Corrosionman, Thanks for your response. I agree with your assesment regarding the use of PP for this type application, and I have specified it in the past for underground routing. Unfortunately, not all engineers agree with us. This system will be run above ground and it has been determined that a basalt lined pipe would be better suited due to various construction and pipe support issues. In order to save money, our partners are trying to skimp by stating that straight sections of the piping run need not be basalt lined. I am tasked to provide a technical basis (by calculation) to show that although an economic analysis may prove that using unprotected steel pipe for straight sections will reduce upfront capital cost, periodic replacement of these sections due to erosion in this type of abrasive service will, in the course of a 20 year design life of the system, prove that it is NOT the best decision. What it comes down to is the all too familar argument with the "bean counters" that spending more money initially, will save money through the years. It is tough to collect erosion data on unprotected steel pipe ~other than bends~ and that's where my efforts have proved futile. My gut feel is that it is the wrong decision, however, without a sound technical basis to disprove their decision, I will be forced to accept it.