Table 1: Repair clave and autoclave advantages and disadvantages [14, 28, 29].

Repair clave (for the model in Figure 3)Autoclave

QualificationQualified for repairing composite partsQualified for manufacturing and repair of composite parts
Design considerationsFor a vessel of 4 m (12 ft) length and 0.9 m (3 ft) diameter less than 2 cm thickness neededThickness of vessel has to be large, as when pressure and temperature are applied together the deformation of the vessel is larger (e.g., for a 3 m (9 ft) autoclave, 0.6 m (2 ft) diameter, temperature < 343°C (650°F), a minimum 4.5 cm thickness is needed)
General installationThe only extra equipment it needs is a commercially available air compressorInstallation is an important consideration: foundation, cooling water supply, electrical supply, gas (if used for heating), and pressurization medium supply and exhaust arrangements.
Operating pressureMax to 75 psi (517 kPa)
Higher pressures can be achieved upon request
Max operating pressure to 85 psi (586 kPa)
Pressurizing systemThrough an external air compressor (e.g., for the model in Figure 3, 305 cm long, a 5 HP, 114 liters (30 Gallon) pump fills the clave at a rate of 1 psi/min)Three pressurization gases are typically used for autoclaves: air, nitrogen, and carbon dioxide
Heating systemThrough heat blankets. Heat blanket thermal uniformity is essential for the curing quality. If the heat-up rates for the heat blankets are not respected, cracks can appear in the structuresGas heating is regularly used in autoclaves with maximum operating temperatures of 450 to 540°C (850 to 1000°F). Steam heating is often used for autoclaves operating in the 150 to 175°C (300 to 350°F) range. Most small autoclaves (under 2 m, or 6 ft in diameter) are electrically heated. Gas circulation provides mass flow for temperature uniformity and heat transfer to the part load. However, gas stream can cause thermal or mechanical shock on the manufactured parts
Electrical system“Plug-in wall” (e.g., electrical supply: 90 Volts AC to 264 Volts AC 47 Hz to 63 Hz, 0.15 Amps; power 50 Watts)Even small autoclaves are not designed to just plug in and run (e.g., electrical supply: 230 Volts AC/50 Hz (110 Volts on request); power: 450 Watts)
Vacuum systemSimilar systemSimilar system
Control systemSimilar systemThe cure cycle is controlled by feedback from thermocouples, transducers, and advanced dielectric and ultrasonic sensors. Computer-controlled systems are used, but they are far more complex
Loading systemSimilar systemSimilar system
SafetyHas a pressure relief valve in case of overpressure; because the temperature is separated from the pressure, there is a decreased risk possibilityUse of pressurized gas to cure has redundant safety features on any autoclave because of the potential seriousness of any malfunction
AffordabilityThe electrical system, reduced need for safety features, reduced thickness of vessel, and therefore decreased manufacturing costs
Results from a market investigation analysis are indicatively presented to give a picture of the low-cost press-clave processing:
sales price:  70%  ±  10% less expensive,
operation cost:  80%  ±  10% less expensive,
maintenance cost:  30%  ±  10% less expensive
High costs can come from various factors; electrical consuming system, gas used for pressurization (nitrogen can be very expensive and air is very dangerous), requires redundant safety features
Repaired/manufactured partsLimited geometries that can be created/repaired due to the 2D heat blanket geometry; also, usage of heat blankets limits the number of plies that can be completely curedTheoretically, any 3D geometry can be manufactured. Higher number of prepreg plies can be processed at the same time. However, when used for repair, areas not being repaired are subject to high temperatures which may cause deterioration to existing bonds and finishes