Considerations for Operating Pressure Vessels Below -20°F.pdf
Considerations for Operating Pressure Vessels Below -20°F
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1 Considerations for Operating Pressure Vessels Below -20°F Rowe Bansch – RVS Corp. INDUSTRIAL REFRIGERATION CONSORTIUM RESEARCH & TECHNOLOGY FORUM MAY 2-3, 2012 ASME Section VIII Design Standard Design Parameters for NH 3 Refrigeration Pressure Vessels Maximum Allowable Working Pressure (MAWP) of 250 PSI Minimum Design Metal Temperature (MDMT) of -20°F
Transcript of Considerations for Operating Pressure Vessels Below -20°F
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Considerations for Operating Pressure Vessels Below -20°F
Rowe Bansch – RVS Corp.
INDUSTRIAL REFRIGERATION CONSORTIUM
RESEARCH & TECHNOLOGY FORUM
MAY 2-3, 2012
ASME Section VIII Design
Standard Design Parameters for NH3 Refrigeration Pressure Vessels
Maximum Allowable Working Pressure (MAWP) of 250 PSI
Minimum Design Metal Temperature (MDMT) of -20°F
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Considerations for Operating Pressure Vessels Below -20°F
ASME Section VIII Design
Design for MDMT to -20°F is governed by Paragraph UG-20
Impact testing is not required for carbon steel pressure vessel materials up to 1” thick at design temperatures as low as -20°F
Considerations for Operating Pressure Vessels Below -20°F
ASME Section VIII Design
Design for MDMT below -20°F is governed by Section UCS
Fig. UCS-66 shall be used to establish impact testing exemptions for listed carbon steels
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Considerations for Operating Pressure Vessels Below -20°F
Considerations for Operating Pressure Vessels Below -20°F
ASME Section VIII Design
Figure UCS-66
Impact testing is required for a combination of MDMT and material thickness below the curve
When required, Charpy V-notch impact tests shall be made on weldments and all pressure boundary materials
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Charpy Test Apparatus
NIST Charpy Verification Rig
University of Leeds
Charpy Test
The falling pendulum weight strikes a 10 mm square notched specimen
When struck, the specimen will be broken or severely deform.
The pendulum’s travel distance after striking the specimen is measured on a gauge.
The difference between the initial pendulum height and the height after strike is related to the energy absorbed by the specimen
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Charpy Impact Test Results
FATT - Fibrous (shear) Appearance Transition Temperature
Here is a technician performing a Charpy impact test
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Considerations for Operating Pressure Vessels Below -20°F
ASME Section VIII Design
Figure UCS-66
Standard materials (Curve B) are only exempt to -20°F
SA516-70N, SA333 Gr6 (Curve C & D) are exempt to -55°F
Considerations for Operating Pressure Vessels Below -20°F
ASME Section VIII Design
Figure UCS-66.1
When the coincident ratio (trE*/tn) is less than one, Fig. UCS-66.1 provides a basis for a further reduction in MDMT to as low as -55°F
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Considerations for Operating Pressure Vessels Below -20°F
Considerations for Operating Pressure Vessels Below -20°F
ASME Section VIII Design
Paragraph UCS-66(b)(3)
When the coincident ratio (trE*/tn) is less than or equal to 0.35, impact testing is not required for MDMT as low as -155°F
This is primary basis for what we often refer to as “dual stamping”
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Considerations for Operating Pressure Vessels Below -20°F
ASME Section VIII Design
“Dual Stamping”
Primary Rating of 250 PSI MAWP @ -20°F to 300°F
Secondary Rating of 87.5 PSI (35%) @ -60°F
Considerations for Operating Pressure Vessels Below -20°F
ASME Section VIII Design
“Dual Stamping”
Accepted practice for refrigeration vessels in which the operating temperature is a function of the pressure
Relief valve setting is based on the most severe condition of coincident pressure and temperature which is the 250 PSI @ -20 to 300°F
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Considerations for Operating Pressure Vessels Below -20°F
ASME Section VIII Design
Recommendation
Specify “dual stamping” for all low side vessels
MAWP 250 PSI @ -20 to 300°F and 87.5 PSI @ -60°F
Considerations for Operating Pressure Vessels Below -20°F
ASME Section VIII Design
Existing vessel operating below MDMT?
Often discovered during Mechanical Integrity Inspection
Operating temperature has been lowered to increase production or product quality
Original MDMT was not consistent with actual operating temperature
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Reducing Original MDMT
National Board Inspection Code (NBIC)
Provides rules for inspection, repair and alteration of vessels in service
Provides rules for decreasing the MDMT of vessels in service
Considerations for Operating Pressure Vessels Below -20°F
Reducing Original MDMT
NBIC Requirements
Revise calculations verifying the new MDMT in accordance with the “R” Certificate Holder’s Quality Control System
Re-ratings shall be in accordance with the original Code Addenda to which the pressure vessel was built
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Considerations for Operating Pressure Vessels Below -20°F
Reducing Original MDMT
NBIC Requirements continued
Current inspection records verify the pressure vessel is satisfactory for the proposed service
All NBIC requirements have been met to the satisfaction of the Authorized Inspector and the Jurisdiction at the location of the installation
Reducing Original MDMT
Re-rating Documentation
“R” Certificate Holder Nameplate
Specifying new MDMT and coincident pressure rating
Attachment to pressure vessel witnessed by Authorized Inspector
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Considerations for Operating Pressure Vessels Below -20°F
Considerations for Operating Pressure Vessels Below -20°F
Reducing Original MDMT
Re-rating Documentation
Form R-2 Report of Alteration
Documenting new MDMT and coincident pressure rating
Design Certified by “R” Certificate Holder and Authorized Inspector
Certificate of Inspection by witnessing Authorized Inspector
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Considerations for Operating Pressure Vessels Below -20°F
Considerations for Operating Pressure Vessels Below -20°F
Reducing Original MDMT
Re-rating
Operating temperature complies with MDMT
Complete documentation for Mechanical Integrity or Jurisdictional Inspection
Minimal cost compared to replacing pressure vessel
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Considerations for Operating Pressure Vessels Below -20°F
Questions?
