Abstract:
This invention relates to a method of repairing a moisture barrier separating a paper machine dryer drum from the dryer journal. Such processes of this type, generally, involve filling the cavity between the dryer drum steam intake pipe and the dryer journal with a flowable moisture barrier material. The flowable moisture barrier seals leaks in the dryer journal moisture barrier

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    The present application is a continuation in part application of Ser. No. 09/571,371, filed May 15, 2000, which is pending.  
         BACKGROUND OF THE INVENTION  
         [0002]    1 Field of the Invention  
           [0003]    This invention relates to a method of repairing the moisture barrier separating a paper machine dryer drum from the dryer journal. Such processes of this type, generally, involve substantially filling the air cavity between the dryer steam intake pipe and the dryer journal with a flowable moisture barrier.  
           [0004]    2 Description of the Prior Art  
           [0005]    In conventional paper making machines several large dryer drums or heated cylinders are located near the end of the paper machine. The dryer drums are conventionally filled with steam at approximately 200 to 300 F degrees under pressure. The dryer drums contact both sides of the paper web and reduce the paper&#39;s water content to approximately 5%. The dryer drums are typically 5 feet wide or wider and typically weigh in excess of 2 tons. Each drum end is supported by a journal head. Each journal head is further supported by a journal assembly at each end.  
           [0006]    [0006]FIG. 1 is a cross-sectional drawing of a prior art journal assembly  2 . The journal assembly  2  acts as an axle to rotate the dryer drum (not shown) about a central axis. The journal assembly  2  typically has a hollow, annular main journal body  3 , hereinafter referred to as the journal. The journal  3  is supported by and rotated via journal bearings  4 . The bearings  4  are typically located in a housing. U.S. Pat. No. 4, 716, 661 by Asman is an exemplary reference of a hollow, annular journal for a paper machine dryer. Typically the dryer drum steam intake pipe  12  is placed into the hollow portion of the journal  3  as shown in FIG. 1. Typically, steam enters into the dryer drum in the direction of arrow A. Typically a steam condensate pipe  8  is located internal to the steam intake pipe  12 . In such cases, the steam condensate exits the dryer drum in the direction of arrow B.  
           [0007]    A thin annular cavity  16  separates the dryer steam intake pipe  12  from the journal  3 . This air cavity, primarily, serves as a heat insulator between the dryer steam intake pipe  12  and the journal  3 . The cavity eliminates most heat transfer from the steam intake pipe  12  to the journal bearings  4 .  
           [0008]    Conventionally a journal moisture barrier  20  is used to prevent steam from leaving the dryer drum and entering the cavity  16 . Typically, the journal moisture barrier  20  is an annular flange with a polymeric coating-based material or other moisture barrier, such as a rubber gasket. The journal moisture barrier is typically secured to the journal  3  by bolts  21  so that the polymeric coating touches the journal  3 . However, conventional journal moisture barriers  20  often fail to withstand the high temperatures of the dryer steam that can reach as high as 390° F. Frequently, the journal moisture barrier  20  breaks down or develops a leak that allows moisture from the dryer drum to enter the cavity  16 . As high temperature moisture enters the cavity  16  unacceptable amounts of heat are transferred through the journal  3  to the journal bearings  4 . High temperature moisture leaks adversely impacts the journal  3  and the bearings  4 . The moisture can cause the journal&#39;s  3  metal surface too pit and can breakdown the bearing&#39;s  4  lubrication (not shown) and lubrication system (not shown). Typically a leak in the journal moisture barrier  20  is detected by moisture exiting the cavity  16  via an opening  14 , such a weep hole.  
           [0009]    It is known to replace conventional journal moisture barriers  20  when they break down or leak. However, this requires many man-hours of labor and downtime for the entire paper machine to replace one moisture barrier, which ultimately leads to reduced paper production. An exemplary description of a conventional replacement or repair method is described in U.S. Pat. No. 4, 716, 661, column 4, lines 55-70. A typical paper machine includes many dryer journal moisture barriers  20  so the potential maintenance cost and paper machine downtime is great. Also, simply replacing one conventional journal moisture barrier  20  with another does not eliminate future replacements. Therefore, a more advantageous repair method for damaged journal moisture barriers  20  is highly desirable.  
           [0010]    It is apparent from the above that there exists a need in the art for a method to quickly and cost effectively repair a paper machine dryer journal moisture barrier. It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.  
         SUMMARY OF THE INVENTION  
         [0011]    Generally speaking, this invention fulfills these needs by providing a method to repair a moisture barrier separating a paper machine dryer drum from the dryer journal. The air cavity located between the dryer steam intake pipe and the dryer journal is filled with a flowable moisture barrier. The flowable moisture barrier in the cavity seals any leaks in the journal moisture barrier.  
           [0012]    The above and other advantages, features and benefits of the present invention will become more apparent by considering the following detailed description and drawings. 
       
    
    
     A BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a prior art, side, cross-sectional view or a paper machine dryer journal with a conventional moisture barrier; and  
         [0014]    [0014]FIG. 2 is a side, cross-sectional view of a paper machine dryer journal with a repaired moisture barrier according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    With Reference to FIG. 2, a leak in the dryer journal moisture barrier  20  typically occurs every 6 to 24 months. In order to repair the moisture barrier  20 , the entire paper machine must be shut down. In an exemplary embodiment according to the invention, the cavity  16  of FIG. 1, which separates the dryer journal  3  from the dryer drum steam intake pipe  12  can be filled with a flowable moisture barrier  18  (FIG. 2). The flowable moisture barrier  18  seals any damaged areas, such as for example steam leaks, in the journal moisture barrier  20 .  
         [0016]    In an exemplary embodiment, the flowable moisture barrier  18  is placed in the cavity  16  (FIG. 1) while the paper making machine is shut down. The repair method according to the present invention is much faster and cheaper than conventional methods. No worker entry into the dryer drum is required and the overall speed of the repair is much greater. In addition, if shut down, the papermaking machine can be returned to operation much sooner than under conventional moisture barrier repair methods. It is to be understood that the scope of the invention is not limited to repairs made while the machine is shut down. The invention covers filling cavity  16  during machine operation.  
         [0017]    The flowable moisture barrier  18  must be able to flow from an opening  14  in the cavity  16  such as weep hole  14  or any other cavity opening to the journal moisture barrier  20 . The flowable moisture barrier  18  is ideally paste-like with a cure time of 1 hour or less. The flowable moisture barrier  18  must be able to withstand potential temperatures of up to 500 degrees F. The cavity opening  14  can be permanently or temporary sealed after the flowable moisture barrier  18  has been placed in the cavity  16 . Exemplary flowable moisture barrier  18  materials include pastes such as PVR manufactured in Luke, Md. In addition the barrier  18  can contain fibers, thermosetting organic resins, graphite or Teflon ® based compounds containing polytetrafluoroethylene (PTFE).  
         [0018]    In order to demonstrate the problem solved by the present invention, temperature readings of several locations of the journal assembly  2 , for both non-leaking and leaking conventional journal moisture barriers  20 , were taken, as shown below in the following TABLE.  
                                                 TABLE                                       Outside   Temperature           Condition of Journal   Temperature of   of Journal           Moisture Barrier   Steam Intake Pipe   Bearing Housing                                    1.   Journal Moisture Barrier   251° F.   190° F.           not leaking       2.   Journal Moisture Barrier   250° F.   208° F.           leaking                  
 
         [0019]    The table displays the temperature at both the outside of the dryer drum steam intake pipe  12  and the housing of the journal bearing  4  for both leaking and non-leaking conditions of the journal moisture barrier  20 . Item 1 displays the temperature at the two locations when the dryer journal moisture barrier  20  is not leaking. Item 2 displays the temperature at the two locations when the dryer journal moisture barrier  20  is leaking; i.e. when steam is entering into cavity  16 . The journal bearings  4  experiences temperatures over 18 degree higher when the journal moisture barrier  20  is leaking.  
         [0020]    For a journal moisture barrier  20  repaired according to the method of the invention, an exemplary temperature difference of 54 degrees was measured between the journal bearing  4  versus the temperature of the steam intake pipe  12 . This temperature was in the range expected for a non-leaking journal moisture barrier as demonstrated in item 1. The repair according to the invention resulted in acceptable temperature ranges for the journal bearings  4 . As discussed above, this reduction in heat at the journal bearing  4  improves the operational efficiency of the journal bearing  4 .  
         [0021]    Once given the above disclosure, many other features, modifications or improvements will become apparent to the skilled artisan. Such features, modifications or improvements are, therefore, considered to be a part of this invention, the scope of which is to be determined by the following claims.