Abstract: An insulated pipework system comprises an outer sleeve, an inner flow pipe and one or more evacuated volumes in the space therebetween defined by annular plugs of a setting polymeric composition such as epoxy resin or a syntactic foam, typically at regular intervals along the length of the pipeline. The epoxy resins (for example) are ideally of sufficient rigidity to allow effective transfer of longitudinal forces between the inner and outer pipes. Thus, the evacuated volumes will themselves be annular. Other plugs of different orientation (for example longitudinal) could be included to subdivide the evacuated volumes further. The plugs allow the space between the pipes to be partitioned so that air can be evacuated from the sections so formed to provide the vacuum that acts as the insulating layer. Also, the plugs replace the need for bulkheads in that the partitioning of the inter-pipe space provides the desired water-stopping means.

Abstract: The application discloses an insulated pipework system comprising an outer sleeve, an inner flow pipe and an insulating layer within the space therewith, characterized in that the insulating layer comprises at least one discrete block of a first insulating material substantially surrounded by a second insulating material in particulate form. This enables the discrete blocks of the first insulating material to provide the majority or all of the necessary insulation, whilst the particulate second insulating material can be packed around the first material in order to provide the necessary shear force transfer. It is preferred if the first insulating material has a lower thermal conductivity than the second, more preferably a thermal conductivity of less than half of the second. It is still more preferred if the thermal conductivity of the first material is less than 35% of the second, yet still more preferably less than 25%. It is also preferred if the first insulating material is silica block.

Abstract: Two embodiments of insulated pipework system are described. The first comprises an outer sleeve, an inner flow pipe and insulating material within the space therebetween and is characterised by the use of a longitudinally compressed elastomeric member in the space between the inner and outer pipes as the primary means for transferring longitudinal forces between the inner and outer pipes. The second comprises an outer sleeve pipe, an inner flow pipe, an insulating material within the space therebetween, other than hollow alumina-silicate microspheres, wherein a longitudinally compressed elastomeric member is provided at intervals in the space between the inner and outer pipes. Compression of the elastomeric member is preferably by way of rigid plates on either side thereof which compress an the elastomeric member. For example, bolts can be passed through bores in the plates and elastomeric member and tightened thereby to compress the said member.