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Conducting Effective Visual Conducting Effective Visual Inspections:Inspections:Mechanical Integrity for Refrigeration Mechanical Integrity for Refrigeration SystemsSystems
Daniel DettmersDaniel DettmersAssociate Researcher, IRCAssociate Researcher, IRC
What is an Effective Visual Inspection?What is an Effective Visual Inspection?
• Thorough inspection of the exterior of the refrigeration system– Insulated and uninsulated components– Easily accessible and less than accessible components– No drive-by’s
• What’s included?– Piping & valves– Vessels– Heat exchangers– Ammonia pumps– Etc.
Origin of the RequirementOrigin of the Requirement29 CFR 1910.119 (j)(4)29 CFR 1910.119 (j)(4)– (j)(4)(i) Inspections and tests shallshall be performed on
process equipment– (j)(4)(ii) Inspection and testing procedures shall follow
recognized and generally accepted good engineering good engineering practicespractices
– (j)(4)(iii) The frequency of inspections & tests of process equipment shall be consistent with applicable applicable manufacturers‘ recommendationsmanufacturers‘ recommendations and good engineering good engineering practicespractices, and more frequentlymore frequently if determined to be necessary by prior operating experience
Good Engineering Practice?Good Engineering Practice?• Manufacturers’ recommendations• Industry standards
– ASME B31.5 or B31.3 • Pre-startup inspection
– NB-23 (National Board Inspection Code)• Refers to ASME Boiler
& Pressure Vessel Code
• Guidelines– IIAR Bulletin 109 – IIAR Bulletin 110– IRC Mechanical Integrity Guidebook
• Currently in trial use
IIAR 109 & 110IIAR 109 & 110109:4.7.3109:4.7.3 – “Ammonia piping should be inspected…”109:4.7.4109:4.7.4 – “Uninsulated refrigerant piping should be
inspected…110:6.4.2.1110:6.4.2.1 - While the system is operational, the external
appearance of the surface of vessels or heat exchangers … should be visually inspected weekly by the system operating staff for any departures from normal.”
110:6.4.3110:6.4.3 – “The external surface or the insulation and associated vapor barrier applied to…vessels and heat exchangers should be inspected no less than once every 12 months.”
IIAR 109 & 110IIAR 109 & 110110:6.7.1110:6.7.1 – “All uninsulated piping and associated
components…shall be inspected annually for any damage or deterioration…”
110:6.7.2110:6.7.2 – “At least as part of the annual piping inspection, but preferably more frequently, the external condition of the insulation and supports shall be inspected.”
• Additional components for yearly inspection in 110– Ammonia pumps– Shut-off valves
• 6 months for exposed stems
– Relief valves
Conducting the InspectionConducting the Inspection• Establish a plan– Identify and categorize equipment within scope of
1910.119 §(j)– Establish prioritized list of appropriate inspections &
tests– Conduct necessary tests and inspections within
prescribed frequencies– Train all personnel –- consistent inspectionsconsistent inspections– Establish “go, no-go” criteria for continued service–– DocumentDocument inspection and tests
Conducting the InspectionConducting the Inspection• Assign inspection duties & timeframe– Undesirable:
• All inspection duties fall on 1 person• All inspections are planned for the day they are due
– Desirable:• Diversify inspection duties
– Be certain inspection criteria is consistentconsistent– Incorporate with other inspection/maintenance of valves, valve
tags, vessels, evaporators, etc.– Involve new hires in process as part of OTJ training
• Plan inspection at least 1 month before due• Train all involved and document their training
Potential Failure MechanicsPotential Failure Mechanics• Weld Failure• Stress Corrosion Cracking (SCC)• Internal Erosion• External Corrosion– Corrosion Under Insulation (CUI)
Which can we catch in a visual inspection?No
NoNo
Yes!Yes!AlmostAlmost
CorrosionCorrosion• “The deterioration of a material, usually a metal,
by reaction with its environment.”- National Association of Corrosion Engineers (NACE)
• An anodic-cathodic reaction– Positive ions travel through
an electrolyte (i.e. water, ice, etc.)
– Material is sacrificed• General (Uniform) Corrosion• Pitting Corrosion
CorrosionCorrosion• Positive ions detach at the anode and
travel through a electrolyte (i.e. water, ice, etc.) which acts as a carrier connecting to the cathode the anode and cathodes need to be joined to complete the circuit– Anode => metal of the refrigeration system– Cathode => metal of the refrigeration system– Electrolyte => water
Controlling water is essential!!Controlling water is essential!!
Corrosion “Low Risk” AreasCorrosion “Low Risk” Areas• Uninsulated, painted pipe
– Easy to see any corrosion forming
• High temperature pipe– If pipe is on the high side of the
system and insulated (i.e. HPL) there aren’t large driving forces pulling moisture into the insulation system
• “Always Frozen”– Ice is a poor electrolyte slowing
the corrosion process– Be careful of what is defined as
“always frozen”
SolidSolidIceIce
FrozenFrozenInsulationInsulation
WetWetInsulationInsulation
Froz
enFr
ozen
Pipe
Pipe
Corrosion Under Insulation (CUI)Corrosion Under Insulation (CUI)• CUI is general corrosion that occurs undetected
under piping insulation– Water infiltrates the insulation system through a
break in the jacket/vapor barrier– Insulation then becomes an enabler which aids in
corrosion by holding the water tight to the pipe
– Pipe must also be without or have a failure in the surface protection (i.e. pipe paint)
Corrosion Under Insulation (CUI)Corrosion Under Insulation (CUI)““Vapor Barrier”Vapor Barrier”
Inside InsulationInside Insulation
Outside InsulationOutside Insulation
PipePipe
Rust/InsulationRust/Insulation
Soaked InsulationSoaked Insulation
How Does Moisture Enter?How Does Moisture Enter?• Insulation system failures
– Breaches in jacket, vapor retarder and insulation
– Travel under/through the insulation from a breach elsewhere in the system
• Water trapped at time of installation
• Diffusion of water vapor in the air into insulation– Driving forces pull moisture laden
air through cracks, holes and unsealed joints
– Vapor retarder not barrier
Corrosion “High Risk” AreasCorrosion “High Risk” Areas• Piping that is near to or above the
freezing point• Piping that cycles temp (defrost
condensate)• Piping that has circumferential
temp distribution (wet suction)• Low points in the piping system
– Dips in line or end/corner of horizontal run
– Bottom of vertical run– Bottom edge of a horizontal pip run
• Piping that is hard to inspect– under supports– Behind walls/piping chases
Other TellOther Tell--Tale SignsTale Signs
Corrosion Corrosion of theof theJacketJacket
Biological GrowthBiological Growth
External FrostExternal FrostEspecially in SummerEspecially in Summer
Wet Suction ReturnsWet Suction Returns• Vapor sits in bottom of pipe– Bottom always frozen– Top can freeze-thaw
• CUI at mid-pipe or higher• Look for bottom frost/water
CrossCross--sectionsection
VaporVaporNHNH33
Ammonia Condensate Defrost LinesAmmonia Condensate Defrost Lines• Large swings in
temperature– Above and below
freezing (32oF)– Large driving
force for moisture – Multiple freeze/thaw cycles
that tear apart the insulation
0
20
40
60
80
2 4 6 8 10 12 14 16 18 20 22 24
Physical ImpactPhysical Impact• Physical damage to insulation, pipe or vessel is usually
easy to spot• Equipment susceptible to damage is often located in
areas of heavy traffic, outside (exposed to the elements) or in an area subject to frequent clean-up wash downs
• Look anywhere fork trucks can reach (and areas they can’t)– Behind guards– Ceiling hung evaps– Piping running up or along walls– Vessels in spaces
DocumentationDocumentation1910.119 (j)(4)(iv) The employer shall document each
inspection and test that has been performed on process equipment. The documentation shall identify the date of the inspection or test, the name of the person who performed the inspection or test, the serial number or other identifier of the equipment on which the inspection or test was performed, a description of the inspection or test performed, and the results of the inspection or test.
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