US3049145A

US3049145A - Boiler control system

Info

Publication number: US3049145A
Authority: US
Inventors: Leopold J Kmiecik; Leo W Kaczmarek
Original assignee: McDonnell and Miller Inc
Current assignee: McDonnell and Miller Inc
Priority date: 1959-08-07
Filing date: 1959-08-07
Publication date: 1962-08-14
Anticipated expiration: 1979-08-14

Description

Aug. 14, 1962 L. J. KMIECIK ETAL BOILER CONTROL SYSTEM Filed Aug. 7, 1959 mare/v,

ite

Patented Aug. 14, 1962 3,049,145 BOILER CGNTROL SYSTEM Leopold J. Kmiecik and Leo W. Kaczmarek, Chicago, Ill., assignors to McDonnell & Miller, Inc., Chicago, Ill., a corporation of Delaware Filed Aug. 7, 1959, Ser. No. 832,184 3 Claims. (Cl. 137-414) Our present invention relates to control systems for boilers, and more particularly to a control system for maintaining the water level in a boiler at a substantially constant predetermined level.

Steam is used in rnany commercial processes in the treatment of materials and otherwise, and in most instances it is desirable that the steam be utilized at a constant predetermined pressure to be satisfactory. A boiler is usually employed to afford a steam source and as the steam is exhausted from the boiler the liquid within it is consumed and must be replenished. In conventional systems presently in use, the liquid level is usually sensed by a oat, and after the float has dropped a predetermined amount, liquid is fed to the boiler until a desired level is reached. In present systems before supply liquid is fed to the boiler, the liquid level must drop appreciably and to an extent causing undue lowering of the pressure within the boiler for appropriate use in certain processes of the steam generated in the boiler. Thus, when the liquid in the boiler has diminished so that it is at a level at which supply liquid is fed to the boiler, the pressure within the boiler and the discharge pressure of the steam from the boiler may be below the desired pressure for the process in which the steam is being used, or the level of the liquid in the boiler at which feeding of the supply liquid is terminated may be such that the pressure within the boiler is in excess of that desired or required.

lt is an object of our invention to avoid the aforementioned shortcomings by providing a control system for a steam boiler in which, when steam is discharged from the boiler, supply liquid is delivered to the boiler at a rate to maintain liquid in the boiler substantially at a constant predetermined level.

ln order to achieve the aforementioned object, we provide a control system for a boiler affording a source of steam comprising, level sensing means associated with the boiler, means affording a continuous circulating source of supply liquid for the boiler, and flow control valve means between the supply liquid and the boiler caused to be actuated by the level sensing means to afford upon discharge of steam from the boiler for the feeding of supply liquid to the boiler at a rate to maintain the liquid in the boiler at a substantially constant predetermined level.

A further object of our invention is to provide a control system as above related in which the level sensing means has connection with a source of fluid under pressure and includes a oat responsive to the liquid level in the boiler, and in which movement of the float effects control of the application of the source of fluid under pressure to the aforementioned ow control valve means so that the latter controls the flow of liquid from a liquid supply source to the boiler to maintain the level of the liquid in the latter at a substantially constant predetermined level.

A further object is to provide acontrol system as last described in lwhich means including a pump, is provided to maintain liquid of the liquid supply source for the boiler in continuous movement for delivery to the boiler without starting and stopping of such supply liquid.

A further object of our invention is to provide a system as noted in -which a common liquid source serves as the aforementioned source of uid under pressure associated with the level sensing means and flow control valve means, and for replenishing the liquid supply source for the boiler.

A further object of our invention is to provide a system as aforementioned in which the liquid supply source for the boiler is retained in a receiving tank which in turn has connection with the common liquid supply, and with conventional feeder means being provided for regulating the flow of liquid into the receiving tank.

The above and other objects and advantages of our invention will appear from the following detailed description of a preferred embodiment of our invention.

Now in order to acquaint those skilled in the art with the manner of constructing and utilizing a control system in accordance with the principles of our invention, we shall describe in connection with the accompanying drawing a preferred embodiment of our invention.

The single lFIGURE. of the drawing is a largely diagrammatic view of a control system for maintaining a predetermined substantially constant liquid level. in a boiler.

In the drawing the control system of our invention is shown largely diagrammatically for purposes of simplicity and in View of the fact that the several components of the system .may comprise any of many well and long known devices and appurtenances of the art.

A steam generator, which may take the form of a boiler for providing a source of steam is indicated at 1 in the drawing. The boiler may be of any conventional and desired construction, fired in any known manner, for converting a body of liquid to vapor, such as water to steam, which is drawn off in any suitable manner as indicated through an outlet conduit `3. A source of water under pressure for replenishing the boiler 1 is afforded by a pipe line 4 from which a branch pipe 5 extends to the inlet of a known water feeder device 6. A pipe 7 extends from the outlet of feeder 6 to a liquid or water supply source, such as a conventional receiving tank 8. The feeder v6, as shown, is connected by conduits 9 and 10 to the top and bottom, respectively, of the receiving tank 8, and provides a -water level in the float chamber 12 of the feeder 6 corresponding to the water level of the receiving tank. A pivoted oat 13 for feeder 6 controls connecting and disconnecting of the inlet and outlet of the feeder 6 to provide for the admission of water to receiving tank 8 as dictated by position of the float 13 all as is well known. Outlet means for the receiving tank comprises an outlet pipe 14 extending from the bottom of receiving tank 8 to the inlet of a one way check valve 15, a pipe 16 which extends from the outlet of check valve 15 to the inlet of a known form of centrifugal pump 17, and a pipe 13 which extends from the outlet of the centrifugal pump 17 to the inlet of a flow control valve 19. A .pipe or boiler feed line 20 extends from the outlet of flow control valve 19 to the water chamber of the boiler 1. It will be observed that bypass piping 23 including a pressure relief valve 24 is connected at one end in advance of the inlet of centrifugal pump 17 and at the other end beyond the outlet of the pump. The pump 17, when the system is in operation is continuously driven and when valve 19 is in open position, water from the liquid supply source or receiving tank 8 flows through pipe 14, the one-way check valve 15, pipe 16, into the inlet of the pump 17, out the outlet of the pump through pipe 18, control valve 19, and pipe or boiler feed line 20 into the boiler. When the control valve 19 is closed and it being remembered that the pump 17 is continuously in operation, the pressure relief valve 24 opens and water in the supply line for the boiler circulates from the outlet of the pump 17 through bypass piping 23 including valve 24 and back into the inlet of the pump and continues in that fashion until valve 19 is opened -whereupon pressure relief valve 24 closes.

The control system of our invention further includes a level sensing device or means indicated generally at 39 and which device is of known conventional construction. It in its broad aspects comprises a oat chamber 32 within which a `iioat 33 is disposed with the oat chamber being connected by

pipes

34 and 35, respectively, to upper and lower portions of the water compartment of boiler 1. The oat 33 is movable in response to the liquid level in the boiler 1. The oat 33 has connection through suitable'linkage 38 with a valve 39 for disposing the latter in open and closed positions with respect to valve seat 40; The previously mentioned source of liquid under pressure at pipe 4, has connection by means of pipe 42 to pressure reducing valve 43, and by pipe 44 to a balancing valve 46 from which pipe 47 extends to the inlet of a valve housing 41 at the lower end of the level sensing device 30 and above valve seat 4i). The outlet of the valve housing of the level sensing device below valve seat 40 is connected by pipe 50 to the receiving tank 8. As shown, the valve housing 41 is in fluid sealed relation with respect to float chamber 32 of the level sensing device as afforded by the partition 60 and bellows 61 extending between valve 39 and partition 60. The

pipes

47 and 50 may be considered `as constituting a supply line through which fiow of liquid under pressure is under the control of the valve means afforded by valve 39 and its seat 40. As shown, a vent 53 is provided for venting the receiving tank 8. It will be observed also that a pipe or uid pressure line 55 ahead of the inlet of the level sensing device extends from conduit 47 to the flow control valve 19. In the particular embodiment of our invention herein shown and described, the yiiow control valve means 19 includes servo operating means in the form of a diaphragm S7, and a valve member '58 cooperating with a valve seat 59 between the inlet and outlet of the valve for opening and closing the same.

In the control system above described, as steam is withdrawn from boiler 1 through the steam take-oi means 3, the water is, of counse, consumed and the iloat 33 of the level sensing device 30 responds to change in the aforementioned liquid level, which is effective to dispose the valve 39 in open position with respect to valve seat 40. When the liquid level in boiler 1 is at the desired predetermined level affording the desired pressure condition in the boiler, the valve 39 is seated on valve seat 40, and the full pressure of the source of liquid under pressure in the supply pipe is imposed on diaphragm 57 of valve -19 seating valve S on seat 59 and no Water from the receiving tank 8 is admitted to the boiler 1. Upon lowering movement of float 33 `of the float sensing device 30 causing valve seat 39 to assume an open position relative to valve seat 40, liquid flow is established from the inlet to the outlet of the valve means of the level sensing device, which movement of liquid elects reduction in pressure in pipe or uid pressure line 55 acting on the diaphragm 57 of the diaphragm valve thus moving valve 58 oit of valve seat 59 so that water is admitted through pipe or boiler feed line into the boiler. As before lmentioned in the closed position of valve 5S on valve seat 59, water from 4 the outlet of centrifugal pump 17 passes through the pressure relief valve 24 and into the inlet of the pump so that a portion of the supply water for the boiler is always in motion. Thus, immediately upon opening of the diaphragm valve, a moving source of supply water is immed iately fed into the boiler 1.

In the operation of the control system of our invention the movement of the lioat 33 of the valve means of the level sensing device 30 responds to minor change of liquid level in the boiler, and, in fact, the valve 39 has a substantially continuous modulating eect with respect to its valve seat 4l). Thus, minor changes of pressure are applied to diaphragm 57 of the llow control valve 19 to dispose valve 58 to open and closed positions with respect to seat 59, affording the substantially continuous replenishment of water to the boiler in an amount equal to the steam being withdrawn from the boiler so as to maintain the level of the ywater in the boiler at a substantially constant predetermined level.

In the preferred form of our invention the water under pressure at pipe 4 serves to feed the receiving tank 8 and also serves to provide a pressure source of fluid pressureV acting through the valve means of the level sensing device 30 for actuating valve 19. However, it will be clear that another and different form of iluid pressure source mayl be resorted to for the aspect last noted although for purposes of economy the common source disclosed is preferred.

While We have shown and described what We consider to be a preferred embodiment of our invention, it will be apparent that revisions and modications may be readily made therein without departing from the spirit and scope of our invention.

We claim:

l. A control system for a boiler comprising level sensing means including a iloat chamber having fluid connection with the boiler; a iloat in said float chamber movable in response to the liquid level in the boiler; a supply line having connection with a source of liquid under pressure; valve means including a valve housing connected in said supply line and in iluid lsealed relation with respect to said float chamber; said valve means including a valve seat and a cooperating valve member movable relativeto said valve seat for modulating the rate of liquid ow therethrough in accordance with movement of said valve member toward and away from said valve seat; pressure operated control valve means having an inlet, an outlet, and servo operating means between said inlet and said outlet for controlling ilow of liquid under pressure therethrough; a boiler feed line extending between the outlet of said control valve means and said boiler for conducting liquid to said boiler; a fluid pressure line connecting said supply line with said servo operating means of said control valve means; a receiving tank having an inlet and an outlet; said supply line down stream of said valve in said supply line having connection with the inlet of said receiving tank; outlet means for said receiving tank connecting the outlet of the same with the inlet of said control valve means; and means connecting said float with said valve member providing for conjoint movement of said valve member with said iloat so that as said valve member moves away from said valve seat upon lowering of the liquid level in the boiler, the pressure in said supply line is reduced, and as said valve member moves toward saidV 2. The control system of claim l characterized by the provision of bypass means associated with said outlet References Cited in the lile of this patent UNITED STATES PATENTS Connet Mar. 14, 1911 Williams May 30, 1911 Osbourn Nov. 17, 1914 Rodenacker Sept. 11, 1956 Thomas Apr. 30, 1957 Topol Ian. 27, 1959