ASME Temporary Repairs 101410-1 (1)

Temporary Repairs Presented by: Charlie Rutan

Formally Senior Engineering Advisor for LyondellBasell

Fixed Equipment Inspection, Repair, and Failure AnalysisHouston, TexasOctober 14, 2010

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Special Acknowledgements

• Michael Guillot, Ph.D., P.E. Stress Engineering Services, Inc.; mike.guillot@stress.com

ASME Fixed Equipment Inspection, Repair, and Failure Analysis Seminar Houston, TexasAugust 18–20, 2009

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Contents of Presentation

• Repairs made at every plant to keep things running, but considered as temporary repairs by API or other governing bodies

On-line, non-welded repairs

On-line, welded repairs

• Documentation and tracking of temporary repairs

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Temporary Repairs – Definitions

• From API 510 – 3.60:

Repairs made to pressure vessels to restore sufficient integrity to continue safe operation until permanent repairs can be conducted

• From API 570 – 3.45:

Repairs made to piping systems to restore sufficient integrity to continue safe operation until permanent repairs can be scheduled and accomplished within a time period acceptable to the Inspector or Piping Engineer

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Temporary Repairs – Definitions (Continued)

• On-line, non-welded repairs• Flange repair• Enclosures

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Flange Repair

• Wire-wrap procedure

Used in flange gaps up to 10 mm (0.4 inches)

Pressure limitations

Immediate off-the-truck repair

Excessive peening must be avoided to prevent bolts from being overloaded

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Mechanical Clamp Repair (continued)• Hot Tapping can be performed through

mechanical clamps. This is a very effective way of preventing a crack to propagate.

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Hot Tap

• Hot Tapping• Line Stops

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• Physical limitations (continued)

Metal Thickness > 0.75” – Difficulties – excessive metal shavings– Required thickness calculations, body bound bolts, and no

pilot drill

Hot Tapping in the horizontal direction – Turn the valve up side down and let the shavings fall into the valve bonnet

Local stress relieving may be required for carbon steels due to the steels thickness – This may be a real issue! (Cooper Heat)

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On-Line Weld Repairs (continued)• In some cases these repairs can be considered

permanent repairs.• Allow clamp to come to line temperature• Use the proper welding procedure

First weld will be a circumferential weld at one end of the clamp

Second welds are the longitudinal welds

After welds have cooled the circumferential weld can be made.

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On-Line Weld Repairs Welding Procedures (continued)

Process conditions are key and will define the welding criteria

TIG welding is preferred for the first 3 or 4 passes.

A 3/32 ” diameter weld rod should be used for the next 3 to 4 passes

Typically then a 1/8 ” diameter rod can then be used

Note: on the inside of a 6” pipe with a wall thickness of 0.280” the wall temperature was measured to be 740oF with the TIG heat area of .39 in2 while the 3/32 ” diameter weld rod had the same temperature but the area was increased 1.83 times from 0.39 in2

to 0.95 in2

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History of Hot Tapping

• The first hot taps were made with sledgehammers and pointed bars

• H. Muller, founder of Muller Company, patented first tapping machine (1872)

• Frank Wheatley Company of Tulsa Oklahoma developed first tapping machine for oil and gas industry

• In 1932, J. E. Polston and A. M. Hill invented P&H Tapping Machine. A telescoping boring bar was the special design feature.

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Very Early Hot Tap

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Tapping Through A Pipe Wall

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Pipe ID Flow Stop

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Modified Muller Hot Tap

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Modified Muller Line Stop

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Hot Tap vs. Clamp for Repair

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Hot Tap for Repairs

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• Lap patch in a refinery FCCU

In FCCU units, catalyst continually circulates at temperatures of 1200 to 1400°F (650 to 750°C). Catalyst is circulating at high velocity, so it is extremely erosive.

Carbon steel is used in services < 750°F (400°C). At higher temperatures, it loses mechanical strength, and therefore its ability to withstand pressure.

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Documentation & Tracking of Temporary Repairs

• API 510 8.1.5.1 – Temporary Repairs

8.1.5.1.1 – General– Temporary repairs should be removed and replaced with suitable permanent

repairs at next available maintenance opportunity.– Temporary repairs may remain in place for a longer period of time only if

evaluated, approved, and documented by engineer and inspector.

Documentation of temporary repairs should include

– Location of temporary repair– Specific details, e.g., material of construction, thickness, size of welds, NDE

performed– Details of analyses performed– Requirements for future inspections– Due date for installing permanent repair

Inspection plans shall include monitoring integrity of temporary repair until permanent repairs are complete

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Documentation & Tracking of Temporary Repairs

• API 510 8.1.5.1 – Temporary Repairs (cont’d.)

8.1.5.1.2 – Fillet-Welded Patches– Fillet-welded patches may be used to make temporary repairs to

damaged, corroded, or eroded areas of pressure vessel components.– Cracks shall not be repaired in this manner unless the engineer

determines that cracks will not be expected to propagate from under the patch. In some cases, the engineer may need to perform a fitness-for-service analysis.

– Temporary repairs using fillet-welded patches shall be approved by an inspector and engineer. Use of fillet-welded patches may be subject to acceptance of governing jurisdiction.

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Documentation & Tracking of Temporary Repairs• API 570 – 7.6 Reporting and Records for Piping System

Inspection

Any significant increase in corrosion rates shall be reported to owner/user for appropriate action (Change in process conditions)

Owner/user shall maintain appropriate permanent and progressive records of each piping system covered by API 570.

These records shall contain pertinent data such a

– Piping system service– Classification– Identification numbers– Inspection intervals– Documents necessary to record name of individual performing testing, date,

types of testing, results of thickness measurements and other tests, inspections, repairs (temporary and permanent), alterations, or rerating.

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Documentation & Tracking of Temporary Repairs• API 570 – 8.1.3 Welding Repairs (including on-stream)

8.1.3.1 – Temporary Repairs– For temporary repairs, including on-stream, a full encirclement

welded split sleeve or box-type enclosure designed by piping engineer may be applied over damaged or corroded area.

– Longitudinal cracks shall not be repaired in this manner unless piping engineer has determined that cracks would not be expected to propagate from under the sleeve. In some cases, piping engineer will need to consult with a fracture analyst.

– If repair area is located (for example, pitting or pinholes) and specified minimum yield strength (SMYS) of the pipe is < 40 ksi (276 MPa), a temporary repair may be made by fillet welding a properly designed split coupling or plate patch over pitted area.

– Material for the repair shall match base metal unless approved by piping engineer.

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Documentation & Tracking of Temporary Repairs• API 570 – 8.1.3 Welding Repairs (including on-stream)

8.1.3.1 – Temporary Repairs (cont’d.)– For minor leaks, properly designed enclosures may be welded over

the leak while piping system is in service, provided inspector is satisfied that adequate thickness remains near weld, and piping component can withstand welding without likelihood of further material damage, such as from caustic service.

– Temporary repairs should be removed and replaced with a suitable permanent repair at next available maintenance opportunity. Temporary repairs may remain in place for a longer time only if approved and documented by piping engineer.

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Documentation & Tracking of Temporary Repairs

• Temporary repairs should be removed and replaced with a suitable permanent repair at the next available maintenance opportunity.

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Questions and Comments