Process Industries

Dependencies of the possibility of pitting on temperature and the chloride and sulfate contents of the environment were determined for stainless steels UNS S31726 and UNS S31254 using laboratory experiments with a strongly oxidizing chlorine dioxide environment.

Austenitic stainless steels are susceptible to caustic stress corrosion cracking (SCC) above 121°C.  When sulfides are present in caustic solutions the SCC has been reported to occur at lower temperatures. This paper discusses a study of the role of sulfide in caustic solutions on SCC of austenitic stainless at T=~50°C.

The approach to the commissioning of a heat-recovery steam generator in the industry has varied from project to project. One school of thought contends that no chemical cleaning (or minimal) is required. The second school of thought contends that a complete chemical cleaning is required. This report discusses these differences, and a properly designed and well executed cleaning with desired results.

Thermoplastic and thermoplastic lined RTP equipment (Dual Laminates) have been used for years in the Chemical Process Industry. Compiled in this paper are several of those applications that have been successful and those that have not. Reasons for either success or failure are given and how to avoid problems in the future is discussed.

In the Chemical Process Industry every type of the C-series (NiCrMo Alloys) is used. These materials are being replaced by higher alloyed types such as Alloy 22 or Alloy 59.  This paper will examine the behaviour of the welding consumables FM 22 and FM 59, together with the base material combinations of the second series, which are used in the Process Industry.

Under-deposit corrosion is a common mode of failure in boiler tubes. Mechanisms include phosphate attack, caustic gouging, hydrogen damage, and wall thinning due to metal loss. Many aspects of these mechanisms and their mitigation are well-understood, while certain specific details remain uncertain or subject to controversy.

If the iron concentration in an alkaline chelant boiler cleaning solution reaches a high value when dissolving magnetite, it sometimes continues to increase rapidly and not level, indicating corrosion of the boiler metal. A laboratory study of “runaway iron increases” investigated the cause and the best mitigation methods.

Corrosion and stress corroson cracking (SCC) susceptibility of duplex stainless steels (DSS) depend on alloy composition, microstructure and temperature. In this study the effect of sulfide containing caustic environment and material properties (DSS composition and microstructure) on the corrosion and SCC of DSS in pulping liquors (synthetic white liquor) was evaluated.

Stress assisted corrosion (SAC) is a major concern for kraft recovery boilers in the pulp and paper industry. A water leak can cause a smelt-water explosion in the boiler. A number of carbon steel tubes showed a deep decarburized layer on the inner surface (water-touched) and also an unusually large grain size at the inner tube surface.

An equipment integrity management system (IMS) requires focused effort from many disciplines to ensure that it is fully integrated and sustainable.  The systems necessary to manage inventory, schedule inspections and capture inspection data are key elements of the IMS.

This paper traces the development of the superaustenitic grade 254 SMO (UNS S31254) as a solution to recurrent corrosion problems within the pulp and paper industry.

This paper describes three corrosion case histories caused by overconfidence and lack of thorough understanding of the corroding systems. 1. Exchanger tube failure. 2. Hydrogen induced cracking. 3. Inappropriate mixing of process streams.