A substack reader (thanks Alex) recently asked me two questions that I think deserve a proper answer, because they come up more often than you'd think in the field. Questions: 1. When repairing a rotor, are you trying to match the original hardness of the material? 2. Are there situations where you would intentionally coat a section of the rotor with a harder material to prevent future damage? I will start by providing a very short answer to your questions before diving into deeper...

When a turbomachinery failure happens, the questions that follow are expensive ones... I have had the privilege of working for an independent service provider of turbomachinery repairs for almost 25 years. I work at a place that has built itself to be like a hospital for machines. I use this analogy when giving tours to visitors. It is easy to describe what we do if I say: “Imagine this place is like a hospital. Most of our work we do, can be considered routine, or scheduled work. Just like...

One of the first things I was taught as an engineer involved in specifying materials for steam turbine or compressor parts was that the material hardness for shafts was supposed to be between 28 and 32 Rockwell C Scale hardness. What is hardness? What does range of numbers mean? Why is this the proper range? Where is this written? What is hardness? A simple definition: Hardness is a measure of a material’s resistance to local plastic deformation, usually from pressing. Let’s break this...