INSPECT and Auto-Refrigeration

Minimum Safe Operating Temperature (MSOT) curves, also referred to as Minimum Pressurization Temperature (MPT) curves, are used to ensure that carbon steel equipment can safely operate when exposed to low temperature conditions. Common applications include the olefin and hydrocarbon processing industries where safety concerns created by auto-refrigeration may occur. MSOT curves are employed to determine which process conditions put equipment at risk of failure by brittle fracture. They are created by performing API 579 Part 3 assessments for all pressure-temperature conditions expected in service. Because of the number of calculations required, this has historically been an expensive, time consuming task. INSPECT automates this RAGAGEP procedure and shows how process conditions interact with the equipment’s Minimum Allowable Temperature (MAT).

INSPECT’s MSOT Curve Benefits

  • MDMT (minimum design metal temperature) data may not be  available for old or undocumented vessels. Creating a MSOT curve with INSPECT solves this problem quickly.

  • INSPECT’s MSOT curves are plotted against process vapor pressure curves.  This information can then be used for creating integrity operating windows (IOW’s).

  • Reduces time and expense when creating MSOT’s manually or through outsourcing to 3rd parties.  They can also be used to validate newly acquired older plants. In this context, older refers to facilities constructed prior to 1987, the year ASME rules for brittle fracture were introduced.

INSPECT's MSOT Curves Compare Equipment Brittle Fracture Ratings to Process Conditions
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INSPECT's Brittle Fracture Assessments Consider Process Vapor Pressures and Auto-Refrigeration

Custom Vapor Pressure Curves

Custom vapor pressure curves are used by INSPECT to identify process conditions that exceed the equipment’s MSOT. Vapor pressure temperature curves, as many as required, can be specified. Individual user defined pressure-temperature (upset) conditions can also be created.

In addition to being plotted in the MSOT, vapor pressure curves in tabular form are also presented in the summary report.

Creating a Master MSOT Curve in INSPECT

For more information on brittle fracture and auto-refrigeration please visit:

Prevent Brittle Fracture Failures by Following UCS-66 in COMPRESS and INSPECT

Auto-Refrigeration: When Bad Things Happen to Good Pressure Vessels by The National Board of Boiler and Pressure Vessel Inspectors

Auto-Refrigeration / Brittle Fracture Prevention And Process Safety Mitigation by Inspectioneering

Fitness-for-Service Forum: Minimum Pressurization Temperature (MPT) Curves: Why and How they are Going to Change by Inspectioneering

INSPECT Featured Capabilities