US3004502A - Furnace seal means - Google Patents

Description

Oct 17, 1961 DE Los E. HIBNER, JR 3,004,502

FURNACE SEAL MEANS 2 Sheets-Sheet 1 Filed June 26, 1957 INVENTOR Oct 17, 1961 DE Los E. HIBNER, JR 3,004,502

FURNACE SEAL MEANS Filed June 25, 1957 2 Sheets-Sheet 2 De Los E. Hibner, Jr.

3,004,502 FURNACE SEAL MEANS De Los E. Hibner, Jr., Du Bois, Pa., assignor to Blaw- Knox Company, Pittsburgh, Pa., a corporation of Delaware Filed June 26, 1957, Ser. No. 668,182 1 Claim. (Cl. 110-179) In the operation of furnaces, particularly for steam boilers and the like, it is necessary to provide access to the furnace at a number of different places. For example, access is required to a boiler furnace to insert tools and accessories such as soot blowers, deslaggers, temperature probes and the like which may be required inside the furnace. Heretofore, boiler furnaces have customarily been operated with a pressure slightly below that existing in the boiler room. The pressure differential may result from I'natural draft of the chinmey, the effect of induced draft fans, or from forced draft in the boiler room. In such installations, relatively cool air will pass from the boiler room into the furnace at every opening. This introduction of cool air is undesirable in that it reduces the temperature within the furnace and further introduces excess oxygen. The scope of the problem is indicated bythe fact that large size modern boilers may have fifty or more soot blowers anddeslaggers installed on each boiler. Each opening for a soot blower or other tool is a source of additional leakage. It is necessary to make such tools extensible and retractable for eicient operation and for the further reason that they cannot be subjected continuously to the hot furnace gases without premature failure. The amount of leakage into conventional furnaces has been held within reasonable limits by proper sizing of the openings and of the tools to be inserted therethrough to reduce clearances to a minimum. It has been proposed to use seals to reduce the air leakage, but they have been Subj ect to disadvantages and have not been universally used.

Many boiler furnaces are now being designed to operate at a pressure exceeding that in the boiler room itself. Furnaces are being designed to operate with a positive pressure differential of perhaps twenty-five inches of water. It has further been proposed to employ waste heat boilers in conjunction with gas turbines and to deliver the exhaust from a gas turbine directly to a boiler furnace. In such cases, the pressure within the furnace may range as high as 40 to 60 pounds per square inch. When furnaces using a positive pressure are employed, it is essential to seal the openings to prevent hot gases and combustion products, including y ash and carbon monoxide, from being thrown outwardly into the boiler room.

I have invented new and useful seal means which may be employed with a furnace operating at a higher or lower pressure than in the adjoining space. I provide means to seal an opening in the wall of a furnace comprising a member abutting the furnace wall adjacent the opening and, with the furnace wall, forming a chamber into which said opening leads, a gate member movably positioned within the chamber to selectively mask or give access to the opening, and an opening in the wall of the abutting member aligned with the opening in the furnace wall. I preferably provide a member surmounting the abutting member and having a furnace tool mounted therein for advance and retraction, seal means sealing the furnace tool to the surmounting member, and means to introduce a sealing fluid into the assembly of said members. I prefer to provide a cap-like member surmounting the abutting member and having an opening aligned with the openings in the furnace wall and in the abutting member. I preferably introduce a sealing fluid into the cap-like member and into the chamber formed by the abutting member at a pressure higher than the pressure within the boiler furnace.

ares lf arent fuice Other details, objects and advantages of my invention will become apparent as the following description of a present preferred embodiment thereof proceeds.

In the accompanying drawings I have illustrated a present preferred embodiment of my invention arranged for use with a soot blower in which:

-FIGURE 1 is an elevational view looking toward the wall of the furnace;

FIGURE 2 is a sectional view taken along line II--II of FIGURE 1; and

FIGURE 3 is a schematic diagram of control means for operation of the gate end sealing fluid supply means.

The seal is mounted upon a base 1 which is attached to the outer shell of the furnace wall. For purposes of the present invention, base 1 may be considered a part of the furnace wall, and it is so described generically. It is most convenient to fabricate base 1 as a separate piece andV then to weld it integral with the furnace wall before attaching other elements of the furnace seal assembly. A box-like housing 2 is attached to base 1 by cap screws 3. The housing is comprised of a back wall 4 which is generally parallel Ito base 1, and side Walls which are formed integral with back wall 4 Cover plates 5 and 6 are positioned top and bottom and may be removed to clean out the interior. The housing forms a generally flat chamber 7 between back wall 4 and base 1. A circular opening is formed in base 1 and has a ring-like bearing member 8 iixed therein. A stepped cylinder 9 abuts bearing member 8 and projects from the forward face of base 1. A tube 10 iitted within cylinder 9 extends through the water wall of the furnace into the furnace proper. An opening 11 is formed in back wall 4 and is aligned with the opening in base 1. A cylindrical cap comprising a tube 12, to which a bottom plate 13 has been welded, is bolted to the rear face of wall 4 with an opening 14 in plate 13 aligned with the openings in base 1 and wall 4.

An associated soot blower lance 15 is shown in Vretracted position. Two scrapers 16 and 17 are positioned between plate 13 and the rear face of back Wall 4. They are held in separated and opposed position by a cylindrical spacer 18 and a coil spring 19 surrounding spacer 18. The Scrapers are a close tit on the outer diameter `of the soot blower lance. They serve to seal against leakage along the lance and also scrape oif deposits of fly ash and the like which accumulate on the lance. The soot blower operating' mechanism is not shown but is of aconventional and well-known type. The soot blower is mounted on a frame 2) from which a lug 21 projects on eitherv side of the frame. The lugs 21 are pinned to similar lugs 22 extending from the base 1. The lugs and pins act as a hinge. The water wall of the furnace is subjected to heavy expansion and contraction between operating and shutdown periods. The hinge permits such expansion and allows a working relationship to be maintained between the soot blower proper and the seal assembly. A'sleeve 23 is threaded into the upper half of wall 4 and has a shaft 24 journaled therein having squared end portions. Handle 25 is pinned to one end of shaft 24 and a gate 26 is pinned to the other end of shaft 24. Gate 26 has two lobes 27 and 28 projecting from its central axis. Lobe 27 is imperforate, but lobe 28 has an opening 29 formed therein. When gate 26 is in the open position as shown in the drawings, opening 29 is aligned with openings 11, 14 and the opening defined by the inner circumference of bearing member 8.

A ring-shaped seal 30 is fitted in a recess in the inner face of wall 4. It surrounds opening 29 when gate 26 is in the open position as shown. Limited clearance is provided between seal 30 and the rear face of gate 26.

A port 31 is provided in housing 4. A similar port 32 is provided in tube 12. These ports are tapped and have pipes threaded in them (not shown) which are conopposite end of cylinder 3 5 is pinned to operating handle 36 of a three-way valve 37. Spring 38 urges, operating handle 36A toward the seal assembly. Opposite ends of cylinder 35 are connected through lengths of flexible tubing 39 and 40 to a four-way valve 41 operated by solenoid 42. Three-way valve 37 is connected by a pipe to port 31 and, also has an air supply pipe 43 and a pipe 44 connecting it to port 32. When the valve is in the position shown, port 32 will be connected to the supply pipeV and pont 31 will be shut off. When piston rod 34 is in extended position, port 31 will be connected to supply pipe 43 and port 32 will be shut olf.

When the -seal is arranged either for hand or for automatic operation, soot blower lance is normally retracted and is inserted only during cleaning cycles. When the gate is arranged for hand operation, a hand-operated valve similar to that shown in FIGURE 3 may be employed. It is normally set to supply air to port 32,. Combustion prodllcts and ily ash will eddy outwardly into chamber 7. Air flowing into port 3 2, however, will prevent outward leakage of combustion products into the boiler room. The soot blower is operated from time to time in the customary fashion and is withdrawn after each operating cycle.

When the soot blower lance is removed for repairs or replacement, gate 26 is rst closed manually, and the air valve is shifted to supply air to port 31. The air pressure in chamber 7, at a pressure of perhaps 6 inches of water above the furnace pressure, will exert a force against the rear face of gate 26 forcing it against bearing member 8. This will tend to seal the furnace mechanically against leakage. Whatever leakage does exist will be of air inwardly from chamber 7 around gate 26 into the furnace. The limited clearance between gate 26 and seal 30 prevents an undue amount of air from escaping as well as maintaining a positive pressure in chamber 7. Normal leakage of air from the seal assembly will equaliz e the internal pressures when air is not supplied through ports 31 or 32.

Optionally, the seal assembly may be arranged for automatic operation as illustrated in FIGURE 3. figure, the gate is shown in open position which is employed when the soot blower is operating. When the soot blowing operation is concluded and the soot blower is Ifully retracted, solenoid 42 is energized to operate fourway valve 41 to supply air .through tube 40 and to Vent tube 39. Solenoid 42 is energized by Well-known means from the soot blower control mechanism for automatic timed operation. As air is supplied to tube 40, piston rod 34 will' extend until gate 26 is in closed position, at which time further extension of the piston rod will result fromv movement of cylinder 35. Spring 38 holds handle 3.6 against movement until gate 2,6 is in closed` position. Fur- In that l i ther extension of piston rod 34 will be by movement of cylinder 35, thereby moving handle 36 and connecting pont 31 to air pipe 43. Thus, the gate will be moved to closed position before air is applied to the rear face of the gate to press it against bearing member 8. When `sate 26 is to be opened.. solenoid; 42. is. energized to eX- haust air from tube 40 and to. supply pressure to tube '39. 'Ir-'he combined frictional force of gate 26 against bearing member 8Y and the pull of spring 38 will cause initial movement to be of handle 36, cutting otf the air pressure to port 31. After the air pressure has been relieved in chamber 7 by normal leakage, gate 26, is opened by further movement of piston rod` 34. Air continues to be supplied to port 32 kso-that the seal around the soot blower itself will continue to exclude combustion products from leakage outwardly. The limited clearance between seal 30 and gate 26 will allow chamber 7 to be at reduced pressure even thoughy air is being supplied at port 32.

From the foregoing, it will be apparent that my invention provides a furnace seal which Will readily admit tools and accessories to the furnace but will prevent un.- due leakage of cool air into the furnace or of combustion products out of the furnace. Y

While I have described and illustratedv a present preferred embodiment of my invention, it is to be understood that it is not limited thereto and that it mayy be otherwise variously practiced Within the scope of the following claim- I claim:

Means to provide access for a furnace accessory to al furnace at, Selected times through an opening in a wall of, the furnace and -to prevent leakage through said opening at other times comprising a member adapted to abut the exterior of the furnace wall surrounding Ysaid opening and adapted to form a chamber between said member and the furnace wall, a gate member movably positioned in the chamber operable to a position to mask the opening and to a position to unmask the, opening, an opening in said member aligned with the furnace wall opening for access by the furnace accessory, furnace accessory guide means mounted on said member, and means sealing said guide means and adapted to seal a furnace accessory, a sealing member abutting the interior wall of said chamber forming member adjacent the opening therein, said sealing member being in close proximity to one face of the gate member when it is in masking' position, means to admit a sealing uid to the chamber, and means to admit a sealing fluid to the interior of said guide means,.- 1

France ruf---. uv- July 23 19.27

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