US2563692A - Yankee drier - Google Patents

Description

Aug. 7, 1951 H. M. OSTRTAG ET AL YANKEE DRIER 3 sheen-sheet 1 Filed Sept. 2L, 1944 Aug- 7, 1951 H. M. OSTERTAG ET AL 2,563,692

v YANKEE DRIER Filed Sept. 2l, 1944 3 Sheets-Sheet 2 Aug. 7, 1951 H. M. osTERTAG ET AL YANKEE DRIER 3 SheeYs-Sheet 5 Filed Sept. 2l, 1944 L ffw Patented Aug. 7, 1951 YANKEE DRIER Harry M. Ostertag, Drexel Hill, and John H. Masshard, Springfield, Pa., assignors to Scott `Paper Company, Chester, Pa.,ia corporation of Pennsylvania Application September 2l, 19.44, Serial N o.` 555,146

9 Claims. l

A primary object of this invention is to provide a Yankee drier capable of operating .safely at steam. pressures materially in excess of those heretofore found practicable.

To this primary end the invention contemplates a `novel structural design calculated to eliminate the critical points of failure and toavoid inlarge part the hazardsexisting in driers of conventional form and responsible for the inability of those driers to operate with reasonable safety at higher steam pressures.

Another and more specific object of the invention is to provide improved and readily accessible means for distribution .of steam within the drier and for removal of condensate.

The invention resides further incertain structural details and devices hereinafter described and illustrated in the attached drawings wherein;

Fig. 1 is a longitudinal sectional view of a-drier made in accordance with the invention, said-section being taken on the line I-I of Fig. 2;

Fig.i2 is a sectionalview on the line 2-2,1Fig. V.1

Fig. 3 is an enlarged fragmentary sectional view illustrating certain details of structure;

Fig. 4 is a View in perspective of one of .the elements of the structure, and

Figs. 5 and 6 are enlarged sectional Views corresponding to Fig. 3 but illustrating modications within the scope of the invention,

Figure 7 is a line diagram illustrating graphically the interrelation of certain elements of the structure, as hereinafter more fully set forth.

The conventional Yankee drier consists of a cylindrical cast iron shell mounted on journals through the medium of dished heads, .said shell and heads forming together a cylindrical drum. Steam is introduced through the journalsto the interior of the cylindersubjecting the .entire internal area to full steam pressure. condensate is removed by scoops which operate either .as clippers or, in the blow-through type of removal, as intake nozzles.

This type of construction possesses certain undesirable characteristics. (1) The pressure acting on the heads produces stresses and deflectionsof the heads which are transmitted through the rim bolts or studs to the shell; (2) Accumulation of condensate may occur in the large interior space of the drier causing dangerous loading and .creating additional hazard in event of failurein the possibility of the accumulated water flashing into a large volume of steam. Even if condensate accumulation is not present at the time of failure the contained steam alone may expand to a large volume when freed from the cylinder; (3) There is difficulty in maintaining concentricity at the outer edges of theshell due in part to head deflection; (4) Utilization of a small number of relativelsT spaced scoops tends to result in the creation of local hot spots in the shell Where the exhaust steam sweeps the drier surface, with resultant uneven drying of the` paper; (5) There are points of critical weakness. While some failures of Yankee driers have occurred in the head, the majority are in the outer shell, and these latter failures almost invariably occur at the edges of the shell and usually at a rim bolt or stud.`

All of the foregoing factors have contributed to a necessity for employing relatively low steam pressures. As previously set, forth, the present lnvention provides a drier structure which, byeliminating the aforedescribed hazards and areas of critical weakness, permits the safe use of materially higher steam pressures within the drier thanV have heretofore'been found practical. 'The invention also corrects in substantial degreethe several faults above enumerated of the prior conventional type of drier.

`With reference to the drawings, the improved drier consists of an outer cylindrical shell I of cast iron, which metal provides the best creping surface, and an inner shell 2 which is made of steel so as to meet the standard specicationsfor uniired pressure vessels. These shellsare spaced apart through the medium of hollow rims 3 and 4, one at each end, which serve also as Aannular steam chambers. The rims and Yshells are concentrically mounted, through the medium of spokes 5, upon a central axle 6, said axle comprising journal elements l and 8, from which the said spokes radiate, and an intermediate hollow shaft 9 which extends between and unites the said journals. Steam is introduced through `the journal 'l by way of a pipe Il which is secured to the outer end of the journal through the medium of a flange l2 and screws t3, as hereinafter more specifically described. From the journal member 1, steam passesthrough a port M to the hollow shaft` 9, thence through the spokes 5 at both ends of the structure to the rims 3 and '4, and from these hollow rimsthrough apertures l5 and IB to the space Il between the shells I and 2. As shown in Fig. V2, the apertures I5 are uniformly spaced in annular series around the inner side of the rim 3, and the apertures i6 vare correspondingly arranged in the rim 4.

To remove condensate and reduce the thickness of water iilm on the shell, exhaust steam is evacuated from the chamber VI'l by Way of 3 a plurality of nozzles I8. These nozzles project from pipes I9, a plurality of which extend longitudinally in the interior of the steam chamber I1 and are connected at one end through pipes 2| and 22 and ports 29 -with the interior of the journal 8. Exhaust steam discharges through the journal and through a pipe 23 secured within the latter. The nozzles I8 have their outer ends arranged in close proximity to the inner surface of the outer shell I so as to restrict the openings through which the steam must pass in entering the nozzles, and preferably the outer ends of the nozzles are for-med, as shown in Fig. 4, with lugs I8a which preclude approach of the ends of of the inner surface of the outer shell adjacent to the nozzle tips. Since the exhaust steam can enter the nozzles from all directions approximately in the plane of the drier surface the aforesaid sweeping action is effective over a circular area surrounding each nozzle. The nozzles are closely spaced so that the combinedV area thus swept may in aggregate cover substantially the entire inner surface of the shell. The exhausting steam carries with it the condensate which is similarly exhausted through the journal 8 and pipe 23 as described. l

Opposite the outer end of each of the spokes is a tie rod 24. These rods are secured under tension, by means of nuts 25 and 2E at the respective ends thereof, in the outer walls of the rims 3 and 4, and extend longitudinally through the chamber I1. The rods pass through apertures 21 and 28 in the inner walls of the rims 3 and 4, which apertures correspond to the apertures I5 and I6 previously described.

These rods, in conjunction with the pipes 19,'

act under tension to carry the relatively small component of the pressure of the steam in the chamber I1 which tends to separate the rims. The outer shell I is stiffened by inwardly projecting integral flanges 29, and the rims 3 and are secured to these flanges by screws 3l which pass through outwardly extending flanges 32 on the said rims and through the iianges 29 and are threaded into a segmented retaining ring 33, the segments of said ring seating against the inner faces of the anges 29 as best illustrated in Fig. 3.

The manner in which the nozzle pipes or manifolds I3k may be secured under tension in the rims 3 and 4, is best shownin Fig. 3. The outer walls of the rims are provided with a series of uniformly spaced elongated apertures 34 which are located respectively approximately mid-way between the points where the spokes join the rim. The location and arrangement of these apertures 34 is well illustrated in Fig. 2. The apertures are dimensioned and positioned so that the respective pipes I9 with their nozzles may be inserted therethrough into the chamber I'I, and for this purpose corresponding apertures 35 are provided in the inner walls of the said rims. The apertures 34 are normally closed by cover elements 36 which are secured against the outer walls of the rims by screws 31, and each of the caps 3B has on its inner face a projecting annular wall 38 which forms a recess on the inside of the cap functioning for a purpose hereinafter described. Each of the pipes I9 has at one end an L fitting 39 which is attached by threads to the pipe I9 and which has at its outer end a projecting boss 4I which ts into the aforesaid recess embraced by the wall 38 on the associated cap 36 as Vpreviously set forth. A screw 42 passes through an aperture 43 Ain the cap 36 and through the aforesaid recess and is threaded into a tapped hole in the outer face of the boss 4I. Suitable packing 44 is inserted between the said outer end of the boss 4 1 Aand the bottom of the recess in the cap 36 so as to seal the opening 43. A corresponding connection, see Fig. 1, is established between the pipe I9 and the rim 3 with the exception that in this case the l.. tting 39 is replaced by a terminal cap 45 which fits into the packing recess on the inner side of the cap 33 and into which the screw 42 is threaded as described. `By tightening the screws 42 at the opposite ends of the pipe I9 the latter is placed under tension between the rims 3 and 4. ln the present instance the fittings 45 are provided with projecting bosses 46 which can be utilized in applying or removing the terminal cap to the pipe I9.

Since the pressure component carried by the tie rods and pipes is relatively small, it may be desirable in some instances to eliminateV the tie As shown most clearly in Fig. 3 the outer ends of the pipes 2I arethreaded into the respective ttings 39, and the inner peripheral wall of the rim 4 is provided with a series of apertures for passage of the said pipes 2I into the interior ofY the rim. Each of these openings, which areY designated in Figure 3 by the reference numeral 41, is provided with a stuifing box indicated generally by the reference numeral 48 which seals the opening around the pipe 2I. The rim 3 is similarly provided with series of openings corresponding to the openings 41 and to the ports 20 which receive the pipes 22, said openings and ports being designated by the same reference numerals, but in the rim 3 these openings are normally closed by means of suitable caps 49 and 50 screwed to the rim.

In accordance with the present invention, the inner shell 2 is mounted on the rims 3 and 4 through the medium of floating joints designated generally by the reference numeral 5I.

One part of the joint is formed by a iiangelike annular projection 52 having its outer face 53 inclined to the axis of the roll. The other part of the joint is formed by an in-turned iiange 54 at the end of the inner shell 2, the inner faces 55 of the flanges 54 being inclined in conformity with the face 53 of the flange 52 and seating upon the latter. The joint between the faces 53 and 55 is sealed by a exible sealing ring 56 which is secured at the inner end of the joint with its inner and outer peripheral edges secured by screws 51 and 58 to the ilanges 52 and 54 respectively. This seal being exible is of a character to afford limited relative movement between the rims and the inner shell.

The llocus of a point on the end of the inner shell moving as a result of thermal expansion is a line the slope of which is determined by the relation of the diameter of the shell to its length. By proper determination of this locus,

it is possible to design the joint 5I so that expansion of the shell and rims will not open the joint i. e. so that the surfaces `53 and l55 will remain in contact with each other during the heating period from room temperature to the full operating temperature of the roll. In this respect, it should be noted that the cross sections of the elements of the head members `of the roll including the journals, the spokes, and the rims are preferably kept as nearly equal in thickness :as possible so as to obtain a substantially uniiorm rate `of heating and resultant expension; and that the entire structure with the exception of the outer shell is subjected to substantially full steam pressure and temperature. The louter shell, while subjected to full steam pressure will be cooled by the application of the wet web.

The axial expansion of the steel inner shell Vmay be expressed as follows:

ea-L. C(T2T) 'eu-:axial 'expansion lL=length of shell :coefficient of expansion for steel T=room temperature where and T2`==`operating temperature .'-Ifhe .radial expansion of the shell will be:

A fer=R C(Tz-T) where Rrradius of the shell It may be assumed that one-half oi the axial expansion will occur at each end of the shell.

Thesaid slope will, therefore, be the ratio of the expansions or where a "is the angle of the locus, neglecting radial .deflection due to pressure, and D is the mean diameter of the shell. The equation is illustrated geometrically in Figure 7 wherein a corresponds to the angle formed between the surfaces '53 55 (as shown in Fig. 3) and the rotary axis of the dryer.

'The central journal, the hollow shaft vEl, the spokes 15, and the rims 3 and Il maybe practically considered as a unitary structure since all are of the same material and are securely fastened together. The surface 53 is also determined as the loci of'jpoints moving due to thermal expansion and a similar calculation applied to the above structure considered as a unit will determine the slope 'as the ratio of D/L.

It will b'e seen that regardless of a difference in coefficient of expansion each point on the shell land rims will "follow the line dened by D/L, and as a result the `joint will remain tight without restraining the expansion and with consequent avoidance of stresses. The flexible seal 56 will 'prevent the escape of any small quantity of steam which might find its way through the joint.

"Withfurth'er reference to the pipes I9, it will be `noted 'that by reason of the fact that all connections are external or readily accessible, the pipes 'may be installed and as readily removed without affecting the rest of the structure. In the assembly operation, the nozzles, pipe, ter- :min'al fitting 45, and L Y39 may be assembled 'and then inserted between the shells through oneof the openings 34. This sub-assembly after insertion fis rotated through an angle of 90 to fthe fina-l position and the packing and cover .plates installed :and secured. The pipe 2l listhen inserted through the aperture-41 and threaded into the L after which the packing -is inserted andthe gland drawn-tight. Finally the S pipe 2'2 is installed between the nippleand the hub casting and'is bolted -iast to complete the connection. Dismantling may be quickly accomplished A'by reversing this procedure and may be accomplished without Vwaiting for the drier to cool.

The aforedescribed drier structure 4has certain advantageous `features which may besummarized as follows:

1. Distor-tio'ntati-the enls of the heated outer shell is resisted by a stiening ring or flange through which the shell is fastened to a heavy rim section Tin a manner approaching an vintegral structure.

The bolt arrangement `is such that the stressed therein are limited substantially to those of drawing up, all load being carried `directly by the rim section.

"Forces -due to weight or 'external load `are transmitted to the journals through the spokes radially in a plane perpendicular to the axis and close to the bearing support, thereby reducing bending moments to a minimum.

'4. Both end pressure and water load are reduced to -a practical minimum by employing a double shell. This reduces stress and deflection in the heads and shell and also reduces the hazard of large volumes of escaping steam should fail-ure occur.

Tie rods and the 4pipes I9 may be used to `carry end pressure .forces rather than utilizing the outer shell and heads thereby further re ducing stresses and deflections in the heads and shell.

i6. Provision has been made to equalize exparisien where possible and to provide an expanding joint between dissimilar .metals whereby variations in expansion will not produce undue stresses.

7-. Steam is Yintroduced between the shells from a large number of apertures to provide uniform Adistribution and does not impinge on the outer shell, which avoids creation oi' hot spots.

'8. The condensate-removal nozzles are desig-ned 'and located to produce exhaust steam velocities suflicient to sweep a circular area about eachjnozzle. A number of nozzles are provided so that the area `swept by each may overlap the area swept'by an adjoining nozzle thus sweeping substantially the" entire shell surface to reduce the water film thickness and increase heat transfer. i

59. The condensate removal system has been designed for accessibility and easy removal to reduce operati-ng delays when maintenance .is required.

In Figure 5 we have illustrated a design wherein the expanding joint principle has been applied to the outer shell. This construction has a special application where external loads and the matter ci shell end distortion are factors of less importance. In this case vthe outer shell 6l is supported by the rims, `one of which is shown 'at e2, through the medium of a floating joint 53 `of the 'character described, the inner shell Ell being rigidly connected to the 'rims 'by studs 65. In this case the entire structure is of steel vwith the exception of the `outer shell, although the joint is applicable to a design incorporating the same materials throughout. Theoa'ting `'shell is intended primarily to compensate for the differential in average tempera-v ture between the outer shell which is cooled byapplication of Vwet paper, and the rest of the structure. The slope of the locus in this case can be derived as the angle whose tangent is D/L, if the radial deflection due to pressure is neglected. Since deflection due to pressure andA distortion due to unequal temperatures in the outer shell'would tend to open the joint, minor adjustments to the slope of the meeting faces may bemade to approximately compensate for the deflection and distortion at the condition of pressure and temperature to be utilized.

In the embodiment illustrated in Fig. 6 both the inner and outer shells, 66 and 61 respectively, are connected to the rims 68 by floating joints, 69 and 10. This embodiment may be applied when it is undesirable to restrict the relative movement of either shell Vdue to unequal thermal expansions of the components of the drier structure.

Reference is hereby made to U. S. application Serial No. 631,886, filed November 30, 1945, and constituting a division of the present application.

We claim: i

1.'Inv a drier of the rotary cylinder type, an outer cylindrical shell, an inner co-axial shell radially spaced from the outer shell so as to provide therebetween a chamber for reception of a heating medium, means for supporting the shells for rotation about the common axis, and means for flexibly joining at least one of the shells to said support so as to aord freedom for relative movement between the joined parts in response to differing thermal expansions of the latter, said flexible joining means comprising meeting surfaces on said shell and support having a slope approximated by the ratio D/L, where D is the mean diameter and L is the length of the shell.

2. In a drier ofthe rotary cylinder type, an outer cylindrical shell, an inner co-axial shell radially spaced from the outer shell so as to` provide therebetween a chamber for reception of a heating medium, means for supporting the shells for rotation about the common axis, and means for flexibly joining the inner of said shells to said support so as to afford freedom for relative movement between the said shell and the support in response to differing thermal expansions thereof, said flexible joining means comprising meeting surfaces on said shell and support having a slope approximated by the ratio of D/L, where D is the mean diameter and L is the length of the shell.

3. In a drier of the rotary cylinder type, an outer cylindrical shell, an inner co-axial shell radially spaced from the outer shell so as to provide therebetween a chamber for reception of a heating medium, means for supporting the shells for rotation about the common axis, and means for flexibly joining the outer of said shells to said support so as to afford freedom for relative movement between the shell and the support in response to differing thermal expansions thereof, said flexibly joining means comprising meeting surfaces on said shell and support having a slope approximated by the ratio of D/L, where D is the mean diameter and L is the length of the'shell.

4. In a drier of the rotary cylinder type, a cylindrical shell, means Vfor supporting said shell for rotation about the axis of the cylinder, and means for flexibly joining said shell and the support means so as to afford freedom for relative movement between the shell and said support means in response to differing thermal expansions therein, said flexible joining meanscomprising meeting surfaces on said shell and support having a slope approximated by the ratiov of VD/L, where D is the mean diameterY and L is the length of the shell.

Y 5. In a drier of the rotary cylinder type,Y an outer cylindrical shell, an innerco-axial shell in radially spaced relation to said outer shell, a rim member uniting the ends of said shells, and means for flexibly joining both the innerand outer shells to the rim members so as to afford freedom ofv movement of the shells with respect to the rims in response to differing thermal expansions of ysaid rim and shells, each of said flexible joining means comprising meeting surfaces on said shell and support having a slope approximated by the ratiol of D/L,'where D is the mean diameter and L is the length of the shell.

6. In a drier of the rotary cylinder-type, an outer cylindrical rigid shell, an inner coaxial shell also rigid and radially spaced from the outer shell so as to provide therebetween a chamber for reception of a heating medium, rigid means-for supporting the shells for rotation about a common` axis, a means for mounting at least one of the shells onV said support for substantially unrestrained thermal expansion and contraction in both axial and radial directions, said means including an inwardly facing frusto-conical interseating surface between the support and the shell whereof `the imaginary apex lies in the axis of the cylinder. Y

7. In a drier of the rotary cylinder type, an outer cylindrical shell, a rigid inner coaxial shell radially spaced from the outer shell so as to provide therebetween a chamber forireception of a heating medium, rigid means for supporting the shells for rotation about the common axis, and means for mounting the inner of said shells on said support for substantially unrestrained thermal expansion and contraction in both axial'and radial directions, said means including an inwardly facing frusto-conical.interseating surface between the support and the shell whereof Vthe imaginary apex lies in the axis of the'frcylinder.

8. In a drier of the rotary cylinder type, an cuter cylindrical rigid shell, an inner coaxial shell radially spaced from the outer shell so as to provide therebetween a chamber for reception of a heating medium, rigid means for supporting the shells forV rotation about the common axis, and means for Imounting the outer of said vshells on said support for substantially unrestrained thermal expansion and contraction in both axial and radial directions, said means including an in-f wardly facing frusto-conical interseating surface between the support and the shell whereof the imaginary apex lies in the axis of the cylinder.

9. In a drier of the rotary-cylinder type, an outer cylindrical substantially 'rigid shell, an inner coaxial shell also substantially rigid and radially spaced from the outer shell so as to provide therebetween a chamber for reception of a heating medium, a'substantially rigid shell-supporting structure, and means in said structure forming an independent supporting seat for each of the opposite ends of at least one ofsaid shells upon which the shell is free to slide simultaneously in both axial and radial directions in response to differing thermal expansions and contractions of the structure and the shell, said seats beingV inclined to the axis of the drumandn opposite directions thereby immobilizing the shell Number against bodily movement in the axial direction. 1,030,210 HARRY M. OSTERTAG. 1,604,197 JOHN H. MASSHARD. 1,642,361 1,664,656 REFERENCES CITED 1,718,209 The following references are of record in the LS1-9,534 file of this patent: UNITED STATES PATENTS lo Number Name Date 153,775 Mason Aug. 4, 1874 Number 266,104 Crowley Oct. 17, 1882 112.352 977,376 Dodge Nov. 29, 1910 Name Date Simon et a1 June 18, 1912 Rushmore Oct. 26, 1926 Crowell Sept. 13, 1927 Berry Apr, 3, 1928 Aldrich et a1 June 25, 1929 Akerlow Aug. 18, 1931 Buettner July 16, 1935 Helin Jan. 16, 1945 FOREIGN PATENTS Country Date Germany Aulg. 31, 1900

Images