1 ozone and oxygen gas system cleaning and verification presented by: daryl l. roll, p.e
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OZONE AND OXYGEN OZONE AND OXYGEN GAS SYSTEM GAS SYSTEM
CLEANING AND VERIFICATIONCLEANING AND VERIFICATION
PRESENTED BY:
DARYL L. ROLL, P.E.
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OZONE SYSTEM CLEANINGOZONE SYSTEM CLEANING
Cleanliness requirements and protocol
Fabrication and installation strategies
Welding effects
Qualified subcontractor for component and system cleaning
Ozone system preparations
Basic cleaning and passivation chemistries
Testing and verification
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THEORY OF PASSIVATIONTHEORY OF PASSIVATION
Passive Layer
Transition Zone
Base Metal
SURFACE
2 Chrome: 1 Iron
1 Chrome: 4 Iron
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CLEANING AND CLEANING AND PASSIVATION BENEFITSPASSIVATION BENEFITS
Chemical cleaning and flushing removes particulate contamination and organic filmsPassivation increases corrosion protection at weld areas and mechanically damaged surfacesEliminates potential oxidation of contaminants within distribution systemClean systems maintain product purityReduction of particulate generation
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SPECIFICATIONS FOR SPECIFICATIONS FOR CLEANLINESSCLEANLINESS
CGA G – 4.1, 1996CGA G – 4.4, 1993CGA P – 34, 2001ASTM G93 – 96ASTM A380 – 99ASTM A967 – 99ASTM F312 – 97ASTM F331 – 98
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OXYGEN GAS CLEANING OXYGEN GAS CLEANING REQUIREMENTSREQUIREMENTS
The CGA requirements include cleanliness testing of the system after cleaning to meet 47.5 mg/sq.ft. of contamination on the surface
ASTM requirements include alkaline degreasing and passivation of welded and mechanically finished stainless steel
Passivation guidelines are reviewed in ASTM A380 and A967
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CGA G-4.1 REQUIREMENTSCGA G-4.1 REQUIREMENTS
Cleaning Methods Steam Vapor degreasing Solvent washing Alkaline cleaning Acid cleaning Mechanical cleaning Purging
Packaging and Labeling
Inspection
Record Keeping
White light
UV light
Wipe test
Solvent extraction
SafetySafety
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WELD AND FABRICATION WELD AND FABRICATION EFFECTSEFFECTS
Corrosion resistance of surface effected by grinding, welding and mechanical polishing Chrome to iron ratio of surface at weld areas or after grinding will be equal to the base metal (0.25) or lessOxidation of active surfaces will generate iron oxide particlesPassivation will restore surface corrosion resistance and a chrome to iron ratio of 2.0 or greater
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WELD SEAM ANALYSIS:WELD SEAM ANALYSIS:BEFORE PASSIVATIONBEFORE PASSIVATION
0
10
20
30
40
50
60
70
80
9 7 5 3 1 1 3 5 7 9
OXYGENIRONCHROMIUM
Heat Affected Zone
%
Millimeters
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WELD SEAM ANALYSIS:WELD SEAM ANALYSIS:AFTER PASSIVATIONAFTER PASSIVATION
0
10
20
30
40
50
60
70
80
9 7 5 3 1 1 3 5 7
OXYGENIRONCHROMIUM
Heat Affected Zone
%
Millimeters
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FITTINGS & CONNECTIONSFITTINGS & CONNECTIONS
Butt Welds – Smoothest transition
Flanges – Maintenance, accessibility
Socket Welds – Create particle entrapment areas
Preclean of Weld Areas
Post Clean of Weld Areas
Threaded Connections – Particle entrapment
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VALVE CONSIDERATIONSVALVE CONSIDERATIONS
Connection TypesFlangeThreadsSocket weldButt weld
Valve TypesBall - Small diameterButterflyGate or Globe
Removable spools for cleaning & replacementComponents must be oxygen pre-cleaned and replaced during cleaning operations, installed under purge
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PREOPERATIONAL CLEANING PREOPERATIONAL CLEANING REQUIREMENTSREQUIREMENTS
The system must be free of metal grindings, construction debris and organics (oil and grease)The system must contain necessary low point drains and high point ventsThe gas distribution system within the ozone contactor chamber shall be pre-cleaned and installed cleanPneumatic gas test with all components installedQuality welds with no excessive heat effected zonesSpool replacements for all components
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CHEMICAL CLEANING PROCEDURESCHEMICAL CLEANING PROCEDURES
Initial DI flush and leak testAlkaline cleaning with detergents remove surface debris and organic filmsDI water rinse between stagesAcid passivation solution for iron removalFinal DI water rinse and particle count testingDry with clean, dry air or nitrogen and test for dew point. Use solvent (IPA) to test for NVR and total solids. Purge system for installation of components and final pneumatic testing.
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POST CLEANING POST CLEANING REQUIREMENTSREQUIREMENTS
Precleaned and certified components
Removal of spools & replacement of components within clean area & gas purge
Final gas testing of system
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SOLVENT CLEANING & DRYINGSOLVENT CLEANING & DRYING
PART 1: CLEANING Solvent specifications require use of non-
flammable organic solvents 1,1,1 Trichloroethane and Freon are very
expensive regulated solvents ($100 - $300/gal)
N-Propyl Bromide, AK-225, & Vertrel MCA
are replacement solvents “Ozone Depleting” or regulated solvents
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SOLVENT CLEANING & DRYINGSOLVENT CLEANING & DRYING
PART 2: DRYING
Alkaline replacement cleaners require final DI water rinse
Complex piping systems = difficult to dry with traps
Flushing with IPA plus nitrogen gas purge will blend residual water and lower vapor pressure
Allow attainment of -30°F dew point or better
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SUMMARYSUMMARY
Ozone and oxygen enriched generation and
distribution piping systems require a clean and organic free distribution system.
Fabrication operations reduce cleanliness and corrosion resistance which is why cleaning and passivation is required.
Compliance with CGA / ASTM regulations
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SUMMARYSUMMARY (Cont’d)(Cont’d)
Proper testing and certification of cleanliness is required.
Collaboration between engineering design, mechanical installation and precision cleaning contractor is needed.
Systematic preparation, clean fabrication and proper cleaning methods result in improved component performance, ease of system maintenance and overall safety of operations.