Home > Bag penetration fittings for composites
There are various ways of providing a vacuum or resin feed penetration through a vacuum bag. One solution is to run a tube in under the perimeter of the bag and sealing the tube in the perimeter mastic. While generally less reliable from a sealing perspective, the bag film can also be penetrated by a tee or elbow mastic sealed through a hole in the bag film. More reliable bag film penetrations are conical infusion ports or multipart fittings specifically designed for the purpose. Conical infusion ports provide a rigid and easily sealed socket for polyethylene vacuum tubing. If made from a suitable plastic and treated with mould release, these will be reusable many times in resin infusion applications. Multipart bag fittings are not suited to infusion applications because they are not easy to clean, but they are often a good choice for vacuum bagging over wet laid laminate and pre-preg.
We offer both one-piece plastic fittings and multipart screw together bag fittings.
Our infusion ports are machined from solid ultra-high molecular weight polyethylene (UHMWPE). This material is resistant to almost all composite industry solvents and resins. These fittings are designed primarily for resin infusion. If treated prior to each use with a liquid mould release, these fittings will be reusable many times. Infusion ports are placed on the laminate prior to application of the bag but, usually, they are not penetrated until after the bag has been evacuated. The normal procedure is described below.
Our multipart bag penetration fittings are designed for applications where resin will not contact the fitting, i.e. in applications where the limited amount of excess resin can be absorbed in bleeder fabric prior to reaching the fitting. Multipart fittings are not suited to resin infusion use.
At present, our bag fittings are only made to suit ½” to 13 mm outside diameter (OD) tubing directly. To fit other tubing sizes, adapting tubes will be required. (Adapting to other tubes sizes is usually quite simple. See Vacmans note “Joining polyethylene tubing”.)
Multipart bag fittings are located and sealed to the bag film prior to evacuation of the bag. The typical procedure is described below.
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