PLN Besai Steel Liner Installation Report

1. Project Data

- Name of Project:    Besai Hydroelectric Power Project, Steel Liner Installation

- Location: Jl. PLTA Way Besai Desa Sukapura Sumberjaya, Lampung Barat

- The Employer: PT. PLN (Persero)

- The Engineer: Nippon Koei Co., Ltd. in association with PT. Indra Karya and PT. Kwarsa Hexagon

- The Contractor: Sakai Amarta Joint Operation (This Report was written by Site Manager Akihiko Takase)

- Scope of Work

    One (1) lane of steel liner

- Design Data

    Concrete Tunnel Internal Diameter: 4,300 mm

    Internal Diameter of Steel Liner: 4,100 mm

    Thickness of Steel Liner: 20 mm

    Length of Steel Liner: 300 m

    Weight of Steel Liner: 622 ton

    Maximum Static Head: 83.161 m

    Maximum Water Hammer: 16.9 m

    Design External Pressure: 0.4903 MPa (5.0 kgf/cm2)

    Backfill Mortar Filling Pressure: 0.1961 MPa (2.0 kg/cm2)

- Special Site Condition

    Erection site is 4 km far from portal

2. Construction Schedule

    Please refer to the attached "Work Schedule". < WorkSchedule.xls >

    Particularity of the Besai Steel Liner job was very short construction period.

    Our construction period was 9.3 months as a result. But it included "Other Civil Remedial Work" that is totally different from our job. If we exclude it, total duration will become 8.2 months.

    We did not occupy the tunnel before 20 August 2000, 3.7 months after start.

    Therefore, if a tunnel is available for 4.5 months, we will be able to install 622-ton steel liner in a horizontal tunnel.

3. Secret of Short Construction Period

    In order to complete the job within the very short construction period, we took the following methods.

- We applied two (2) shifts 20-hour per day working hour system.

- A ring was divided into three (3) segments and they were expanded and made to complete ring at site using specially designed hinges.  

- We used a specially designed pipe transporter for the long tunnel access.

- We prepared spare machines for machine trouble.

- We fabricated the pipe at three (3) factories.

- We separated unit ring fitting and girth fitting at site in tunnel.

- We applied Ultrasonic Test for welding joints.

4. Photos

A Bulkhead and Two Sets of 900mmφ Contrafan

kept clean air in the 5 km length tunnel

Semi-assembled Ring at Intake Area

Lowering Semi-assembled Ring at Inlet Portal by 20-ton Truck Crane

Ring Lowering on Incline Near Intake Using 5-ton Winch

8-ton Forklift Lowering on Incline

Wheel of Specially Designed Pipe Transporter Which Has Self-Steering Controller

Ring Arrival to Erection Site

Expansion of Ring By Both Forklift and Chain Block

Expansion of Ring Completed






Girth Fitting

Welding

Ultrasonic Test for Welding Joints

Liquid Penetrant Test for Welding of Grout Plug Closure

End of Document