Industrial Park



THE SIGNAL October 2014


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Case Study: Reduction of Minimum Allowable Metal Temperature of a Refrigerated Vessel

At a recent technical conference, an ammonia producer learned about the benefits of fitness-for-service. Inspired by the example discussed during a technical presentation, the producer identified a vessel at one facility that had recently been listed for replacement due to insufficiently low minimum temperature ratings.

The vessel, a NH3 refrigerated gas chiller, was identified as having a minimum temperature rating of -10°F, higher than the low gas temperature. Using all available documentation, a quick Level 2 Brittle Fracture assessment of the vessel determined that it could be operated at a minimum metal temperature of -35°F. The producer was able to keep the vessel in service and spend the planned replacement funds on other reliability projects.

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Quiz Question

What is the lowest minimum allowable metal temperature (MAT) allowed by a brittle fracture assessment?

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Quiz Answer:

-155° F