US2561874A - Apparatus for venting heat transfer units of a steam-heated drying system or the like - Google Patents

Description

July 24, 1951 c, J LAHMAN 2,561,874

APPARATUS FOR VENTING HEAT TRANSFER UNITS OF A STEAM HEATED DRYING SYSTEM OR THE LIKE Flled May 19, 1948" 2 Sheets-Sheet l NW MUN July 24, 1951 C. J. LAHMAN APPARATUS FOR VENTIN A STEAM HEATED DRY Filed May 19, 1948 2,561,874 (2 HEAT TRANSFER UNITS OF ING SYSTEM OR THE LIKE 2 Sheets-Sheet 2 K E MN T INVENTOR. [HQ/@455 J [i /MW 'issreturned to; the. boiler.

Patented July 24, 1951 APPARATUS FER. UNITS.

OF A ST SYSTEMOE THE LI FOR VENTIN G HEAT TRANS- EAM HEATED DRYING KE Charles J. Lahman, Dayton, Ohio Application May 19, 1948, Serial No. 27,976

This invention relates to an apparatus for venting heattransfe'r units of a. steam heated'drying system or the. like.

A common. type of drier used in connection with paper making. machines, and for other purposes comprisesta series .of steam heated heat exchange units, such as rotating drums, about which the paper oroth'er material. to. .be dried passesv successively. The steam is introduced intoeachl unit throughan axial passage and the condensateis.withdrawn from the unit. through an eduction pipeextending through the steam supply passage. Inthe operation of such a drier or. during, the. intervals when itis not in. opera tion air and .non-cond'ensible gases or vapors ontel theunits andadversely affect the dryingoperatlonh Forexample when the drier is shut down, and-'thesteam. supplycut off, the cooling of. the. systemcondenses the steamremaining in the systern. and. creates therein. .a partial vacuum, or a pressure lower than.atmosphericlpressure, and airlissdrawn into the system through an leaks whichmay exist therein. Steam entering theunits from. the boiler may carrywithit vapors or gases whichare non-condensibleunder the conditi'onsrexisting in therunits: Such air'andcnoncondensible gases or'vapors reduce. the transfer ofl'heatlfrom the unit to the materialbeing; dried asllcy reducing.thetemperature. in the units and by forming an insulating, film. between the steam and. the heat transfersurfaces of the units. The air andnon-condensible gases and vapors entering the units-are withdrawn therefrom through the eduction pipes and areoarried. with the con densaterto aheader with which the. several. units are: connected andfrom which: the condensate When: the. condensate discharged'from the: units. moves rapidly through the: header the pressure; of the-latte is reduced below thepressurerin the unitsandthe heat units containedrin thecondensate in excessof'the-temperature-corresponding to this lower pressure are released. in the form of flash steam which, hayingv a lowerv specifics gravity than the conden sate; tends toiacoumulate at the'high point in the return line. and to choke or otherwise obstruct the; flow: of condensate through Likewise air? and non-condensible vapors and gases entering the header with the condensate; being'of" lower specific gravity than the condensate; tend to accumulate at the high point in the return line-andto obstruct the latter;

One object of the" invention is to" provide a steam heated heat for. continuously the return line;

transfer system with means removing air" and other non-- c'ondensible gases or vapors from the unit or units of the system without obstructing or otherwise disturbing the continuous and rapid discharge of condensate from said unit or units, thus permitting the maximum transfer of heat from said unit or unitsto material incontacttherewith' A further object of the invention is to provide such a'system with means for preventing air or other non-condenslble gases or vapors whichhave been removed from a heat transfer unit or units, or'steamflashed from the discharged condensate. from accumulating at a high point in. the condensate return line and obstructing the flow of condensate therethrough.

A further object of the invention" is to provide such a system in which the removal of air, gases, vapors and flash steam will be automatie cally controlled.

A further object of the invention is to provide such a system in which the air, gases, vapors and condensate are removed in such a manner as to provide equal distribution of eralflunits and to. prevent short circuiting one or more portions of the system.

In the accompanying drawings. Fig. 1 is. a schematic side elevation, partly broken away, of a drying apparatus embodying the invention; Fig. 2 is a horizontal sectional view taken through the rotary joint between the steam supply pipe and the drum; and Fig. 3. is a sectional view, partly in elevation, of a temperature controlled relief valve.

In these drawings I have illustrated. one embodiment of my invention and have shown the same as applied to a. web drying apparatus of the type which comprises a series of rotatable heat transfer units or drums, but it is to be understood that. the invention may take various forms and may be applied to heat transfer units of various kinds, used either for drying materials or; for other purposes, and the. word1drum as hereinafter usedis intended to include any heat transfer unit to which the invention may be applied.

p The: drying. apparatus in which the invention ishere-embodied is of a well known type and comprises aseries of rotatable .drums'i of whichthere: is. usually a relatively large number, three drums only beingshown for the purpose of illus-- tration. The several drumsare mounted for ro-- tation about parallel axes and are so arranged that: a Web of material may pass successively about the several drums in contact with a relatively large part of the outer or heat transfer. surface of each drum. The drums may be supthe steam to the sevported and rotated in the conventional manner or in any other suitable manner and these features are not illustrated except that Fig. 2 shows the trunnion and bearing for one end of one of the drums. Each drum is separately connected with a source, of steam supply, and in the arrangement shown a steam supply pipe 6 is con nected at one end with a steam. inlet at the axis of the drum and at its other end with a steam supply manifold or header I, each steam supply pipe being provided with a cutoff valve 8. The header 1 may be connected with any suitable source of steam supply and in the present instance it is connected by a'pipe 9 with a boiler Hi, the pipe 9 being provided with a cutoff valve II and a pressure reducing valve l2. The manifold itself is provided adjacent the reducing valve with a safety valve I3 and a pressure gauge M,

Portions of the steam introduced into the drums to heat the same-will condense and the condensate must be removed from the drums. Further, as above explained, more or less air will frequently enter'the drums and non-condensible gases and vapors will find their way into the drums, and these also must be removed. For this purpose each drum is provided with'an eduction pipe I5 which, by siphoning or otherwise, withdraws both the condensate and the gaseous substances from the drum. Heretofore both the condensate and the gaseous substances have been delivered from the eduction pipe through a discharge conduit IE to a condensate manifold or header ll, from which the condensate is returned to the boiler, as by a pumping type steam trap [8 connected by a conduit |9- with a combined water heater and tank 20, the tank being connected by a pipe 2| with a feed water pump 22 which delivers the heated water through a pipe 23 to the boiler.

I The steam supply pipe and the eduction pipe may be of any suitable character and may be connected with the drum in any suitable manner. Usually the connection is made through a rotary joint'such as is shown in Fig. 2. As there shown the steam inlet for the drum comprises a tubular element,.or nipple, 24 rigidly connected with the drum at the axis thereof for rotation with the drum and communicating with the interior thereof. 1 In the arrangement shown the tubular member has the inner end thereof screw threaded into an opening in the outer end wall of a hollow trunnion 25 by which one end of the drum is supported in its bearing 26. Mounted about the openouter end of this tubular mem her is a housing 21 which may be supported and held against rotation in any suitable. manner.

The tubular member extends through a relatively large opening 28 in the inner end wall of the housing, that is the end wall adjacent the trunnion, and is freely rotatable therein. Within the housing the tubular member isprovided with an abutment 29 having a convex surface 30 which bears against a concave surface on an annular sealing member 3| extending about the tubular member 24 between the abutment and the end wall of the housing. A second abutment 32 is slidably mounted on the outer end portion of the tubular member and is also provided with a convex surface 33 engaging a concave surface on a second annular sealing member 34. The sealing members may be of any suitable heat resisting bearing material, such as graphite. A spring 35 confined between the abutments' 29 and 32 presses the two abutments against the,

respective sealing members and thus tightly seals the joint. The outer end of the housing is closed 4 by a removable head 36 which is spaced a short distance beyond the end of the tubular member and against which the sealing member 34 bears. Thisend wall is provided with an extension 31 which projects outwardly beyond the body of the housing and has therein a passage 38 connecting the steam supply pipe 6 with the interior of the housing and, therefore, with theinterior of the drum 5. The eduction pipe l5'comprises a second tubular member which extends through the tubular member 24 and is of an exterior diameter substantially less than the interior diameter of the tubular member 24, so as to provide a passage for the free flow of the steam from the supply pipe to the drum. The eduction pipe, or tubular member, extends through the hollow trunnion 25 and then downwardly, as shown at 25a, to apoint near the bottom of the drum,

, with which it is in open communication. The

outer end of the eduction pipe extends beyond the outer end of the tubular steam inlet 24 and is mounted in and supported by the head 36 of "the housing. The extension 31 of the housing is provided with a second passage 39 with which the eduction pipe is in open communication and which isconnected with and in open communication with a short pipe 40 forming a part of the condensate discharge line. When, as has been heretofore customary, the condensate and gas eous substances withdrawn from the drum are all delivered through the condensate discharge conduit to the condensate header 11, the gaseous substances, having a lower specific gravity than the condensate, will separate therefrom and tend to accumulate at a high point in the discharge system and to obstruct the flow of condensate through the system, and this obstruction may be sufficient to completely block the flowof con densate from one or more of the drums. The main purpose of the present inventionis to sepa rate the gaseous substances from the condensate before the latter is delivered to the condensate header; To this end the connection between'th'e main portion of the condensate discharge line l6 and the pipe 40 is in the nature of a two way coupling, one outlet of which is connected with the condensate discharge line and the other out-" let of which is connected with a second conduit 4| and so arranged that the gaseous substanceswill separate from the condensate and rise through the conduit 4|, while the condensate flows by gravity to the header H. In the present instance the short pipe 40 is in a substantially} horizontal position and the coupling is in the na ture of a vertical T-eoupling. Thecondensate discharge conduit I6 is directly connected with the lower end of the coupling and the second con-- duit, 4|, is directly connected with the upper end of the coupling. The discharge conduit 4|.for the gaseous substances of each drum is connectedwith an air and vapor manifold or header 42.

It will be understood that more or-1ess steam= will be withdrawn from the drum alongwith theair and vapors and for the purpose of limiting: the escape of steam from the drum each conduit 4| is provided with a restricted orifice 43. This :1 orifice not only restricts the flow of steam but it also restricts the flow of other gaseous substances and thus prevents an excessive flow of steam, air

or vapors from any one drum, which would tend; to obstruct the air and vapor header and might; so restrict the fiow through the header as to 150,"

late or short circuit one or more of the drums.

The illustrated apparatus usually operates at a steam drying pressure above eleven pounds, gauge, and at such pressure the air and non-cone...

air and vapor escapes densible vapors entering the header areofalower specificgravitythan the steam and dash steam.

Therefore theair and, vapor header 42 is slightly inclined, that end thereof adjacentthe boiler being the, higher, so that theair and non-cone densible, vapors entering .the same .will accumulate at the higher end of the header, and must be: from time to time withdrawn. For this purpose, I have provided an automatic temperature controlled relief. va1ve-whichis .soiarranged that I when the temperature. in thehigherend ofuthe header falls below a predeterminedtemperature, due to the accumulation of air and'vapor therein, the valve-willopento vent the'header, thus permittingjithe air and vaporize-escape, andzas the steam moves into "the upper/end portion of the header and restores the desired high temperature, and upon suchlrestorationthe relief valve is again closed. Thehrelief "valve maybe of any suitable character which can be controlledinthe manner stated. As here shown it comprises a valvec'asmg 44 the end 45 of which constitutes therinlet and is connected by a pipe 45 with thehigher end of the header 42, the latter being provided with a dome 47 with which the pipe 4 3 is connected. The other end of the valve casing is in open communication with the atmosphere. The flow of fluid through the valve is controlled by a spring seated valve member 48 the stem of which extends upwardly into a cylinder 49 Where it is connected with a piston 50. The cylinder 49, above the piston, is connected with the intake side of the valve by a conduit comprising a part 5! and a part 52, the connection between the two parts being normally closed by a valve 53. The stem of the valve 53 bears against a diaphragm 54 and a plunger 55 is urged by a spring 56 in a direction to depress the diaphragm 54 and thus open the valve 53 and permit air to flow from the intake side of the valve casing to the cylinder 49 and thus open the valve and vent the header. The plunger 55 is held normally against movement by the spring 56 by a lever 51, the outer end of which is connected by a rod 58 with a plunger 59 which engages the lower side of a diaphragm 6G in a diaphragm chamber 61. The chamber 6| above the diaphragm is connected by a flexible conduit 62 with a thermostat tube 53 containing an expansible fiuid. The expansion of the fluid in the thermostat exerts a downward pressure on the diaphragm which resists the upward pressure of a spring 64 acting on the plunger 55. The pressure so exerted on the diaphragm by the thermostat is such as to prevent the upward movement of the plunger 59 so long as the temperature to which the thermostat is subjected is at or above a predetermined temperature. When that temperature falls below the predetermined temperature the pressure on the diaphragm is reduced and the sprin 64 is permitted to move the plunger 59 upwardly and thus release the lever 5'! and the plunger 55 for movement by the spring 56 and thereby cause the operation of the valve member 48 to open the valve. When, as shown in Fig. 1, the thermostat tube 63 is inserted in the higher end of the header 42 a fall in the reduction of temperature in the latter will result in the opening of the relief valve to permit the escape of air and as the air escapes steam moves into contact with the thermostat tube and the valve is again closed. The diaphragm spring 64 is adjustable to vary the pressure at which the valve will open and a thermostat 64a is mounted in the header '42 asv a ment.

Each air and Vapor discharge conduit 4i is provided with a cutoff valve 65 anda forwardlyopening check valve 66. Any condensate resulting from the condensation of steamin the 'header 42 maybewithdrawn through a steam trapfi l tozthe pumping trap [8, by which it will be returned to the'boiler. Likewise any condensate accumulatiingin the steam supply header I may be withdrawn through asteam trap 58 to the pumping trap I8. Each condensate discharge conduit. l6 is provided with a cutoiT valve li and alforwardly opening check valve ill. some air, flash steam or thelike may pass into the condensate header I! along with the condensate. That header preferably has a slight pitch, so that the gaseous substances will accumulate at thehigher end thereof and that endJis vented to permit the escape ofthe gaseous substances, :as by a pipe Ti connecting the higher end of the header ll with the higher end of. the. header 42 andprovided with a check valve 12 to. prevent reverse flow of the vapors therethrough.

While I have shown and described one embodiment of my invention I wish it to be understood that I do not desire to be limited to the details thereof as various modifications may occur to a person skilled in the art.

Having now fully described my invention what I claim as new and desire to secure by Letters Patent is:

1. In an apparatus comprising a plurality of rotatable drums, means for connecting each drum with a source of steam supply, means connected with the respective drums at the axes thereof for withdrawing therefrom condensates and gaseous substances, normally open conduits for condensates connected with the respective withdrawing means and extending downwardly therefrom, a header below the axes of said drums connected with said conduits to receive said condensates therefrom, normally open conduits for gaseous substances connected with the respective withdrawing means and extending upwardly therefrom, a normally closed header above the axes of said drums connected with said upwardly extending conduits to receive gaseous substances therefrom, the last mentioned header being inclined to cause gaseous substances to flow toward the higher end thereof and having an outlet adjacent said higher end, and means controlled by the temperature in said last mentioned header to control the flow of gaseous substances through said outlet.

2. In an apparatus comprising a plurality of rotatable drums, means for connecting each drum with a source of steam supply, means conguide inmaking the'adjuste respective withdrawing means and extending upwardly therefrom, a normally closed header above the axes of said drums connected with said. up-

gaseous substances from open conduits forcondensates connected with the respective withdrawing means and extending downwardly therefrom, a header below said axes connected with said downwardly extending conduits to receive said condensates therefrom, the lower header being connected at one end with a trap, having its other end closed and so arranged that gaseous substances entering the same with said condensates will move to the closed end thereof, and means for conducting said gaseous substances from said lower header to the upper header. 7

3. m an'apparatus comprising a plurality of rotatable drums, means for connecting each drum with a' source of steam supply, means connected with'the respective drums at the axes thereof for withdrawing therefrom condensates and gaseous substances, normally open conduits for condensates connected with the respective withdrawing means and extending downwardly therefrom, a header'below the axes of said drums connected withsaid conduits to receive said condensates therefrom, normally open conduits for gaseous substances connected with the respective withdrawing means and extending upwardly therefrom, a normally closed header above the axes of said drums connected with said upwardly extending conduits to receive gaseous substances therefrom, said headers beinginclined to cause gaseous substances to flow to the higher ends thereof, means for connecting the higher ends of said headersto cause gaseous substanc'es t o flow from said lower header to said higherheader a trap connected with the lower endor saidlower header, and means for connecting thelower end of said upper header with said trap to conduct condensates from the upper header to'said trap.

CHARLES J; L MAn,

REFERENCES CITED The following references are of record in'the file of this patent:

UNITED STATES PATEN'IS

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