US2986209A - Safety burner control - Google Patents

Description

May 30, 1961 H. c. MITTENDORF 2,986,209

SAFETY BURNER CONTROL Filed May 1, 1957 E N N INVENTOR Harvey C. Miflendorf ATTORNEY Safety Switch SAFETY BURNER CONTROL Harvey C. Mittendorf, East Orange, N.J., assignor to Combustion Engineering, Inc., New York, N'.Y., a corporation of Delaware Filed May 1, 1957, Ser. No. 656,288

1 Claim. (Cl. 153-28) This invention relates to burners and particularly to a safety burner control organization for boilers.

In the operation of burners employed with industrial and other type boilers it is very desirable when initiating operation of the burner to slowly open the valve that controls the supply of fuel to the burners so that a minimum firing rate will be first provided and gradually built up to its maximum value. If this is not done and fuel is supplied initially at its full rate, a puff in the nature of an explosion will occur and which may damage the boiler installation. In the past the gradual building up of the firing rate was accomplished through the manipulation of a hand operated fuel control valve which was slowly opened by the operator. However, it is now the practice to have the fuel control valves for the main burner automatically actuated with these valves being automatically opened a predetermined time after the igniter torch has been lit. It is thus necessary to provide an automatically controlled valve actuation which will provide for slow opening of the valve controlling the supply of fuel to the main burner with it being preferable to be able to adjust the rate of the valve opening in order that the optimum operation with difierent fuels may be had.

This result is accomplished with the present invention through the use of a fluid pressure operated main valve. In accordance with the invention there is provided a main burner and an igniter torch adjacent to the burner for initially lighting the burner. Fuel supply to the main burner is controlled by means of a valve which is biased to the closed position and moved to the open position by means of a fluid pressure operated motor such as a diaphragm motor. The operation of this motor is controlled by an electromagnetic pilot valve which is effective in one position to supply fluid pressure to the motor to move the fuel valve to its open position and in another position to release fluid pressure from the motor to permit the valve to move to its closed position. This electromagnetically operated pilot valve is normally urged to its pressure releasing position and is moved to the position where it supplies pressure to the fluid motor when its solenoid actuator is energized. The rate at which fluid pressure is supplied to the motor is controlled by an adjustable restrictor which is upstream of the pilot valve and which may be adjusted as desired to control the rate of fluid pressure supply and accordingly the rate at which the motor will open the valve. The fuel supply to the igniter torch is controlled by means of an electromagnetically operated valve andan electrical control organization is provided whereby the electromagnetically operated pilot valve is automatically energized and accordingly moved to its position for supplying pressure to the fluid motor a predetermined time after thevalve controlling the supply of fuel to the igniter torch is opened provided the torch is lit after this valve is opened. If, for some reason, the igniter torch should not light, however, the pilot valve will not be energized and in a short time the valve controlling the supply of fuel to the igniter torch will be closed,

nited States Patent Patented May 30 1961 2 It is an object of this invention to provide an improved burner control.

A further object is to provide a burner control wherein the main fuel supply valve is automatically operated and the rate at which the valve opens may be controlled as desired. 7

Other and further objects of the invention will become apparent to those skilled in the art as the description proceeds.

With the aforementioned objects in view, the invention comprises an arrangement, construction and combination of the elements of the inventive organization in such a manner as to attain the results desired as hereinafter more particularlyset forth in the following detailed description of an illustrative organization which represents only one embodiment of the basic invention, said embodiment being shown by the accompanying drawings wherein the single figure is a diagrammatic representation of an industrial boiler provided with the burner control of this invention.

Referring now to the drawing wherein like reference characters are used throughout to designate like elements, the illustrative embodiment of this invention shown therein comprises an industrial boiler it) having upper and lower drums 12 and 14, respectively, and between which are connected steam generating tubes 16 in the usual manner.

Fuel is introduced into the boiler through the main burner 16a which is supplied with fuel such as oil or gas through the supply conduit 18 with the supply of fuel to burner 16a through conduit 18 being controlled by valve 20. This valve includes body 22 into which extends stem 24 with the lower end of the stern being provided with valve head 26 which is normally biased into engagement with a suitable valve seat formed in the body'22. This is accomplished by means of spring 28 which is disposed between the upper end of stem 24 and a stationary housing 27 so that it is effective to urge the stem upward and accordingly bias the valve to its closed position. In order to open the valve there is provided a diaphragm motor 29 mounted on the upper end of housing 2.7 and which includes flexible diaphragm 32 secured to or disposed against the upper end of stem 24 and forming the lower portion of chamber 34 so that upon supply of fluid pressure to chamber 34 diaphragm 32. will move stem 24 downward and accordingly open the valve.

Fluid pressure may be supplied to diaphragm motor 29 from any suitable source that has a fairly constant pressure, such as the air supply of the plant, with the source being diagrammatically represented in the drawing as 36. This source of pressure 36 is connected with chamber 34 through conduits 37 and 37' and the supply of pressure to and exhaust of pressure from chamber34 is controlled by the supply and exhaust pilot valve 38. The valve 38 is biased by spring 40 to a positionpreventing communication between pressure source 3 6 and,chamber 34 and venting chamber 34 to the atmosphere through conduit 42. In this position valve head 44 of. the pilot valve is in engagement with seat 46. and displaced from seat d8. By means of electromagnetic actuator 50, to which the upper end of the valve stem of pilot valve 3 8 is secured, the pilot valve may be moved to a position where it prevents communication of chamber 34 with the atmosphere and establishes communication between this chamber and pressure source 36. When in this latter position valve head 44 is in engagement with seat 48 and displaced from seat 46.

In order to control the rate at which the main valve 20 is opened when electromagnetic actuated pilot valve 38 is energized and moved to a position to admit pressure fluid from source 36 to the fluid pressure operated motor 2-9 needle valve 52 is provided in conduit 37 between the pilot valve and the pressure source 36 with this valve being adjustable and forming an adjustable restrictor to control the rate to which fluid pressure from source 36 is supplied to the fluid pressure operated motor. Through the adjustment of this needle valve 52 the rate at which valve 20 is opened may be controlled as desired so that a slow opening of valve 20 may be had as is required and so the rate of the opening may be adjusted for different fuels and operating conditions. While it will generally be desirable to close valve 20 as fast as possible, under some circumstances a retarded closing may be required and for this purpose adjustable needle valve 54 is provided in the exhaust conduit 42 so that the rate at which fluid pressure is exhausted from chamber 34 to atmosphere may be controlled.

Ignition of burner 16a is bad by means of igniter torch 56 which is placed adjacent the burner as shown and which is supplied with fuel through conduit 58 with the supply of fuel to the igniter torch being controlled by electromagnetically operated valve 60 positioned in this conduit.

Activation of igniter torch 56 is had through completion of the circuit that includes the solenoid of valve 60 and the primary transformer winding 65 of spark igniter 62 with this circuit including conductors 64 and 66 which connect the solenoid of valve 60 across a potential with which the leads 68 and 70 communicate. Primary winding 63 is connected with lead 70 by conductor 72 and with conductor 64 by conductor 74. The circuit 65 of the spark igniter 62 includes secondary winding 67 of the step-up transformer. Energization of these circuits is controlled by master switch 76 which may be manually operated and when closed completes these circuits which causes energization of the solenoid of solenoid operated valve 60 and activation of spark igniter 62 resulting in the lighting off of ignition torch 56.

A short time after energization of solenoid valve 60 and spark igniter 62 pilot valve 38 is moved from its normally exhausting position to its supply position. In order to effect this result solenoid operator '0 of valve 38 is connected across leads 68 and 70 by conductors 78 and 80 respectively, with master switch 76 being connected in the circuit of conductor 78. In series with conductor 80 is the normally open temperature responsive switch 82. This switch. upon being heated. moves to the closed position and to effect this result heating element 84 is positioned adjacent the switch and is connected 4 the circuit of relay 98 but is operative in response to the illumination produced by the igniter flame to energize relay 98. Thus upon closing master switch 76 if the igniter torch 56 is lit relay 98 is activated and accordingly breaks the circuit for heater 92 rendering the heater inoperative and permitting the igniter torch to function in the normal manner. However, should the igniter torch not be lit, then heater 92 will be effective a short time after closing switch 67 to heat the temperature responsive switch 90 sufficiently to cause it to interrupt the circuit for the electromagnetically operated valve 60 and the spark igniter 62 as well as the circuit for heater 84 thereby deactivating the igniter and preventing actuation of main fuel supply valve 20. The period of time required for heater 92 to heat temperature responsive switch 90 sufficiently to cause it to open is sufliciently less than the time required for heater 84 to heat temperature responsive switch 82 sufficiently to cause it to close so as to insure that solenoid 50 is not energized and valve 20 opened it the igniter torch does not light.

The temperature responsive switch 90 is preferably of the manual reset type so that once it is opened it remains with conductor 64 through conductor 86 and with lead 70 through conductor 88 so that upon completion of the circuit of solenoid valve 60 heater 84 is activated. After heater 84 has been activated a predetermined time it is effective to heat switch element 82 sufficiently to cause it to close whereupon solenoid will be energized and pilot valve 38 moved from its exhaust to its supply position admitting fluid pressure to motor 29 and causing valve 20 to slowly open.

In order to deactivate the igniter torch and to prevent the main fuel supply valve 20 from opening in the event that igniter 56 should. for any reason. not light. there is provided. in series with conductor 64 temperature responsive switch 90 immediately adjacent which is disposed heating element 92 which is connected with conductor 64 by conductor 94 and with lead 70 by conductor 96. In series with conductor 96 is the normally closed relay 98 which is connected across the leads 68 and 70, as shown. through conductors 100 and 102 and which is controlled by light sensitive control device 104. This relay 98 includes electromagnetic actuator 97 operatively connected with movable contact 99 which is effective in its closed position to bridge the gap between stationary contacts 101 while being spaced from these contacts in its open position. This control device is positioned to observe the flame produced by igniter 56 and is normally efiective to interrupt or prevent current flow through in the open position until manually reset.

With the organization of this invention the rate of opening of main fuel supply valve 20 may be regulated as desired while the operation of the main burner is automatic.

While I have illustrated and described a preferred embodiment of my invention it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the spirit and scope of the invention. I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes as fall within the purview of my invention.

What is claimed is:

A burner organization comprising a main burner, a main control valve operative to control the supply of fuel to said burner, means biasing said valve to the closed position, a fiuid pressure operated motor for moving said valve to the open position, means operative to control the supply of fiuid pressure to and exhaust of fluid pressure from said motor including a pilot valve operative in one position to admit fluid pressure to said motor and in another position to exhaust fluid pressure from said motor, means biasing said pilot valve to said other position, an electromagnetic actuator operative when energized to move said pilot valve to said one position, a manually adjustable restrictor metering the delivery of fluid pressure to said pilot valve, a separate manually adjustable restrictor metering the delivery of fluid pressure from said pilot valve, an igniter burner juxtaposed to said main burner, a valve controlling the delivery of fuel to said ignitor and normally biased to the closed position, an electromagnetic actuator for the last mentioned valve operative when energized to move the valve to the open position, a spark igniter means adjacent said igniter burner, an electric circuit including the last mentioned actuator and the spark igniter means and effective when energized to cause the igniter control valve to open and the spark igniter to be actuated, said circuit including a thermally operated switch normally closed but moved to an open position upon being heated, an electric heater in shunt with said circuit and disposed adjacent said switch to heat the same and being effective a predetermined time after energization to cause said switch to open, a relay having an electromagnetic actuator and a switch operatively connected therewith, this switch being in series with said heater and in shunt with the thermally operated switch, this relay being biased so the switch thereof is closed and upon enerization of the actuator is opened, means responsive to the formation of flame from the igniter burner effective to energize the actuator of the relay in response to flame formation, another electric circuit having the electromagnet of the pilot valve disposed References Cited in the file of this patent therein, this other circuit including a thermally opereted UNITED STATES PATENTS switch normally open but moved to the closed position uponbeing heated, an electric heater adjacent this last 568,950 Johnson 6) i mention thermally operated switch to heat the same, 5 2,003,624 Bower June 41 1935 said last recited heater requin'ng a time after energiza- 2,047,445 Stephens July 1936 tion to close the lastmamed switch greater than said 2,175,866 Arnold 1939 predetermined time and, said last recited heater being 2,282,197 Maynard May 2 connected in series with the first mentioned thermally 2,388,124 Crews 06L 1945 operated switch so as to be deenergized upon opening 10 2,689,000 Musat 6t P 14, 1954 of the first mentioned thermal switch. 2,714,290 Raching 2, 1955

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