News

Tetra In Action #4 - July, 2016

Come see us at the PowerGen Asia conference in Seoul!

Chief Engineer David Moelling of Tetra Engineering is presenting the Tetra/R&R Consult paper Root Cause Failure Analysis of Superheater Tubes Using Computational Fluid Dynamics Simulations at the PowerGen conference in Seoul on the 20th of September at 2PM. 

“As the electricity market has evolved with the addition of renewables to the generation mix, Heat Recovery Steam Generators (HRSG) that were originally designed for base load conditions are now frequently forced to operate in a cycling and/or low-load regime. This can lead to front end tube-to-header fatigue, creep or creep-fatigue failures, often induced by GT flow imbalances causing locally-elevated tube temperatures and/or bending stresses on joints due to large temperature differences between tube rows. This paper focuses on the use of Computational Fluid Dynamics (CFD) as a tool to analyze the root cause of Superheater tube failures. Exhaust gas flow profiles were analyzed for base load and low load conditions for a vertical Heat Recovery Steam Generator (HRSG). The plant suffered from tube failures that could be shown to be directly related to low-load (and start-up) exhaust gas flow patterns. The contribution of CFD to identifying these conditions that lead to the failures are presented and mechanisms to reduce future risk of failure, such as addition of flow-conditioning devices, are investigated and presented."

More details about the Tetra presentation and the conference can be found here and here.


Boiler Preservation Engineering

OEM or industry guidelines for Boiler or HRSG waterside and gas-side preservation (or “layup”) are useful but typically don’t go further than general advice on the different available options (wet vs. dry etc.). The difficulty is in moving from the general to the specific for a given plant. Tetra can define viable preservation options and help you choose an optimal strategy from among these that fits your budget and operational constraints. If desired, Tetra will then develop a detailed engineering specification for your preservation system.   For more information about the service send us an This email address is being protected from spambots. You need JavaScript enabled to view it..


HRSG Inspection Planning Guide Snapshots

The following HRSG locations are affected by external corrosion and oxidation:

  • External Corrosion (Evaporators, Economizers, Feedwater Preheaters)
  • Acid Dew Point Corrosion (Feedwater Pre-Heaters)
  • Oxidation on High Temperature Tubes (Superheaters, Reheaters)

External corrosion, as the name implies, occurs on the exterior surface of steel components in the HRSG. It affects both pressure parts and structural elements and requires the presence of corrosive agents to drive the reaction with the metal.  The most common agents are oxygen and water.  When shutdown these are present in the air and when running are present as components in the gas stream.  

If you are interested in the full version of the HRSG Inspection Planning Guide (2nd edition) contact Ms Christine Vallon at This email address is being protected from spambots. You need JavaScript enabled to view it..