API 571 QUESTIONS

API 510 CERT

API RP 571:CONTENTS

Now we will look at the second group of damage mechanisms covered by API 571 4.2.3 – Temper Embri Embrittleme ttlement nt 4.2.7 – Brittle Fract Fracture ure 4.2.9 4.2 .9 – The Thermal rmal Fatig Fatigue ue 4.2.14 – Erosion Erosion/Eros /Erosion-C ion-Corro orrosion sion These are mainly low 4.2.16 – Mecha Mechanical nical Fatig Fatigue ue temperature ,fairly 4.3.2 – Atmos Atmospheric pheric Corro Corrosion sion 4.3.3 – Corro Corrosion sion Under Insulat Insulation ion (CUI) (CUI) straightforward corrosion 4.3.4 – Cooli Cooling ng Water Corro Corrosion sion mechanisms 4.3.5 – Boiler Water Water Condensate Condensate Corrosio Corrosion n 4.4.2 4.4 .2 – Sul Sulfid fidati ation on 4.5.1 – Chlori Chloride de Stress Stress Corro Corrosion sion Crac Cracking king (Cl-SCC) 4.5.2 – Corro Corrosion sion Fati Fatigue gue 4.5.3 – Caustic Stress Corrosion Cracking Cracking (Caustic Embrittlement) 5.1. 5. 1.2. 2.3 3 – We Wett H2S Damage (Blistering/HIC/SOHI (Blistering/HIC/SOHIC/SCC) C/SCC) 5.1.3.1 5.1.3. 1 – High Temperatur Temperaturee Hydrogen Attack Attack (HTHA

© Mat Matthew thewss Engine Engineeri ering ng Train Training ing Ltd Ltd

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API 510 CERT

REMEMBER THE WAY THAT API 571 COVERS EACH OF THE MECHANISMS

Description/appearance of the damage mechanism

Critical factors

Affected equipment Prevention/ mitigation

Related mechanisms

Inspection/ monitoring

© Matthews Engineering Training Ltd

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API 510 CERT

EROSION-CORROSION

Erosion and corrosion act together to significantly increase the rate of corrosion Oxide film cannot form on the surface as it is continually swept away by high velocity fluid flow impingement

Surface shows extended pits,holes and valleys


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API 510 CERT

EROSION/CORROSION High fluid velocities cause scouring

Notice the serious wallthinning Tube-bends are particularly susceptible TO REDUCE EROSIONCORROSION •Reduce fluid velocity •Use a more resistant material (harder alloys may be better)


Slide 4

API 510 CERT

ATMOSPHERIC CORROSION(RUST)

Caused by atmospheric moisture Marine environments are the worst

Corrosion increases with temperature up about 250 degF (121 degC)

Pollution(e.g. acidic) makes it worse


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API 510 CERT

CORROSION UNDER INSULATION (CUI)


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API 510 CERT

CUI

4 COMMON LOCATIONS •All LCS pipework operating continually at – 4 120 degC BUT INTERMITTENTLY •Austenitic Stainless steel at 65-205 DegC (for SCC) •Piping systems that vibrate a lot (insulation becomes damaged) © Matthews Engineering Training Ltd

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API 510 CERT

CUI LOCATIONS

Areas around leaks

Areas of vibration

Chloride contamination something done about places CUI – Getwater (from or lagging) makes where you have to step on insulation much worse to access equipment Corrosion under Insulation


Where lagging is damaged Slide 8

API 510 CERT

CUI CAN BECOME SEVERE UT thickness checks are used to measure the wall-thinning


Slide 9

API 510 CERT

COOLING WATER CORROSION Look at section 4.3.4 of API 571

Think of it as a general and widespread corrosion mechanisms spread across most industries

Pipework

Heat exchangers


Slide 10

API 510 CERT

COOLING WATER CORROSION

4 KEY POINTS(highlight these in your code) It affects almost all materials Corrosion can be general or localised It is made worse by high fluid velocities (giving erosion/corrosion) It is made worse by: •Increased Oxygen content •Temperatures > 57 degC


Slide 11

API 510 CERT

COOLING WATER CORROSION

Preventative measures are fairly obvious

•Keep the temperature below 50 degC •Avoid too-low velocity ‘stagnant' conditions •Chemical water treatment (e.g in condensers) •Use linings or more corrosion-resistant materials


Slide 12

API 510 CERT

BOILER WATER CONDENSATE CORROSION

A very common mechanism in boiler condensate systems

•Deaerators •Condensate return pipework •Feed heaters and pipework


Slide 13

API 510 CERT

BOILER CONDENSATE CORROSION

This is a specific corrosion mechanism of boiler systems and condensate piping

Dissolved Oxygen results in pitting-type damage

Pits can sometimes be hidden under ‘tubercles’ (oxide caps) Internal surface of boiler tube © Matthews Engineering Training Ltd

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API 510 CERT

OXYGEN PITTING

pH and temperature will make it worse

Extreme cases lead to leakage © Matthews Engineering Training Ltd

Slide 15

API 510 CERT

2

MAIN CAUSES OF O2 PITTING

Too much O2 (poor deaerator in the system and/or not enough hydrazinetype O2 scavenger chemical)

Too much CO2 (typically in the condensate part of the system) © Matthews Engineering Training Ltd

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API 510 CERT

OXYGEN PITTING:

Advanced pitting of a condensate line

CO2 is normally the cause in condensate return lines


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API 510 CERT

API RP 571:CONTENTS

This PowerPoint presentation has looked at these

5 damage

mechanisms covered by API 571

4.2.3 – Temper Embrittlement 4.2.7 – Brittle Fracture 4.2.9 – Thermal Fatigue 4.2.14 – Erosion/Erosion-Corrosion 4.2.16 – Mechanical Fatigue 4.3.2 – Atmospheric Corrosion 4.3.3 – Corrosion Under Insulation (CUI) 4.3.4 – Cooling Water Corrosion 4.3.5 – Boiler Water Condensate Corrosion 4.4.2 – Sulfidation 4.5.1 – Chloride Stress Corrosion Cracking (Cl-SCC) 4.5.2 – Corrosion Fatigue 4.5.3 – Caustic Stress Corrosion Cracking (Caustic Embrittlement) 5.1.2.3 – Wet H2S Damage (Blistering/HIC/SOHIC/SCC) 5.1.3.1 – High Temperature Hydrogen Attack (HTHA

NEXT STEP


In the last presentation we will look at the remaining ones.First,return to the module text

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API 571 QUESTIONS

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