Steel-in-steel pipe
Steel-in-steel pipe — SIS-pipe
SIS-pipes are suitable for temperatures up to 400°C and can transport various media such as thermal water, steam, condensate, thermal oil or environmentally dangerous media. They are a reliable solution for medium transport, even in difficult outdoor conditions – with extensive design and detection measures to ensure a high level of safety and efficiency. They are used in our areas of application listed below, in geothermal energy and in secondary networks for the transport of hot water or steam.
Product information
Steel casings have an inner steel pipe that carries the medium to be transported and an encasing steel pipe.
In general, between these two pipes there is thermal insulation made of mineral wool shells, which reduce heat losses and the temperature of the outer casing. The service pipe is freely movable. With local fixing between the inner and outer casing at the fixed points, the direction of the temperature-related length change of the inner pipes is predetermined. No external constructions or concrete foundations are required at the fix points of the SIS-pipes.
The inner- and encasing pipe connections on site are made using conventional welding techniques.
Key-features
- High stability and strength due to the inner- and encasing pipes made of steel
- Project-based calculation, design and manufacturing with high and route-related degree of off-site manufacturing
- Available with single, twin or multi inner pipes
- Route and temperature-dependent expansion concepts
- Special solutions as pipe bridges
- Ground water tightness thanks to the welded outer casing
- Inner pipes: seamless pipes to EN 10216 or welded pipes to EN 10217, materials P235GH to P355NH, austenitic steel in case of condensate or environmentally dangerous fluids
- Encasing pipes: welded pipes to EN 10217, materials P235TR1 to P355N, austenitic steel for environmentally dangerous media, outer anti-corrosion coating made of PE to DIN 30670 - N or S - n or v, PP coating to EN ISO 21809, paint coating
Product Specifications
In various industrial and infrastructure applications, which have high temperature, pressure and mechanical loadability requirements.
- Standard lengths up to 16m, longer lengths by arrangement
- SIS- components such as bends, fix points, encasing pipe reductions, wall ducts, vacuum-tight enclosures are integrated in prefabricated SIS- units.
- Length of the SIS- units according to the routing
- Fitting lengths by arrangement
The mineral wool insulation shells are located between the inner and encasing pipe and serve to reduce heat losses and to reduce heat flow to the outer casing.
The project-related technical design and economic planning for SIS-lines includes the concept and construction for both underground and above-ground laying, including the calculation of heat and pressure losses and the development of expansion concepts and the dimensioning of the materials. This also includes the planning of prestressing techniques, evacuation of ring space, quality management and comprehensive testing and documentation procedures.
There are various types of laying, including conventional underground laying, trenchless methods (e.g. HDD) and above-ground installation.
The pipes are often operated with vacuum in the ring space to minimise heat losses, to monitor tightness and to prevent corrosion. Laying of SIS-lines requires significantly less space than concrete sewers.
Operation with a vacuum in the ring space reduces heat losses by up to 30% and, by excluding oxygen and moisture from the ring space, permanently prevents corrosion. In addition, the tightness of the pipe is ensured, as the ring space between the inner and encasing pipes is sealed vacuum-tight at the ends and at all connections and operating safety is increased by vacuum sections and a vacuum pumping station.
- Natural compensation in the route trenches
- Compensation with U-bends, axial or lateral expansion joints
- Reduction or prevention of the temperature-induced change in length of the inner pipes by thermal prestressing or a combination of thermal prestressing and natural expansion
The following certificates are available for the steel outer casing manufacturing:
- EN ISO 3834-2 (Comprehensive quality requirements for welding)
- Module A2 (Internal production control plus supervised pressure equipment checks at random intervals according to directive 2014/68/EU)
- AD 2000 - HP0 / HP100R (Certified manufacturer of pressure equipment and pipes according to the rules of AD 2000 - HP0 / HP100R)
The internal production control and regular external checks by a notified body as part of the certifications ensure the highest quality and safety.
Please let us know if you have any questions about our products.