Integripedia Topic
Condition Monitoring Locations (CMLs)
Condition Monitoring Locations (CMLs) are designated locations on pressure vessels and piping where thickness monitoring is conducted to monitor the presence and rate of damage and corrosion.
Most CMLs consist of at least one examination point, usually a two to three-inch diameter circle on the surface of the equipment. It’s within these circles that the inspection takes place. The number of specific spots where individual readings are taken within these areas varies. API 510 and API 570 recommend recording either the lowest or an average of several readings within the area of the examination point.2,3
The number and location of CMLs need to be a sampling that covers the entire population range. Additionally, the number is based on the user’s desired confidence in the sample data. In other words, more CMLs will produce more sample data, which, in turn, should increase a user’s confidence in the estimated condition. More locations should be used to monitor higher risk equipment. For sites that have implemented risk-based inspection, the number of CMLs will typically depend on the desired level of risk mitigation.
A Note on Thickness Monitoring Locations (TMLs)
Prior to the 9th edition of API 510 and 3rd edition of API 570, a thickness measurement location (TML) referred to a single examination point where thickness measurements would be performed in order to establish general and localized corrosion rates. Whereas a CML can include one or more of these points, CMLs now include what were previously referred to as TMLs. Upon publication of the 9th edition of API 510 and 3rd edition of API 570, API codes no longer use the designation TML independent of CML.
References
- Gysbers, A.C. “A Discussion on the Piping Thickness Management Process: Determining Corrosion Monitoring Locations.” Inspectioneering Journal, vol. 18, no. 6, 2012.
- API 510 — Pressure Vessel Inspection Code: In-Service Inspection, Rating, Repair, and Alteration, The American Petroleum Institute, ed. 9, 2006.
- API 570 — Piping Inspection Code: In-service Inspection, Rating, Repair, and Alteration of Piping Systems, The American Petroleum Institute, ed. 3, 2009.
Related Topics
- Cathodic Protection
- Coatings
- Corrosion Control Documents (CCDs)
- Damage Mechanisms
- Flue Gas Dew Point Corrosion
- Green Rot
- Pitting Corrosion
- Positive Material Identification (PMI)
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January/February 2021 Inspectioneering JournalBy Mike Sparago at The Equity Engineering Group, and Chris Massengale at The Equity Engineering Group
“Condition monitoring location (CML) optimization” is a frequently used term, particularly for piping circuits. Everyone wants their circuits to be “CML optimized,” but what does this truly mean?
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BlogFebruary 15, 2021 By Mark Geisenhoff at Flint Hills Resources, and Sascha Schieke at Molex
Temporarily or permanently installed thickness monitors can help to overcome shortcomings and uncertainties associated with manual ultrasonic inspections and can lead to significantly improved maintenance and asset replacement forecasting.
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May/June 2020 Inspectioneering JournalBy Spencer Rex at Trinity Bridge
This article dives into continuous thickness monitoring, which in the opinion of the author is one of the more innovative technologies for corrosion control in the refining industry to come about in the last two decades.
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September/October 2019 Inspectioneering JournalBy Michael Nugent at LPI, Inc., Steve Strachan at Sensor Networks Inc., and Art Leach at Sensor Networks Inc.
Thickness readings are critical for today's inspectors to accurately judge the state of their equipment. Recent advancements in sensors, software, and data management tools have made this easier, safer, and more efficient than ever before.
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November/December 2017 Inspectioneering JournalBy Geoff Clarkson at UTComp, Inc.
This article, part two in a series, provides a case study of an inspection and evaluation of a Fiberglass Reinforced Polymer (FRP) column using nondestructive ultrasound readings on the outer surface of the FRP.
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May/June 2017 Inspectioneering JournalBy Ryan Myers at Pinnacle, and Brian Marino at Pinnacle
Effective condition monitoring location selection is a key component of a best-in-class mechanical integrity program. Learn how moving beyond traditional qualitative approaches to optimized CML selection can reduce risk and maximize the value of...
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March/April 2017 Inspectioneering JournalBy Fernando Vicente at ABB, and Laza Krstin at ABB
Myths, challenges, and good practices related to process piping integrity management activities that help inspection and maintenance managers make the right decisions to develop cost-effective piping inspection plans without compromising the...
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January/February 2017 Inspectioneering JournalBy Israel D. Martinez at ORPIC
Evaluating remaining wall thickness of an asset is not enough to ensure its continued safe operation. Proactive strategies should be implemented to assess the entire environment affecting an asset’s condition, including the development of more...
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November/December 2016 Inspectioneering JournalBy Loganatha Pandian at Meridium, Inc.
This article summarizes seven key questions that an organization needs to answer to create a robust mechanical integrity program that is properly designed to monitor corrosion and indicate when issues increase to a level requiring review or...
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November/December 2016 Inspectioneering JournalBy Marc McConnell, P.E. at Pro-Surve Technical Services, and Grady Hatton at Versa Integrity Group
The concept of reducing Condition Monitoring Locations (CMLs) is misguided, and the number and location of CMLs should be OPTIMIZED, not systematically reduced. CML allocation in piping requires a good process, otherwise, you can run into a lot of...
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July/August 2014 Inspectioneering JournalBy A.C. Gysbers at The Equity Engineering Group, Inc.
One of the more common inspection monitoring programs for pressure vessels is to perform thickness measurement at Corrosion Monitoring Locations (CMLs) to allow monitoring of minimum thicknesses and provide estimates for corrosion rates. These...
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BlogJanuary 6, 2014 By Nick Schmoyer at Inspectioneering
In 2013 Inspectioneering published content covering a wide array of topics, from risk-based inspection, to advanced nondestructive testing methods, to pipeline integrity management systems. Last year, we published more content than any year prior;...
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BlogJuly 1, 2013 By John Reynolds at Intertek
I will emphasize the systems, work processes and procedures for identifying and controlling the rate and types of deterioration in pressure equipment. These are not in any particular order, as they are meant to operate interdependently.
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May/June 2013 Inspectioneering JournalBy A.C. Gysbers at The Equity Engineering Group, Inc.
Piping failures still represent a frustrating and ongoing problem for processing plants. Failures are still commonly reported and contribute to large losses. In the author’s experience, piping represents the highest percentage of fixed equipment...
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A Discussion on the Piping Thickness Management Process - Part 2: Determining Corrosion Monitoring LocationsNovember/December 2012 Inspectioneering JournalBy A.C. Gysbers at The Equity Engineering Group, Inc.
Piping failures still represent a frustrating and ongoing problem for processing plants. Failures are still commonly reported and contribute to large losses. In the author’s experience, piping represents the highest percentage of fixed equipment...
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September/October 2007 Inspectioneering JournalBy Greg Alvarado at Inspectioneering Journal
The Inspectioneering Journal Discussion Forum is a great storehouse of knowledge and experience for people involved in fixed equipment reliability. A few samples of discussions follow, to motivate you to participate.
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November/December 1998 Inspectioneering JournalBy Michael Twomey at CONAM Inspection Inc., and Jay N. Rothbart at Conam Inspection Inc.
We have been asked many times by existing and prospective users of PCMS (a computerized, inspection database management system), how many TMLs (Thickness Management Locations) should be installed per piping circuit. These inquiries must be addressed...
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September/October 1997 Inspectioneering JournalBy Michael Twomey at CONAM Inspection Inc., and Jay N. Rothbart at Conam Inspection Inc.
This task though tedious and exasperating is a key part of the operation. Plant personnel often find ingenious uses and filing systems for key data such as UW 1 forms. The more remote the plant site is, the more extraordinary the hiding places. In...
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