US2376029A - Boiler feed water regulation - Google Patents

Description

i' May'l5, 1945. J. A. CAMBELL 2,375,029 I Y. BOILER LFEED WATER REGULATION Filed March 28, 1942 OOO km, S

Patented May 15, 1945l BOILER FEED WATER REGULATION Julian A.v Campbell, Long Beach', Calif. t ,n l Application March 28, 1942, Serial No. 436,592

4 claims. (ci. 12a-451.1)

. This invention has to do generally with liquid level control apparatus, e. g. for boiler feed Water regulation, in which the feed water control valve is operated in response to displacement of an` element movable in accordance with changes in the boiler water level. l Although' independent lin ycertain raspects of the particular type and "form of primary control element whose movements regulate the operation of the feed control valve,`the invention aims'particularly to :provide improvements in? regulating apparatus ofthe expansible tube type as shown in United States Letters Patenty No. 2,207,214, issued July 9.

l940 tome on'Boilerfeedwate'r control-'and in my later issued` Patent No.`2,284,130 granted May 26, 1942, on Boiler feed' control.

used in the claims'is not intended to be inclusive of the usual interengaging threads on the valve stem and the valve body.

Another feature of the invention is the provision of a manually operated control for subiecting the upper portion of the expansion tube to cooling, for the purpose of restoring the tube to normal condition after abnormal expansion resulting from blowing-down the tube. From time to time it may be necessary to blow-down they tube to *prevent excessive accumulations therein of hardened )scale-forming substances tending to interfere with proper operation of One of my principal objects isto providean' y improved mechanism` for operating the feed water control valve, permitting the use of valves', for

example globe valves, capable of most sensitiveA throttling of the feed water stream and yet iinposing the least restriction to vflow under normal conditions.. Itis also proposed tominimizevalve stern leakage and the possibility of stemv corro-i` sion that'so frequently interferes with the neces-v sary free operation of the valve. In accordance with the invention, axial movement of the valve'A stem to effect opening and closing movements of the valve is' accomplished to particular mechanical advantage, with minimum friction, and independently of the usual stem propulsion screw threads in the valve structure. In fact, such threads may be entirelyeliminated,

Considering theexpansion tube as typical of any suitable movable element responsive to the boiler Water level changes, operationl of the feed Water control valve yoccurs by a connection between the valve stem and the expansion tube producing rotation of the`stem,'and a cam device,

producing axialV movement ofthe stemby virtue of its rotation. Preferably, I employ a rack-andgear type of connection "between the expansion tube and* valve stem, gaining the advantages of a positive connection between the lparts, while allowing axial or vlongitudinal movement of the valve stem. AA further advantage of this type of lconnection is that it 'permits continued displacel ment ofthe expansion tube in a valve-closing diy 1 rection, after the feed 4water control valve has become fully closed, all as will hereinafter ap'- pear. The .cam device has the advantagey of minimized friction, and therefore greater sensitivity and freedom in the valve stem movement Incidentally, the word caniv as feed water regulating valve.

cooling system is to be distinguished in that nor- .than is possible with the usual screw thread operi. f ated stems.

the tube. As will appear, the tube may be purged by closing its water liner connection with the boiler, and sweeping the tube with steam, or the` water line may be left open and a mixture of steam and water blown from the tube, however without excessive water loss. After thetube blow-down, hot water then rushes into the tube from the boiler, tending to excessively expand the tube unless the latter is promptly cooled. *In accordance with the invention, excessive expansion' of the tube is prevented by introducing directly into theupper interior of thetube a cooling uid, lpreferably'water from the feed line, only fora short internal of time required for reduction of the tube temperature to normal.

In yPatent No. 2,284,130, I disclose a system` vfor cooling the expansion tube by maintaining a 't more or less continuous ow of water intovthe tube under control of a Valve operated automatically in accordance with movements of the The present tube mallyv no flow of water occurs into the tube, and cooling thereof is to be accomplished by opening the manually controlledV valve only at suchtimes as the tube is to be contracted after an abnormal expansion, say following the tube blow-down.

Allv the' various` features and objects of the invention will be understood to better advantage from the following detailed description of ther invention as embodied in the typical and il1ustrative form shown in the accompanying drawing,

and in which:

Fig. l is a general view showing the apparatus connected to a conventionally illustrated boiler;

f Eig. 2 is an end elevation of the regulator assembly Fig. 3 is an enlarged cross-,section on line -3-3 of Fig. 2;

Fig. 4 is a lsection von line 4 4 of Fis.v 3;,

and

Fig. 5 is a fragmentary view showing the rack and gear connections between the expansion tube and feed water valve stem,

Referring rst to Fig. l, the part of the regulator primarily responsive to liquid Water level changes in the conventionally illustrated boiler IIJ, comprises a tube II made of brass or other suitable metal rendering the tube longitudinally expansiblein accordance with its temperature changes resulting from variations of the water level within the tube. It will be understood that the tube may be mounted in so that the water level normally stands in the tube intermediate its ends. Typically, the tube is shown to be placed in an inclined position with the upper and lower ends of the tube connected with the steam chamber and water space, the boiler, respectively, by a flexible conduit I2 and pipe I3. The connection at I4 between conduit I2 and the expansion tube may consist of a coupling I5 attaching the conduit to `fitting I6 threaded into a hollow casting- I'I on the end of the tube. Arm I3 projecting from the cast ing I1 may be connected 4with other apparatus, such as a signaling system, not shown, to be operated by or in accordance with the movements of the expansion tube II. The lower end of the tube is attached by fitting I9 to a suitable frame structure comprising an upright member 2! and base angle iron 22, these members being interconnected by a diagonal brace 23. Casting I1 is pivotally connected at 24 with `a rod 25, the opposite end of which is attached at 26 tosupport 2l by way of an adjustable yoke, generally indicated at 21.

As' will be understood, the water normally stands in tube Il at a level L-.L intermediate its ends,lthe upper interior of the tube above the water level being directly exposed to steam communicatedthrough conduit l2. Upon lowering of the water level, the tube expands due to the increased length of heating by direct contact with the steam, producing, by virtue of the rigid rod connection 25, upward lateral deflection of the tube and its later described connection with the feed water control valve. As the water level rises inl the tube, the cooling eifect causes its contraction and downward deliection of the tube and rod assembly. Heat radiation from the lower extent of the tube may be increased considerably by use of ns 28, the particular advantages of which areV discussed in greater detail in the first issued patent referred to hereinabove.

Feed water is supplied to the boiler through line 30 under control of valve 3| operated in accordance with movements of the expansion tube II. The invention is primarily concerned with the operating mechanism, generally indicated at 32, by means of which lateral movements of the expansion tube produce opening and closing movements of the feed control valve 3|. As shown particularly in Figs. 2 and 4. the valve 3l is operated by a stem 33 which may be formed integrally with a shaft 34 having a rack and gear connection at 35 with rod 36 pivotally at-` tached at 31 to casting I1, on the end of the expansion tube. Referring to Fig. 5. the connection 35 between the valve stem 33 and rod 36 comprises a gear 38 fixed to shaft 34 and engaging a rack 39 carried by and movable with relation to rod 36. The rack has a longitudinal bore 46 through which rod 36 is inserted. and

normally the position of the rack with relation to the rod is determined by engagement of the bottom extension of the rack with nut 43. Downany suitable position ward movement of the rod is transmitted to rack 39 by wayl of coil spring 4| engaged by nut 42, the spring being sufficiently strong to undergo no appreciable deformation during normal operations, and to permit vertical movement of the rack, and therefore rotation of the gear 38 and valve stem 33, in exact accordance with downward deflections of the expansion tube II. The relative positions of nuts 42 and 43 may be adjusted to take up*v any looseness in the spring position on the rod, but without cause ing the spring at any time to undergo excessive orfatigue strains. The lower portion of rod 36 Amay be guided within an opening 44 in a hori- Zontal support 45 extending between the body of valveA 3 I and bracket 46.

Axial movement of the valve stem 33 and attached shaft 34. in accordance with their rotation is effected by a cam mechanism, generally indicated at 48, which, together with the shaft assembly, is supported by bracket 46, the latter being attached by screws 49 to an angle base 53. A s shown in Figs. 3 and 4, the cam properl comprises a cylindric body 5I clamped against rotational movement within opening 52 bf the split bracket 46. The cam body is clamped endeV wise within the bracket 'by plates 53 and 54 attached tothe bracket by bolts or screws 55; Shaft 34 may be journaled at 56 in a bearing formed by the plate 53, `and also` within ay roller bearing assembly, conventionally illustrated by the dotted lines at 51, contained within a housing 58 integral with plate 54. The body 5I contains a pair of oppositely positioned. helical cam slots 59 receiving a pair of rollers 6I) rotating on pin 6I carried by the shaft 34, the diameter of rollers 60 being just slightly less than the width of the cam slots 59. The angularity of the slots as viewed in Fig. 4 may, of course, be predetermined to produce the desired axial movement of the valve stem for a given degree of rotation.

In considering the operation of the valve operating mechanism 32, assume rst that the water levels in the boiler and tube II lower to cause upward deflection of the tube and rod assembly. Such upward movement is transmitted through rod 36, rack 39, and the gear 38, to rotate shaft 34 and the valve stem 33 in exact accordance with the expansion tube deflection. The resulting rotation of rollers 6I! within cam slots 59 moves the valve stem 33 toward the right, opening the feed control valve 3l to increase the rate of water supply to the boiler. As the normal water levels are restored, the end of the expansion tube and4 rod 36 move downwardly, such movement beingr transmitted through coil spring 4I and the rack-and-gear assembly 35. to reversely rotate the valve stem and cam rollers '6U and thereby move the feed control valve in a closing direction. As will be understood. when the boiler and expansion tube water levels rise above normal, causing downward deflection of the tube, the feed control valve. is operated by mechanism 32 in a sequence opposite to that resulting from lowering of the water levels.

Rod 36 and the spring` IH provide. in eiect. a

lost motion, connection between the expansion ing, spring 4I is compressed to allow continued y downward movement of the tube and rod, lowering nut 43 from engagement with the bottom` end ofthe rack 39.. This is a safety feature of importance in that it prevents deformation or in- .iury of any parts of the equipment that might otherwise result in the absence ofsuch provision permitting continued displacement of the expansion tube assembly beyond the closed valve position.

The mechanism 32 may carry suitable indicating means by which the' operator may at any time ascertain the degree of opening of the feed water valve, and therefore the `:boiler load in terms of water throughput, and also at any time the condition of steaming as indicated by the boiler water level. As illustrative, vthe bearing housing 58 may carry a dial plate 63 having indicia in the form of a series of holes'M visible from either side ofthe dial. Shaft 34 may carry a pair of indicators 65 and 66 adjustably mounted on the shaft. I'he relation of the indicators may be such'that when valve 3| is fu1ly closed, indicator 65 will be in a horizontal position and indicator 66 will be swung to the right of vertical a distance such that when the valve is opened to normal position (corresponding to normal water level), indicator 65 will have swung opposite the uppermost opening 64. As the valve opens and the boiler water reachesnormal level, the indicators swing counter-clockwise to substantially the position shown. The `operator, thereafter can observe Awith reference to indicator 66, the condition of theboiler water level, i. e. the direction and extent of any changes from normal, causedy by variations in the rate of steam gen- 'eration,or for any other reason. At the same time, the position of the feed water valve, and therefore the rate of water delivery to the boiler, are shown by the position of indicator 65.

I have previously referred to the Aprovision of a normally closed'connection between the feed water line and the upper portion of the expansion tube Il, whereby water may be introduced to the tube after abnormal expansions thereof, to cool and thereby returnthe tube to normalelongation. Such cooling water may be delivered through a line 68 connecting with pipe 30 at the inlet side of valve 3| and connecting at 69, see Fig. 2, with the hollow casting l1 on the end of the expansion tube. Line 68 contains a valve 'IU operated by lever ll, to an extension 'Ha of which is connected a coil spring 'l2 normally maintaining the valve in closed 'position and` preventing the flow of water to the expansion tube.

' When the expansion tube H is to be blowndown for the removal'of scale and other accumulations, valve 80 in water line I3 leading to the boiler may be closed, and valve 8l opened to permit steam from line l2 to sweep through and displace the contents of the tube through the outlet 82. As an alternate procedure, both valves 80 and 8| may be opened, permitting the steam being blown through the tube and pipes to withdraw some water from the. boiler, this method being preferred by reason ofthe effectiveness of the water and steam mixture to thoroughly Viiush out sediment from the valves and fittings.

After blowing-down the tube as described, valve 10 may be opened for a short while, say about ten seconds, to admit a small stream of water directly into the upper or hot end of the tube, thus quickly cooling the tubel to restore the feed water control valve to normal position andv thereby avoid any appreciable change in the boiler water level.

I claim: y

1.*In boiler water level control apparatus including a longitudinally expansible tube adapted to be connected with water and vapor spaces in the boiler so that the water stands in the tube at a level intermediate its ends and surges therein as the boiler water level changes to produce lateral deflection of the tube, and a boiler feed water control valve; the combination comprising a stem connected to said valve, means for rotatingthe valvestem by lateral deflection of said tube, and a cam means connectedto said stem and operable to axially move the stem in accordance with its rotation, -said cam means comprising a member having'a cam surface, and a roller carried by said stemand engaging said surface.

2. In boiler water level control aparatus including a member movable positively in response to changes of the boiler water level, and a feed water control valve contained within a body; the combination comprising a stem conneotedg to said'valve, yielding means for transmitting movement of said member to the stem andnormally resisting deformationto produce rotation of the 'stem in a valve closing direction, said yielding means beingy deformable toL permit continued movement of said member in a valve closing direction after the valve has fully closed, and cam means operable to axially move the stem in accordance with its rotation as thus produced.

3. In boiler water level control apparatus including a member movable positively in response to changes of the boiler water level, and a feed water control valve contained within a body; the combination comprising a stem connected to said valve, a bearing within which said stem is journaled at a location in spaced relation to said body, yielding means for transmitting movement of said member to the stem at a location between said body and bearing and normally resisting' deformation to produce rotation of the stem in a valve closing direction, said yielding means being deformable to permit continued movement i of said member in a valve closing direction after the valve has fully closed, and cam means operable to axially -move the stem in accordance with its rotation as thus produced.

4. In boiler water level control apparatus including a, member movable positively in response to changes of the boiler water level, and a feed water control valve contained within a body; the combination comprising a stem connected to said valve, a rack-and-gear connectionbetween said member and stem for rotating the stem in accordance with changes of the boiler water level, said connection comprising a gear carried by the stem, a toothed rack engaging said gear, a spring for transmitting movement of said member to the rack and normally resisting deformation to produce rotation of the stern in a closing direction, said spring being deformable to permit continued movement of said member in a valve closing direction after the valve has fully closed, and cam means for axially moving the stem in accordance with its rotation.

v JULIAN A. CAMPBELL.

Images