Introduction

Deposits or scale on the water/steam sides of boiler tubes result from in situ oxidation of the tube material, transport and precipitation of corrosion products from other locations within the system, and precipitation of mineral impurities from the boiler feedwater. Because boiler deposits or scaling can interfere with efficient operation of the boiler and lead to lost revenue from boiler tube failures, periodic cleaning of pertinent boiler components is performed. One effective tool that has been used to determine whether boiler cleaning is required involves deposit removal and quantification from areas in the steam generator where the heaviest and most complex deposits have accumulated.

An Electric Power Research Institute (EPRI)⁽¹⁾ report¹ presents chemical cleaning guidelines related to deposit weight results for mechanical scraping and solvent removal methods of deposits from fossil-fueled steam-generating boiler tube components.

There are three methods typically used for determining the specific deposit mass loading (DWD) from boiler tube surfaces: (a) mechanical scraping and vibratory tool cleaning; (b) chemical solvent cleaning; and (c) glass bead blasting cleaning. The first two methods are described in ASTM⁽²⁾ D3483.² The third procedure is a more recently developed method that is similar in approach to mechanical scraping but utilizes a different medium.3

⁽¹⁾ Electric Power Research Institute (EPRI), P.O. Box 10412, Palo Alto, CA 94303.

⁽²⁾ ASTM International (ASTM), 100 Barr Harbor Dr., West Conshohocken, PA 19428-2959.