US1792086A - Temperature-indicating means - Google Patents

Description

Patented F eb. 10, 1931 UNITED STATES} CHARLES w. .eonnolv, or. rnEAsAN'rvI LE, NEW YORK, AssIeNon TO THE surna- T NT OFFICE HEATERC OMPANY, OF- NEW YORK, N. Y.

TEMPERATURE-INDIGATING MEANS Application filed. February 9, 1929. Serial No. 338,789.

My invention relates to means for indicating temperatures and hasparticular reference to means for indicating whether or not predetermined temperatures have been exceeded by the heated fluidin a'heat exchanging apparatus of the surface or non-contact type, such for example as a stea'msuperheater or an oil heating or cracking still.

In apparatus of this character'the heating elements through'which'the fluid to be heated is passed are frequently located in zones of extremely high temperature produced by combustion gases, and the conditions to which such elements are subjected are so se- V61?! that the cooling action of the fluid passing through them must be depended upon to save them from destruction; The fluids'heated are, moreover, often raised innormal operation to a temperature such that if the'desired temperature of the heatedfiuidis exceeded by any substantial amountfor a ma terial length of time the heating elements are badly damaged, if not entirely destroyed, through over-heating. s i a The conditions" during starting up and shutting down periods are particularly severe, especially in thecase 'of steam'super heaters, asduring these periods intense heat,

may be generated in the furnace when there i so is insuflicient steam flow through the heating elements to properly carry away the heat which they absorb. Assuming the equipment to be properly designed, the life thereof 7 depends largely upon: the proper :operation of the apparatus,'and in case of failure of any part of it, due to over-heating, the firstrques-- tion which arises'is whether such failure has been caused by. defective design ormaterial,

or by improper-operation which'has permit;

ted the temperature of theheated fluidto rise materially beyond thetem'perature forwhich the apparatus was "designed:

- The principalobjectof thepresent invention is the provision "ofsimple and inexpensive means by which it can be readily determined whether or not a" certain predeter mined maximum temperaturelof the heated fluidlhas. been exceededfor aperiod long enough to, damagethe heating elements. A to further object of the invention is the preg vision of means of this character accomplishing its function through the medium of a fusible indicator or indicators, and a still fur ther object of theinvention is the provision of a fusible indicator of this character which is located out of contact with the heated fluid s'othat-the heat transmittedtothe indicator passes from the heated fluid thereto by conduction through a wall of the heatingapparatus. The further and more detailed objects of the invention will become apparentfroma consideration of theensuing description of' 'a preferred form of the invention which has forillustrative purposes beenshown'as ap' plied to a steam superheater. V J1 In the accompanying drawings, forminga part'hereof, Fig. 1 is a fragmentary vertical section of a superheater boiler to which the invention has been applied; Fig. 2'is a broken elevation, on an enlargedscale, ofthe superheater headers and connections, as viewed from the left of'Fig. 1; Fig. 3; is a fragmentary section on an enlarged scale taken along. the: line 33 of Fig.2, and Figst'and 5 are plan and elevation views respectively of the fusible elements employed. 7 1 i Referring now @toFig. 1, the boiler illustrated-is of the semi-vertical or Stirling type, comprising a plurality of steam and waterdrums 1, 2 and 3, said drums being connected respectively by the banks of'gencrating tubes l, 5 and I6 to'the usual mud drum (not shown). The upper drums'are further connectedv by means of the usual steam and water circulators 7 and'8, and"'the steam generated in the boiler is takenv off through the pipe 9 to the saturated steam header 1 0 of the superheater, which is of known form and comprises header 10, asimilar header-11 for the superheated steam and a plurality-of tubular superheating elements 12 connecting thetwo headers and located in V theinter-tube space of the first bank of boiler tubes 43 Steam fromthe superheater header about a quarter of an inch from the inner surface of the header wall. The amountof metal left between the bottom of the recess and the inner surface of the header wall will obviously differ depending upon the condi tions for which the header is designed.

A minimum thickness of metal at this point suficient to withstand safely the 1 ressures imposed on the header is obviously required, and. the maximum thickness is limited by the factor of heat conduction through the metal from the interior of the header.

In the embodiment shown, the fusible elements 15 and 16 comprise two semi-cylindrical stepped plugs having relatively large bases resting on the bottom of the recess and held in position bythe plug 17 screwed into the threaded wall of the recess 14.

The fusible elements 15 and 16 may be of any suitable material which will fuse at the desired temperature which it is desired to indicate. In the present instance, as applied to a superheater working in the usual range of temperatures now employed, it is desir able to detect superheat temperatures much in excess of 800 and the element 15 is there fore made of an alloy whose fusing point is in the neighborhood of 850 F. ,Such an alloy may comprise a mixture of 35.4% lead, 35. 1% zinc and 29.2% antimony. In-addition to an element indicating this temperature, it is also desirable, in many instances, to provide means for indicating whether or not the normal temperature has been very greatly exceeded, and for this purpose the element 16 is provided having a fusing temperature of approximately 950 F. This element may be made of a mixture of 19.12% lead, 19.12% zinc and 61.75% antimony.

Obviously, the fusible element or elements may be of any material or composition which will fuse at the temperature or temperatures it is desired to record.

In order to prevent or to make known any unauthorized tampering with the fusible elements the plug 1. may be spot-welded as at 18 to form a seal which must be broken before the fusible elements can be reached for inspection or replacement.

The functioning of the device will be large ly evident from the foregoing description of the illustrative embodiment shown, as any over-hea ting of the header will be immediately reflected in the fusing of one or both of the fusible elements located therein. In this connection. it is important to note that the location of the header in which the fusible elements are placed with respect to the combustion gases or other heating medium, is immaterial. The heating medium is in sub stantially all cases at a temperature sufficient to fuse the fusible elements andthe determining factor in their condition and also the condition of the heating elements. is the cooling effect of the medium being heated. It is the quantity and temperature of the medium passing through the heating apparatus which determines the temperature of the. latter, and consequently of the fusible elements, so that the action of the fusing elements will be the same whether they be placed in a header located in the path of the heatin medium or outside such path.

It is furthermore to be noted that with the fusible elements employed in accordance with the present invention a momentary fluctuation in furnace conditions or in the condition of flow or temperature of the fluid being heated will not affect the fusible elements, inasmuch as they are affected only by heat conducted through the wall of the header, which will reach a temperature suilicient to fuse the elementsonly after abnormal conditions have obtained for a length of time suilicient to cause probable damage to the apparatus. In the specific form of superheater chosen for illustrative purposes, the preferred location for the fusible elements is adjacent to the exit end of the superheated sea a header, but this exact location need not necessarily be employed, particularly in other specific forms of apparatus to which the invention'may be applied, as the principal requirement is simply that the fusible elements be exposed to the heating effect of the heated fluid at some point in the path of flow which will give an accurate indication of the final temperature of substantially the entire bot y of heated fluid leaving the heating apparatus.

It is to be understood that the form of apparatus hereinbefore described is illustrative only and that the invention is to be considered as embracing all such changes and modifications as may fall within the terms of the appended claims.

I claim: 1

1. The combination, with heat exchange apparatus of the surface type having a conduit conveying fluid heated. in said apparatus, of temperature indicating means comprising a plurality of fusible elements out of contact with the heated fluid passing through said apparatus and receiving heat from said fluid by conduction through a portion of the wall of said conduits, each of said elements fusing at a different temperature.

2. The combination, with heat exchange apparatus comprising a plurality of heating elements and a header into which they discharge a heated fluid, of temperature indicating means comprising a plurality of ele ments each adapted to fuse at a different predetermined temperature, said elements being located in juxtaposition and in thermal contact with a portion of the wall of said header, and outof contact with the heated fluid there- 1n.

3. In heat exchange apparatus, a vconduit for conveying fluid heated in said apparatus, a recess extending inwardly from .the exterior of the wall of said conduit to a point adjacent to the inner surface of said wall, a'

fuse at a different temperature and each having a plane surface contacting with a portion of said bottom, and means for holding said elements in position.

9. In heat exchange apparatus, a conduit for conveying fluid heated in said apparatus, a threaded cylindrical recess extending inwardly from the exterior of the Wall of said conduit and having a bottom adjacent to the innersurface of the wall, an element adapted to fuse at a predetermined temperature, said elementhaving a base contacting with said bottom, a'plug screwed into said recess over said fusible element and holding the latter in position, and means for detecting tampering with said plug comprising a seal arranged to be broken by a movement of the plug.

1 CHARLES W. GORDON.

5. In heat exchange apparatus, a conduit for conveying fluid heated in said apparatus, a threaded cylindrical recess, extending inwardly from the exterior of the wall of said conduit and having a plane bottom adjacent to the inner surface of the wall, an element adapted to fuse at a predetermined temperature, said element having a plane surface contacting with said bottom, and a plug screwed i into said recess over said fusible element to hold the latter in position. 7 i

6. In heat exchange apparatus, a conduit for conveying fluid heated in said apparatus,

a threaded cylindrical recess extending inwardly from the exteriorof the wall of said 7 conduit and having a plane bottom adjacent l to the inner surface of the-wall, anelement "l adapted to fuse at a predetermined temperature, said element having a plane surface con tacting with said bottom, a plug screwed into said recess over said fusible element to hold the latter in position, andvmeans for detecting tampering with said plug comprising a seal arranged to be brokenby movement of the lug.

' 7 The combination with heat exchange apparatus having a conduit for conveying heated fluid, said conduit having a recess extend ing inwardly from the exterior wall thereof, of an element adapted to fuse at a predetermined temperature and having a base contacting with the bottom of sa1d recess, and a closure for sa1d recess over sa1d 'fuslble ele ment holding the latter against the bottom of I the recess.

8. In heat exchange apparatus, a conduit for conveying fluid heated in said apparatus, a recess extending inwardly from the exterior of the wall of said conduit and having a bottom adjacent to the inner surface of the' wall, a pair of elements each adapted t'ofuse at a different temperature and each having a base contacting with a portion of said bottom and means for holding said elements in position.

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