US1769139A - Automatic boiler-control system - Google Patents

Description

July 1, 1930. B. JONES AUTOMATIC BOILER CONTROL SYSTEM Filed Sept. 17, 1928 lummgrrzzz INVENTOR: .Barton- Jone l IF W WM ATTORNEY Patented July 1, 1930 raras ear T FFICE' BARTON JONES, or LOS Antennas, CALIFORNIA AutroMArI'c BOILER-CONTROL sxs'rmvr Application filed September 17, 1 928. Serial No. 306,334.

'5. jects. I do not limit myself to the forms dis- 1Q. other than those specifically mentioned, are

closed, since various changes and adaptations may be made therein Without departing from the essence of my invention-as here-. inafterclaimed and objects and advantages,

included within its scope.- 1

My invention relates to automatic control systems for steam boilers and other types of liquid vaporizers",fi whereby steam pressure 155 and other operating conditions may be kept constant within narrow limits. Its principal objects include: first, to provide very simple automatic means for regulating dampers, fuel valves, and" the like, to maintain'thedesired operating conditions; second, to pro- 25 sistance, and solely with respect to the oper-' ating conditions thatlarefto be controlled;

duce a control system of this kind that possesses great inherent power, and that is capable, within its "capacity, of Working the regulating equipment'regardless of 1ts rethird,to supply a control system that is sensitive and responsive to very small changes in the controlled conditions fourth, to furnish a system of this nature that is capable'of working under very small dilierences of pressure, so as to minimize thev elfects of wire drawing in the sensitive control valves that necessarily have to be employed; fifth, to

i make it possible to operate a boiler regulating system on a closed cycle, without waste-of steam or hot water with the attendant loss of quire attention.

energy and inconvenience in taking care of the waste ;*sixth, to make available acontrol system of this nature that requires no auxil iaryv power; and, seventh, to accomplish the above by means of'simple. and relatively inexpensive construction, that embodies very few moving parts or other features that re- My objects are attained in themanner illustrated in the accompanying drawings, in which Fig. 1 is an elevation of a generic form of my invention applied to. a steam boiler, cer

tionable.

tain parts being shown broken and in section; Fig. 2 is a sectional longitudinal elevation of a suitable pilot valve employed with my inventionwhere it is desired to maintain a constant boiler pressure; and

Fig- 3 illustrates in connection with the other figures, in elevation, an alternative method and auxiliary apparatus for installing and utilizing my invention, in cases where head-room is very limited andwasteof a small amount of boiler water is not objec- Similar reference numerals refer tosimilar parts throughout the "several views.

In the drawings, a portion of a steam boiler is shown at 5',provided with an ordinary watercolumn 6. Normally the water in the boiler stands at level 7,half way up the gauge glass 8. l

- In the form of my control shown in Fig. 1, P

there is an upper base 9 and a lower base 10, mounted vertically upon a wall, as by means of the bolts 11, and connected by a pair of tension rods 12. A relatively long expansion tube 13 is tapped into the upper base. At the lower end of this tube is a T fitting 14;, below which is a short cylindrical strut 15, slidably passing through the lower base and guided thereby, the strutbeing coaxial with the expansion tube. At the lower end of the strut isa coaxial bolt 16 and lock nut 17, for adjusting the operating length of the expan sion element. Below the expansion element is an operating lever 18 of relatively large ratio, pivoted to the lower base at 19, at one side of theaxi's of the expansion element. A series of small'holes 2 0, at the free end ofthe lever, provide means for eifectively varying the lever ratio. Obviously the described arrangement is capable of causingdever 18 to move upwardly or downwardly, when the temperature of the expansion element is changed to'vary its length. This provides means for controlling dampers or fuel valves, by connecting them to the free end of the lever by suitable cords or linkages. The upper end of expansion tube 13 communicates with steam space 21 ot'the boiler through nipple 22, pilot valve 23, and pipe line 24, therebeinginterposed' in this pipe line a small condensing device 25 in case the boiler is sup- In the light of the above descri plying superheated steam. Otherwise this condenser may be dispensed with.

The lower end of the expansion element is connected to water space 26 of the boiler, through pipes 27, 2S, and 29. Flexibility in this connection is provided, for the movement of the expansion tube, and is furnished by the use of the elbow fittings 30, connected as shown. It is desirable to have this water connection form a loop, its lower portion lieing considerably below the level of the water in the boiler.

Pilot valve 23 contains a pressure chamber 31, having an inlet connected to pipe line 2 1, and an outletconnected to nipple 22. The outlet is variably closed by a needle valve 32,

coaxially mounted upon diaphragm 33 which.

closes thepressure chamber at the top.

Compression spring 34, above the diaphragm, is adjusted by means of the tubular bolt 35, to exactly balance the normal pressure acting upon the lower surface of the diaphragm. lVhen the pressure is normal, valve 32 will be slightly off its seat, and permit a flow from pressure chamber 31 through nip- I ple 22 into the expansion tube 13.

'ption of the apparatus, its operation is as follows:

lVe will first assume that boiler 5 is cold and, that there is no steam pressure thereon. Valve 32 "will be closed by the pressure of spring 34. Water, under'these, conditions, ordinarily will stand in pipe 28 at about the same level it does in the boiler, and expansion tube 13 will be empty. As the boiler becomes heated and generates steam, the pressure will cause cold water to flow into tube 13. The first step is to remove any entrapped air that may be in this tube, by opening pet-cock36, which is provided for this purpose. When the boiler pressure has increased sufficiently to-fill tube 13, and to cause water to escape through the pet-cock, the latter is closed.

Whenthe boiler pressure builds up to the point at which it is desired to operate (the pressure for which valve 23 is adjusted), the upward pressure upon diaphragm 33 will be exactly counterbalanced by the downward pressure of spring 34.. If the boiler pressure rises above. this point, valve 32 will be slightly lifted from its seat, and allow steam to flow into the expansion tube. The water in the tube will then immediately fall under the; action of gravity, and expose the income ing steam to the cooling effect of the wall of the tube. This wall comprises a very considerable condensing surface, and the steam in space37 above the water will be rapidly condensed and reduce the pressure in this space. This reduced pressure will prevent water 38 from wholly leaving the tube, and it will stand at some intermediate level as at 39. The heating of the upper portion of the expansion tube by the steam in space 37 will the difference between the boiler pressure and the pressure in space 37, will be just sufiicient to support the weight of water column 38 above the level of the boiler water line. An equilibrium will be quickly established between the rate of condensation in space 37 and the flow of steam past valve 32. Tube 13 will assume a definite length due to the combined effect of the temperature of its hot and cold portions, and it will move lever 18 to the proper position for maintaining constant boiler conditions.

- If now the operating conditions of the boilershould change, as by reason of a falling off I of-the load, so that its pressure increases, diaphragm 33 will be deflected further upward and cause valve 32 to open stillmore to increase the flow of steam into space 37. This added rate of steam flow cannot be condensed by the then exposed wall of steam space 37. It will have the effect of increasing the pressure therein, so as to force water level 39 downward and expose more wall until a new equilibrium is established. A greater length of the expansion tube will now be exposed to steam temperature, and it will further increase its length and cause lever 18 to rise to a new position correspondingto the changed boiler conditions.-

Conversely, if the boiler pressure should drop below normalfor any reason, valve 32 will close. Whatever steam is then within space 37 will quickly condense, and water line 39 will rise; Thusthe expansion tube will be cooled and contract, and lever 18 will be allowed to fall to open up the boiler damper, fuel valves, or other boiler regulating equip! ment. y

, The general operation of my control system will bereadily understood from the foregoing description, but the. use of condenser 25 is still to be explained. When the boiler is supplying superheated steam, the latter obviously must lose a considerable portion of its heat content before it can condense. This would have have the efi'ect of retarding the operation of my device and can be overcome by the useof this small condenser. ,This is merely an introduction of sufiicient radiating surface to dissipate the superheat of the steam, so that steam passing it into space 31 will be approximately saturated. A simple and sufiicient condenser for this purpose comprises a short length of tubing provided with radiating fins.

It is to be particularly noted that valve 32 operates under a very small pressure difiieren- The life of the valve and seat will be greatly prolonged for this reason, and they should in fact last indefinitely. It is further to be noted that the system is a closed one, in which there is no waste drip whatever, and in which the only loss of energy due to operation is .that resulting from the radiation of heat through the wall of the expansion tube above water line 39. Still further, it will be seenthat the expansion effect of tube 13 may be made to yield a very powerful thrust upon lever 18.

A suitable form of pilot valve at 23 is, of course, an essential part of my control system. The actuation of the valve itself may be accomplished in a variety ofways, other than by the use of the pressure differentials ob; tained in the manner described and illustrated. The valve may, for instance, be a thermostatic valve, or it may be actuated by pressure differentials obtained in other ways than as herein set forth. a

The normal method of installing my control system is to place the expansion tube of Fig. 1, well above water line 7 of the boiler. In such installations the system is .a closed one. There is no waste drip to be disposed of, and no operating losses other than the slight loss of heat due to radiation from the hot portions of tube 13; and, in case of the use of superheated steam, of radiation from condenser 25.

In certain cases, by reason of lack of headroom, it is impractical toinstall the apparatus in the above manner. In these instances it still is possible to make full use of the major features of my invention, but the advantage of a closed system will have to be sacrificed.

When it is required to locate the expansion tube below the boiler water line, or partially below the-same, I employ a suitable steam trap 50. The steam space of this trap is connected through nipple 51 and pipe 52 to steam space 21 of the boiler. It is also connected through nipple 51 to pipe 2 1 of my system. The water space of the trap is connected to pipes 29 and 28 of my system. The trap is arranged to maintain'a maximum level above which the water within it cannot rise, any excess water being discharged from time to time through its waste pipe 53. It is, of course, essential that the trap should have sufficient water space to insure offilling the expansion tube therefrom, at all times. My system thus arranged will operate in the manner first described, except for the periodic waste of a small amount of hot Water through the trap discharge pipe 53.

Having thus fullydescribed my invention 7 in a manner that will be readily understood by engineers, and those familiar with the art involved, I claim:

1. A device of the character described, comprising; a vapor generator; an, automatic valve having-its inlet communicating with the vapor space of said generator, adapted for actuation by changes of pressure therein, an upwardly extending tube adapted for condensing vapor, communicating at its upper end with the outlet of said valve; and means associated with said tube whereby changes in the rate of condensation of vapor therein by affecting the length thereof may be made available for actuating external meactuation by changes in pressure of the steam therefrom, an upwardly extending tube adapted for condensing steam, above the water level of said boiler, communicating at its upper end with the outlet of said valve and'at its lower end with the water space of said boiler; and a lever-engaging said tube whereby changes in the rate of condensation of steam within said tube, by changing its effective length as the result of temperature, may be made effectivefor controlling the op eration of said boiler.

3. The construction set forth in claim 1 in combination with a heat exchanger intermediate the generator and automatic valve; whereby superheated vapor from the genprior to entering said valve.

BARTON JONES.

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