Earth-Laid Transport Pipes for -162°C to +400°C
Proceedings Publication Date
David Fröhlich
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Since many years, steel-in-steel pipelines (SIS) have proven to be safe for the conveyance of media at high temperatures of up to 400 °C and/or in difficult soils. SIS pipelines typically consist of a medium pipe made of steel, thermal insulating shells, bearings in the ring space and an encasing steel pipe with a corrosion protection coating as well as vacuum in the ring space.

The operation of FW-STEEL-CASED PIPE-IN-PIPE with vacuum in the ring space offers many advantages:
  • The system is permanently controlled as to its leak tightness
  • Heat losses are reduced by up to 40%
  • By the extraction of oxygen and humidity the possibility of corrosion of the medium pipe (outside), the encasingpipe (inside) as well as all fittings (e. g. bearings) is eliminated.
This well-known construction of SIS pipelines is qualified for the following conditions:
  • In case of high operating temperatures of 130 °C to 400 °C
  • In difficult soils (with high water content, in case of settling risks, flood areas)
  • For the crossing of canals, rivers, railway constructions, roads
  • For the conveyance of environmentally hazardous media.
Recently, the FW-KAMMER-PIPE was developed for high thermal and mechanical stresses. The FW-KAMMER-PIPE does not only protect the insulating material from humidity or penetrating water during operation, but in addition already at the time of laying. This is achieved by integrating the insulating material in vacuum sealed chambers welded on the inner pipe. The construction is carried out without thermal bridges.  Within the FW-KAMMER-PIPE the medium pipe bearings do not directly contact the encasing pipe. The pipes are supported as follows:
  • The chamber pipe is supported by bearings within the encasing pipe
  • The medium pipe is supported by bearings within the chamber pipe.
Each construction unit is provided with a chamber. The remaining ring space between the chamber pipe and the encasing pipe is also operated with vacuum. Penetrating media remain in the chamber and do not contact the encasing pipe. The media stay within the chamber (max. 16 m) and do not spread into the ring space. Thanks to this safety feature the FW-KAMMER-PIPE can be recommended also for sea-laid oil pipelines. In case of an encasing pipe leakage neither the medium pipe nor their bearing supports get into contact with penetrating water. With LNG pipelines a freezing of the ring space due to penetrating humidity can be excluded because of the avoided thermal bridges to the medium pipe.

For high or deep temperatures FW STEEL-CASED PIPE-IN-PIPE and FW-KAMMER-PIPE offer the advantage to apply proven technology to cutting-edge tasks. In this way, the application of state-of-the-art technology for the compensation of thermal expansion, such as the compensation in the bends of the route or the use of angular compensators, is possible.  By this, the FW-KAMMER-PIPE holds up the tradition of “TWO-IN-ONE“.

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