From experience, we know that a 9.5 bar pressure at 20°C is already high for a standard aluminum can and a standard can seal. Therefore, special attention should be given to can, valve and crimping specifications. The next step is for the aerosol can internal pressure maximum to follow the new European legislation for compressed gas: 15 bar pressure at 50°C (P50) for non-flammable products. This will be a significant challenge for existing standard can and valve assembly. In a clinch Clinching (called crimping in the U.S.) is a basic operation used to seal an aerosol— how does it work? Valve crimping is accomplished in two steps. The first step consists of compressing the valve and the gasket onto the bead, pushing the top of the valve against the can bead. The second step is to deform the valve mounting cup using the crimping clamps in view to keeping the gasket well compressed against the can bead. The aerosol can and the valve are then sealed together. The can bead is the metal curl at the top of the can onto which the mounting cup valve will be fitted. The contact height is a point defined by the center position of a round touch contact diam 3mm. The measurement point location is fixed as standard at 24,7 mm diameter. See the red spot in Figure A. The link is an assembly between the standard 1" opening of the can bead and the valve mounting cup. In order to control the assembly process, the bead dimensions are standardized and the contact height is defined as the distance between the top surface of the bead and the point of "hard contact." This is specified within the EN 15006 "ex FEA Standards 203." The resulting can seal is all about product parameters and process control. Can sealing relevant FEA standards: • FEA 202 Standard valve mounting cups. • EN15006 "ex FEA 203" Aluminum can opening and shoulder dimensions. • FEA 204 Can geometry specs. • FEA 216 Crimping. Dimensions of the bearing surfaces of clinching jaws • FEA 220 Aluminum can dimension/Filling. • FEA 222 Guideline for achieving optimum crimp conditions for containers with 1 inch opening. • FEA 401 Contact height. In order to optimize can sealing on an aluminum can with a 1" opening using liquefied gases, it is necessary—for aluminum cans with a diameter above 53mm—to check case by case. For specific applications, it is worth testing a milled or flattened bead. For aluminum cans with a diameter equal or below 53mm, there is no need for a milled or flattened bead. However, I do not advise using a milled bead for an aerosol can filled with a Dimethyl Ether propellant and hydro-alcoholic formula, as there is a risk of corrosion on the milled bead. With compressed gases, it is necessary to used milled beads for aluminum cans with a diameter above 45mm. For aluminum cans with a diameter between 40mm and 45mm, it is necessary to check case by case. For aluminum cans with a diameter below 40mm, there is no need for milled beads, especially on standard can diameters of 35mm and 38mm. 1: Can curl bead; 2: Valve mounting cup; 3: Gasket; 4: Crimping clamp Valve mounting cup, gasket, can bead curl and crimping clamp before crimping operation Crimping operation 1st Gasket compression 2cd Mounting cup deformation Valve mounting cup, gasket and Can curl bead after the crimping operation showing a slight gasket compression release Figure A November 2015 Spray 39
Spray November 2015
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