This invention relates to a process for filling cavities, in particular the cavity between a conduit pipe and its jacket, with insulating material by introducing a liquid foamable reaction mixture, in particular one which forms a polyurethane foam, into the cavity. The apparatus used for this process consists of containers for the reactants from which pipes with pumps lead to a mixing head.
It is known to fill narrow cavities and insulate pipe conduits by using a mixing head with an insertion lance which is pushed into the gap between a pipe and its jacket and to slowly withdraw the mixing head while the cavity is filled with the reaction mixture. Although this method ensures that the mixture will always be introduced at the correct position so that it flows directly to the points where it is required to foam up, such an apparatus is very inconvenient to handle and is only suitable for short pipes of up to about 5 meters in length. For longer pipes additional equipment is needed to support the lance. Additionally, the lance must not be too long because the reaction may start to take place in the lance. Another serious problem with this apparatus is the cleaning of the lance between the individual operations. The loss of material and time is relatively high and consequently the apparatus is uneconomical.
It is therefore an object of this invention to provide a process which is suitable for filling longer cavities and which is designed such that the time at which the reaction mixture starts to react is accelerated from the beginning of the filling procedure to its end so that the mixture foams up simultaneously over the length of the cavity. The process may be employed, for example, for filling long, slender hollow bodies such as structural elements, safety planks or tubes with foam. When used for insulating pipes, the foam will adhere on all sides to both the pipe enclosed by it and to the jacket around it. In addition, the process should be applicable to seamless pipe jackets.