Tetra Engineering will have a booth next month at the upcoming PowerGen Middle East in Abu Dhabi on October 12-14. We will present our latest service offerings including Field Services, Engineering Analysis, 3rd Party Engineering, and Training. Come see us at the N21 booth, and enter your business card for your chance to win a Wilesco Steam Engine Generator!
Announcing Tetra Engineering's Fall 2014 USA Training Seminar: Effective Operation of HRSGs on November 12 & 13 at The Simsbury Inn, Simsbury, Connecticut USA. See this link for more information on the syllabus.
The modern power generation market is very different to what it was ten or even five years ago. The requirement to provide network load flexibility is falling on combined cycle plants with HRSGs, they are having to fill the supply gap between base loaded nuclear and large coal plants and the highly variable renewable energy generators. The result of operating at lower loads means the HRSG operating conditions may be very different from what was envisaged in the design case. Equally the increased number of startups and shutdowns presents problems for components designed for baseload. The problems faced by plants that are cycling or operating at off-design conditions can include:
- Water chemistry instability due to transient conditions
- Quenching problems in superheater and reheater tubes during condensate formation
- Attemporator and Bypass Spray problems handling increased demand
- Economiser shock
- High temperatures at superheaters and reheaters leading to creep failures
- Higher heat flux in the HP Evaporator leading to increased deposit loading
- Increased FAC risk due to increased heat at the LP Evaporator
Tetra develops inspection plans to address these and other issues using:
- Visual Inspection of the HRSG hot gas path
- Borescope/videoscope inspection of waterside conditions of lead high-pressure (HP) evaporator tube panels and other areas
- Ultrasonic testing (UT) of wall thickness for selected (high-risk) tube, header, and riser components
- Magnetic particle testing of all accessible tube-header weld connections in the HP steam and reheater tube panels
- UT shear wave or UT phased-array inspection of Grade 91 components
- Visual inspection of accessible HRSG waterside components
- External walkdown and thermography
Flow-Accelerated Corrosion (FAC) or Erosions-Corrosion remains a common cause of failure in HRSGs and conventional boilers, yet the underlying causes and solutions have been well understood for more than 25 years. The two factors influencing the susceptibility to FAC are: a) Unit Design and b) Process Conditions. It is important to know how FAC-prone your HRSG or boiler design are, this will help you optimise your operating conditions to suit that design.
When assessing design factors, the primary question is whether the HRSG/boiler tubes and pipes' geometries and materials are suited to their flow profiles across the range of operating load cases. Operational factors are primarily concerned with assuring good control of water chemistry parameters (pH, dissolved oxygen or ORP, iron levels).
Since 2007 the ASME B31.1 Power Piping Code has included Chapter VII, establishing mandatory requirements for Operation and Maintenance. The key elements of this program are discussed here, and require that Operators outline a detailed maintenance plan for their Covered Piping Systems (CPSs). The Code also requires that operators perform regular Condition Assessments of their CPS ensuring that relevant degradation mechanisms are being covered.
At the 2014 ASME Power Conference in Baltimore, David Moelling of Tetra Engineering presented the recent research paper titled: Role of Boiling Mode and Rate in Formation of Waterside Deposits in Heat Recovery Steam Generator Evaporator Tubes, written by David Moelling and James Malloy.
The paper discusses results from research in the theory of boiling mode and deposit formation, employing advanced thermal simulation of evaporation in real boiler models, and compares results with actual experiences in recent years.
See the abstract to the paper below:
Tetra Engineering has announced the opening of its new office in Dubai. We expect the improved proximity to our clients in the region will enable us to continue in delivering a better service. See our contact page for more details.
Tetra Engineering will once again be offering its popular HRSG training courses at a number of locations this year. Currently scheduled are sessions at several locations in the US as well as in France and in Dubai.
Please click here for the full list of courses, dates, and locations
Tetra will present their paper 'Design Factors For Avoiding FAC Erosion in HRSG Low Pressure Evaporators' at this years ASME Power Conference in Boston, Massachusetts, USA. Session times will be posted as soon as they are confirmed.
For more information on this conference please click here.