US3921546A

US3921546A - Implosion door operating mechanism

Info

Publication number: US3921546A
Authority: US
Inventors: John Andrew Makuch
Original assignee: Combustion Engineering Inc
Current assignee: Combustion Engineering Inc
Priority date: 1974-12-30
Filing date: 1974-12-30
Publication date: 1975-11-25
Anticipated expiration: 1992-11-25
Also published as: CA1023227A; JPS5193437A

Abstract

An implosion door to protect against the adverse effects attendant with an excessive negative fluid pressure in the furnace chamber of a balanced draft vapor generator is provided with mechanism for automatically operating the door to its released and closed positions respectively. The mechanism comprises an arrangement of counterweights including an enclosed chamber containing a body of liquid that is shiftable into two different positions and, in shifting, operates to release or close the door.

Description

United States Patent 1191 Makuch 5] Nov. 25, 1975 [5 IMPLOSION DOOR OPERATING 2,126,994 8/1938 lrsch Ct 211...... 236/45 MECHANISM 2,160,262 5/1939 Engels 110/173 3,071,448 1/1963 Hochmuth.. 122/478 X 1 inventor- J Andrew Makuch, Granby, 3,782,411 1/1974 Turner 137/526 Conn.

[73] Assignee: Combustion Engineering, Inc., Primary ExaminerKenneth Spmgue Windsor Conn. Attorney, Agent, or Firm--Eldon H. Luther 1 1 PP ,816 An implosion door to protect against the adverse effects attendant with an excessive negative fluid pres- 521 U.s. c1 110/173 B; 137/526; 236/45 Sure the furnace chamber of a balanced draft [51] 1m. 01. F23M 11/00 generator is Provided with mechanism for automat" [58] Field of Searchm 110/173 R, 173 B; 122/478; cally operating the door to its released and closed po- 236/45; 137/526 sitions respectively. The mechanism comprises an arrangement of counterweights including an enclosed [56] References Cited chamber containing a body 011' liquid that is shiftable UNITED STATES PATENTS into two different positions and, in shifting, operates to release or close the door. 2,004,947 6/1935 lrsch et a1. 236/45 2,004,948 6/1935 lrsch 813.1. 236/45 16 Claims, 4 Drawing Figures E II 1 I 38' Z55 I 40 I I 52/ 5 14\ S 2 IO 24 Sc 72 ab? 3 3O 8 Sheet 1 of 2 A Patent Nov. 25, 1975 Patent N0v.25, 1975 Sheet20f2 3,921,546

FIG. 5

FIG. 4

IMPLOSION DOOR OPERATING MECHANISM BACKGROUND OF THE INVENTION Vapor generators operating on the balanced draft principle have long been known. In such units a forced draft fan operates to impart air for combustion to the furnace chamber while an induced draft fan operates to extract the generated combustion gas from the unit for ultimate discharge from the stack. According to common practice the forced draft fan is operated in response to the demand for combustion air as indicated by the combustion controls. The induced draft fan, on the other hand, is controlled to provide a slightly negative (e.g., 0.5 inch water gauge) fluid pressure in the furnace cavity thereby preventing the possibility of leakage of combustion gases from the furnace chamber to the exterior of the unit.

In US Pat. application Ser. No. 535,742 to B. J. Round for Furnace Implosion Door which is assigned to the assignee of the present application there is described apparatus operative to alleviate the problems caused by the occurrence of excess negative fluid pressure in the furnace chamber of a balanced draft vapor generator. The apparatus involves one or more openings provided in the duct work defining the downstream region of the combustion gas flow passage, each of which openings are normally closed by a closure door that operates as a swing damper during periods of excess negative fluid pressure in the furnace chamber. When released, the door operates to obstruct the flow of combustion gas from the furnace chamber and, in association with the forced draft fan, pressurizes the furnace chamber thereby reducing the possibility of the excess negative pressure reaching an implosive level.

Certain disadvantages characterize the closure door and latching mechanism described in the aforesaid application. Moments attendant with the release of the door due to the physical geometry of the apparatus and the differential pressures experienced thereby render it difficult to achieve a full transverse positioning across the duct. Similar characteristics render it difficult to return the door to its fully closed position upon decay of the excess negative furnace pressure. In addition, since the latching mechanism is actuated by an electrically operated solenoid, operation of the door is dependent upon the existance of electric power, the loss of which would render the protective apparatus inoperative.

It is to the provision, therefore, of an improved implosion door of the type described and of means for operating the same that the present invention is directed.

SUMMARY OF THE INVENTION According to the present invention there is provided mechanism to induce pivotal movement in a member that is connected to a base by means of a pivot shaft fixedly attached to said member and bracket means on said base adapted to receive said pivot shaft for pivotal movement therein, said mechanism comprising: a hollow body defining a container fixedly attached to said pivot pin; a pair of compartments formed in said container each being disposed on opposite sides of the axis of said pivot pin; a body of liquid housed in said container; and means for transferring said liquid body between said compartments upon-angular movement of said member.

The described operating mechanism has as its particular objective to more effectively actuate an implosion 2 door operative to protect a vapor generator of the balanced draft type against the effects of an excess negative fluid pressure in the furnace chamber.

Another object of the present invention is to provide an implosion door operating mechanism in which the moments produced upon initially urging the door to its released position are such as will offer the least resis tance in the doors reaching its full released position.

Still another object of the invention is to provide mechanism of the described type which is effective to enable the implosion door to achieve its fully closed position when the fluid pressure in the system returns to an acceptable negative value.

For better understanding of the invention, its operating advantages and the specific objectives obtained by its use, reference should be made to the accompanying drawings and description which relate to a preferred embodiment thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational schematic representation ofa balanced draft vapor generator having an implosion dooroperated by mechanism according to the present ,invention;

FIG. 2 is an end view taken along line 2--2 of FIG. 1;

FIG. 3 is a fragmentary elevational section of the implosion door and its associated operating mechanism illustrated in its closed position; and

FIG. 4 is a view similar to FIG. 3 showing the implos'ion door and operating mechanism in its released positron.

DESCRIPTION OF THE PREFERRED EMBODIMENT The vapor generator organization 10 illustrated in FIG. 1 includes a vapor drum 12. This drum supplies liquid separated from the vapor-liquid mixture supplied thereto through downcomers 14 to the lower

water wall headers

16, 18 and 20 to which are connected the lower ends of water cooled tubes 22 forming walls and roof of the furnace chamber 24. The upper ends of some of the aforesaid water cooled tubes 22 are connected directly to vapor drum 12. Others terminate in the upper wall header 26 which, in turn, communicate with drum 12 through connecting tubes.

Burners 30 are located in the lower portion of the furnace chamber 24. Fuel and air are discharged through these burners into the furnace chamber 24 where combustion occurs. The combustion gases generated in the furnace chamber are caused to flow upwardly toward the furnace outlet 32 while giving off a substantial portion of the heat contained therein to the tubes 22 for vapor generation purposes. In leaving the furnace chamber 24 the gases enter the horizontal and vertical gas passes 34 and 36 respectively in which vapor heating devices, such as the primary and secondary superheaters, 38 and 40 respectively, are located. Additional heat absorbing surface such as economizer 42 may be arranged in the gas pass 36 through which the gases flow on their way to a stack (not shown).

The herein described vapor generator organization is of the balanced draft type in which forced draft fan 44 in association with dampers (not shown) controls the flow of combustion air to burners 30 while induced draft fan 46 operates to regulate the extraction flow of combustion gases from the unit for ultimate discharge from the stack. The forced draft fan 44 communicates with the burner wind box 48 through a duct 50 which passes incoming air through the air side 52 of an air heater 54. The induced draft fan 46 connects with the discharge end of the gas pass 36 by means of duct 56 that extends through the gas side 58 of the air heater 54. In practice, operation of the induced draft fan is such as to maintain fluid pressure in the furnace chamber 24 at slightly below atmospheric pressure. In this way leakage of combustion gas from the unit is prevented.

The wall in a vertical run of the duct 56 is provided with a through opening 60 by means of which open communication is made between the interior of the combustion gas flow passage and the exterior of the unit. The opening 60 is closed by a closure door 62 which is adapted for pivotal movement into the interior of the duct 56. The door is preferably sized to extend substantially fully transversely of the duct interior and a stop in the form of angle member 66 is provided on the duct wall opposite that containing the opening 60 to locate the door-in its released position across the duct section. As shown in FIG. 3, the closure door 62 is vertically suspended from the wall of the duct 56 by means of a pivot shaft 68 to which the plate forming the door is attached. The pivot shaft 68 is mounted for pivotal movement in brackets (not shown) attached to the duct wall and adapted to receive the shaft. As shown in the figure, the closed position of the door is defined by the stop shoulder 71 formed by the offset in the peripheral wall of the duct 56.

As described in greater detail in the aforesaid U.S. Pat. application Ser. No. 535,742 to B. J. Round the closure door 62 is arranged to be released for pivotal movement to its open position upon the occurence of an excess negative pressure in the furnace chamber 14 such that the door acts as a damper in the combustion gas flow passage obstructing the flow of combustion gas from the furnace chamber thus to alleviate the excess negative pressure therein. In being released the closure door 62 exposes the opening 60 to admit air from the exterior of the unit thereby preventing the development of an inordinate negative static pressure adjacent the door by the continued operation of the induced draft fan which would otherwise hinder the doors achieving its fully released position.

According to the present invention operating mechanism is provided for use in an arrangement such as that described in the aforesaid patent application but without need for the mechanical latching apparatus described therein and in a manner more effective to achieve automatic operation of the implosion door. The operating mechanism of the present invention is indicated generally in FIG. 2 as 72. It is fixedly mounted by means of bracket 74 to one end of the pivot shaft 68 externally of the duct 56. The mechanism includes a hollow body 76 of generally Z-shaped configuration forming a container. The container 76 includes a pair of oppositely extending

compartments

78 and 80 that are arranged to be disposed on opposite sides of the pivotal axis formed by the shaft 68. The compartments are interconnected in open fluid communication by a hollow nexus section 82. A body of liquid 84 is housed in the container and it is of such amount that it can be contained in one compartment or the other depending on the position of the closure door. Preferably, the liquid should have antifreezing characteristics, such as that provided by ethylene glycol, or the like, in applications where the duct 56 is exposed to the atmosphere in cold climates. As shown,

4 the compartments 78 and are radially spaced from the pivot shaft axis in order that the liquid body can generate a sufficient moment about the axis to release or close the door 62 as is hereinafter more fully described.

In the preferred embodiment of the invention additional weight is provided to one side of the container 76 by a body of material 86 that is fixedly attached to the peripheral wall of the compartment 78 in container 76. The body 86 is disposed in a position upon the container 76 that locates it in vertical alignment with the plate forming the closure door 62 and the axis of pivot shaft 68 when the door is in its fully released, or ductclosing position illustrated in FIG. 4.

A vent line 88 disposed externally of the container 76 may be provided with its opposite ends in open fluid communication with one each of the

respective compartments

78 and 80. The vent line is intended to accommodate any air that may be entrapped in the container so as to prevent hindrance of transfer of the liquid between the respective compartments.

In operation of the herein described closure door operating mechanism the value of the respective weights defined by the liquid body 84 and the body of material 86 are selected such as to substantially balance the weight of the closure door 62 in its closed position at differential pressure values up to a predetermined amount across the door 62. In practice, the closure door 62 should remain closed until an excess negative fluid pressure is experienced in the furnace chamber 14 to present a pressure differential of about 20 inches water gauge across the door 62. The moment produced by the weight of the liquid body and that of the body 86 is substantially equal to the moments produced by the weight of the door and the force on the door caused by the differential pressure across it in this position. When the differential pressure across the door exceeds this predetermined value it will create a force acting on the door causing it to pivot clockwise as it is viewed in FIG. 3 toward its fully released position against the stop 66. Once movement of the closure door 62 is initiated transfer of the liquid body 84 from the compartment 78 to compartment 80 commences thereby reducing the moment tending to close the door and increasing that tending to move it toward the stop.

With the closure door 62 in its fully released position against the stop 66 the moment produced by the liquid body 84 in compartment 80 in association with the differential pressure across the door offsets that produced by the doors weight such that it will be balanced in its fully released position.

Upon decay of the excess negative pressure in the furnace chamber 14 a counterclockwise movement toward the doors closed position is initiated. When this occurs, liquid is transferred from the compartment 80 back into compartment 78 thereby reducing the moment tending to maintain the door in its released position and increasing that tending to close it against the stop shoulder 71. In this way a full closure of the door can be insured even with negative pressure remaining in the fluid passage.

It will be understood that various changes in the details, materials and arrangement of parts which have been herein described and illustrated in order to explain the nature of the invention may be made by those skilled in the art within the principal and scope of the invention as expressed in the appended claims.

What is claimed is:

l. Mechanism for inducing pivotal movement in a member that is connected to a base by means of a pivot shaft fixedly attached to said member and bracket means on said base adapted to receive said pivot shaft for pivotal movement therein, said mechanism comprising:

a. a hollow body defining a container fixedly attached to said pivot pin;

b. a pair of compartments formed in said container each being disposed on opposite sides of the axis of said pivot pin;

c. a body of liquid housed in said container; and

d. means for transferring said liquid body between said compartments upon angular movement of said member.

2. Mechanism according to claim 1 wherein the weight of said liquid body is not greater than the weight of said member.

3. Mechanism according to claim 2 wherein said liquid body-transferring means comprises a hollow nexus section in said container extending between said compartments, said nexus section having its opposite ends disposed each in open fluid communication with one of said compartments.

4. Mechanism according to claim 2 wherein said compartments are radially spaced from the axis of said pivot pin.

5. Mechanism according to claim 3 wherein said hollow body is generally Z-shaped in longitudinal section.

6. Mechanism according to claim 1 including means for venting air from each of said compartments.

7. Mechanism according to claim 6 wherein said air venting means comprises a tubular line extending between said compartments and having its opposite ends in communication with one each of said compartments.

8. In a balanced draft vapor generator organization including a furnace chamber in which fuel is burned for the generation of combustion gases, means forming a passage communicating with said furnace chamber for the discharge of combustion gases therefrom, a forced draft fan operative to supply combustion air to said furnace chamber, and an induced draft fan operative to induce flow of combustion gas therethrough, means forming an opening in said passage-forming means, a releasable closure door mounted by a pivot pin for pivotal movement on said passage-forming means between a released position in which said passage is obstructed LII 6 and a closed position in which said opening is closed, the improvement comprising means for pivotally operating said closure door including:

a. a hollow body defining a container fixedly attached to said pivot pin;

c. a body of liquid housed in said container; and

d. means for transferring said liquid body between said compartments upon angular movement of said closure door.

9. The improvement according to claim 8 wherein the weight of said liquid body is not greater than the weight of said door.

10. The improvement according to claim 9 wherein said liquid body-transferring means comprises a hollow nexus section in said container extending between said compartments, said nexus section having its opposite ends disposed in open fluid communication with one each of said compartment.

11. The improvement according to claim 10 wherein said compartments are radially spaced from the axis of 'said pivot pin.

12. The improvement according to claim 11 wherein said hollow body is generally Z-shaped in longitudinal section.

13. The improvement according toclaim l0 including means for venting air from each of said compartments.

14. The improvement according to claim 13 wherein said air venting means comprises a tubular line extending between said compartments and having its opposite ends in communication with one each of said compartments.

15. The improvement according to claim 12 including a weighted body attached to said container in a position operative to generate a moment tending to move the door toward its closed position, said position being in vertical alignment with the pivot shaft axis with the door in its fully released position.

16. The improvement as recited in claim 15 wherein said weighted body has a weight operative to produce a force sufficient to balance the differential pressure across the door in its closed position.

Claims

1. Mechanism for inducing pivotal movement in a member that is connected to a base by means of a pivot shaft fixedly attached to said member and bracket means on said base adapted to receive said pivot shaft for pivotal movement therein, said mechanism comprising: a. a hollow body defining a container fixedly attached to said pivot pin; b. a pair of compartments formed in said container each being disposed on opposite sides of the axis of said pivot pin; c. a body of liquid housed in said container; and d. means for transferring said liquid body between said compartments upon angular movement of said member.

8. In a balanced draft vapor generator organization including a furnace chamber in which fuel is burned for the generation of combustion gases, means forming a passage communicating with said furnace chamber for the discharge of combustion gases therefrom, a forced draft fan operative to supply combustion air to said furnace chamber, and an induced draft fan operative to induce flow of combustion gas therethrough, means forming an opening in said passage-forming means, a releasable closure door mounted by a pivot pin for pivotal movement on said passage-forming means between a released position in which said passage is obstructed and a closed position in which said opening is closed, the improvement comprising means for pivotally operating said closure door including: a. a hollow body defining a container fixedly attached to said pivot pin; b. a pair of compartments formed in said container each being disposed on opposite sides of the axis of said pivot pin; c. a body of liquid housed in said container; and d. means for transferring said liquid body between said compartments upon angular movement of said closure door.

11. The improvement according to claim 10 wherein said compartments are radially spaced from the axis of said pivot pin.

13. The improvement according to claim 10 including means for venting air from each of said compartments.