Power generation: boilers, HRSGs, and the outage record

A steam plant lives or dies on tube metal. Boiler tube failure remains the leading cause of forced outages in coal and gas-fired steam units, and every failure has a history: a wear pattern that was visible two outages ago, a repair whose weld was never surveyed again, a cycling regime that changed after the unit moved to load-following. The inspection record is where that history either exists or does not. This paper is about what power plant inspection software has to do to make the outage record useful for the next outage, and defensible to the jurisdictional inspector who will ask for it.

What does the boiler record have to carry under ASME I and NBIC?

ASME Section I is the construction code. It set the original design basis: materials, minimum wall for tubes and headers, allowable stresses at temperature, and the pressure relief arrangement. Once the boiler is in service, the governing document in most jurisdictions is the National Board Inspection Code (NBIC), which covers in-service inspection, repairs, and alterations, with the jurisdiction adding inspection frequencies and requiring an authorized inspector for internal inspections and for acceptance of pressure-part repairs.

What the record has to produce on demand:

• The original nameplate data and Section I data report.
• Every internal and external inspection, with the inspector, the date, and the findings.
• Every repair and alteration to a pressure part, with the repair organization, the procedure, the NDE, and the authorized inspector's acceptance.
• Tube and header thickness history by location.
• Safety valve testing and setting records.

The gap most plants have is the fourth item. The nameplate is on the drum and the repair forms are in a binder, but tube thickness lives in a different spreadsheet for each outage, and comparing them means rebuilding the geometry. In intelliSPEC, the asset hierarchy is a graph with roles down to component and weld, so a boiler can be modeled as assemblies (waterwall panels, superheater and reheater sections, economizer banks, headers) with tubes as components and welds as nodes. Each CML point carries 64 fields including nominal thickness, tMin and its method, material, and three corrosion rates. Section I minimum wall is recorded as the tMin with the method noted, so every reading is compared against the right basis.

How should tube thickness surveys be organized?

A waterwall UT survey during an outage can produce thousands of readings. If they are organized by tube number, elevation, and position (fireside, casing side, left, right), then the record can show a wear pattern across the bank, compare each location to the same location last outage, and compute a rate that means something. If they are filed as a spreadsheet per outage, they are a report.

The specific requirements:

• Location identity stable across outages, so tube 47 at elevation 1240 is the same point every time.
• Readings entered from the gauge without retyping, because retyping thousands of numbers is where errors enter.
• A rate per location, with a governing rate for the assembly, and remaining life against the minimum wall.
• The ability to flag locations below a threshold for pad weld or replacement scope before the outage ends.

intelliSPEC connects to seven instrument profiles over Bluetooth or keyboard wedge, including the Evident 38DL Plus and DeFelsko PosiTector UTG, so readings enter the record at the tube. The corrosion summary computes short-term, long-term, and maximum rates with the maximum governing, and remaining life as (t minus tMin) divided by the governing rate. NDE work in the boiler, including UT, PAUT on headers, and RT on repair welds, is recorded through intelliNDT.

What is different about HRSGs?

A heat recovery steam generator behind a gas turbine fails differently from a fired boiler. There is no flame, so short-term overheating is rare. Instead the mechanisms come from cycling and water chemistry:

• Thermal fatigue at tube-to-header welds, especially in superheater and reheater harps, driven by fast starts, attemperator spray quench, and condensate at startup.
• Flow-accelerated corrosion in low-pressure evaporator tubes, economizers, and feedwater piping, where single-phase or two-phase flow strips the protective oxide.
• Under-deposit corrosion where chemistry excursions have left deposits on the waterside.
• Dew-point corrosion at the cold end when exhaust temperature drops below the acid dew point during low-load operation.

The record has to be organized by harp, header, and tube row, because that is how the failures cluster. It also has to record the operating regime: a unit that moved from baseload to two-shifting has had its damage mechanisms changed, and the inspection plan should change with it. In intelliSPEC damage mechanisms are first-class records attached to the equipment, so a thermal fatigue mechanism recorded on a reheater harp drives the NDE scope for that harp at the next outage. Access to HRSG tubes is limited, so much of the evidence is borescope visual and header PAUT rather than a full tube survey; visual work is recorded through intelliINSPECT.

How should the outage itself be managed in the record?

A major boiler outage runs a few weeks with a large crew, much of it contract. The inspection work competes for access with mechanical work, scaffolding, and cleaning. The failure mode is not that inspection does not happen; it is that its output ends up in the contractor's system and arrives at the plant as a PDF after the unit is back online.

The controls that protect the record:

• Inspection activities in the outage plan, linked to the assemblies they cover, with daily progress visible.
• Findings recorded by an identified person on the component, with photos bound at capture time.
• A workflow for findings: submitted, reviewed, repair planned, repaired, verified, closed.
• Repairs recorded against the finding and the weld, with post-repair NDE attached, in the form the authorized inspector will want.
• Delay events recorded, because outage overruns are usually attributed after the fact and from memory.

intelliPROJECTS models the outage as an event with activities, crews, daily progress, delay events, gate reviews, and cost entries, and findings land on equipment rather than on the event. intelliCREW carries member, team, dispatch, unavailability, qualification, skills, and training records, so the question of who is qualified to perform a given NDE technique is answered from the record rather than from a phone call. The field app works fully offline with no time limit on the local store, which matters inside a boiler where there is no signal, and field-level conflict records show what happened when two technicians touched the same tube.

What does the jurisdictional inspector expect to see?

The authorized inspector's questions are predictable: show me the last internal, show me the repairs since then, show me the NDE on those repairs, show me the safety valve records, show me the tube thickness where you had the last failure. The answer should be a record that opens, not a binder that is searched.

Three properties make that possible:

• Attribution. Every entry carries who made it and when. intelliSPEC records every create, update, delete, and export with actor, tenant, request id, IP, and user agent.
• Integrity of the log. The audit trail is chained per tenant with SHA-256 hashes, and a verify routine recomputes the chain so an auditor can confirm nothing was removed. Audit events are never auto-deleted.
• Stability of the rendered record. Completed records pin the form, locale, and reference options they were executed with, so an inspection recorded five outages ago renders exactly as it did then.

Reports for the jurisdiction are generated from report definitions with datasets and layouts, produced as PDFs with cover, header, and footer, and can be scheduled. The signature widget records per-signer identity even on a shared tablet, which is the common case at the boiler.

What about the rest of the plant?

Boilers get the attention, but a power station also has Section VIII vessels (deaerators, feedwater heaters, air receivers), B31.1 piping, tanks, cooling water systems, and fireproofing and coatings on structures. The same record serves them. In intelliSPEC the tMin engine routes vessels to ASME VIII Div 1, piping to ASME B31.3, and tanks to API 653, and returns the design code and formula with each number. Coating and fireproofing work is recorded through DFT verification and statistics, coating exception reports, and PFP appendices. For plants with a 3D model, Navisworks models convert to glTF or streamed 3D Tiles, and a new model version updates the same asset nodes in place so the inspection history stays attached.

How intelliSPEC handles it

For a power plant integrity team preparing for the next outage, the relevant facts:

• The asset hierarchy is a graph with roles down to component and weld, so boilers, HRSG harps, headers, and tubes are real objects with CMLs attached.
• CML points carry 64 fields including tMin and its method; Section I minimum wall is recorded as the basis for tubes and headers, and the engine routes vessels, piping, and tanks to their design codes.
• Seven instrument profiles bring gauge readings into the record without retyping.
• Damage mechanisms are first-class records, so thermal fatigue and flow-accelerated corrosion drive the NDE scope where they are credible.
• intelliPROJECTS and intelliCREW carry the outage plan, crews, progress, delays, and qualifications.
• Full offline capture with no time limit, field-level conflict records, and per-signer signatures on shared devices.
• Hash-chained, verifiable audit trail; completed records render as executed.

The power solutions page describes the module mix for generation. Bring the last outage's tube survey and repair package to an evaluation and see whether the next outage's scope can be built from it.