LNG: cryogenic assets and the inspection program

An LNG plant has the longest inspection horizon in the process industries and the least access. The storage tanks are designed for a service life measured in decades and are almost never opened, because warming, purging, inspecting, and re-cooling a full containment tank is a project on its own. The cryogenic piping runs at temperatures where most inspection methods behave differently and most insulation systems are the real point of failure. The inspection program is therefore built on external evidence, instrumentation, and long intervals, and the record has to carry that evidence for the life of the plant. This paper is about what LNG inspection software has to do to hold up over that horizon.

What do API 620 and API 625 ask the in-service record to show?

API 620 is the design and construction standard for large welded low-pressure storage tanks, and its Appendix Q covers tanks for liquefied gases stored at cryogenic temperatures, with material requirements (typically 9 percent nickel steel or stainless for the inner tank), impact testing, and weld examination rules. API 625 covers the tank system: the containment concept (single, double, or full containment), the inner tank, the outer tank or concrete container, the insulation system, the foundation and its heating, and the instrumentation.

Neither standard is an in-service inspection code in the way API 653 is for atmospheric tanks, and API 653 itself acknowledges that refrigerated tanks need a different approach. What the two standards do is define the design basis that every later measurement is compared against, and the tank system elements whose condition the program has to track. In practice the in-service record must hold:

• Construction data: materials, thicknesses, weld maps, and the original radiographic and leak test results.
• Foundation settlement surveys and heating system performance over time.
• Annular space and insulation monitoring: temperature profiles, gas detection, and perlite settlement.
• External shell, roof, and appurtenance condition, including the outer tank or concrete container and its liner.
• Any internal inspection, with the justification for it and the findings.

In intelliSPEC the asset hierarchy is a graph of nodes with roles (company, site, facility, asset, component, weld), so a tank system can be modeled with the inner tank, outer container, foundation, and insulation system as components and the shell welds as nodes, each carrying its own history. The tMin engine routes tanks to API 653 and returns the design code and formula with the number, which suits the outer container and atmospheric tanks on the site; for the inner tank, the Appendix Q design thickness is recorded as the tMin with its method noted, so the basis stays with the point.

How do you run an integrity program on a tank you cannot open?

The answer every LNG operator has arrived at is to replace internal inspection with a body of external evidence and to justify the interval on it. The record has to support that argument to a regulator or insurer who asks why the tank has not been opened.

The elements of the argument:

• Continuous monitoring data trended over years: annular space temperatures, gas readings, foundation temperatures, settlement.
• Periodic external inspections with consistent scope and stable location identity, so a change is detectable.
• Non-intrusive techniques applied at defined intervals, such as acoustic emission on the inner tank or specialized inspection of the outer container.
• A documented engineering assessment that ties the evidence to the interval decision, revisited on a schedule.
• A defined trigger list: what evidence would justify internal entry.

The software requirement is that monitoring records, inspection records, and assessments all sit on the same asset, and that the assessment can cite the records it relies on. Ten intelliSPEC modules write to one asset record, and intelliINTEGRITY is where the assessment and its basis live. Because completed records pin the field configuration, locale, and reference options they were executed with, an external inspection recorded in the plant's first decade renders exactly as executed in its third.

What does cryogenic piping need from the inspection record?

Cryogenic piping is mostly austenitic stainless steel, with some aluminum and 9 percent nickel in specific services, and it lives through cool-down and warm-up cycles that a warm plant never sees. The damage mechanisms that matter:

• Thermal fatigue at supports, branch connections, and anchor points from cyclic contraction.
• Corrosion under insulation on stainless where the cold insulation system has been breached and moisture condenses continuously. Chloride from the marine atmosphere makes this a cracking concern, not only a thinning one.
• Mechanical damage to insulation, cladding, and vapor barriers from ice formation and from maintenance traffic.
• Support and pipe shoe degradation, including cold spots where the insulation at a support has failed.

The record therefore has to follow the insulation system as a component in its own right, with its own condition history, not treat it as a note on the pipe. intelliSPEC's CUI wizard family covers visual, suspect area, insulation removal, NDE UT, advanced NDE, repairs, recoat, inspection test plan, and frequency assessment as connected steps on the same component, which is the shape of a cold-insulation program. The tMin engine routes piping to ASME B31.3. Damage mechanisms are first-class records, so a chloride cracking mechanism recorded on a stainless line drives the NDE method at the next examination. Visual work runs through intelliINSPECT.

How are cold boxes and cryogenic exchangers handled?

The main cryogenic heat exchanger and the cold boxes around it are the least accessible pressure equipment on the site. Brazed aluminum exchangers sit inside insulated boxes filled with perlite, and the practical inspection is of the box, its purge, and its instrumentation, with the exchanger itself examined only at major shutdowns and often by the manufacturer.

The record has to hold:

• Box purge and leak monitoring history, since a rising purge gas concentration is the first sign of an internal leak.
• External box condition, including cold spots that indicate perlite settlement or insulation failure.
• Any internal work, with the manufacturer's findings attached to the equipment rather than filed as a vendor report.
• The design basis for the exchanger, since brazed aluminum has different acceptance criteria from steel.

The same principles apply as for tanks: monitoring data and inspection records on one asset, and an assessment that cites them. PDF and drawing annotation in intelliSPEC lets a manufacturer's report be attached and marked against the component it describes.

Why do fireproofing and spill protection belong in the integrity record?

An LNG plant's passive protection is part of its integrity case. Cryogenic spill protection on structural steel and vessel supports prevents brittle fracture if LNG contacts warm steel, and fireproofing protects the same structures against a pool fire. Both degrade, both are inspected, and both are usually recorded somewhere other than the pressure equipment record.

Keeping them beside the pressure equipment matters because the consequence analysis for the equipment assumes the protection is in place. A degraded fireproofing record on a vessel skirt changes the risk ranking of the vessel.

intelliSPEC records coating and fireproofing work through DFT verification and statistics, coating exception reports, and PFP appendices, with intelliFIRE for fireproofing and intelliPAINT for coatings, and both write to the same asset record as the pressure equipment. Instrument profiles for the DeFelsko PosiTector 6000 and Elcometer 224T bring coating thickness readings in without retyping.

What does the field environment demand?

LNG sites are large, often remote, and their tank tops, bund areas, and pipe racks have poor connectivity. Inspection crews work in cold, wind, and sometimes marine conditions, frequently on shared tablets. The demands on the field application:

• Full offline capture for forms, photos, and workflows, with no time limit on how long the device can be away from a network.
• Encrypted data on the device, since the tablet may leave the site.
• A clear conflict record when two technicians touch the same item offline.
• Signatures that identify the signer even on a shared device.
• GPS location capture for findings on long pipe racks where a tag number alone does not locate the defect.

intelliSPEC's field app captures fully offline for all inspection modules, with no time limit on the local store, encryption at rest on the device, field-level conflict records that show the local value, the remote value, who resolved it, and when, per-signer identity on shared devices, and a GPS location picker. Photo and video capture (video up to 120 seconds by default) and QR and barcode reading are built in.

How intelliSPEC handles it

For an LNG integrity team, the facts that matter:

• Ten modules write to one asset record, so monitoring data, inspection findings, coating and fireproofing condition, and engineering assessments are views of the same equipment.
• The asset hierarchy is a graph with roles down to component and weld, so tank systems, insulation systems, and cold boxes are real objects with their own history.
• CML points carry 64 fields including tMin and its method; the engine routes tanks to API 653 and piping to ASME B31.3, and returns the design code and formula with the number. Design thicknesses from API 620 Appendix Q are recorded as the basis where the code routing does not apply.
• Damage mechanisms are first-class records, and the full CUI wizard family handles cold-insulation programs.
• Coating and fireproofing records (DFT statistics, exception reports, PFP appendices) sit beside the pressure equipment.
• Full offline capture with no time limit, device encryption, field-level conflicts, and per-signer signatures.
• Completed records pin their configuration and render as executed; the audit trail is hash-chained per tenant and never auto-deleted.

The LNG solutions page describes how the modules map onto a liquefaction or import terminal. The evaluation that fits this industry is a long one: load a tank system's history and see whether the interval argument can be made from the record.