THERMALSHOCK

 

   THERMALSHOCK RESISTANCE DIAGRAMS

 

     When a glass-lining or its steel support base is subject to sudden changes in

     temperature on one side only, stresses are induced in the glass layer so that if above

     a certain limit can cause to rupture or fail. This limit is generally the tensile

     strength of the coating, which as in the case of glass is much lower than the

     compressive.
     To widen the range of permissible sudden temperature changes, the composition

     of the glass is arranged so that after coating the glass layer is uniformly pre-

     stressed in compression.

 

 

     THERMAL SHOCK DIAGRAMS FOR THE GLASS-LINING TYPE 808, 809 AND 805

 

 

    GLASS-SIDE SHOCK

 

 

   

 

    JACKET-SIDE SHOCK

 

 

 

 

 

Tp = Temperature of glass-lined wall

 

Th = Temperature of the heating fluid

 

Tk = Temperature of the cooling fluid

 

Tw = Temperature of glass-lined wall

 

 


     The diagrams that follow show the maximum/minimum allowable temperatures for

     808, 809 and 805 glasses for all the types of thermal shock that can occur, i.e. 

 

  • introduction of hot product directly onto a cold glass lining
  • introduction of cold product directly onto a hot glass lining
  • introduction of hot fluid into the jacket when the glass lining is cold
  • introduction of cold fluid into the jacket when the glass lining is hot 

 

     The thermal shock diagrams have been derived from laboratory tests taking into

     account a suitable safety margin and have then been confirmed directly on working

     vessels.

    

 

 

    INFORMATION REGARDING INTERPRETATION OF THE DIAGRAMS
            
  • When thermal shock occurs on the jacket side, it is assumed that the temperature
    of the glass-coated wall is the same as that of the product.
  • If in the jacket a heating fluid is used that has a heat  transfer coefficient less
    than that of steam (e.g. diathermic oil), greater differences in temperature can be allowed.