Ninety Nine Diseases of Pressure Equipment

in the Hydrocarbon Process Industry

National Pressure Equipment Conference

Banff, Alberta 10 February, 2005 John Reynolds

Shell Global Solutions, USHouston, Texas

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What will I talk about this morning?

• What’s in the title (why the 99 Diseases)?• Who should know about the 99 Diseases?• How to use the 99 diseases to prepare RBI

plans• Establishing Integrity Operating Windows

(IOW’s) to avoid the 99 Diseases• Where to learn more about the 99 Diseases?• Then we’ll cover a few of the 99 Diseases

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What are the 99 Diseases?• General types of degradation mechanisms

that can cause failure of pressure equipment, like:- General and localized corrosion and erosion- Environmentally caused cracking- Metallurgical aging and degradation- High temperature degradation and brittle

fracture- Mechanical cracking and damage- Welding and fabrication flaws

• Anything that will cause materials of construction to degrade and possibly cause failure of pressure equipment in service

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Who should know about the Diseases?

• Not just materials and corrosion specialists, but also:- Inspectors- Operators- Process and technology engineers- RBI teams and PHA teams- Project and equipment engineers- Maintenance personnel- Everyone that has a stake or role in

preventing pressure equipment failures

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What do “others” need to know?• Enough to help them recognize degradation

issues and to seek help from materials and corrosion specialists, when necessary

• Enough to help them understand the importance of operating within the integrity operating windows (IOW’s)

• Enough to help them understand and assess when changes to equipment and/or process conditions might cause changes in types of degradation or changes in rates of degradation

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Why Spread the Knowledge?

• Because in many cases of equipment failure, the materials and corrosion engineer is the one person that “knew” what could happen and could have helped to prevent the incident; but was not in a position to do anything about it when it occurred

• Because the people on the front lines or the people making changes sometimes do not know about the types of degradation that might happen and what their role is in preventing pressure equipment failures

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Why call them the 99 Diseases?• There’s a good analogy with the medical profession

• It’s much easier, much less expensive, and healthier (safer) to prevent diseases than it is to cure them

• We would all rather know and practice the necessary lifestyles that will prevent us from having lung cancer or heart disease than it is to cure either after we contract them

• Same is true with the 99 diseases of pressure equipment

• Preventing cracks, high corrosion rates, and metallurgical degradation is usually easier, much less expensive, and safer than coping with the aftermath of unexpected vessel and piping failures.

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Automobile Analogy• With good care, automobiles can operate

dependably for well over 200,000 miles• But it takes knowledge of what can go wrong and

then doing the necessary preventive maintenance (ie, taking good care of our automobiles)

• Same is true for pressure vessels, heat exchangers, tanks, and piping

• If we take care of them, understand what can make them “break down” (ie, fail unexpectedly), and “drive them” with care (ie, operate them within the properly designated integrity operating window (IOW), they will provide reliable, safe service throughout the life of our process plants

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The 99 Diseases as input for RBI• The 99 Diseases can be used as a checklist

of possible causes of failure from which we glean the probable causes of degradation and failure

• Identifying all the possible degradation mechanisms is a critical success factor for RBI

• RBI team members each need to know a minimum amount about each possible/probable degradation mechanism in order to contribute effectively

• But only one RBI team member needs to be a materials and corrosion specialist

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Where can you learn more?• Hundreds of materials and corrosion references

that are available, but a new one really stands out: • API RP 571, Damage Mechanisms Affecting Fixed

Equipment in the Refining Industry – it’s written for the non-materials/corrosion specialist

• Or for other industries: WRC 488 - Damage Mechanisms Affecting Fixed Equipment In Fossil Electric Power Industry and WRC 489 - Damage Mechanisms Affecting Fixed Equipment In The Pulp And Paper Industry

• Follow the whole series of the 99 Diseases in the Inspectioneering Journal, starting with the Jan/Feb 2003 edition

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Organization of Each Section in API 571

• Description of each damage mechanism• Construction materials affected• Critical factors that cause the damage• Affected equipment and process units• Description of the appearance of the damage• Prevention and mitigation• Inspection and monitoring• Related damage mechanisms• Other references on each type of damage

mechanism• Photos (macroscopic and microscopic)• Very concise – all this condensed into just ~2-4

pages for each damage mechanism

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Let’s Cover a Few of the 99 Diseases• Caustic Cracking

• Vibration Fatigue• 885 Embrittlement• Short-Term Overheating (Stress Rupture)• Liquid Metal Cracking (LMC)• Repair Welds• External Chloride Stress Corrosion Cracking• Naphthenic Acid Corrosion (NAC)• Inadequate Overlay Weld

Thickness/Chemistry

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Caustic Cracking• One of the most common and best understood types of

environmental cracking – often results in white crystalline external deposits near leaks

• Cracks often wide-open, easy to see, but can be fine/tight• Typically in non-PWHT weldments and other areas of high

residual stresses• Some common causes:

- steaming out and carry-over into non-PWHT equipment- Inadequately designed caustic injection nozzles- Inadequate PWHT and non-PWHT repair welds - Heat tracing in direct contact with caustic containing equipment- Operators and maintenance people that don’t understand the

issue• Would your RBI team know about all the potential sources

of caustic that might crack your equipment in service?

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Vibration Fatigue• Can lead to catastrophic consequences when vibrating

nozzles fall off equipment or full bore piping separation occurs

• Often associated with SBP and screwed connections• Usually associated with proximity to rotating machinery,

but can also be associated with flow induced vibrations• Inspection is not typically useful for avoidance• Design modifications are key to corrective action• Don’t let vibration become the accepted norm at your

plant! • Do your operators know enough about the

consequences of vibration fatigue such that they would report equipment vibration for possible mitigation?

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885 Embrittlement• One of many types of embrittlement phenomena that

can lead to brittle fracture of equipment in service• Most commonly affects 400 series stainless steels in

temperature range of 600-1000 F (highest embrittlement occurs at 885 F)

• Susceptible alloys suffer from toughness deterioration due to metallurgical changes in service

• Only detectable through some form of physical or mechanical testing (not NDE or inspection)

• Do you know about all the potential factors and conditions that might lead to embrittlement of your equipment in service?

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Short Term Overheating• Also known as “stress rupture” – not uncommon form

of deterioration – sometimes leads to catastrophic rupture

• Involves localized exposure to higher than design temperature at design operating pressures – sometimes just a few degrees can substantially shorten service life

• Some susceptible equipment – furnace tubes – refractory lined equipment – exothermic reactors

• Canadian HPU furnace hot spot rupture resulted in explosion –> fire –> fatality

• Preventable with IOW’s, hot spot monitoring, IR scanning, heat sensitive paint, burner management, temperature monitoring, etc.

• Do your operators have all the tools and knowledge to avoid short-term overheating failures?

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Liquid Metal Cracking (LMC)

• A very insidious and very rapid cracking mechanism

• Also known as Liquid Metal Embrittlement (LME)• Affects numerous alloys of Al, Cu, Ni, and Fe (SS)• Aluminum core exchangers have failed due to

Mercury LMC – two incidents with huge consequences

• Galvanized coating (Zn) melts at 780F and drips on SS equipment causing LMC

• Cadmium plating on bolts melts at 480F --> LMC• Do you know if some of your equipment may be

susceptible to LMC?

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Repair Welds• Another potentially undetected flaw, sometimes with

fairly insidious consequences• Repair welds are not infrequently the initiation site for

cracking or corrosion failures• Often repair welds (both shop and field) don’t get

reported or recorded and can have inadequate QA/QC• Some construction codes don’t treat repair welds

adequately in terms of specified QA/QC• Repair welds can produce metallurgical notches, stress

raisers, high hardness, and dissimilar weld issues• Do you require your fabricators and maintenance

forces to record and report all repair welds for your records?

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External Chloride Stress Corrosion Cracking

• ECSCC is an off-shoot of effective CUI programs and is difficult to avoid and inspect for

• Affects insulated solid SS equipment in CUI range from 140F (60C) to 300F (150C), and higher temps

• Even good CUI coatings break down after 10-15 years allowing moisture and chlorides to contact the external surfaces under insulation

• Chlorides come from insulation and the atmosphere

• Fortunately SS toughness “usually” leads to LBB• Do you have insulated solid SS equipment that

may be susceptible to ECSCC?

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Naphthenic Acid Corrosion (NAC)• An old problem that we are continuing to learn more about

• Higher severity operations sometimes lead to more NAC in places where we did not find it before

• TAN, organic acids, sulfur content, temperature, and velocity all combine to determine extent of NAC

• Usually results in highly localized corrosion, but can be general thinning in lower alloys

• Prevention includes upgrading to higher Moly containing alloys or blending crude diets

• NAC susceptibility can be predicted with the CORAS model• Would your MOC program be able to predict accelerated

NAC problems from changes in crude diets?

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Weld Overlay Thickness/Chemistry• Steel vessels, exchangers, flanges commonly weld

overlaid with high alloy for corrosion resistance• It’s vital that the top surface of the overlay be the

right alloy content to resist process corrosion, especially if there will be final grinding or machining

• The proper thickness and chemistry QA/QC should be specified following multiple layers of weld overlay

• Don’t count on the machinist or grinder to know that he is defeating your corrosion allowance!

• Have you ever seen localized corrosion or rust stains bleeding through a weld overlaid surface?

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Some More of the 99 Diseases• Graphitization - Temper Embrittlement – Strain Aging – Soil

Corrosion – Atmospheric Corrosion- CUI – Reheat Cracking – Dealloying – Condensate Corrosion – Oxidation – Sulfidation – MIC – CO2 Corrosion – Cavitation – Thermal Shock – Carburization – Hydrogen Embrittlement – Sour Water Corrosion – Ti Hydriding – HTHA – HCl Corrosion – Overhead Corrosion – Dew Point Corrosion – Delayed Hydrogen Cracking – ECSCC – NAC – HIC – SOHIC – PASCC – Metal Dusting – Fuel Ash Corrosion – Corrosion Fatigue – Chloride Cracking – Nitriding – Brittle Fracture – Cavitation – Thermal Fatigue – Steam Blanketing – Erosion – Refractory Failure – Cooling Water Corrosion – Graphitic Corrosion – DMW Cracking – Sigma Phase Embrittlement – Mechanical Fatigue – Spheroidization – Erosion-Corrosion – Galvanic Corrosion – Carbonate Cracking – Green Rot

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Questions to Ponder• Do all the right people at your operating

plant know enough about the 99 Diseases in order to do their part in preventing pressure equipment failures?

• Do you have integrity operating windows (IOW’s) established for all the 99 Diseases to which you may be susceptible?

• Do your RBI plans consider all the 99 Diseases when considering the risk of failure at your plant?

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Ninety Nine Diseases of Pressure Equipment in the Hydrocarbon

Process Industry

Time for Questions?

John.reynolds@shell.comHouston, Texas