State inspectors, insurers and in-service inspection

When Kiera started her apprenticeship, the inspector was the person who turned up at a hold point and looked at her fit-up. In the code block she learns that the same people, and others she has never met, follow every boiler and vessel for its whole working life. In May, Peg Lindqvist, Riverbend's owner's inspector, comes to class with her inspection schedule on a laptop. "You build it once," she says. "I look after it for forty years. Every time I open it up, I'm asking the same question: is it still fit for the pressure on its nameplate?" This lesson covers who inspects pressure equipment once it is in service, what the owner must do, how inspection intervals are set, what an inspector looks for, and what happens when an inspection finds a problem.

The owner's duties

Once a boiler or vessel is installed, the owner is responsible for it. The owner must make sure it is registered, operated within the limits on its nameplate, protected by working safety devices, inspected at the required intervals and repaired only by authorized organizations. The owner must keep the records: the data report, the drawings and calculations, the inspection reports, and the repair and alteration reports. When an item is sold, moved or retired, the records go with it or are reported to the authority.

In Louisiana, the state's boiler rules put these duties on the owner of a boiler: the boiler must be inspected at set intervals and hold a current certificate of operation. Vessels at refineries and chemical plants are usually inspected under the owner's own program to API 510, the pressure vessel inspection code, often with the insurer's inspector reviewing it. API 510 sets out the duties of an owner-user inspection organization, the qualifications of its inspectors and how intervals are set.

Who inspects in service

In the United States, in-service inspections of boilers are done by state inspectors or by commissioned inspectors employed by the insurer, depending on the state. Most states let an insurer's commissioned inspector do the certificate inspection of an insured boiler and report it to the state. Refinery and chemical plant owners run their own inspection programs, with inspectors certified to API 510 for vessels, API 570 for piping and API 653 for tanks. Riverbend and Northgate are owner-users of this kind: Peg and her team do most of the inspections, the insurer's inspector does the jurisdictional boiler inspections, and both keep records.

Kinds of inspection

An external inspection is made with the equipment in service, or at least closed up. The inspector looks at the outside of the shell and heads, supports, insulation, nozzles, flanges and gaskets for leaks, safety devices and their seals, gauges and controls, and the condition of the surroundings. For a boiler in service, the inspector also checks that the water level controls, low-water cutoffs and safety valves are working, and that the operators know how to use them.

An internal inspection is made with the equipment shut down, isolated, drained, cleaned and open. The inspector looks at the inside surfaces for corrosion, erosion, cracking, pitting, deposits and damage to internals, and measures thickness where metal loss is expected. In a boiler, the inspector looks at the drums, tube ends, headers and the fireside of the tubes. This is where boilermakers come in: before Peg can see anything, the equipment has to be blinded, vented, opened, cleaned and made safe to enter, and scaffold built inside it, all under the confined space and isolation rules of BLR-110.

Not every inspection needs the vessel opened. Thickness can often be measured from the outside with ultrasonics, and other methods, such as phased-array ultrasonics, radiography of nozzles and acoustic emission, can sometimes replace part of an internal inspection when the owner's program and the authority allow it. An inspector chooses methods according to the ways the equipment is expected to deteriorate: thinning, cracking from stress corrosion or fatigue, creep in hot parts, or damage from fire or upset conditions.

Setting the interval

Louisiana's rules set intervals for boilers: a power boiler gets an annual external certificate inspection and an internal inspection at intervals the rules limit, with longer intervals possible for boilers in continuous service that meet conditions for water treatment and records; low-pressure boilers are inspected every two years. For vessels, API 510 sets intervals from the remaining life: generally no more than half the remaining corrosion life, up to a maximum, or by risk-based inspection.

Corrosion rate and remaining life are simple ideas. If a shell has lost 0.08 in over 10 years, its long-term corrosion rate is 0.008 in a year. If it has 0.16 in of metal left above its required thickness, its remaining life is about 20 years, and an interval of half that, or less, means the inspector will see it again well before it gets near its limit.

# When is each item due for inspection? (US units; boiler intervals of the kind in the Louisiana rules, vessel intervals from the owner's API 510 program)
from datetime import date

def add_months(d, m):
    y, mo = divmod(d.month - 1 + m, 12)
    return date(d.year + y, mo + 1, min(d.day, 28))

today = date(2029, 5, 1)
items = [("Riverbend Unit 2 boiler", "internal", date(2028, 4, 20), 12), ("Riverbend Unit 2 boiler", "external", date(2028, 10, 22), 12), ("V-412 knockout drum", "internal", date(2027, 3, 30), 24), ("E-1105 exchanger shell", "external", date(2026, 9, 10), 36), ("school hot water boiler", "external", date(2027, 6, 1), 24)]          # (item, kind of inspection, last done, interval in months)
for name, kind, last, months in items:
    due = add_months(last, months)
    days = (due - today).days
    flag = "OVERDUE" if days < 0 else ("due within 60 days" if days <= 60 else "")
    print(f"{name:26} {kind:9} last {last.isoformat()} next {due.isoformat()} {flag}")

Riverbend Unit 2 boiler    internal  last 2028-04-20 next 2029-04-20 OVERDUE
Riverbend Unit 2 boiler    external  last 2028-10-22 next 2029-10-22 
V-412 knockout drum        internal  last 2027-03-30 next 2029-03-28 OVERDUE
E-1105 exchanger shell     external  last 2026-09-10 next 2029-09-10 
school hot water boiler    external  last 2027-06-01 next 2029-06-01 due within 60 days

An overdue inspection is not something an owner can just accept. For Riverbend Unit 2, Peg's team asked the state for an extension before the due date, with the reasons, the boiler's recent operating and water chemistry records and the results of an external inspection done in April, and the extension was granted to the June outage. V-412, under Northgate's own program, needed a documented deferral approved by the program's responsible engineer, with a note in the records.

What the inspector looks for

Peg tells the class that most of what she finds is ordinary: thinning where flow is fast or turns a corner, pitting under deposits, cracking at nozzle welds where the vessel breathes with pressure and temperature, corrosion under insulation where rain gets in, and damage from overheating in boiler tubes. Her job is to measure how bad it is, compare it with what the vessel needs and decide whether it can run, can run with a lower pressure, needs a repair, or needs more examination before anyone can say.

When a finding needs a repair, the work goes to an authorized repair organization, which is where Ironbridge comes in. The owner's inspector writes the finding and the requirement, the repair organization writes a repair plan, the inspector accepts the plan, and only then does the boilermaker pick up a grinder. Lesson 9 covers repairs and alterations, and the capstone follows one through.

When an inspector says stop

A state inspector can refuse to issue or renew a certificate of operation, or can order a boiler out of service, when it is unsafe. Operating a boiler without a valid certificate is an offense under the state law. Most problems are fixed when the inspector points them out, without any order, but the power is there.

For a boilermaker the lesson is simple. If an inspector, an owner's inspector or a repair organization's inspector says a piece of equipment is not to be returned to service, nobody on the crew argues the point or works around it. The decision is recorded, the reasons are investigated and the equipment stays out of service until the inspector says otherwise.

Preparing equipment for the inspector

Peg's internal inspections depend on the crews who open the equipment. Before an inspector can enter a drum, it must be isolated from every source of pressure and process fluid by blinds or by removing spool pieces, drained, steamed or washed out, ventilated, tested for oxygen and toxic or flammable gases, and covered by a confined space entry permit with a trained attendant outside. Internals such as trays, demister pads or baffles may have to be removed so the shell can be seen. Scale and deposits are cleaned off the areas the inspector wants to examine, by hydroblasting, scraping or abrasive blasting, and lights and scaffold are set up. A poorly cleaned vessel wastes an inspector's day and can hide the very cracking she is looking for.

Boilermakers also make the inspection openings: removing manway covers, cutting inspection windows in tubes where the plan calls for it, and drilling small holes for internal cameras. Each of these is work on a pressure part and is restored afterwards under the repair rules, with the inspector's knowledge.

When the inspection is finished, the inspector releases the equipment for closing. The boilermakers reinstall internals, fit new gaskets, close manways with the correct bolting procedure from BLR-230 and remove blinds, and the owner returns the equipment to service only after any required pressure test or leak test.

Peg has one more point for the class. Inspectors rely on what the crew tells them. If a boilermaker sees something during cleaning that looks wrong, such as a crack, a bulge, a pit that goes deeper than the others, or a weld that looks unlike its neighbors, the right thing is to stop and show the inspector, not to clean it off and carry on. Some of the most serious findings she has made were pointed out to her by the crew that opened the vessel.