Some Common design defects are: 1. ___ to ___ or ___ areas. 2. ___ ___ or other connectors. 3. ___ 4. Gaps (Particularly ___ ___ or surfaces ___ ___. 5. ___ surfaces. (Roof plates in water tanks.) 6. Angle iron badly ___ or in __ ___. 7. ___ areas. 8. ___ metals. 9. ___ edges, particularly on corners or rough cut plate. 10. ___ aids.

1. Hard to reach or inaccessible areas. 2. Rivets, Bolts, or other connectors. 3. Welds 4. Skip Welds or surfaces close together. 5. Overlapping Surfaces. 6. Angle iron badly oriented or in complex arrangements. 7. Threaded areas. 8. Dissimilar metals. 9. Sharp edges. 10. Construction Aids.

Design and Fabrication Defects Flashcards by Sara Sheppard

Many structures are not designed with the ___ ___ in mind.

Coating Process.

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___ ___ and ___ ___ can complicate surface prep and application of a coating system.

Design Flaws and Fabrication faults.

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Neither the ___, the ___, or even the ___ can be blamed for problems engendered by the work of designers, engineers, and/or fabricators.

Applicator, the inspector, or even the coatings.

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In some cases, specialized ___ ___ or partially disassembly of them can take care of inaccessible area surface prep issues.

Blast Nozzles

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Some Common design defects are:

___ to ___ or ___ areas.
___ ___ or other connectors.
___
Gaps (Particularly ___ ___ or surfaces ___ ___.
___ surfaces. (Roof plates in water tanks.)
Angle iron badly ___ or in __ ___.
___ areas.
___ metals.
___ edges, particularly on corners or rough cut plate.
___ aids.

Hard to reach or inaccessible areas.
Rivets, Bolts, or other connectors.
Welds
Skip Welds or surfaces close together.
Overlapping Surfaces.
Angle iron badly oriented or in complex arrangements.
Threaded areas.
Dissimilar metals.
Sharp edges.
Construction Aids.

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Hard to reach areas:

Stiffening members on the inside of a vessel create areas that are easy to coat. True or False?

False.

These are hard to reach areas and require special attention to ensure proper coating.

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Maintenance of all kinds, including corrosion prevention methods, are so vital to the life of facilities/structures, designers should incorporate supports for ___, ___, and ___ ___ in order to allow easy access and stow equipment/materials while working.

Cleaning, coating and repair tools.

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Designs that feature riveted or bolted areas can leave 1 ___ and ___ ___ that are next to impossible to clean and coat. It is also extremely difficult to protect 2___ in these design configurations.

Gaps and tight areas.

2. Bolts.

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Welds generally present 1___, ___ areas on a plane and may have 2___ ___.

Rough, discontinuous areas.

2. Sharp edges.

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Too frequently welds are not cleaning properly leaving ___ ___, ___, and ___ ___ residues.

Weld spatter, slag and acid flux residues.

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Weld spatter, slag and acid flux residues must be removed or corrosion may be?

Encouraged.

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Clean weld areas, especially in tanks and vessels, 1. ___ them ___/___ depending on operating conditions, then 2___ ___.

Grind them smooth/flush.

2. Stripe coat.

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It is not always advisable to ___ welds so inspectors should not authorize grinding of welds without consulting the structural engineer.

Grind

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Inspectors should consult the structural engineer before authorizing the ___ of welds.

Grinding

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When inspections are required on welds, the visual comparator associated with NACE SP178 may be useful and allow the inspector to identify and report the weld condition on a scale ranging from __ to __.

A to F.

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Welds are often tested for cracks with 1___ ___ ___. (e.g. 2. __-___ ___.)

Chemical test solutions.

2. Dye-penetrant solutions.

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Contamination on the surface of welds left by chemical test solutions must be removed as coatings will not bond well and coating failure may occur. True or False?

True.

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Removing contamination from welds left chemical test solutions is difficult. Apply a ___ solvent as needed until any remaining traces cannot affect coating adhesion or bleed back into the coating.

Prescribed solvent.

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Skip Welds, gaps, sharp edges, crevices and back to back angles can lead to early coating failures. True or False?

True

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Overlapping plates/roof plates are generally?

Skip Welded.

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Overlapping plates/roof plates create areas inaccessible for either ___ or ___.

Cleaning or coating.

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Overlapping plates create ___ and ___ ___ which makes corrosion occur.

Crevices and moisture accumulation.

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Angles are frequently used in construction? True or False?

True.

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Often the back sides of angles created during construction are not coated but are sometimes pre-coated with ___ or ___ ___.

Galvanizing or inorganic zinc.

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The areas between angles may be impossible to ___ and ___.

Clean and coat.

With angles created during construction, seal the void space around the angles with 1. ___ or ___ to prevent corrosion and the possible 2. ___ of coating at the edges.

1. Caulking or Mastic. | 2. Undercutting

An alternative to Caulking angles is to use ___ ___.

Penetrating Sealers.

Threaded areas are very difficult to coat. Take care to ensure workers adequately ___ and ___ all surfaces.

Clean and Coat.

There are many ___ and ___ ___ with threads that can encourage corrosion.

Crevices and sharp edges.

Since threads are difficult to clean and coat properly, replace threaded outlets, when possible, with ___ or ___-___ outlets, which are generally more accessible.

Flanged or pad-type outlets.

Dissimilar metals that come into contact with each other create a ___ ___ which can start corrosion resulting in coating failure.

Galvanic Cell.

Whenever dissimilar metals are connected, ___ all connected dissimilar metals.

Coat

Where dissimilar metals connect, a 1___ ___ forms opening the possibility for 2___ ___.

1. Metallic Pathway | 2. Bimetallic Corrosion

With connected dissimilar metals, an unfavorable ___ to ___ relationship may exist.

Anode-to-cathode

When the anode is relatively small compared to the cathodic area, the corrosion effect at the anode may be severe, leading to ___ ___ and probably ___ at the anodic area.

Rapid corrosion and probably pitting.

A typical structure may contain edges that are many linear feet long, most of which have no ___ ___.

Rounded edges.

Sheared edges and flame-cut edges created during fabrication are likely to be ___ and very ___ in the coating process.

Sharp and very problematic.

Coatings generally have a tendency to ___ and ___ ___ from edges leaving a thin, less protective coating.

Shrink and pull back.

Construction aids such as hold downs, brackets, etc are often ___ to the structure with ___ ___ or with only one side of the joint welded.

Welded to the structure with skip welds.

Construction aids are designed to be removed after construction but are sometimes left in place and coated. True or False?

True

When a construction aid is coated, surface prep and coating application are not affected. True or False.

False. Surface prep and coating may be less than ideal and could result in early coating failures.

When a construction aid is coated, surface prep and coating application are not affected. True or False.

False. Surface prep and coating may be less than ideal and could result in early coating failures.

Though they present a problem, do not remove construction aids in the field without ___ ___.

Engineering Approval

If unable to remove construction aids, or unable to apply for engineering approval, prepare the surface per the spec and apply a proper coating. True or False

True

Depressions in the outer surfaces can accelerate corrosion by restricting 1___-___ ___, 2___ ___, or by collecting 3___ or other ___.

1. Run-off flow 2. Water drainage. 3. Dirt or other trash.

Crevices that ___ ___ or ___ ___ can lead to early coating failure.

Trap Water or Corrosive Liquids

Poor ventilation, which ___ ___ of condensing moisture can lead to early coating failure.

Slows Evaporation

Corners, like sharp edges, have the same tendencies for corrosion. True or False.

True.

Corners should be ___ ___.

Stripe Coated

Coatings applied over interior corners will shrink by forming a ___ with poor contact to the substrate.

Bridge

The Wallpaper Effect is?

Coating shrinking away from sharp corners forming thin bridge of sorts with very low adhesion.

Corners may allow accumulation of dirt or trash and ___ the surface for coating.

Contaminate

Like other surfaces, inside corners should be clean, free of dirt/dust/ect and ___ ___.

Stripe Coated.

Faying surfaces are?

Surfaces joined together to create a friction grip.

Faying surfaces are a special case. Clean and leave uncoated or clean and coat with a tested/approved coated for Faying surfaces. True or False?

True

___ ___ coatings are the most common coating for Faying surfaces.

Inorganic Zinc

Surface prep for coating includes suitable prep of the steel substrate to remove all ___ ___ that could break through the coating film or prove difficult to adequately protect with coatings.

Surface Defects

Typical examples of Surface Defects include?

Surface Laminations and Inclusions

Where defects are exposed by blast cleaning and subsequently removed by grinding, it is necessary to?

Re-prepare the immediate area to retain the surface profile.

Surface Lamination is the least common surface defect on steel substrates? True or False?

False. They are the most common.

Surface Laminations are typically caused by ___ the ___.

Rolling the Steel.

Surface Laminations must be removed by ___ since no coating system can fully protect the surface if they are left intact.

Grinding.

Small surface laminations (Even if they do not yet project above the surface.) may later curl upwards and penetrate or disrupt the coating system. True or False.

True

Remove inclusions in all forms. Methods including ___ and/or ___.

Chipping and/or Grinding

Sometimes ___ ___ can restore the surface marred by inclusions.

Weld filling

Fabrication errors should be addressed in the job specification and discussed at the pre-job meeting. True or False?

True

Inspectors should ensure defects are corrected in accordance with?

The Specification.

If correction of defects are not called for in the specification, make sure workers ___ and __ the defects as well as possible.

Prepare and coat.

___ and ___ each defects precise location in the daily inspection report. This information will be useful to the owner for future maintenance and hep determine if future failures loom.

Find and document

If the specification calls for repair of defects, then complete the repairs?

Before further work proceeds.

Fabrication defects are very similar to design defects. However, design defects are flaws made when designing the structure and fabrication defects are created during the construction/repair/work of the structure. True or False?

True.

Weld spatter/splatter describes particles of ___ ___ from welding that are thrown onto the surface adjacent to the weld.

Molten metal

Sometimes weld splatter removes easily with an impact tool such as a 1___ ___. But, generally, removal requires 2___ ___ with a disk or angle grinder in order to remove it successfully.

1. Chipping Hammer | 2. Grinding down.

Weld splatter may be up to ___ ___ or more in height over the substrate.

20 mils.

___ ___ can be difficult to cover using only a coating of appropriate thickness. The resulting film may break down early and allow corrosion which may later spread beneath the film.

Weld splatter

Treatment of weld splatter is?

Important.

Weld splatter must be removed by ___ ___ before blasting.

Mechanical means.

In tanks/vessels, where coating are in immersion service and where frequent inspection is impractical, it is most ___ to ___ all ___ ___ to minimize or eliminate the opportunity for corrosion to occur.

Most critical to remove all well splatter.

Proper welding technique is important to avoid __ ___.

Skip welds.

Welding should be ___ rather than spot or intermittent to avoid skip welds.

Continuous

Continuous welding is more expensive than spot welding. However, extending the life of the coating generally more than offsets the extra cost. True or False?

True

Report any ___ in welds to the owner for further evaluation before coating.

Cracks

The best method to seal skip welds is to make a ___ ___ then ___ ___ it before proceeding with the regular coating.

Continuous weld, then strip coat it

The second best method for sealing skip welds is to use ___ ___ or ___ in the overlap joints.

Penetrating sealer or caulking

Caulking/penetrating sealers must be ____ with the coating system.

Compatible

___ and ___ based caulking have been used with success in sealing skip welds prior to coating.

Epoxy and Silicone

Rough welds must be ___ ___ or repaired to remove sharp edges and/or other irregularities to prevent the coating from bridging over voids in the weld.

Ground smooth

Sharp ridges and spikes are difficult to coat. The coating pulls back from the edges of the ridge and is ___ ___ at those points.

Much thinner.

Fill undercuts and pinholes with?

Welding

Correct laminations, scabs, rollovers, and other defects of this type to expose areas that are otherwise ____ for cleaning and coating.

Inaccessible

Be sure to remove slivers, laminations, and other defects that may?

Penetrate the coating.

Gouges or sharp indentations of any kind limits the effectiveness of ___ ___

Coating films.

Applying coatings over gouges may merely ___ over the gouge creating voids where corrosion can occur.

Bridge

___ ___ gouges so the entire surface can be evenly and completely coated.

Round out

Sharp corners and edges cause ___ ___ which causes coating to pull back.

Surface tension.

Sharp corners and edges cause surface tension which causes coating to pull back. Particularly during ___ and/or ___, Round all sharp edges.

Drying and/or curing.

Sharp bends or edges can also cause the coating to ___ over areas of the substrate creating voids which can capture moisture and cause corrosion.

Bridge

Coatings that have bridged over are not easy to correct so extra care should be taken to prevent this. True or False

True.

The design engineer, working with the coatings engineer/specifier can use this illustrated standard along with accompanying weld replica as a guide to avoid many common design faults and fabrication defects that can adversely affect the entire coating system.

NACE SP0178 (Fabrication Defects , Surface Finish Requirements, and Proper Design Considerations for Tanks and Vessels to be Listed For Immersion Service.)

It is important to identify ___ ___ that could lead to inadequate coating performance.

Fabrication Defects.

___, ___, and ___ defects.

Identify, Document, and Correct.

Responsibility for remedial action is often a subject of ___.

Dispute

Design and Fabrication Defects Flashcards

(102 cards)