PREFACE This chapter is one of a series which make up the manual@ Guide for Inspection of Refinery Equipment. It has been formulated by the joint effort of the Subcommittee of Refinery Inspection Supervisors and the Designers' Subcommittee on Refinery Inspections@ and has been reviewed and approved by the Committee on Refinery Equipment. The information contained in this publication has been arranged in its present form as a means of facilitating continuity of presentation and convenience of reference. It does not constitute@ and should not be construed to be@ a code of rules@ regulations@ or minimum safe practices. It is not intended that the practices described in this publication supplant practices that have been proven satisfactory . Nor is it intended that this publication discourage innovation and originality in the inspection of refineries Users of the publication are reminded that no book or manual a substitute for the judgment of a responsible engineer.