Abstract:
A sealing system for quick-closing doors of pressure vessels, either by providing under pressure from both sides of a gasket, or by using overpressure between two special gaskets.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This kind of door is well known, e.g. it is used for hot-air-autoclaves, autoclaves for steam curing and for heat treatment of metals under protective atmosphere in overpressure- and underpressure ranges of −1/+20 or more bar.  
         [0002]     As long as the protective atmosphere is inert, it is no problem to vary the process pressure during operation from underpressure to overpressure and visa versa.  
         [0003]     In case, that the protective atmosphere is burnable or explosive when it is mixed with oxygen, safety questions have to be considered.  
         [0004]     The quick-closing doors are equipped with a special gasket, which ensures safe operation when the vessel is on overpressure as well as when it is at underpressure. A risk is seen at ambient pressure in the vessel, when no pressure—difference is sealing the gasket.  
         [0005]     For safe use of the pressure vessels with quick-closing doors, in case of variable inner pressure from underpressure to overpressure and with burnable atmosphere, e.g. hydrogen, measurements have to be found, which avoid a leakage at ambient pressure, and which gave alarm, when a leakage should occur.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     The aim of the present invention is to propose a sealing system for quick closing doors for pressure vessels, enabling the disadvantages described above to overcome.  
         [0007]     Two different ways were found for safe sealing also for the use of hydrogen atmosphere in the pressure vessel.  
         [0008]     The first method is to use underpressure from both sides of the gasket to avoid penetration of hydrogen to the ambient air, or of air into the pressure vessel.  
         [0009]     The second method is to use overpressure between two special gaskets, which keeps the sealing tight, independent of the pressure in the vessel.  
         [0010]     In both cases the function of the sealing will be continuously measured, and a signal of any malfunction would bring the pressure vessel into a safe mode. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a cross section along the center line of the quick-closing door of a pressure vessel in the existing design.  
         [0012]      FIG. 2  is showing the sealing area in a larger scale.  
         [0013]      FIG. 3  is a cross section along the center line of the quick-closing door of a pressure vessel with underpressure design.  
         [0014]      FIG. 4  is showing the sealing area of  FIG. 3  in a larger scale.  
         [0015]      FIG. 5  is a cross section along the center line of the quick-closing door of a pressure vessel with overpressure design.  
         [0016]      FIG. 6  is showing the sealing area of  FIG. 5  in a larger scale.  
         [0017]      FIG. 7  is a front view of a quick-closing door of a pressure vessel. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     In the various figures, the same reference numbers designate identical elements, e.g. number  1  designates always the flange of the pressure vessel, even when the flange has different design in the  FIGS. 1-7 .  
         [0019]     The invention relates to a method of sealing quick-closing doors  2 ,  4 ,  5 ,  6 ,  7 ,  9  for pressure vessels  1 ,  10 ,  11  which are locked by a turnable ring  3  and sealed with a lip-gasket  8 , and waterjacket all around  12 ,  13 .  
         [0020]     The inner space  30  of the vessel contains the load which has to be treated, devices for heating, cooling thermal isolation, an atmosphere of protection-, or reaction-gas, gas circulating and gas guiding systems.  
         [0021]     Compared with the ambient atmosphere  31 , the inner pressure can be underpressure, overpressure, or as well ambient pressure.  
         [0022]     When the inner pressure is at underpressure, the ambient pressure presses the door towards the gasket and makes it tight.  
         [0023]     When the inner pressure is at overpressure, this pressure presses the lip of the gasket to the doorflange  2 , and also makes it tight.  
         [0024]     When the inner pressure is at ambient pressure, the sealing in undefined and this can create danger, if the atmosphere consists of burnable gas, e.g. hydrogen.  
         [0025]     According to the invention, a first method is suggested to get a safe sealing by using two gaskets  8 ,  21 , and an overpressure space  24 ,  25 , with a fitting  23  for a connection to a nitrogen source, which supplies a pressure in space  25 , which is 1, 2 to 2, 0 times so high, as the maximum pressure in the vessel  30 .  
         [0026]     The pressure in space  25  will press the lips of the gaskets to the flange  2  of the door, and will give tight sealing of the pressure vessel independent of the inner pressure. The pressure in space  25  will be continuously controlled during the whole process in the vessel, by connecting the pressure space via a fitting  22  with a pressure controller with alarm switch.  
         [0027]     In case of any malfunction the vessel will be brought into safe mode, depending on the actual stage of the process in the vessel, which can mean purging with nitrogen or backfilling with nitrogen and/or stopping the process.  
         [0028]     A second method is suggested to get safe sealing by having an underpressure space  15 ,  16 ,  18  around the gasket  8  on the flange  1  of the pressure vessel, and an underpressure space  26 ,  14 ,  17  around the gasket on the flange  2  of the door. This underpressure space will be connected by flanges  19 ,  20  with a suction pump, and the pressure will be in the range of 1-50 mbar, and will be continuously controlled. In case of a leakage at the gasket, the underpressure controller will give a signal to bring the vessel in safe mode, depending on the actual stage of the process in the vessel.  
         [0029]     For loading and unloading, the door can be opened after bringing the inner pressure and the overpressure or underpressure spaces at the gaskets to ambient pressure, turning the locking ring  3  with a hydraulic cylinder  41 , till the clamping teeth  44  are in the gaps  43 , by pulling the handle  42  and turning the door around the hinge  40 .