Fastening method and matters needing attention of ConFlat flange
Dec 31, 2021| Fastening method and matters needing attention of ConFlat flange
Choose the right gasket, silver-plated gasket is strongly recommended for ultra-high vacuum applications where baking at high temperatures is required. For applications where baking temperatures exceed 200°C, it is recommended to use silver-plated bolts (silver as a lubricant) or apply a high-temperature lubricant to the threads to prevent thread damage or bite. When handling and installing ConFlat flanges, dust-free gloves are recommended during assembly. Sweat stains, oil stains, and other residues on hands, even the slightest fingerprint, can affect the efficiency of vacuuming. Carefully check flange knife-edge for notch, scratch, then place gasket in flange groove, make sure gasket is in place correctly. If the flange face is vertical, the following auxiliary tools can be used to prevent the gasket from falling or misplacing during installation.
Tighten all bolts individually by hand, then tighten the bolts 1/4 to 1/2 turns at a time according to the principle of cross tightening until appropriate torque values or the two flange planes contact each other. High and ultra-high vacuum equipment is usually a precision instrument with high requirements on the location of each part of the equipment, which may result in a partial concentration of parts or a lack of wrench space in a particular location. In these areas, ordinary nuts can be replaced by Plate nuts as follows. When baking, pay attention to temperature control, the metal gasket in the process of gasket deformation will produce work hardening, which makes the gasket will produce a certain "elasticity", can still maintain the seal when the temperature changes dramatically. There is evidence that prolonged baking to 550°C partially anneals the copper from its work-hardened state and loses its elasticity, resulting in leakage of the flange as it cools.
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