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Home / IS-Bauen / Projects / Timber / Staved pipes |
For a small water-power plant an approximately 2km long pressure pipe was needed. The underground pipe was made of staved timber in the straight sections and of steel in the curves or below roads. The staved timber pipe was fitted together using offset tongue and groove parts and steel rings for the staves. Because of the prestressed staves and the swelling capacity of timber the flooded pipe seals itself automatically. Short time after flooding the staved pipe a lubricating film is built, considerably reducing the flow resistance. Thus the flow resistance of the timper pipe even is getting better then the flow resistance of a steel pipe.
The straved pipes were calculated and verified using the german ATV-DVWK-standard and the german DIN-1052 for timber works. The stability of the cross section (ovalization) was verified considering the elastic bedding from the filling in the ditch and the opening gaps in the tongue-groove connections of the staved pipes. The afore described verifications involved the conditions to be kept during fabrication.
Near the uncercrossing of a street a leakage in the staved pipe occured. The manufacturer of the staved pipe confirmed the usage of irregular staves in this area. Too short staves have been delivered and to enlarge the staves they have been disconnected and lengthened by welding in an intermediate piece. It could be verified that the welding was not done professionally neglecting the problems of the zinc coated staves. With the failure of the first stave a domino effect occurred, resulting in the complete damage of the pipe in this area. An out-washed timper piece of this area showed increased branched structure but within the allowed tolerance for the specified sorting class.
Broken welding in the stave
Broken timber piece