Tetra has published a series of guides which are available for ordering.
A selection of technical papers available for reference.
Selected papers, presentations and articles from major industry conferences and events.
With over 30 years of experience in power and industrial steam generation services, Tetra Engineering has along history of projects.
After several tube failures in recent years in the 1st row of LTRH hanger tubes, Tetra was tasked with performing a Root Cause Analysis (RCA) to determine the underlying cause of the failures. A detailed review of operating data, failure reports and design information was carried out and potential causes investigated. The tube failure mechanism as determined by metallurgy was short-term overheating, with temperatures likely exceeding 700°C prior to failures. Two contributing causes were identified by elimination of all other possibilities: temporary loss of steam flow in affected leading row tubes coupled with high flue gas temperatures in certain tubes at the side of the boiler gas path. Unfortunately, the underlying root cause of the loss of flow could not be confirmed, whereas the asymmetric flue gas temperature distribution is a known issue since commissioning.
During a recent condenser tube leak at a CCGT Power Station in the Middle East, two trips occurred on the boiler feedwater pumps leading to trips of one of the HRSGs. During that time, three tubes failed on the HP Evaporator. Tetra Engineering performed an investigation into the failures with the aim of determining the failure mechanism, to estimate the root cause of failure, and to identify inspection priorities in case damage may have gone undetected. This work included metallurgical analysis and a review of key operating data. Failures were located directly under the risers at extreme ends of the HP Drum. The most probable source of tensile overload is tube quenching when flow restarted
In 2015, it was discovered that the thermal sleeve in the attemperator in a client’s power station hot reheat line had failed, resulting in fracture around the circumferential weld in the sleeve’s mid section. For this reason, Tetra was engaged by the owner to investigate. The investigation showed failure from fatigue cracking. There were no signs of thermal fatigue damage, hence quenching from over-spraying was discounted as the root cause. The cracked area showed signs of high cyclic local strain, and given the moderate number of starts low-cycle fatigue was thought to be the root cause. Differential thermal expansion between the Grade 22 sleeve and the Grade 91 pipe, combined with lock-in of the sleeve on the pin locations, would raise sufficiently high stresses
Tetra was engaged by a client to perform a finite element analysis of the HP Bypass valve reducer, using measured displacements as input. Results from a strain gauge/displacement survey showed a large strain effect occurring during the start-up of the boiler. Initially, both the left and right side strain gauges on the reducer showed compressive strain. During the start something triggered the reducer to experience tensile strain that differed in its intensity between left and right. The purpose of the study was to try to simulate the observed strain fields and determine the root cause.
