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Power Plant Training Hosted by Tetra Engineering and TG Advisers in Florida
TETRA and TG advisers held a successful week of power plant training in Tampa, Florida...
Join us in Deer Park Utah, USA in May or Sophia-Antipolis, France in June for HRSG & Combined Cycle training. Don't miss our Early-bird discounts! See our training page for more details.
TETRA Engineering was recently contacted by a client in Asia concerning Superheater tube failures in a supercritical coal boiler and asked to conduct a Root Cause Analysis (RCA). A senior Tetra engineer visited the plant to gather information on the history of the failures and relevant data to be used for the RCA. The failures were occurring in one specific region of the boiler (in one instance not long after tube replacement), on hanger tubes concentrated at the right-hand side of the unit. Observations made on the tube failures included
After the elimination of other possibilities, it was hypothesized that the tubes were overheating due to temporary loss of steam flow which, when combined with the higher gas temperatures at the RHS, led to a concentration of failures. Following this, the operating conditions were modelled using Power Plant Simulator and Designer (PPSD) to evaluate the necessary conditions for these failures to occur.
It was shown that the under low loads, the steam may have been condensing at the bottom of the investigated hanger tubes due to low flue gas temperatures in this region (it entered the tubes only just above saturation). This led to blockage of the tube and restricted steam flow. When load increases, and gas temperatures increase, the tubes overheat – particularly at the RHS due to flue gas temperature skew.
For more information about this project contact Fraser Davidson at fraser.davidson@tetra-eng.com . For more information about our Failure Analysis Services contact James Malloy at jim.malloy@tetra-eng.com .
Thermal overstress is generally associated with the high temperature sections of the HRSG (HP Superheater and Reheater). Flow starvation in a tube relative to its neighbors results in the tube metal temperature approaching the gas temperature. In that case, tube-to-tube differential temperatures may exceed 500°F (260°C). The enormous thermal stress that results exceed material yield stress and cause permanent bowing…
If you are interested in the full version of the HRSG Inspection Planning Guide (2nd edition) contact Ms Christine Vallon at christine.vallon@tetra-eng.com.
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TETRA and TG advisers held a successful week of power plant training in Tampa, Florida...
Two of the most common issues that power plant owners and operators face in the HP Evaporator section areUnder-deposit Corrosion (UDC) andCorrosion-Fatigue. In this short article we will cover UDC and what key actions should be taken to predict and prevent costly forced outages.
The latest updated edition of Tetra Engineering's HRSG Tube Failure Diagnostic Guide will be published August 15, 2016. Thousands of combined cycle professionals are familiar with Tetra's HRSG Tube Failure Diagnostic Guide; first published during the 'bubble' in construction in the early 2000s.
