although this would vary according to the specific application the number of layers of flat substrate 30 depends on the end use application but 1 12 layers are preferred it should be noted that the flat substrates comprising the tubular substrate are independent of each other and are preferably not permanently or semi permanently attached to each other through adhesives stitching mechanical or frictional cinching devices or the like this allows the lining system to slide and expand to accommodate the size and shape of the host pipe it is important that the width of overlapping portions are properly calculated so as to prevent expansion in use that would create a void or gap between layers the quantity orientation and thickness of flat substrates 30 in lining system 10 will depend on the end use specifications by way of example a lining system for a host pipe having a 24 u2033 diameter and 2 u2033 overlap on each longitudinal edge would require a flat substrate having a width approximately 79 4 u2033 this is calculated as the diameter of the host pipe 24 u2033 multiplied by pi 3 14 plus total overlap 4 u2033 referring to fig4 c tubular substrate 35 defines channel 45 which receives bladder 40 including air duct 50 bladder 40 is preferably constructed of an airtight temperature and pressure resistant material such as colamin 110 c with a pa pp configuration a thickness of 110 u03bcm and weight of 116 g m 2 from obermuhle polymertechnik gmbh of germany end caps 71 are fabricated to a specific size to allow.