The Dual Barrier System waterproof telescopic covers use telescopic covers and bellows that are heat sealed together.In hydrostatic support machines, typically the large boring machines, a film of oil is used instead of the traditional rails with rollers and balls. The machine runs on this very special layer of hydraulic oil, characterised by a very high purity, an indispensable condition to guarantee performance. On the other hand, these machines also use the usual coolant to cool the tool: it is therefore necessary to be absolutely certain that this oil cannot in any way penetrate the support system, contaminating and compromising the entire system with severe damage. The standard solution generally adopted is “double insulation” that is a heat-sealed bellows under a telescopic cover.Each of these systems has its own rails, so it is necessary to ensure perfect alignment between them, not to mention the time required for a double assembly and the negative repercussions on the space that is always scarce on the machines. PEI, being aware of these problems, has developed an original solution, which integrates fabric bellows together with a telescopic steel cover. If the necessary technical and safety conditions are present, the Dual Barrier System telescopic covers can be made walkable.