strength when not fully supported to withstand pressures within the pipes 3 5 during use without damaging or separating from the pipe ends such a gasket has been found to be extremely efficient and appropriate in hygienic food processing systems which in the past have relied heavily on elastomeric gaskets application_number US 88295701 A description with reference to fig1 of the drawings a de mountable pipe joint 1 of an hygienic food processing system is shown the pipe joint 1 joins the ends of two adjacent flow pipes 3 5 each pipe carries a flange 7 9 adjacent its end which is soldered to the outside of the pipe 3 5 in the embodiment shown each flange 7 9 includes an outer screw thread 11 13 which mates with a ring nut 15 as shown although not necessarily the preferred way of drawing the two pipe ends together the ring nut 15 can have two threads of different pitches for engaging the screw threads 11 13 of the two different flanges 7 9 as a result rotation of the ring nut 15 can draw together or separate the two flanges 7 9 in an accurate fashion other ways of securing the two flanges 7 9 together such as by using a chamfered clamping ring tightened by a wing or butterfly nut can of course be envisaged by those skilled in the relevant art a gasket 17 is positioned between the ends of the pipes 3 5 and the flanges 7 9 as seen more clearly in fig2 4 the gasket 17 is annular in shape and comprises an inner ring 19 of polyetheretherketone peek or any other appropriate plastics material.