US2885790A - Drainage system and moisture control - Google Patents

Description

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l DRAINAGE SYSTEM AND MOISTURE GOH'JIROI.v

s 'sheets-'sneervz Filed Hay 24, 1957 LM M me me EY VE Nv. IR E H Ml Z .2 3 8 3 v v A P l n0 May l2, 1959 H. G. CRAM DRAINAGE SYSTEM AND MOISTURE coNTRox.

5 Sheets-Sheet 3 l Filed May 24, 1957 lNvcNroR ATTORNEYS United Staf@ Patent DRAINAGE SYSTEM AND MOISTURE CONTROL Hervey G. Cram, Appleton, Wis. Application May 24, 1957, Serial No. 661,457

6 claims. (c1. s44s) This invention relates to a drainage system for dryers of the rotary, cylindrical type and a moisture control for the sheet passing over'the cylinders of the dryers; the invention being an advancement over the art as illustrated by my prior Patents No. 2,242,778 and No. 2,696,679 issued respectively on May 20, 1941 and December 14, 1954.

An object of my present invention is to provide maximum eiliciency in the transfer of the latent heat in the steam, to and through the shell of each cylindrical dryer to the sheet of the paper in contact therewith.

t In order to obtain maximum efficiency it is necessary to prevent the accumulation of air and other non-condensable gases within the cylindrical dryers during operation, in view of the fact such gases have an insulating elfect rated at approximately 2000/1 with relation to the metal shell of the dryer and to maintain a xed minimum accumulation of condensate within the cylindrical dryers during operation, in that such an accumulation of con densate in a dryer reduces the amount of shell surface in direct contact with the steam, the insulating effect of the condensate being approximately 85/1 with relation to the metal shell of the dryer, plus the fact that the amount of accumulated condensate in the dryers has a very delinite veffect upon the power required for the rotation thereof, andfurther to dry the sheet with the least possible steam consumption per ton of paper dried.

It is therefore a further object of my present invention to provide a` continuous blow-through system in the cylindrical dryers so that there will be a fast and continu-- ous circulation of steam through each dryer for the con tinuous removal of the condensate, air and other non condensable gases, and, with a lixed pressure diiferential across each dryer suticient to serve this purpose.

' A further important object of my invention is to provide adryer drainage system and moisture control that will be automatic in operation, and, with unnecessary troublesome and-space consuming equipment.

A further salient object of my invention is to provide a novel means for maintaining a tixed required moisture content in the sheet of paper as the same leaves the cylindrical dryers so that the sheet will be satisfactory for use by the paper manufacturer and consumer. Maintenance of aixed required moisture content in the sheet is of prime importance, in that, the cost of paper making is materially reduced relative to an increase in the moisture contentn the sheet, Le., an increase in the moisture content inthe sheet of 1% with a machine or machines producing 100 tons of paper per day, means a reduction in cost of paper making material of 1% and an equivalent reduction in the steam requirement for drying, or in other words, an extra ton of paper per day without additional cost; also, a variation in the moisture content in the sheet is not only detrimental to the consumer requirement but it may also effect the operation of the paper drying machine, i.e., an excessively high or low mositure content in thev sheet may cause diculty at the calendar stacker, inpassing thedryers.

It is obvious that the rate of condensation in a paper machine dryer is relative to the moisture content in the sheet of paper in contact with the cylindrical dryers during operation, therefore, an increase or decrease in the moisture content of the sheet effects a relative variation in the rate of condensation in the dryer; a relative steam demand, and a consequent variation in pressure in the steam headers supplying the dryers.

It is therefore, a still further object of my invention to maintain a required moisture content in the sheet by providing an extremely sensitive and accurate control of the rate of ow of the steam to the dryers relative to the demand.

Another, still further object of my invention is to provide a proportional reduction in pressure automatically when the sheet is temporarily olf the drying cylinders so that the dryers will be at the proper drying rate to receive and accept the sheet when the sheet is again passed over the cylindrical dryers.

With these and other objects in view, the invention consists in the novel construction, arrangement and formation of parts, as will be hereinafter more specifically described and claimed, and illustrated in the accompanying drawings, in which drawings,

Figure 1 is a diagrammatic view in side elevation showing my improved drainage system and moisture control incorporated with a battery of dryers in a paper making machine;

Figure 2 is an enlarged central vertical sectional view taken through the novel condenser utilized in the system;

Figure 3 is a horizontal sectional view through the condenser taken on the line 3-3 of Figure 2, looking in the direction of the arrows, and

Figure 4 is an enlarged vertical sectional view through a pressure balanced diaphragm control valve of a type preferably used in my system.

Referring to the drawings in detail and more particularly to Figure l, I have shown diagrammatically a battery B of dryers, of a paper making machine and these dryers are of the rotating, cylindrical type, over which and in contact with a continuous sheet of paper (not shown) is passing for the purpose of drying.

In accordance with my present invention, the battery B of dryers is divided into a primary section 5 of any number of cylindrical dryers; a section 6 of cylindrical dryers composed of a less number of dryers than the primary section 5 and a condensate section 7, composed of a less number of dryers than the secondary section 6. The primary section 5 can include, say 25 dryers, the secondary section 4 dryers (as illustrated) and the condensate or third section, a single dryer. It is to be noted that in the drawings I have only shown four dryers in the primary section in order that certain controls can be clearly illustrated, but it is again to be understood that the primary section 5 includes a greater number of dryers than the secondary section 6 and the condensate section 7.

Steam is supplied to the primary section 5 through the primary header 8 and this header is fed with steam from a supply line 9 leading from a suitable source (not shown). Each of the dryers of the primary section 5, the secondary section 6 and the condensate section 7 is provided with a hollow journal (see my above-mentioned patents), and coupled with the journals of the primary section 5 are feeder pipes 10 leading from the header 8. Connected with the coupling of the dryers of the secondary section 6 are feeder pipes 11, which will be later referred to. Connected with the coupling of the dryer of the condensate section 7 is a feeder pipe 12, which will also be later referred to.

Water ofcondensation, air and other-non-condensable gases and steam from the various dryers of the primary section 5 are removed by syphons 13 and these syphons extend through the hollow journals of these dryers and are connected with a primary condensate headerA 14 whichextends along the-primary steam-header 8. Water ofV condensation, air and other non-condensable gases andsteam from the various dryers of the secondary section 6'are removed by syphons 15 of the same character as theisyphons 13 and these syphons-extend through the journals of the dryers of the secondary section and these syphons 15 will be later referred to. Water of condensation, air and other non-condensable gases and any steam will be-removed from the dryer of-.the condensate sectionbya syphon 16 which is the same-as the syphons13` and-15and this-syphon 16 willbe--later-referred to. The syphons are well shown in my Patents Numbers -2,617,205 and 2, 696,679 .issued- .to me respectively von November ll; 1952- and-Deccmber -14,y ,1954.1 f

Extending along.;the dryers .of-the?. secondary section! 6is a se'condary'steam header- 17 and the feeder 'pipes- 11 `of the dryers of this section-communicate with-the header 17. The primary condensate header 14 iscoupled with and leads into the secondary steam header'17. Extending along the secondary steam header 17 is a secondary condensate header 18 and the syphons 15 of the section 6 are connected and communicate with the condensate header 18. The feeder pipe 12 for' the dryer of the condensate section 7 is connected and communicates with the secondary vcondensate header 18.v

Briey, from the description so far, it can be seen, steam is supplied to the dryers of the primary section 5 from the header -8 and the condensate and gases are removed from these dryers to the condensate header 14 and this header, in turn, supplies the dryers of the secondary section 6 with steam for heating these dryers and that the condensate and gases from the dryers of the secondary section 6 are removed by the syphons 15 to the secondary header 18 for condensate and that steam from the condensate header 18 is supplied through the feeder 12 to the dryer of the condensate section 7 and that condensate and gases are removed from this dryer by the syphon 16.

If desired, additional live steam can be supplied from the primary steam header 8 to the secondary steam header 17 through a connection 19 having interposed therein a pressure differential unit or control 20. The control operating on a differential (in the present instance) of 2 pounds; the unit being in .proportion to other'controls, which will be nowset forth.

The removal of the condensate, air and other noncondensable gases from the dryers forms an important part of this invention and in-conjunction with-this removal, I utilize a novel condenser 21 which will be later described'in detail. At the present moment, however, it

can be seen that condensate is discharged from the f primary condensate header 14, through a pipe 22 to and through a pipe 23 which leads and communicates with the lower end of the condenser- 21. The condensate is removed from the condenser by a pump 24. The pump 24 can be of any desired character and operated in any desired way. In the present instance, the pump 24 is shownto be of the rotary type and its outlet has cornmunicating therewith a riser pipe 25 which leads back to the boiler plant (not shown). Condensate and gases` are discharged from the secondary condensate header 18 through a pipe 26 to the pipe 23 leading to 'the condenser and ultimatelyv to the pump 24 and the boiler` plant.' Condensate and a minimum amount of steam` is` discharged from the dryer of thel condensate-l section-71o a pipe 27 thatv leads to and communicates directly with the condenser 21 at a point above the pipe 23 and at a point above the lwater or condensatev level inthe condenser. To maintain the water-or condensate at a fixed-level within the condenser, l employv a liqudv level controller 28. A branch pipe 29 connects the condenser with-the condensate return pipe 25 and the valve 30 of the liquid level vcontroller 28 is interposed inl the length of this" branch pipe. It is to be noted that the branch pipe 29 is disposed at a point above the condensate feed pipe 23 and at a point materially below the condensate and steam return pipe 27. The level of condensate within the condenser 21 as communicated to the float chamber of the liquid level controller 28 provides the means to position thevalve 30 to provide the required amount of,v con-v densate return from the discharge of the pump 24 to the condenser 21v to maintain a-constant fixed-level within the condenser 21. The purposeof. the communicating pipe 31 top of liquid level controller'28 to the condenser 21 is to prevent any accumulationS-ofai'r or other noncondensable gases at the top of the liquid level controller 28. The liquid level controller 28 is of a type commonly found on the open market.

The pipe r 22 has-interposed iu-the 'lengththereof a pressureirdiierential: valve 32,which in'the Ipresent application operates: on. a `'differential loff tive 'pounds. The condensate return pipe '26Hha's --incorporated therein a pressure dierential valve" 33,A which inthe present instance operates on a differential yof threepounds. It is4 to be noted that the pipe 27 is free of a pressure differential valve. Both the condensate pipes 22 and 26 also have preferably interposed-invthelengths thereof a sight glass 34 so-that an'operator can see the ow of condensate. The pressure differential valves-or units 32 and 33 are of the sametype'as-shown in my Patent No. 2,696,679 heretofore mentioned.-

The pipe 23 has also communicating. therewith a pipe- 35. Flow of water through the pipe 35 -is controlled by a -hand valv'e36.- The-'pipe 35. andithe valve 36 are merely used as a clean-out-toa sewer, if such should ever be required.`

All of the syphons 13, 15 and 16 have incorporated iny their lengthsv pressure differential units or valves 37 andv each of these pressure differential unitsg-in the presentinstance, operates on-a differential of two pounds and theser units are exactly ofthe same type' as shown in myv Patent No. 2,696,679.

The condenser 21 includes-a tubular casing shell 38v closed at its'lower end by a head 39 to which is con-- nected the pipe` 23 for condensate and the outlet for the water to the pump 24.l Theupper end of the casing shell 38 has threaded thereon a-*collar 40 and bolted-to this collary is a-head 41. The head-41 in-turncarries a de'` pending annular rib or sleeve-42. Securely welded-or otherwisel fastenedi to the*y rib -or`r sleevev 42 isl a dependinginterior-cooling water'- chamber 43; Thischamber 43 terminates wellabove the water-.flevelin the condenser. Extending entirelythrough the-'colingcwar -cha'mber 43`are-open ended tubes 44;.-so thatst'eain-canv o'w freely therethrough and th'usl--heV expeditiously reduced to water ofl condensate. Extending .into 'the chamber 43 is a water supply pipe 45-andco`n1municating with the upper end of the chamber is a'coolingiwater discharge pipe 46.- The extremelupper endV of the condenser hascommunicating therewith a-dischargepipe 46 for air and other non-condensable 4gases and this pipe can discharge directly ,tortheatmosphere if -so desired.

The moisture control for' the sheets includes a pressure balanced diaphragm-control valve 47 interposed in the steam supply pipe 9. This valve 47 is specially designed to secure super-sensitivity, (see Fig. 4). The control -valve 47 is carried by a--by-pass lineI 48,.theflegs 49l of which .communicate with the steamsupply pipe 49l on oppositesidesof a *handoperat'edvalve' 50.- The-legs 49 also have incorporatedy therein-hand operated valves 51. Normally, the valve 50 is# closed and the valves 51 are open so that steam' will-flow through the by-pass pipe 48 and into theprimar-ysteam-header4 8 andbe controlled by the valve 47. The-i control valve 47- includes the valve section 52 andL-the-control-.diaphragm section 53. The valve -sectionzSZ-fin'eludes `the valve-casing -54 having valve seats 55 on which are adapted to seat valve bodies 56 carried by a stem 57 attached to and operated by the diaphragm 58. The diaphragm 58 is rmly clamped at its periphery by the sections 59 of the diaphragm housing 60, forming a part of the diaphragm section 53. Obviously, when the diaphragm 58 rises, the valve bodies 56 will be moved from their seats 55 allowing free ow of steam and when the diaphragm moves down the llow of steam will be regulated until the valve bodies 56 are firmly seated at which time the supply of steam will be entirely cut oi. The diaphragm 58 is pressure balanced and operates as follows: steam ilows into the upper end of the diaphragm housing through the medium of a supply line 61 which has direct communication with the steam by-pass line 48 down stream of the valve 47. Attention is now directed to, and this forms an important part of the invention, the branch line 62 which communicates with and connects the line 61 with the secondary condensate header 18. This line 62 has interposed in its length a pressure differential unit or valve 63 which is of the same type as the pressure diiferential valves or units 37. However, in the present instance, the pressure differential valve 63 operates on a pressure diierential of four pounds. In order to prevent direct contact of the steam with the diaphragm a column of water 64 is placed in the diaphragm housing directly between the upper face of the diaphragm 5-8 and the line 61.

Communicating with the lower end of the diaphragm housing 60 is an air supply pipe 65. Compressed air is supplied to line 65 from any suitable source and pressure is normally lixed by a pressure regulator valve 66. Interposed in the line 65 is a pilot 67 of a conventional type and embodying a secording chart and air pressure adjusting knob 68.

Compressed air is delivered to the bottom side of the diaphragm 58 of the pressure balanced diaphragm control valve 47 via the control knob 68 of the pilot 67 at the required pressure, as set up by the operator to eiect a required moisture content in the sheet at the start of an operation. This pressure is equalized by means of the steam from the line 61 and the valve bodies 56 are positioned to effect the required steam pressure in the primary steam header 8. The purpose of the by-pass line 62 with its four pound pressure diierential unit 63 is to increase the sensitivity of the control of the steam supply with relation to the moisture content of the sheet and this functions as follows: an increase in the moisture content in the sheet effects a relative decrease in pressure in the steam header 8 which reacts relatively on the control valve 47 and the initial decrease in pressure in the secondary condensate header 18 effects a relative increase in the pressure dilerential across the four pound pressure differential unit or valve 63, thereby increasing the amount of steam from the line 61, and, thus decreasing the pressure on the upper side of the diaphragm 58 for a more rapid re-positioning of the valve bodies 56 in the readjustment of the drying rate.

The decrease in the moisture content in the sheet effects a relative increase in pressure in the steam header 8, reacting relatively on the control valve 47, and, the increase in pressure in the secondary condensate header 18 effects a relative decrease in the pressure diiferential across the four pound pressure differential unit or valve 63; thereby decreasing the amount of steam by-passed from the line 61. This increases the pressure on the upper side of the diaphragm 58 for a more rapid and accurate re-positioning of the valve bodies 56 for the readjustment thereof relative to the drying rate.

When the paper sheet is ofr the dryers temporarily, through a sheet break, the pressure will increase relatively in the secondary condensate header 18 effecting a decrease in pressure differential across the four pound pressure differential unit 63 and a relative increase in pressure in the line 61 and on the upper side of the diaphragm 58 to re-position the valve bodies 56 for a relative reduction in pressure in line with the dryer pressure requirement for the passing of the new sheet over the dryer cylinders,

It should be borne in mind, that, the four pound pressure dilerential unit 63 is the normal pressure differential between the primary steam header 8 and the secondary condensate header 18 at the required moisture content in the sheet.

Now referring back to the condenser 21, with the liquid level pressure differential controls, it can be seen with a pressure differential of two pounds between the primary condensate header 14 and the secondary condensate header 18 and the discharge line or pipe 27 from the condensate section 7 and within the condenser 21 as fixed by the individual `dryer two pound pressure dilerential units 37: it will be obvious that, the established pressure diierential between the primary condensate header 14 and the condenser 21 will be four pounds and between the secondary condensate header 18 and the condenser 21 will be two pounds.

The purpose of the ve pound pressure dilerential unit or valve 32 is to equalize the discharge from the primary condensate header 14 to the pressure within the water line 23 and Within the condenser 21 and at the same time, provide a column of condensate of approximately (in the present instance) two and one-half feet to prevent the possibility of steam passage through the pipe 23 and the condenser 21.

The purpose of the three pound pressure differential unit or valve 33 is identical with that of the ve pound pressure dierential unit 32, as per the above description.

This arrangement allows for gaseous discharge to the condenser 21 along with the condensate only from the condensate section 7, such gaseous discharge consisting of the air and other non-condensable gases as discharged from all of the drying cylinders and a minimum amount of steam to contact the condensing unit or chamber 43 within the condenser 21 for the separation and discharge of the non-condensable gases through the discharge pipe 46.

Various other changes in details may be made Without departing from the spirit or the scope of this invention, but what I claim as new is:

l. In a paper making machine, a battery of cylindrical dryers over which a paper web is fed including a primary section, a secondary section and a condensate section, means for circulating steam through the dryers of the primary section including a header for steam and means connecting all of the dryers of the primary section with the header, a primary header for condensate and returning steam for all of the dryers of the primary section, a syphon for each of the dryers of the primary section connected with the primary condensate header, means for circulating steam through the secondary section of dryers including a secondary steam header and means connecting all of the dryers of the secondary section with the secondary steam header, means connecting the primary condensate header with the secondary steam header, a secondary condensate header, means including a syphon for each dryer of the secondary section connected with the secondary condensate header for removing condensate and steam from the dryers of the secondary section, means connecting the secondary condensate header with the dryer of the condensate section, means including a siphon for the condensate section for removing condensate from said section automatic means in the syphons of the dryers for the primary, secondary and condensate section for maintaining a iixed predetermined pressure across each dryer, a condenser for receiving condensate and steam from the dryers of all of the sections, means for removing water of condensate from the condenser including a pump, means for maintaining a xed water level in the condenser, an inlet pipe communicating with the conzestig-790i 7. denser below theV \vaterleve1,..independent -return'rpipesf connecting the primary and secondary condensate headerswith the inlet pipe, means for connecting the syphon of the dryer of the condensate section with the condenser above the water level in thecondensenxand automatic pressure differential valves in the pipesfor connecting the primary and secondary condenser headers withathe condenser.

2. In a paper making machine as defined in claim l, and said pressure differential valvefor` the primary'condenser header 'being of a higher" pressure differential than the pressure diierential valve for thesecondary condensate header.

3. Ina paper makingmachine as;deflned1-in claim.1, and said condenser having ,an Youtletfdr lair.'ar1d1noncon densable gases adjacent-.to thertop of..the.fcondenser. and. above the Water level inthe condenser.

4. In a paper making-.machineras denedinclaim-l, and .said 'condenser including .an interior chamberffor-cool-l ing water, .feed vand return pipesfory coolingwater, communicating with the chamber and said chamber having extending therethrough flues for the circulation of steam therethrough for cooling and condensingsaid steam.

5. In a paper making machine as 'defined in claim 2, and means connecting theprimary steam header with the secondary steam header and said connection having interposed therein a pressure differential unit of the same value as the pressure differential units in the syphons.

6. In a paper making machine, a battery ofcylindrical dryers overl which a paper web is fed,including'a primary section and a secondary section means "forV circulating steam through the dryers of the primary sectionincluding a header for steam, means connecting all of the dryers of the primary section withthe header, and asteam supply 'sectionfhaving communication with the secondary condensate header, pressure differential valves in said syphons for the primary and secondary sections of the same -value vfor maintainingA` atixed predetermined pressure across :each dryer,l means for removing condensate from-theprimary and secondary headers and means forcontrolling the rate of ow of steam to the dryers relativetothe demand including'a pressure balanced-diaphragmcontrol valve'inthe steam supply pipe, means connecting: the steam-supplypipewith the control valve on Onesidefof-its diaphragm, a conduit for compressed air having communication with the control valve below the lowerv face of its diaphragm, a pilot including a recording chartand'pressure adjusting valve in said conduit, and a by-pass line connecting thesecondary condensate header with the connection of the steam line with the control valve'and 'said `by-passfline having incorporated therein a pressure'differential unit of a predetermined value.

References Cited in the le of thisv patent UNITED STATES PATENTSY 1,817,110 Stickle Aug. 4, 1931 2,629,939 Bennett -Mar. 3, 1953 2,696,679 Cram Dec. 14, 1954

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