing. The pipe 3i connects to the upper part of the chamber 41.

The casing is adapted to contain a body of liquid 52, a part of which will normally be in the upper chamber 41 and the remainder of which will be in the lower chamber 48. The pipe 49 extends below the liquid level in the lower chamber so that upon changes in the relative pressures in the two chambers liquid will be caused to flow from one to the other at a rate determined by the setting of the valve H.

A similar time delay unit 53 is provided acting on the block 39 in opposition to the diaphragm 38 and its upper chamber is supplied with a regulated air pressure through a conduit 54 from a transmitter 55 similar to the transmitter 29. The transmitter 55 is connected across an orifice 55 in the steam outlet conduit I1 so that its transmitted pressure will be proportional to steam flow from the generator.

In operation of the system assuming a sudden increase in the demand for steam, the pressure in the header I8 will drop and the flow of steam will tend to' increase. The immediate effect will be a decreased pressure of steam effecting the transmitter 29 so that its output pressure through the line 3| will increase. This increased pressure acting on the diaphragm 28 will operate the regulator. to increase the flow of fuel. At the same time it will increase the pressure on the diaphragm 4! tending to rock the beam 33 clockwise so that the pressure behind the nozzle will increase proportionately to rebalance the beam through the diaphragm 38. This increased pressure will also be transmitted to the diaphragm 23 to cause the regulator I3 to open valve I2 thereby to effect an immediate increase in air flow. The increased pressure from transmitter 23 acting on the liquid in the upper chamber 41 will gradually force liquid from this chamber into the lower chamber 43 gradually to build up the pressure on the diaphragm 4| and completely cancels the effect of steam pressure on the controller. At the same time, a similar action will occur in the time delay device 53 to produce a pressure opposing the diaphragm 38 which is proportional to steam flow. By the time steam pressure efiect on the control has been cancelled the full steam flow effect will be present so that the pressure produced behind the nozzle 35 to rebalance the beam 33 will be proportional to a function of steam flow and the air flow will be controlled to be proportional to steam flow. In this way an initial correction is made in response to steam'pressure, and this eifect will gradually be cancelled to be replaced by an efiect responsive to steam flow. In this way a rapid and extremely'accurate control of the air flow is pro duced in the manner desired.

Similar controls of other industrial processes are contemplated such that the initial change will be responsive to one factor or condition and will subsequently be replaced by a control responsive to another factor or condition. Figure 3 illustrates one such alternative control ,applied to a steam generator in which both the fuel and air are controlled in response to steam pressure and an initial adjustment is made in response to steam flow. Parts in Figure 3 corresponding to like parts in Figures 1 and 2 are designated by the same reference numerals plus 100.

In this construction the loading diaphragms I23 and I 28 of the air flow regulator [l5 and the steam flow regulator I25 are both connected to the line I31 to be simultaneously controlled in response to the pressure produced back of the nozzle I35. The pressure responsive transmitter I29 is connected to the pressure responsive device I53 and the flow responsive transmitter is connected to the two devices I4I' and I 43.

With this construction both the fuel and air are normally controlled in response to steam pressure so that the steam pressure will tend to be held constant. Upon a change in demand the change in steam flow will immediately affeet the device MI to change the rates of fuel and air supply. The steam flow effect will gradually be cancelled through the device I43 so that control of the fuel and air will return to a response to steam pressure.

In both of the constructions shown the primary control is responsive to the value of one factor and is modified in response to the rate of change of another factor. Thus in Figure 1 as long as steam pressure remains constant the control is solely in response to steam flow and steam pressure produces an effect only during 1. Control apparatus for interrelated conditions comprising a balance beam, means for producing a'force proportional to one of said 51 conditions, aipairorrrorce respcnsiveidev ce lresponsive to,, $aid, force, and acting, in opposite directions on the balance beam, means to introduce ai'time delay into the: response of one of said? devices; means .to produceasecond force responsive-Ito asecondof said conditions; a force responsive; device responsive to the-second force to urge: thea-beamin one direction; means to introd'uce: a. time. delay into the =response-ofl the lastvnamediidevice, means responsive t'=unba1-- ance:ofs the beam .to produce a 'third force-pa forcea responsive. device responsive to the 'third forceaactingonuthe beamsto balance it, andicontrol means responsive to the third force to control a factor affecting said conditions.

2. Control apparatus for interrelated conditions comprisinga balance beam, an instrument responsive to one of said conditions to produce a fluid pressure proportional to the condition, a pair of pressure responsive devices responsive to the fluid pressure and acting in opposite directions on the beam, means including a variable restriction to introduce a time delay into the response of one of said devices to changes in the fluid pressure, a second instrument responsive to a second of said conditions to produce a second fluid pressure, a pressure responsive device responsive to the second fluid pressure to urge the beam in one direction, means including a variable restriction to introduce a time delay into the response of the last named device to changes in the second fluid pressure, means responsive to unbalance of the beam to produce a third fluid pressure, a pressure responsive device responsive to the third fluid pressure acting on the beam in opposition to the last named device, and control means responsive to the third fluid pressure to control a factor affecting said conditions.

3. Control apparatus for a steam generator having an air supply connection and a steam outlet connection comprising control means for the air supply, a controller for the control means, an operating element in the controller connected to the steam outlet connection and instantaneously responsive to steam pressure, delayed action means in the controller gradually to cancel the effect of the first named means, and a delayed action operating element in the controller responsive to steam flow to operate the control means and thereby vary the air supply.

4. Control apparatus for a steam generator having an air supply connection and a steam outlet connection comprising control means for the air supply, a controller for the control means, means for producing a force proportional to steam pressure, a pair of force responsive devices in the controller acting in opposite directions thereon and responsive to said force, means to introduce a time delay into the response of one of said devices, means to produce a force responsive to steam flow, and a delayed action device in the controller connected to the last named means to respond to the last named force and operating the controller to vary the air supply.

5. Control apparatus for a steam generator having an air supply connection and a steam outlet connection, control means for the air supply, an instrument responsive to the steam pressure in the outlet connection to produce a fluid pressure, a controller including a balance beam, a pair of pressure responsive devices responsive to said fluid pressure and acting in opposite directions on the balance beam, means including a variable restriction to delay the response of one unbalancewoithep balancerbeam top rat sitbe;

control, means thereby, to; control; the-. air; supply: (is-Control, apparatus for a ,1 steam; generator:

having, an; .air supp] y conn ction:- and; a; ste m? outlet connection, ,controli-means,for;,the ai1:.-supep yean. in trument: responsiverli the= team-= res-l; sum in the outlet,connection-to;producelazgfluid.

pressure, a: controller, zincludinai a: ba ancenbeamt a pail:OfpRIBSSLlIE:,I'QSRQIlSiVe devices responsive to said fluid pressure and acting in opposite directions on the balance beam, means including a variable restriction to delay the response of one of said devices to changes in fluid pressure, a second instrument responsive to steam flow through the outlet connection to produce a second fluid pressure, a pressure responsive device responsive to the second fluid pressure and acting on the balance beam, means responsive to unbalance of the balance beam to produce a third fluid pressure, a pressure responsive device responsive to the third fluid pressure and acting on the balance beam to rebalance it, and means responsive to the third fluid pressure to operate the control means thereby to control the air supply.

'7. In a control apparatus, a controller comprising a balance beam, at least three fluid pressure responsive device acting on the beam, each of two of said devices acting in opposite directions on the beam comprising a vertically elongated housing, a diaphragm closing one end of the housing and acting on the beam, a partition in the housing dividing it into two vertically spaced chambers adapted to contain a liquid, a conduit connecting the lower parts of the chambers, a valve variably to restrict the conduit, a fluid pressure connection to the chamber remote from the diaphragm, the third device including a diaphragm, and a substantially unrestricted fluid pressure connection to the last named diaphragm.

8. Control apparatus for a steam generator having an air supply connection, a fuel supply connection and a steam outlet connection comprising devices respectively responsive to steam pressure in and steam flow through the outlet connection to produce forces, and control means for the air and fuel supplies responsive to one of the forces and to the rate of change of the other.

9. Control apparatus for a steam generator having an air supply-connection, a fuel supply connection and a steam outlet connection comprising devices respectively responsive to steam pressure in and steam flow through the outlet connection to produce forces, and control means for the air and fuel supplies responsive to one of the forces and to the rate of change of the other, and means to introduce a time delay into the response of the control means to said one of the forces.

I 10. Control apparatus for interrelated conditions comprising a balance beam, first and second means for producing forces responsive to two of said conditions respectively, a force responsive device connected to one of said means and substantially instantaneously responsive to the force produced thereby to urge the beam in one direction, a pair of vertically elongated housings, diaphragms closing the lower ends of the housings and connected to spaced points on the beam to urge it in opposite directions in response to pressure on the diaphragms, a, partition in each of the housings dividing it into spaced chambers References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Smoot Apr. 30, 1929 McLean Apr. 12, 1932 De Florez June 25, 1935 Miller Feb. 11, 1936 Hewitt Nov. 24, 1936 Moore July 26, 1938 De Florez Nov. 4, 1941 Johnson May 6, 1947 Anderson Apr. 26, 1949