News

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..  

Dubai: September, 2016 - Boiler & Steam Cycle Knowledge Workshops

Tetra Engineering announces a series of targeted workshops to provide thermal and process plant O&M engineers, managers and operators with a working knowledge in several aspects of the boiler and steam process technology. Drawing on our field experience working at power and process plants throughout the world, the objective is to provide attendees with clear instruction on the operator actions and design issues that can impact reliability, efficiency and operating life.  The programme comprises a set of focused, half-day training modules intended to leave attendees with a practical working knowledge on these issues.  A number of outside experts will join Tetra's senior staff in delivering the workshops.

The course syllabus can be found here.

Newly Published Technical Papers by Tetra Engineering Collaborators

An engineering consultant needs to stay up to date in his knowledge and try to contribute to furthering that knowledge.   Therefore, the staff engineers at Tetra don’t just work on commercial projects, they also take the time to do research and development on a variety of boiler and steam cycle engineering issues.  This is actively encouraged by the company as it only increases the level of skill that our collaborators can bring to bear for solving a given client’s problem. 

Over the years Tetra engineers have published many papers and attended numerous technical conferences and forums.   In the past 2 years the following papers were presented or published with collaborators from the various Tetra offices as authors or co-authors:

1. Technical Paper and Presentation:  Impact of Startup Purge Credit on Combined Cycle Plant Operation. Authors: Andreas Fabricius, Mark Taylor, Dave Moelling (all Tetra Engineering); Proceedings of the ASME 2015 Power and Energy Conversion Conference PowerEnergy 2015, June 28-July 2, 2015, San Diego, California; (Link)
2. Technical Presentation:  Chemical Cleaning of the HRSG Waterside: When, Where and How? James Malloy (Tetra Engineering) and Steve Wynne (Chemical Cleaning Consultants), European HRSG Forum, Munich May 11-13 2015. (Link)
3. Technical Paper:  Premature Grade 91 failures - Worldwide Plant Operational Experiences, Authors: Andreas Fabricius and Dr. Peter Jackson (both Tetra Engineering); Journal of Engineering Failure Analysis, August 2016, Volume 66, Pages 398-406. (Link)
4. Technical Paper and Presentation: Understanding Variations in Flow-Accelerated Corrosion Wear Rates in HRSG Evaporator Tubes,  Authors: James Malloy and Mark Taylor (Tetra Engineering) Jan Rusaas (R&R Consult, Denmark); Conference on Flow Accelerated Corrosion 24-27 May, 2016; Lille, France. (Link)
5. Technical Article:  Covered Piping Systems O&M Programs for CCGT Plants, Authors:  Robert Rosario and Dr. Peter Jackson, Power Magazine, April 2016, (Link)

An additional paper by Tetra collaborators Dave Moelling and Andreas Fabricius (and third co-author Jan Rusaas of R&R Consult) has been accepted for presentation at the upcoming Powergen Asia (Tuesday Sept 20th, see details here):  Root Cause Failure Analysis of Superheater Tubes Using Computational Fluid Dynamics Simulations.

Technical Tidbits from Tetra’s HRSG Inspection Planning Guide

HRSG Structures are exposed to weather, hot turbine exhaust gases, steam and water leaks and emissions control chemicals.   Deadweight, wind, thermal and seismic stresses also are applied to the HRSG.  These components are typically inspected on an opportunistic basis, for example during annual statutory inspections by the insurance company’s boiler inspector or during scheduled work on other major components such as the GT.  

Early HRSGs had frequent problems with the duct and casing/liners.  HRSG OEMs have responded to these problems with improved rials, improved bolting patterns and related improvements to designs of other components such as duct burners that have been responsible for damage to liners in certain configurations.

Casing liner plates are often found damaged in the transition duct at the exit of the gas turbine.  This is particularly common in ducts with abrupt geometry changes such as 90° angles in the duct or other sharp angled transitions.  Another common location for liner damage…

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

Managing the Power Piping in CCGT Plants

Risk of failure and attendant personnel safety concerns are always present when operating highly-pressurized systems.  Over the years, the occurrence of catastrophic events has driven improvements in construction codes and updated recommendations for O&M practices.  As part of this trend, expanded requirements for operations and maintenance (O&M) were recently added to the ASME Code for Power Piping—ASME B31.1.   The “Chapter VII Operation and Maintenance” was created in 2007 to prescribe guidelines that promoted early failure detection and overall safety. This was a fundamental change to the scope of B31.1, which up until then was strictly a design code; going forward, it now serves a dual purpose…

Read the full story by our colleague Robert Rosario, published in Power Magazine here

Dubai: September, 2016 - Boiler & Steam Cycle Knowledge Workshops

Tetra Engineering announces a series of targeted workshops to provide thermal and process plant O&M engineers, managers and operators with a working knowledge in several aspects of the boiler and steam process technology. Drawing on our field experience working at power and process plants throughout the world, the objective is to provide attendees with clear instruction on the operator actions and design issues that can impact reliability, efficiency and operating life.  The programme comprises a set of focused, half-day training modules intended to leave attendees with a practical working knowledge on these issues.  A number of outside experts will join Tetra's senior staff in delivering the workshops.
The course syllabus can be found here.

Technical Tidbits from the Tetra HRSG Inspection Planning Guide

The inspection of drums is a key element in determining the general condition of the waterside pressure boundary of the HRSG components and the quality of the water treatment program.  They are a “window” on what the inside of the water-filled or steam and water-filled tubes and headers in the various pressure circuits (HP, IP or LP) might look like.  Basic inspection is visual, yet often complemented by UT, and PT/MT examinations.
One of the key items of interest is surface passivation.  The HP drum should typically have a dark grey adherent surface layer, characteristic of magnetite, below the maximum waterline.  Above the maximum water line there may be some light red coloration, indicating a mix of magnetite and hematite.  Yet surface color can deceive,  drums with “abnormal” color may simply reflect a specific water chemistry and process condition history.  The experience of the inspector comes into play in these cases, to decide whether what is observed is indicative of a real problem or simply reflects a harmless difference.

Figure 1 : Senior Engineer Mark Taylor from Tetra’s European office enjoying some quality Steam Drum time during a recent HRSG inspection campaign. 

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

France: June, 2016 - Effective Operation of the HRSG Course

This seminar is primarily intended for O&M staff at all levels of experience working in combined cycle power plants, but should also be of interest to engineers and managers involved in new project development. The course gives attendees a comprehensive yet in-depth survey of a broad range of topics relating to the design, operation and maintenance of the HRSG and associated steam cycle systems.  Drawing on our field experience working at power plants throughout the world, the objective is to provide attendees with clear instruction on the operator actions and design issues that impact HRSG reliability, efficiency and operating life.

The course syllabus can be found here.

Recent Projects: Site Works Survey SE Asia

TETRA Engineering was engaged by a European client to perform a site works assessment at a Southeast Asian power plant construction site. Work had been delayed for months due to disagreements among two parties involved in the project regarding scope of work, responsibility and scheduling issues.
A Tetra engineer visited the site to meet with key personnel from the parties and to inspect the current state of the works. The results of the survey revealed

• Lack of communication between both parties
• Delays caused by one party in part of their scope of activity significantly delayed the other party’s progress in the project, causing a large financial loss and deterioration of equipment due to excessive exposure to elements.
• Discrepancies in the original scope of work caused added delays in the schedule and increasing the level of discord between the two parties
• As a “neutral” observer, the Tetra engineer was able to identify contradictions in the respective positions of the parties based on actual observations made on site

Technical Tidbits from Tetra’s HRSG Inspection Planning Guide

Analysis of deposits found in the HRSG is a common and very useful way for determining what is occurring on both the waterside and gas side.  Waterside deposits found in the drum are analyzed to determine chemical and elemental composition.  The presence of certain elements such as chlorine might indicate that there is or was a problem with contamination of the boiler water.  Analysis of gas side deposits such as those found on the cold end tubes can identify the various compounds present and their disposition in the deposits.  Excessive cold end deposition results when unit design does not match actual fuel characteristics or from mistuned process conditions.  The deposits are often corrosive and can lead to premature tube failures as well as loss HRSG or boiler performance.

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

Tetra Engineering has announced its schedule for HRSG & Combined Cycle training events in 2016.  This year we will be hosting training courses in Utah and Connecticut, USA, as well as in France and a new event in Dubai, UAE.  See our training page for more details.