A CML is a Condition Monitoring Location (CML): a defined point or area on equipment where condition data are collected and trended over time. A TML is a Thickness Measurement Location (TML), specifically associated with thickness monitoring. Owner-user terminology varies, and some programs use the terms interchangeably, but they are not necessarily identical in every inspection program. The management need is the same: identify where the measurement belongs, preserve the history and make the location understandable to the next inspector. A CML is a physical monitoring location tied to equipment identity, geometry, inspection history, measurement data, and the applicable inspection plan — not merely a database row or point number.
What a CML record should contain
A useful CML record includes the asset, circuit or component, unique point name, drawing or sketch reference, orientation, elevation or grid position, measurement method, units, nominal thickness, reference thickness, required thickness, or other applicable thickness basis where relevant, and inspection history. Add the date, current reading, prior readings, technician notes, calibration or technique information and linked photos where required. If the location is an area rather than a single point, define the boundary or grid so a future measurement is comparable.
Place CMLs where the anticipated damage mechanism, geometry, service and access make monitoring useful. Locations may include susceptible shell or pipe areas, low points, injection points, deadlegs, supports, weld-adjacent areas, nozzles or representative points in a circuit, corrosion circuits, elbows, reducers, mixing points, soil-to-air interfaces, and other locations associated with expected damage mechanisms where applicable. The responsible inspection program determines the locations; software should preserve the rationale and identifiers rather than inventing a monitoring plan.
Number and place CMLs for repeatability
Use a naming convention that reveals enough context to avoid ambiguity. Component prefixes, course or line identifiers, orientation, sequence and grid references can all help. Do not create a new point name because a technician approached the area from a different direction. If a CML is relocated, becomes inaccessible, is replaced after repair, or is subdivided into multiple monitoring locations, preserve the relationship to the historical record rather than silently treating it as the same point.
Link each point to an equipment drawing or field sketch. SketchMapp can connect inspection drawings, CML positions, findings and field references so the point list can be understood spatially. The API/NDE reporting workflow can carry the CML/TML table, readings, trends and evidence into an inspection report. The drawing and the table should use the same identifier and orientation language.
Manage history and trending
Store every valid reading with its date, source, units and measurement context. A trend is meaningful only when the current and prior readings refer to the same physical location and a sufficiently comparable basis. A valid trend requires more than matching identifiers; the physical location, measurement basis, technique, and examination conditions must be sufficiently comparable. Retain superseded or corrected readings with an explanation instead of deleting the history. Link corrosion-rate or remaining-life calculations to the exact readings that produced them, along with the required-thickness basis and reviewer notes.
Review for missing points, duplicate names, mixed unit systems, copied values, changed datum, inconsistent component labels and readings that were taken outside the defined CML. These problems can make a chart appear precise while disconnecting it from the field. A short data-quality review before report compilation is often more valuable than adding another summary page.
Common CML data-management failures
| Problem | Control |
|---|---|
| Disconnected spreadsheets | Keep point identity, drawing, readings and calculations in one traceable project record. |
| Inconsistent point naming | Use a defined convention and document any renamed, moved or split location. |
| Unclear spatial reference | Link the CML to a drawing, sketch, orientation and repeatable field datum. |
| Trend without source data | Retain dates, readings, units, method and the required-thickness basis behind each result. |
Questions inspectors ask
Is a CML always one thickness point?
No. A CML may represent a discrete point, a defined area, a grid, or another repeatable monitoring location depending on the inspection program. A TML is typically more specifically associated with thickness measurement.
What is the difference between a CML and a TML?
A CML is a broader condition-monitoring location. A TML is specifically a thickness-measurement location. Some owner-user programs use the terms interchangeably, so the governing inspection procedure and naming convention should control.
Can a renamed CML keep its old history?
Yes, when the record documents the old and new identifiers and proves they refer to the same physical location. Do not silently merge unrelated points.
Who decides where CMLs should be placed?
The responsible inspection program and qualified personnel decide based on damage mechanisms, geometry, service, access and applicable requirements. Software records and supports that plan.