US2355270A - Boiler feed water control - Google Patents

Description

Aug- 8, l944 J. A. CAMPBELL 2,355,270

BOILER FEED WATER CONTROL Filed NOV. 12, 19.41

fifa/ffy Patented Aug. 8, 1944 UNTED STATES .PATENT OFFICE *l Y "BOILERFEED- WATER CONTROL Julian A.' campbell, Long Beach, Calif. Application November 12, 1941, serial No. 418,718

4 oiaimsl (c1. 122-451.1

This invention relates generally to liquid level .control apparatus, and is Aconcerned particularly with improvements in boiler feed water regulators of the type in which the control element primarily responsive to changes in the boiler water level, comprises a longitudinally deformable tube connected with the water and steam spaces `in the boiler so that the Water normally standsin the tube at a level intermediate its ends, and the tube is caused to expandor contractin accordance with variations in the water level.

f 'The general and primary object of the invention-is to provideimprovements in this type of regulator better adapting it particularly to large capacity boilers, the feed water control valves for which require such large force or range of movement for their operation, as to place serious limitations upon the capacity of the expansion tube to operate the valve by way of the usual direct mechanical connections between the two. These large capacity boilers have relatively large feed water control valves whose operationrequires either a force of considerable magnitude, especially Where the valve is designed for short travel between the open and closed positions,` or a considerably wide range of Valve movement where the valve is designed for both capacity and close throttling action on the feed water stream. In View of these considerations, it is essential that the feed water valve control becapable of supplying both the power or range of movement, as the case may be, required for proper operation of thevalve. l i

Difficulties have been encountered in maintaining proper and` accurate control of the feed water valves in large capacity boiler installations, by directly connectingV the expansion tube with the valve in the usual or conventional manner. The reasons for the difficulty are that the expansive or contractive force of the tube may not be suflicientA to operate the valve, at least without injuryto the expansion element, or that the latter may not possess an expansive or contractive range, especially forv the forces required, to operate the feed water control valve throughout its full range of movement. On the other hand, the expansion tube has proven highly satisfactory and most desirable as a primary control element in that it can be'made highly sensitive and immediately responsive to even slight changes in the boiler Waterlevel. Accordingly, my purpose isf to provide acontrolv system retaining all the characteristic advantages ofthe expansion tube asV the primary control element, and to'obviate its limitations that heretofore have existed when used for large capacity boiler feed water regulation.

In accordance with the invention, the feed Water control valve is regulated indirectly by the expansion element, and by fluid pressure instead of direct connection between the valve and eX- pansion element, by way of a pilot mechanism which supplies operating fluid -to the feed Water valve regulator at a pressure varying automatically with the movements of the expansion element, and therefore changes in the boiler water level. The pilot mechanism comprises a valve, operated by the expansion element to deliver operating fluid to the feed water Valve regulator at increasing pressure as required by the condition of the boiler water level. Provision is made for venting the operating uid to relieve the pressure communicated to the regulator, preferably under control of a vent valve which also is operated in response to movements of the expansion tube. As will later appear, particularly accurate control of the effective operating fluid pressure may be had by simultaneously operating the pilot and vent valves so that as the former opens to increase the supply of operating fluid to the feed Water valve regulator, the vent valve closes `to restrict or cut olf the release of fluid through the vent line.

The pilot mechanism may embody other features and details, such as an arrangement of bypass valves to govern further the sensitivity of the control, but all these, as well as the objects and features referred to in the foregoing, will be understood to better advantage from the following description of a regulator representing a typical and preferred embodiment of the invention. Reference is had to the accompanying drawing, in which:

Fig. 1 is a general view showing the control apparatus in elevation;

Fig. 2 is a fragmentary enlarged side elevation of the pilot mechanism and its connection with the expansion tube, taken on line 2-2 of Fig. 1; and 1 Fig. 3 is an enlarged cross-section on line 3-3 of Fig. 2.

Aspreviously indicated, that part of the apparatus primarily responsive to water level changes in the boiler, is of the type comprising a metallic tube connected to the water and steam spaces in the boiler chamber so that the water normally stands at an intermediate level in the tube and the latter is caused to expand or contract as'the boiler water level lowersor raises. Typ-I ically, the expansion element is shownto comprise an elongated, inclined tube IIJ of brass or other suitable metal, having an end fitting II pivotally attached at I2 to a T-bar support I3 which mounts the tube at an elevation such that the boiler water normally stands in the tube at an intermediate level as indicated by the line L-L. The lower end portion of the tube I is connected by pipe I4 in the usual manner with the water space in the boiler I5. The upper end of the tube carries a hollow casting I6 which is connected by a flexible tube or conduit I1 with the steam space in the boiler, all in a manner such that, through its connections I4 and I1, the tube I0 in effect forms a U-tube with the boiler chamber. Preferably, provision is made for abnormally increasing the rate of heat radiation from the lower extent of the expansion tube (for purposes described in detail in Patent No. 2,207,214, issued July 9, 1940, to me on Boiler feed water control), as by applying to the tube a series of heat radiating iins I3.V

When the water level in the tube drops, the tube undergoes longitudinal expansion due to the increased length of the tube subjected to contact with steam contained in the tube above the water level. Conversely, the tube contracts longitudinally as the water level rises, due to increased length of the tube being contacted by the water, the temperature of which is'lower than the steam in the upper portion of the tube. Longitudinal expansive and contractive movements of the tube are converted or translated into lateral (vertical) movement of the free end portion of the tube, by providing a rigid connection between casting I6 and the fixed support I3. This connection may consist of a rod I9 pivotally attached at to'thecasting and connected to the support I3 by an adjustable yoke 2l.

No novelty is claimed with respect to the expansion tube assembly described thus far. The invention primarily is concerned with the association with the expansion tube of a pilot mechanism by means of which it is possible to sensitize and extend the effective operating control range of the regulator apparatus as a whole, beyond the possibilities of prior regulators in which the feed water control valve has a direct operating connection with the expansion tube. `Operation of the boiler feed water regulator, generally indicated at 22, is controlled by the pilot mechanism 23 which functions to communicate to the regulator 22operating fluid pressure that varies in accordance with deflections of the expansion tube I0, as will presently appear. The regulator 22 may consist of anysuitable Vfluid pressure responsive device `for controlling the rate of boiler feed water supply through the line 24, and is shown typically to consist of a valve 25 :operated by a stem26 connected to a diaphragm in the housing 21, the valve Yopening upwardly against the resistance of coil spring 28. The feedwater valve is iiperratedV under control of `fluid, pressure communicated. to the diaphragm through line 29 leading from the pilot mechanism 23. s I' g As best illustrated in Figf3, pilot mechanism 23 comprises a suitable body 30, shown typically as a metal block secured to the support I3 by bolts 3I extending through spacers 32. YThe body 30 contains three longitudinally extending passages 33, 34, and interconnected by transverse passages 36, 31 and 38, 39. Passages 33 and 35 have their upper endsclosed by plugs 40, while the upper endof passage 34 Vmay communicatel with a gauge 4Iwhich indicates at all times the pressure being applied to the diaphragm 21. A suitable operating fluid, for example air or fuel gas, is fed through line 42 into passage 33, the latter therefore being referred to as the operating fluid inlet passage. Being connected with tube 29 leading to the diaphragm, bore 34 becomes the gas outlet passage, and bore 35 the vent passage by reason of its connection with pipe 44 through which the gas is vented to the atmosphere or into the frebox of the boiler.

The flow of the regulator operating fluid from inlet passage 33 to the outlet passage 34, and the release of fluid from passage 34 to the vent passage 35, are variably and automatically controlled in accordance with the position and deflections of the expansion tube I0. Such control is effected by needle valves 45 and 46 regulating, respectively, the flow of gas from passage 33 into passages 36 and 34, and the gas release from passages 34 and 31 into the vent passage 35. Valves 45 and 46 may have the usual bonnets 41 secured to the block 30, and have a suitable connection 48 with the expansion tube casting I6 whereby Ydeiiection in one direction of the expansion tube produces closing movement of one valve and opening movement of the other valve. The connection at 48 is-shown to comprise a yoke assembly consisting of a cross-bar 49 attached at its center to a rod 59 which carries a 'clevis 5I pivotally connected by bolt 52 with a depending lug 53 on the casting I6. The cross-bar 49 has connections with arms 54 rigidly attached to thev valve stems through bifurcated members 55 carrying pins or bolts 56Y extending through slots 51 in the Vends of the arms 54. The connection at 48 thus permits transmission of movement of members 55 to the arms 54 which have swinging movement in paths at ,variance with the travel of members 55.

Assuming vvalves 45, and 46 to close by clock-Y wise rotation of the valve stems, it will be seen that deflection of the expansion tube I0 in one direction causes the inlet valve 45 to open and the vent valve 46 to close, whereas opposite deflection of the expansion tube causes the vent valve 46 to open and the inlet valve 45 to close. An additional pair of manually adjustable valves 58 and 59 serve to govern the sensitivity" of the pilot mechanism andthe responsiveness of. the regulator 22 to a given deflection of theV expansion tube, by controlling the by-'pass in advance of the valve 45, of uid from passage 33 through 38 Vto the outlet passage 34, and the by-pass of fluid' from passage 34 through 39 to the vent line 44. As willA be readily understood, by proper adjustment of valves 58 and 59, as by maintaining them in relatively closed positions, it is possible for a slight deflection of the expansion tube to produce great variations of pressure on the diaphragm 21,. and correspondingly wide ranges of opening or closing movements of the feed water control valve 25. On the other hand the pilot control may be made less sensitive by other adjustments of the by-pass valves'58 and 59,1as byv opening` them, so thatY a given range of .move-v ment Yof the regulator 22 Vwill require a relatively widevra'nge of deflection in the expansion` tube. The former condition, i.'e., adjustment Vof the pilot control to obtain greater sensitivity, is. most always to be desired, sincethe. force requiredfto closethe feedlwater vcontrol valve 2,5 Vis, greater Vthan lcansatisfactorily7 Vbe served by directcon-f nection V with theexpansion tube, and consequently it isimportant that relatively-smaller slight deflections of the tube be made to govern the feed water valve. Another advantage of the vent by-pass is that it may be opened, taking practically all the pressure 01T the diaphragm and fully opening the feed valve for flushing out pump packing or pipe scale that might accumulate under the seat. Upon closing this vent bypass, normal operations are restored, With no necessity for making adjustments.

To describe the operation of the controller system, assume that the boiler is firing normally with the water standing in the expansion tube at a normal level, as indicated by the line L-L. Assume then a sudden increase in load, which causes the Water level in the tube to drop and thereby expose a greater length of the tube to steam heat, which produces Vexpansion of the tube. The end casting I6 moves upwardly slightly, and through its connection 48 with the pilot mechanism, slightly closes the supply valve 45 and slightly opens the vent valve 46. result is a reduction of the pressure on the diaphragm 21, permitting the coil spring 28 to open the valve against the reduced pressure. The increased rate of water supply to the boiler restores the normal water level and produces a slight downward displacement of the casting I6, accompanied by opening of valve 45 and closing of valve 46, to normal positions. As will be understood, downward displacement of casting I6 and operation of valves 45 and 46 in reverse of the order just described, occurs when the water level in the boiler rises above normal, producing longitudinal contraction of the tube I0.

I claim:

1. Apparatus for controlling the level of heated liquid in a boiler or the like, comprising a thermostatic tube responsive to changes in the boiler water level, a fluid pressure operated regulator for Vcontrolling the supply of liquid to said boiler, and a pilot valve mechanism for controlling the communication of operating fluid pressure to the regulator, said pilot mechanism comprising a pair of separately rotatable valves, one for varying the operating pressure communicated to the regulator and the other for venting the operating fluid, a pair of arms connected to said valves, a member interconnecting said arms, and means connecting said member with the thermostatic tube whereby both valves are simultaneously rotated by movement of the tube to open one valve and close the other valve.

The

2. Apparatus for controlling the level of heated liquid in a boiler or the like, comprising a thermostatic tube responsive by lateral deflection to changes in the boiler water level, a fluid pressure operated regulator for controlling the supply of liquid to said boiler, and a pilot valve mechanism for controlling the communication of operating fluid pressure to the regulator, said pilot mechanism comprising a pair of separately rotatable valves, one for varying the operating pressure communicated to the regulator and the other for venting the operating uid, and connecting means comprising a pair of engaging members relatively movable in different paths whereby both valves are simultaneously rotated by lateral movement of the tube.

3. Apparatus for controlling the level of heated liquid in a boiler or the like, comprising an inclined thermostatic tube deilectible vertically in response to changes in the boiler water level, a fluid pressure operated regulator for controlling the supply of liquid to said boiler, and a pilot valve mechanism positioned opposite said tube and acting to control communication of operating fluid pressure to the regulator, said pilot mechanism comprising a. pair of rotatable valves, one for varying the operating pressure communicated to the regulator and the other for venting the4 operating uid, and relatively movable slidably engaged elements forming a connection b etween said valves and the tube whereby lateral deflection of the tube simultaneously rotates both valves.

4. Apparatus for controlling the level of heated liquid in a boiler or the like, comprising an ing clined thermostatic tube deilectible vertically in response to changes in the boiler water level, a fluid pressure operated regulator for controlling the supply of liquid to said boiler, and a pilot valve mechanism positioned opposite said tube and acting to control communication of operating fluid pressure to the regulator, said pilot mechanism comprising a body containing a pair of separately rotatable needle valves, one for f varying the operating pressure communicated to the regulator` and the other for venting the operating fluid, a pair of arms connected to said valves, and means interconnecting and slidably engaging said arms and movable vertically vto simultaneously open one valve and close the other valve.

JULIAN A. CAMPBELL.

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