Sheaths for Prestressed Concrete

A few decades have passed since the early ideas for prestressing concrete. Today the use of prestressed concrete is a tried and tested construction technique, indispensable for modern projects. The requirements for the prestressing processes are laid down in national and international regulations. This also includes the execution of prestressing work, including the applicable requirements for the companies that carry out the work and for specialized suppliers.

Accordingly, the requirements for sheathing pipes to hold prestressing steel are clearly defined and regulated in EN 523. Analogously to this European standard, the sheaths are subject to certain regulations relating to material and technical requirements. The high standards of quality of the HYDRA sheathing pipes are therefore maintained by monitoring through continuous production checks.

In order to document this quality standard independently, an extensive series of tests was carried out on the longitudinally welded pipes at the material testing institute at the University of Karlsruhe in 2008.
This affords us the chance and the security of applying the “CE mark” to HYDRA sheathing pipes in the future, and supplying our customers with the corresponding declaration of conformity.  This in turn has that advantage of allowing our customers to document the required quality accordingly to construction supervisors and approval authorities.

Shape of the Profile

By means of an appropriate design, Hydra sheaths allow for an easy and total filling of the cavities between the tendons and the sheath walls with compressed mortar. This guarantees corrosion protection for the tendons and the connection required for the transmission of force from the tendon to the sheath as well as from the sheath to the surrounding structural concrete.

Your Advantage:

  • Corrosion protection
  • High expenditures in time and money
  • Collecting of air bubbles to avoid their contact with the prestressing
  • Sufficent shearing connection by sufficient profile heigth
  • Short installation periods



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Schraubverbinder für längsgeschweißtes Rohr
Das wendelförmig umlaufende Wellenprofil der Hydra Hüllwellrohre dient als Gewindegang für die Verbindungsteile. Bezüglich der Dichtheit ist zu beachten, dass nur durch Bandagieren oder gleichwertige Maßnahmen (Stülpkragen) eine dichte Stoßstelle gewährleistet ist.

cold-rolled strip DC 01,
EN 10139,
thickness tolerance
DIN 10140

Packed in bags or cardboard boxes, labelled with DN and Quantity

The spiral corrugation of the HYDRA corrugated sheaths serves as thread for the connecting parts. The only way of guaranteeing leakage resistance of the sheath by means of a tight butt joint is to wind a strip of insulating material around the joint or to apply a design which has an equal effect (collar).

For the transition from the sheath to the tensioning grip, we recommend the use of sheaths of the next nominal diameter but one as telescoping pipes. Our product range also includes adapters for coupling and anchor points. These adapters are available in fixed and movable version, with threaded fasteners for connection with the sheaths or with a snap-on connection for sleeves or telescoping pipes.

Attachable discharge parts have turned out to be very
appropriate in practice for the venting and draining of the
prestressing ducts. These discharge parts have the shape
of half shells whose corrugated profile fits the corrugation
of the sheath. The discharge fitting is designed for the
connection of a plastic hose. Further accessories, such
as plugs or gate valves are available for this purpose.