Simple way of draining is to create the least resistant pathfor the water to flow. That is, provide a sump just below theautoclave heat exchanger and then pump back the water tothe cooling water sump. This also reduces water wastage andprevents hot water/steam entering the cooling tower.The modern autoclaves employ seamless stainless steel(SS) tubes with extruded fins on the tube, which minimizepressure losses. These SS tubes have high heat-transfer areaper unit volume of space they occupy.6. Pressurization SystemThe system must ensure that the required pressurizationrates in the autoclave are met. The average pressurizationrate in modern autoclaves is 2 bar/min. Nowadays, manyautoclaves use nitrogen as the pressurization medium insteadof air. This is because the autoclave cure consumables arehighly inflammable in the air medium due to the presenceof oxygen. There have been several reports of autoclave fireresulting invariably in the loss of the component. Thoughthe nitrogen medium ensures fire-free autoclave cure cycles,care must be taken to avoid danger to personnel (possibilityof asphyxiation) in nitrogen environments due to the loweroxygen levels.The nitrogen gas pressurization system consists of aprimary compressor, nitrogen plant, booster compressor,storage tanks, and associated piping circuitry as shown inFigure 7. The primary compressor takes in the air fromthe atmosphere and pressurizes it to 7 bar(g). The nitrogenplant receives the air at 7 bar(g) and by a process knownas Pressure Swing Adsorption (PSA) isolates nitrogen fromthe atmospheric air. The PSA has emerged as one of thepopular methods of producing nitrogen. The nitrogen purityproduced by this method is of the order of 99%, which isadequate for curing of aerospace polymeric composites inautoclaves. The nitrogen, thus, isolated is further pressurizedusing a booster compressor to higher pressures, typically 17–22 bar. Higher pressure is required to create suﬃcient pres-sure differential in order to meet the required pressurizationrate. The nitrogen storage tanks are sized in such a way thatthe free-air delivery (FAD) of these storage tanks is 2.5 timesthe FAD of the autoclave.For example, the FAD of a 200-cubic-meter autoclaveoperating at 7 bar(g) would be 1400 cubic meters andconsequently, the FAD of the nitrogen storage tanks wouldAutoclaveHeat exchangerC tSump for H.E drain waterMain sumpPumpsCBlower motorFanPumpsCooling towerControl valveFigure6: Schematic of cooling system.Nitrogen generation plantNitrogen filter Exhaust silencerNitrogen reservoirsAutoclave shellSeal pressurization tank instrumentation Pressurization tank To pneumatically operated instrumentsPneumatic loading bridgeTo atmosphereFigure7: Schematic of pressurization system.