Flangebolts for Gas Turbine Exhaust
A Norwegian Patent, developed to optimize the relation between tension lenth and the flange with gasket thickness.
Leakages from turbine exhaust ducting are a common operational problem, often caused by loose duct flange bolt connections. Leakages in gas turbine exhaust ducting may occur after only few hours of operation, and may cause damages and unwanted conditions such as:
Cause of problemIn a typical flange bolt connection, the bolt clamping length is equal to the thickness of the flange being bolted. During the turbine start sequence the duct temperature will rise and result in a growth in the flange thickness.
Having a time differential in temperature rise compared to the duct flange the bolt will be exposed to a stretch equal to the difference in thermal growth of the flange and the bolt. The bolt resultant stress, being the bolt prestress and the additional stress due to thermal stretch, may cause plastic deformation in the bolt material.
When the duct system is in stable operating temperature, the plastic deformation of the bolt plus the bolt thermal growth results in bolt relaxation and reduced gasket compression.
Short bolt connection with clamping length equal to flange thickness:
The solutionBy using Thermobolt, a more slender bolt connection with increased clamping length is achieved. Design and material selection is customized for each specific application.
Thermobolt with long clamping length reduces thermal stretch:
The productTypical design parameters for Thermobolt are:
Delivery program for Thermobolt Exhaust Duct Bolting:
Thermobolt Material Selection
Telephone: +47 668 03 390
Fax: +47 668 03 391