Theory and Design basic of static equipment engineering

TYPE OF STRESS OCCURS IN PRESSURE VESSEL:

1)  Circumferential stress

 It is stress which usually is defined as the total circumferential force exerted along the  entire radial thickness as shown in figure.   It is also known as hoop stress.  Due to this stress failure of pressure vessel is lengthwise.   It means entire vessel fails along length. It is given by equation    

                                                     
                                                                 σC=Pd/2t

               

 2)   Longitudinal stress:

 It is stress which usually is defined as the total longitudinal force exerted on ends of               vessel as shown in figure.   Due to this stress, failure of pressure vessel is perpendicular to its axis that divided vessel into two parts.   It is given by equation

                                         σL=Pd/4t

3)  Radial stress 

 This is force exerted into entire body of pressure vessel due to its internal pressure of fluid    contains by vessel

Note : From above definition of stress we can say that circumferential stresses are almost double of longitudinal stresses. so that failure is critical due to circumferential stress then longitudinal stress.