ABSTRACT
The steel lined pressure shafts of Nathpa Jhakri Hydroelectric Project are one of the very high head (maximum design head 600.60m) Pressure shafts in the world. The material being used for steel liner consists of High Tensile Quenched and tempered steel conforming to ASTM-A-517 Grade F., Allthough various international standards recommend stress relieving of steel plates of thicknesses more than 38mm. but there have been variance of opinions about stress relieving of high strength quenched and tempered steels. This paper incorporates views on stress relieving as expressed by various steel manufacturers and organisations dealing in the same field. This paper also describes the concept to possibly avoid stress relieving of quenched and tempered high strength steels by adopting some welding techniques and suitably altering the design assumptions i.e reducing allowable stresses to count for the residual stresses caused by welding.
