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 online in Power Magazine here.
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.
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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.
If you are interested in the full version of the HRSG Inspection Planning Guide (2nd edition) contact Christine Vallon (christine.vallon@tetra-eng.com ) or Natalie Vasa (natalie.vasa@tetra-eng.com )
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OEM upgrade packages to gas turbines (GT) can significantly improve performance, operational flexibility and increase outage intervals. In combined cycle power plants, the impact of these upgrades should also be considered for the HRSG where the design was based on the original GT performance.
Quality Achieved vs. Quality Perceived The quality of the thousands of factory and field welds present in pressure part modules is critical for assuring reliable operation over the life of the plant. But how are these welds performed and checked? Much relies on the quality system of the fabricator, and for many years some companies have been paying only lip service to quality while avoiding the associated costs. It is very easy to tick a box. Let’s take a step back. Companies can be perceived as good, bad, or somewhere in between by potential clients. Rightly or wrongly, quality systems are generally seen as a way for a company to show that it is on the good end of the scale.
Inspection is part of routine maintenance for any Heat Recovery Steam Generator (HRSG). Visual inspections are performed at regular intervals in accordance with the requirements of regulatory bodies and insurers.
