US2242778A - Moisture controller - Google Patents

Description

y 20, 1941 H. G. CRAM I 2,242,778

MOISTURE CONTROLLER Filed Aug. 15, 1938 2 Sheets-Sheet l Inventor Hill-am E Fittarneufls May 20,1941. H. G. cRAM MOISTURE CONTROLLER Filed Aug. 15, 1938 2 Sheets-Sheet 2' a Ht't DTI'IEHS Patented May 20, 1 941 nois'runs con LLER Hervey G. Cram, Appleton, Wis, gnor to P. D. Gram, Appleton, Wis.

Application August 15, 1938, Serial No. 225,4?29

. Claims.

paper-making is the necessity of. maintaining a uniform predetermined moisture content in the sheet as delivered from the paper machine.

It is an established fact that the quality of the finished sheet is enhanced if the moisture content is of the correct amount, and this ratio of moisture to solids is constant. The percentage of moisture in the sheet affects the strength-surface, flexibility, etc. It also afiects the operation of the paper machine, as a sheet over-dried has a tendency to snap ofi in the dryers or at the calender stack, resulting, in a considerable loss of machine time; or, if the sheet contains too much moisture, it may be blackened in passing the rolls of the calender stack. Uneven moisture content along the run of the sheet afiects the gen= eral quality so that these variables are carried through to the printing processes, which result in printing imperfections. Further, anything less than the proper specified moisture content in the sheet will result in a considerable monetary loss to the paper manufacturer, in that the difierence in the percentage of moisture content in the sheet and a greater specified moisture content, based on the cost of. the finished sheet, is. a direct loss. It is, therefore, one of the primaryobjects of my present invention to provide a means to regulate the flow of steam to the dryers of a paper machine, so as to maintain automatically the specified percentage of moisture content in the sheet as it is being made on the paper machine.

Another salient objectof my invention is to provide means for determining the moisture oontent in the sheet by the rate of condensation in one or more of the dryend dryers of the drying section of a paper machine.

A further important object of my invention is -to provide means for automatically regulating the flow of steam to the drying rollers of a papermaking machine according to the rate of. condensation in a. specified drying roll.

A still further object of my invention is to provide a simple and durable means for actuating a steam valve in accordance with the amount of water of condensation being taken from a drying roll.

With these and other objects in view, the invention' consists in the novel construction, ar-

rangement, and formation of parts, as will be hereinafter more specifically described, claimed, and illustrated inthe accompanying drawings, in which drawings:

Figure 1 is a diagrtic view of a ing my novel device incorporated therewith.

Figure 2 is an enlarged, fragmentary, transverse sectional view through a drying roller at the dryend of a paper-g me, showing myim= proved device incorporated therewith, the various or wet end thereoi; and rolls t, i, ii, ii, it, and M at the rear or dry end thereof. There can be as many intermediate drying rolls as may be desired,

and, as stated, Figure l is of a diagrannnatic nature.

The paper sheet 82, shown in dot-and-dash lines in the drawing, is trained over. the various rolls in the usual manner, and these rotating rolls are all connected at their axial centers through couplings it with branch pipes it! leading from a common steam supplying pipe or header it or from any other suitable source of supply. This header i5 is connected by means of a pipe it and suitable couplings with a steam delivery pipe ii. The pipe it has incorporated in the length thereof a valve id for controlling the flow of steam through the pipe it and to the battery of drying rolls.

The water oi condenwtion from the various rolls can be removed in a manner similar to that shown in my prior Patents Nos. 1,919,416 and.

2,045,634, issued respectively on July 25, 1933, and

- June 30, 1936. Thus, positioned in each roll is a syphon pipe is, which leads out of the coupling part of the drying section oi a paper-making machine, showfibrous).

the initial dryers I, 2, 3, etc. at the wet end,

. where the sheet is delivered in its wettest condition, will be greatest, decreasing in each successive dryer as thesheet reaches a drier state,

until at the last dryers l and I! the sheet has very nearly reached the required dryness, and

- the rate of condensation in these dryers is prac-- tically nil under normal operation.

It is obvious that with a flireclfiow'oi steam decreasing on successive dryers until near the I dry-end dryers i, 8, 9, it, and ii a marked variation in steam requirement is apparent. This ,variation is efiected by some variation in the sheet as entering-the driers; that is, the sheet may vary in thickness (weight), or the make-up of the sheet'may vary in freeness (more or less The more fibrous or free sheet is less resistant to the evaporation of moisture, and, naturally, the thicker or heavier sheet, containing proportionately more moisture, is more dimcult to dry.

With an excessive drying burden eifected by one or both of these variables in the sheet, the first dryers I, 2, 3, etc. will transfer this exce sive drying burden to successive dryers in the section. This transfer of drying burden to the dry-end dryers will increase the rate of condensation in these dryers, and this increase is proportional to the amount of moisture in the sheet at that point. Therefore, by selecting a dryer (such as drying roll 3) at the dry end as a test dryer, and measuring the condensate therefrom as to rate of flow, and providing a means for transmitting this variation to the control valve il in the steam supply line II, the rate of drying on the complete section of dryers will vary with the variation in the sheet, with the result that a uniformly dried sheet will be delivered from the dryers.

Referring more particularly to the drying roll 3, it will be seen that the condensate is removed continuously therefrom through the syphon pipe I. to a vertical pipe consisting of an upper section 2|, an intermediate relatively long section 22, and a lower section 23. The upper and intermediate sections are connected through the medium of a desired steam trap 24, and the intermediate and lower pipe sections are connected together through the medium of a desired steam trap 23.

The lower pipe section 23 discharges at a considerably lower pressure into a hot well, vacuum pump, atmosphere, or the like. The intermediate pipe length 22 has incorporated therein, at a point intermediate its length, a moisture control 23. J

A pressure relief is provided for the pipe section 2| by means of a communicating pipe 21,

with a diaphragm pressure differential control valve 23 therein. This differential control valve 23 has one side of its diaphragm equalized as to pressure with the supply pipe l4, and the other side equalized as to pressure with the condensate return pipe section 2|, by means of pipes 23 and 33. The adjustment of differential in pressure across the valve is by means of the spring in the valve, which assures a constant predetermined pressure difl'erential across the dryer.

The trap 24 is provided in the condensate return pipe section 2| to prevent passage of steam and to also prevent the dryer pressure from being transferred to the moisture controller 26. The

moisture controller 23 is in the nature of a valve, and is provided with an orifice 31, the size of which is controlled by means of an adjustable hand wheel 32, actuatinga needle valve body. The discharge from the moisture controller 26 is to the trap 25, which effects a constant pressure on the discharge of the moisture controller 26. A communicating pipe 33 between the intake and discharge of the moisture controller 26 equalizes the differential across the moisture controller 26, except as affected by the hydrostatic head of the column of condensate held back by the moisture controller 2%.

- The pressure head of the column of condensate above the moisture controller 26 is communicated to the diaphragm of the pilot valve 36 through pipe 33, which regulates the pressure to the diaphragm 36 of the control valve it in the steam supply pipe ii.

The upper connection of pipe 33 to the pipe section 22 is purposely high in order to avoid by-passing the condensate past the moisture conthe diaphragm 36. However, the pipe 31 has incorporated in the length thereof the pilot valve 34, which includes the valve body 38 movable toward and away from its seat according tothe pressure of the column of the water of condensate in the pipe 22.

It is to be noted that the control valve I8 is normally held on its seat by the spring 39 thereof, bearing on the diaphragm 36, and that air pressure working on the diaphragm 36 controls the opening of the control valve l8. The air supply pipe 31 can be provided with a strainer 43 and a reducing valve 4 I. The valve 4| reduces the pressure to a constant predetermined amount, which, in the present instance, has been set to fifteen pounds. Thus, the pressure leading toward the valve body 33 is constant. An orifice 42 is provided on the righthand side of the pressure reducing valve 4|, and this orifice is equal in area to the orifice in the pilot valve 34 when the pilot valve is in its wideopen position, that is, when the valve body 38 is entirely oflf its seat. When in this position, the pressure is zero between the orifice l5 and the diaphragm 36 of the steam control valve.

The injection of the valve 38. into the pilot valve reduces the discharge to the atmosphere (pipe 43) proportionately, and raises the pressure in the pipes leading to the diaphragm 36, which results in the forcing of the stem of the control valve l3 downwardly. This opens the control valve I3 againstthe action of its spring variation in the sheet entering the dryers, such as an increase in the weight of the sheet, causes a part of the drying burden to be transferred to the successive dryers in'the section, so that the dry-end dryers are forced to condense a greater amount of steam. This additional rate of flow of condensate will raise the head of the column of condensate in pipe 22 above the orifice of the moisture controller 26; and this pressure head will be communicated through pipe 35 to the pilot valve 34, to the control valve l8, opening the valve l8 and allowing a proportional increase of steam to be supplied to the entire dryer section, suflicient to dry the heavier sheet to the same percentage of dryness as the previous normal weight sheet.

A decrease in the weight of the sheet reduces the head of the column to condensate, and this decrease in pressure head is communicated through the pilot valve 34 to the control valve l8, effecting a proportional closing thereof, This reduces the rate of dryness on the initial dryers, thereby forcing the subsequent dryers to assume their proper share of the drying.

Obviously, my invention can take various forms, and, hence, the form shown and described is merely to be taken as illustrative of one form of my invention.

Changes in details may be made tion, but what I claim as new is 1. In a paper-making machine, a drying section including a plurality of drying rolls, a header pipe for steam, a pipe for supplying steam to said header, a control valve in the supply pipe, means for operating said valve by fluid pressure, a pilot valve for controlling the flow of fluid to the first-mentioned valve, means for supplying steam to the rolls from said header pipe, a header for the water of condensation, pipes for receiving water of eondensation from the rolls and conducting the same to the header for the water of condensation, means for operating the pilot valve from the head of water in one of the pipes receiving water of condensation from one of the rolls, and means for governing the flow of water of condensation through said pipes.

2. In a paper-making machine, a drying section including a plurality of drying rolls, means for supplying steam to all of said rolls including a header and a steam supply pipe leading to the header, a valve in said steam supply pipe, means for removing water of condensation from one of said rolls including a vertically disposed trolling the flow of water of condensation in the vertical pipe.

3. In a paper-making machine, a drying section including a plurality of drying rolls, means for supplying steam to all of said rolls including a header and a steam supply pipe leading to the header, a valve in said steam supply pipe,

without departing from the spirit or scope of my inven-w means for removing water of condensation from one of said rolls including a vertically disposed pipe, steam traps in said last-mentioned pipe, means for operating the valve for the steam supply pipe by fluid pressure, a pilot valve for controlling the flow of fluid pressure to said lastnientioned means, means for operating the pilot valve by the head of water in the vertical pipe between the steam traps, and manually controlled means for governing the flow of water of condensation in the vertical pipebetween the steam traps.

4. In a paper-making machine, a drying section including a plurality of drying rolls, means for supplying steam to the rolls, valve means for regulating the supply of steam to the rolls, and means for regulating the moisture content in the paper sheet leaving said rolls according to the rate of condensation of the steam supplied to said rolls including a condensate-receivingmember, means for governing the rate or flow of the condensate from said member, and means actuated in response to variations in the head of condensate in the condensateand means for controlling the valve in the steam supply delivery pipe according to the head of water of condensation in said measuring member.

HERVEY G. CRAM.

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