US3137279A - Safety device for liquid-cooled furnace doors or the like - Google Patents

Description

June 16, 1954 J. l.. MONTGOMERY ETAL 3,137,279

SAFETY DEVICE FOR LIQUID-COOLED FURNACE DOORS OR THE LIKE Filed July 18, 1960 2 Sheets-Sheet 1 ...www www. f NM., MM mm mm, y

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l l I l l l THE/. A rrae'ue v5 June 16, 1964 J. L. MONTGOMERY ETAL 3,137,279

SAFETY DEVICE FOR LIQUID-COOLED F'URNACE DOORS OR THE LIKE Filed July 1s, 1960 2 sheets-sheet 2 l F i NVENToR JAMeusear aNraoMfev Mele A r roem: Y:

United States Patent O This invention relates to a safety device for liquidcooled furnace doors or the like. More particularly, this invention pertains to a safeguarding combination to protect equipment and personnel upon any cessation of the How of cooling water to open hearth furnace doors and comparable water-cooled equipment used in such furnaces or the like.

Open hearth furnaces are usually provided with watercooled doors for the respective charging openings. Inas- `much as such doors have to be raised and lowered on appropriate occasions, it is a common practice to supply the cooling water to the interior thereof through flexible hoses. The circulation of a continuous stream of cooling water to the interior of such a door increases its life by slowing down the rate of deterioration due to the interior heat of the furnace and protects the operating men who work around the front of the furnace. Sometimes, a liexible hose through which the cooling water is circulated is pinched, for example, shutting off the supply of water to the door interior. In such instances, the door temperature will tend to remain at a safe level while thereis water inside the door to boil, but once that is gone, the metal surfaces of the door will tend to rise to a temperature capable of causing Water to flash into steam. If at that time, the circulation of the cooling water is resumed, or some Water should enter the interior of the door, the resulting instantaneous generation of steam is liable to cause a destructive internal pressure, or even cause the door to explode with likelihood of injury to persons nearby. As a consequence, efforts have been made in some cases to provide one or more weakened areas on such doors in locations not exposed to the interior furnace temperature to rupture whenever a dangerous pressure was generated within the interior of the door in question. However, such rupture equipment is not only relatively expensive and troublesome to install, but, further, may not operate fast enough to avoid damage to the equipment and/ or injury to persons. And, even then the door has to be removed and taken out of service for replacement or repair.

ln the safety system of this invention, a change in the kinetic pressure of the cooling water stream occasioned by the stopping of circulation, or a reduction in the rate of ow thereof to a dangerous level, will automatically raise the door to remove it from its exposure to the interior furnace temperature through the respective charging opening normally closed by that door. In that Way, overheating of the door can be prevented and the cause of the cessation or reduction in coolant circulation can usually be promptly remedied before the door is returned to closure position in front of its charging opening. Preferably, audible and visual alarms are provided to operate when the automatic safety raising of the door occurs and such an alarm may either be proximate or remote to the door, or both, as desired. Further, means may be provided pursuant to this invention to prevent relowering of the door until after the proper flow of liquid coolant therto has been restored.

` Other objects, features and advantages of thisinventionwill be apparent from the following description and the accompanying drawings, which are illustrative of one embodiment only, in which:

FIGURE 1 is a front view of a portion of an open harth furnace to which one mechanism embodiment of this invention has been applied.

FIGURE 2 is a partial view in section taken along lines II-II of FIGURE l, with the door bail removed to show the operation of the limit switch;

FIGURE 3 is a partial view in plan of the furnace portion shown in FIGURE 2;

FIGURE 4 is a somewhat enlarged view of a conventional pressure switch suitable for us in the illustrated embodiment of this invention; and

FIGURE 5 is an illustration of one schematic circuit suitable for use in the operation of the illustrated embodiment.

Referring to the drawings, an illustrative portion of an open hearth furnace 10 is shown having vertical structural binder members 11 and horizontal structural binder members 12. A plurality of the intervals (usually about live) between vertical binder members 11 vare utilized for charging openings 13 into the interior 14 of the furnace 10 in which material to be melted or rened on a refractory hearth 15 attains very high white hot temperatures. Refractory walls 16 and arched room 17 are provided as an enclosure for the furnace in cooperation with the binding members 11 and 12. Metal members comprising a part of the furnace structure such as a skewback beam 18 and door frames 19 are provided with hollow interiors through which a fluid coolant, usually water, is circulated to protect such metal parts, and personnel outside the furnace, from exposure to the high furnace temperature. Each charging opening 13 extends between the legs of such a frame 19 and a bottom generally defined by a water is circulated. The door flanges and rear wall dene a recess 24 for refractory facing furnace interior 14 when door 22 is down closing its respective opening 13. A wicket opening 25 extends through the door including the refractory in the recess so that a person outside the l furnace may readily view the furnace interior during'operation when the door is closed and, further, take out samples from the bath of molten metal in the furnace periodically for inspection and testing.

In the course of a heat, each door l22 may have to be raised on more than one occasion to permit a charging machine to dump material, such as scrap metal to be melted, into the furnace or for some other purpose. At the top of each door, clevises 2 6 are provided to which a bail 27 is pivotally connected. The bail in turn is bolted to the lowermost link of the vertical reach of a door operating chain 28. Each such chain in the illustrated embodiment passes around a fixed sheave 29 mounted on the furnace binding and extends to the drum of a reversible electric motor-reducer 48 shown in FIGURE 5, the operation of which controls the raising and lowering of the respective door connected thereto in accordance with the signal of the person operating the door. Thus, in FIG- URE l, the right-hand door 22 has been raised While the left-hand door is in closed position which is normal during a heating operation. Each bail 27 is provided with a strike plate 40 at its upper end to cooperate with a movable arm 41 of a limit switch 42 mounted on top of the furnace.

' An inlet cooling water manifold 30 extends horizontally and supplies cooling water to each door 22 through a branch conduit 31 having a normally open valve 32 and a pressure switch 33 therein. A portion 34 of branch conduit 31 is flexible to enable water to be supplied through an inlet pipe 35 to its respective door 22 in any vertical position of door 22. An outlet pipe 36 is connected to an outlet branch conduit 37 having a flexible portion 3S for outgoing cooling water' to permit such vertical movement of the door. The outlet branch conduit 37 discharges the cooling water leaving the door into an outlet manifold 39 which may go to a cooling tower or sump where the-water is reduced to inlet temperature before being returned to the inlet manifold 3d. Gther hollow metal members in the furnace which are water cooled may also be connected by conduits to such manifolds, respectively.

Each pressure switch 33 is provided with a plurality of small gap snap action contacts controlled by a slight movement of the stem 43 having a iiexible leaf 44 connected thereto and depending in branch 31, or other part of the circulating water branch for the respective door, so as to be held by the kinetic pressure of' cooling Water owing through `the conduit 31` in the direction of arrow 4S. A seal is provided in the interior of switch 33 to prevent such water from going up into the switch. So long as that kinetic pressure is high enough, it will maintain leaf 44 in the solid line position shown in'FIGURE 4, for example, indicating that circulation of the cooling water is occurring at a rate above a predetermined minimum rate value suicient for the proper cooling of a door 22. However, as and when that circulation is stopped, as by the pinching of hose 34 or 38 in the course of the operation of the door Z2 to which such are connected, leaf 44 will return to approximately the dash line position shown inr FIGURE 4 and operate the contacts in switch 33. Or, switch 33 may beso preset that when leaf 44 moves a predetermined distance from the solid line position illustrated in FIGURE 4 toward the dash line position, it will operate such contacts to indicate a dangerous n reduction in the rate of flow of such cooling water inimicable to the soundness of the cooling operation of that respective door 22. Additionally, a siren alarm 46 and a flashing or steady light alarm 47 may be provided either set up through contact arm 6u, normally closed limit switch contact arm 41 and coil 52 to raise door 22 to the position shown on the right-hand side of FIGURE l. At the same time, the opening of contact arm 59 means that even though Lower button 57 may be pushed, it cannot complete a circuit through contact arm $9 and wire 61 to coil 54 to interfere with the automatic raising of the door due lto the stopping of or reduction in the water flow. When that door 22 reaches its uppermost position, the strike will lift the Contact arm 41 breaking the contact through limit switch 42. Thereafter, door 22 will remain in its raised position removed from exposure and danger of excessive internal steam pressure or eyplosion until the water cooling flow diminution trouble is remedied. l

"Whenthe flow of cooling water to the raised door 22, is restored to normal, stem 43'will move to the left as viewed in FIGURE 4 with leaf 44 assuming its safe posi- Vtion due to the kinetic pressure of the flowing water and the contact arms in switch 33'will return to the position shown in FIGURE 5. Thereupon, when lowering button 57 is depressed, door lowering coil 54 will be energized through an electrical conductor circuit including contact arm 59, wires 62 and wire 63 which lowering action of energized motor 48 will continue, as long as lowering button 57 is held depressed during the closing of door 22. The illustrated circuit includes a conventional overload device 65 with a reset switch 64 therein.

near the furnace 10 or removed therefrom, or both, to

alert the operating personnel to the trouble with the coolant ow.

An exemplary operation of the illustrated embodiment may be described in conjunction with the schematic circuit diagram illustrated in FIGURE 5, which is but one of many ways in which the new mechanism may be operatively connected. As shown, areversible electric motorreducer 48 is provided to operate one of the doors 22 and receives 3-phase power from power lines 49 for rotation in a direction in accordance with whichever of the appropriate starter switches in switch box 50 may be engaged. Thus, when switch 51 is closed by energization of a solenoid coil S2, the energization of the motor 43 will raise the door. When starter switch 53 is engaged by the energization of solenoid coil 54, the motor will cause the door to be lowered until it covers the respective charging opening 13. Normally, a manual push button control 55 having a Raise button 56 and a Lower button 57 is operable to control the raising and lowering of the respective door 22 to which it is connected. Powering of the control circuit is obtained through a stepdown transformer 58.

Switch 33 is provided with a pair of movable contact arms, contact arm 59 being normally closed and contact arm 60 being normally open so long as the flow of cooling water in conduit 31 maintains leaf 44 in a safe position above the predetermined minimum ow needed to protect door 22. Assuming the door connected to the circuit in FIGURE 5 is closed (down) and the flow of cooling water thereto stops or is so reduced as to endanger the door, the movement of Vstern 43 to the right as viewed in FIGURE 4 will open contact arm 59 and close Contact arm 60. In turn, an electrical circuit will be immediately Various modiiications may be made in details and the arrangement of the illustrated embodiment and` other embodiments provided without departing from the spirit of our invention or the scope of the appended claims.

We claim: Y

1. In a safety device for water-cooled open hearth furnace doors or the like to raise the same whenever the kinetic pressure of the cooling water falls below` a predetermined value, apparatus comprising, in combination, a cooling water circulation conduit operatively connected to a furnace door or the like and having an inlet side, door raising means, a snap action kinetic pressure switch engaged by the flow of cooling water in said conduit having a member positioned in the inlet side of said conduit and operatively connected to said door raising means, said switch being actuatable upon a drop in the kinetic ressure of said cooling water below said predetermined value, an alarm operatively connected to said switch when actuated, said door raising means and alarm being responsive to the automatic operation of said switch adapted to be operative upon a` reduction below said predetermined value in the kinetic pressure against said member of cooling water flowing through said inlet side, door lowering means, and means operatively connected to said switch and said door lowering means adapted to prevent the operation of said door lowering means until said` flow of water is restored at least to said predetermined value, whereby said alarm is given and said door is automatically raised and removed from substantial exposure to high temperature in said furnace upon such reduction or cessation of circulation of said cooling water.

2. In a safety device for liquidV cooled furnace doors or the like to raise the same whenever the kinetic pressure of the cooling liquid falls below a predetermined value, apparatus comprising, in combination, a coolant circulation conduit for one of said doors or the like, door raising means, a switch responsive to kinetic liquid tiow pressure inV said conduit and operatively associated with said door raising means for actuation substantially immediately upon a reduction in said pressure below said predetermined value, said door raising means being responsive to the actuation of said switch to raise said door, said switch adapted to operate upon a reduction of said kinetic pressure below said predetermined value, and means adapted to prevent the lowering of said door until said kinetic pressureV is restored at least to said predetermined value.

3. In a safety device for liquid cooled furnace doors or the like to raise the same whenever the kinetic pressure of said cooling liquid falls below a predetermined pressure value, apparatus comprising, in combination, a coolant circulation conduit for at least one of said doors or the like, door raising means, a fast action switch adapted to be responsive to kinetic liquid ilow pressure in said conduit and operatively associated with said door raising means at least when said kinetic ilow pressure falls below said predetermined value, said door raising means adapted to be responsive substantially immediately to the operation of said switch to raise said door upon a reduction of said kinetic pressure below said predetermined value.

4. In a method for safeguarding water-cooled open hearth furnace doors or the like subject to overheating upon a reduction in the kinetic pressure of the cooling water below that provided by a predetermined minimum rate of flow, steps comprising, in combination, supplying a flow of cooling water to the interior of said door or the like at or above a predetermined minimum rate required to keepsaid interior of said door or the like from overheating, continually sensing the rate of ilow of cooling water in said door, raising said door upon sensing a reduction in the ow of said cooling water below said predetermined minimum rate, signaling an alarm upon such reduction in the flow of said water, and maintaining said door in raised position until the 110W of water to the interior of the door is restorted at least to said predetermined minimum rate. y

5. In a method for safeguarding fluid-cooled open i hearth furnace doors or the like subject to overheating upon a reduction in the kinetic pressure of the cooling uid below that provided by a predetermined minimum rate of ow, steps comprising, in combination, supplying a flow of cooling fluid to the interior of said door or the like -at or above a predetermined minimum rate required to keep said interior of said door or the like from overheating, continually sensing the ow of cooling uid through said door and noting deviations from said predetermined minimum rate, automatically and immediately raising said door upon deviation in the flow of said fluid below said predetermined minimum rate, and maintaining said door in raised position until the ow of uid to the interior of the door is restored at least to said predetermined minimum rate.

6. In a safety device for a fluid-cooled open hearth furnace door or the like associated with means for raising said door or the like whenever there is a predetermined reduction in the ow of the cooling iluid, apparatus comprising, in combination, a cooling fluid circulation conduit operatively connected to a furnace door or the like, door raising means, a pressure switch responsive to fluid ow in said conduit and operatively associated with said door raising means for automatic raising of said door upon a predetermined vreduction in said fluid ow, said switch having a snap action member extending into said conduit and adapted -to oper-ate automatically and immediately upon such reduction in said uid flow, door lowering means, and means operatively associated with said switch and said door lowering means adapted to prevent the operation of said door lowering means in the event of and during suchfreduction in fluid W.

References Cited in the le of this patent UNITED STATES PATENTS 829,659 Lennon Aug. 28, 1906 1,944,082 Hegel Jan. 16, 1934 2,487,933 Martin Nov. 15, 1949 2,718,218 Gray Sept. 20, 1955 2,735,386 Longenecker Feb. 21, 1956 2,952,753 Kmiecik et al. Sept. 13, 1960 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nm 3137279 June l@ 1964 James Leroy `IVlontQlomery et al It s hereby certified that error appears n-the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Signed and sealed thi's y.27th day of October 1964.

l(SEAL) Attest:

ERNEST W. SWIDER v y EDWARD J. BRENNE Attesting Officer .f l E 4Commissioner of Patents

Claims (1)

1. IN A SAFETY DEVICE FOR WATER-COOLED OPEN HEARTH FURNACE DOORS OR THE LIKE TO RAISE THE SAME WHENEVER THE KINETIC PRESSURE OF THE COOLING WATER FALLS BELOW A PREDETERMINED VALUE, APPARATUS COMPRISING, A COMBINATION, A COOLING WATER CIRCULATION CONDUIT OPERATIVELY CONNECTED TO A FURNACE DOOR OR THE LIKE AND HAVING AN INLET SIDE, DOOR RAISING MEANS, A SNAP ACTION KINETIC PRESSURE SWITCH ENGAGED BY THE FLOW OF COOLING WATER IN SAID CONDUIT HAVING A MEMBER POSITIONED IN THE INLET SIDE OF SAID CONDUIT AND OPERATIVELY CONNECTED TO SAID DOOR RAISING MEANS, SAID SWITCH BEING ACTUATABLE UPON A DROP IN THE KINETIC PRESSURE OF SAID COOLING WATER BELOW SAID PREDETERMINED VALUE, AN ALARM OPERATIVELY CONNECTED TO SAID SWITCH WHEN ACTUATED, SAID DOOR RAISING MEANS AND ALARM BEING RESPONSIVE TO THE AUTOMATIC OPERATION OF SAID SWITCH ADAPTED TO BE OPERATIVE UPON A REDUCTION BELOW SAID PRE-

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