Linings (Chap 15- API RP652) Flashcards
What is a holiday?
discontinuity in a protective coating that exposes unprotected surface
What is anchor pattern
surface profile or roughness
What is mil?
.001 inches
25.4 um
what is a lining
material applied to the internal surfaces to act as a barrier to corrosion and/or product contamination
thick film lining mils?
thickness of 20 mils
thick film reinforced lining
thick film reinforced with chopped glass fibers and others (often used on aged floors that incurred corrosion and are rough and pitted and thinned bottoms)
thin film lining thickness
less than 20mils or 0.51 um, use for little corrosion (not suitable for heavily pitted tanks)
When is lining neccessary?
- If inspection shows that min thickness of a bottom steel plate is less than 0.1 “
- If corrosive condition exist ( caustic corrosion, chloride SCC, caustic SCC, sulphuric acid corrosion)
Advantage of thin film?(6)
- initial cost is less
- easier to apply
- can be > 20 years if applied properly
- good flexibility
- allow for more accurate MFL scans
- Easier to remove
advantage of thick film reinforce lining(7)
- easier to achiever coverage over rough, pitted steel and surface irregularities
- ability to bridge future penetrations
- resistance to mechanical damage
- laid by hand or chopper gun
- few or no discontinuities to repair following the holiday test
- > 20 years
- provides resistance to moisture permeation
Advantage of thick film UNreinforced linings(9)
- built up to 100 mils in a single coat
- better coverage over rough surface
- generally applied in a single coat, no issues with contaminations between coats
- provides resistance to moisture permeation
- > 20years
- promotes a reduced tank T/A schedule
- reduce labor cost compared to multi coat think fil or labor intensive reinforce thick film linings
- few or no discontinues to repair following holiday test
- fast curing and can be put back in service after 24 hours at normal ambient temp
What are some causes of tank bottom lining failures?(9)
- inadequate surface preparation
- lack of cleanliness (oil, tar and grease must be removed prior to abrasive blasting)
- Presence of salt
- environmental condition during application, (temp at 5F (3C) above the dew point temp , relative humidity should be below 80% at steel surface
- failing to meet the manufacturer requirement regarding recoat intervals. subsequent coats must be applied with recoat interval
- improper mixing
- insufficient coverage (not enough thickness)
- too much paint (too much thickness)
- inadequate curing time
- failure to remove discontinuities from the surface ( esp for thin film)
Holiday testing?
detect discontinuities - thin film should apply at low voltage wet sponge detector
Type of bottom lining materials?
found in tapes 1 and 2 in API RP652 Thin film (mostly epoxy based) Thick film (reinforce) - Polyester mix , vinyl ester, epoxy Think film (unreinforced, same as reinforce)
Surface prepartion?
SP5 - white metal finish = desired
SP10-near white metal finish = minimum
SP11- for small areas to avoid nearby damage
What is require anchor pattern for SP?
1.5 to 4 mils and increase with thickness of the lining, important to achieve anchor pattern is sharps and angular