Abstract
Big scale penstock for the hydropower station is mostly an embedded type to be constructed in the underground tunnel. In addition, due to the increase of the penstock capacity, the superior quality of the joint performance is required with the steel materials of heavier thickness and higher strength.
For the construction of such embedded penstock of big scale, it is essential to overcome the severe conditions of the field welding work under high temperature and high humidity in the tunnel for securing superior joint performance, and to minimize the sectional area of the tunnel for expediting the construction periods and costs of civil work.
To fullfil above two requirements for the field welding of penstock, automatic GTA welding method with remote control system and one side URANAMI welding method with backing metal were developed.
The former was developed to enable the excellent joint performance under the severe field conditions, and the latter was developed to enable the field welding only from the inside of penstock in the narrow tunnel.
