scope:

This Technical Information Paper (TIP) provides guidelines for inspecting cylindrical, steam-heated pressure vessels made from gray cast iron (GCI) and used as rotating dryers in papermaking. These guidelines also apply to unheated GCI cylinders of the same construction. Large Yankee dryers typically used on tissue machines are not addressed in this TIP.

These guidelines are limited to inspection of the dryer pressure vessels themselves. Inspection of related steam and condensate piping, relief valves, bearings and gears, and doctoring devices is not directly covered. Nevertheless, the inspector should report unusual symptoms and conditions in those components and include that information in the inspection findings as soon as they are detected, in order to prioritize the suspect dryers for detailed inspection at the earliest opportunity in the "out of operation" mode (i.e., during a dryer shutdown).

This document complements TAPPI publication, Guidelines for the Safe Operation of Steam Heated Paper Machine Dryers (1). The inspection and NDT methods recommended in these guidelines generally apply to dryers made from other materials, including cast ductile iron and cast carbon steel, although dryers made from ductile materials (> 15% elongation) do not require the same degree of inspection and concern as dryers made from gray cast iron.

This TIP does not describe how to assess the significance of damage revealed by inspections. In that regard, API579-1/ASME FFS-1 "Fitness for service" (2), a post-construction code accepted by the National Board of Inspectors, provides rules for assessing fitness for service of pressure vessels, including a dryer with corrosion and wear damage. Guidelines in this TIP do not supersede local jurisdictional and regulatory requirements.