URI H.E.P. - KASHMIR, INDIA
STEEL TUNNEL LINING (STL) OF TWIN VERTICAL SHAFTS


WORKSCOPE
Whessoe projects are responsible for the design, supply, fabrication, installation, and painting of two 5.0m dia.steel tunnel linings each consisting of a rectangular to round transition, horizontal straight, top and bottom 90 degree bends, 200m deep vertical shaft, bifurcation, horizontal straights, bends and concentric reducers.

Project Data
Location Kashmir, India
Client Kvaerner Boving Ltd.
Owner National Hydroelectric Power Corporation
Contract Period 1992 - 1996
Contract Value £7.0 million
Contract Tonnage 3200 te
Design Code BS5500
Material Specification LT boiler Quality Plate - BS1501-223/224-490A LT30/50
Diameter Range 2.75m - 6.8m
Thickness Range 20mm - 80mm
Post Weld Heat Treatment Bifurcation sickle plate assemblies


 
DESIGN / DRAWINGS

The design was completed by Whessoe to the Clients specifications with special consideration given to the finite element analysis of the bifurcation and bottom bend sections in order to minimise the amount of Post Weld Heat Treatment required.

METHODOLOGY

There were many factors to consider when determining the execution of the construction works including:

  • Remote location
  • Treacherous transport routes
  • Avalability of skilled labour
  • Underground Handling to limit size of excavation
  • Access in vertical shafts
  • Safety underground
With such restrictions it becomes necessary to ensure the design, fabrication and installation proceses were fully integrated.



Lobsterback Installation sequence - bottom bend


 
SITE ESTABLISHMENT

As it was not possible to transport pre-fabricated sections to the site location, a fabrication facility was erected on site adjacent to the installation adit on ground built up using tunnel spoil. Foundations were laid and a large fabrication shop was erected.

FABRICATION

The workshop was serviced by two EOT cranes, and fitted out with a vertical plate rolling m/c, cutting tables, rotators, automatic welding m/c's preheat facilities, assembly jigs, and access platforms. Alongside the workshop a temporary furnace was constructed to carry out the PWHT of the bifurcations.

Some plate preparation work required the use of UK computer controlled marking and cutting equipment. This included the transition plate sections which were fabricated piece small and trial erected, in the UK prior to shipping site.


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