Section 8 - Methods of Inspection Flashcards
Safety precautions dealing with tank entry are discussed in
API 2015 & 2016
Prior to entering a tank, be sure to:
Check condition of overhead structures inside the tank
Prior to entering a floating roof tank, be sure to
Check that there is not a significant amount of liquid on the roof.
Prior to conducting a tank inspection, the inspector should:
read previous inspection reports
Which handrail member should be given special attention
Angle Iron
Bars
T-bars
Tubular–
Which document provides info concerning the use of tank grounding to prevent static electricity
API 545
Which coating problem is the most difficult to detect
Blister
Bonding failure –
Holiday
A tank is insulated. Where is a likely spot for external shell corrosion
Shady side of the tank
CUI in carbon steel is most aggressive at a temp range of:
120 - 200 F
The upper shell of a floating roof tank has the potential for atmospheric corrosion on both sides. On floating roof tanks with uncoated shells, special attention should be given to the shell on the upper:
24”
Hydrogen blistering is most common on the tank’s
bottom and shell
Hydrogen blistering occurs on the tank’s
external and internal
Which of the following is not a cause of tank deformation
Defective vent Earthquake Settlement Wind Exceeded product fill height--
When cracking is suspect in an area of tank deformation, which NDE is preferred?
MT
How can rivets be checked for tightness
Light tapping one side and fingering the other side
Planks used as a walkway on the roof should span at least
2 rafters
A floating roof tank is in a volatile service. When walking on the floating roof, it is advisable that the tank be
High gauged
A floating roof is in a volatile service and is 1/2 full. What is a requirement when walking on it?
Must wear respiratory equipment unless the air is tested
A floating roof is sitting on it’s legs. A blocked roof drain can cause
Sever roof damage
External roof corrosion is most common at
Roof Depressions
What should be done if there is significant distortion discovered at a nozzle?
Clean and examine the distorted area for cracks
What is a common problem for flame arrestors?
Internal screens get plugged
Which of the following is not a common way for flame arrestors to get plugged?
Bees, mud daubers or insects
corrosion build up
solidification of tank vapors
tank over pressure–
Which of the following is NOT a problem that can occur if a flame arrestor gets plugged
Tank over pressures
Tank roof-to-shell weld fails
Tank sucks in due to vacuum
Floating roof sucks in–
What is a useful method for checking the tank bottom for soil-side corrosion
ROBOTS
The owner elects to tunnel under a tank to visually inspect a portion of the soil-side of the tank bottom. What is the primary problem with tunneling?
Difficult to compact the fill
When cutting rouf coupons, the coupons must have
rounded corners
If there are leaks in a floating roof or the pontoons, what is likely to occur?
The roof may tilt and turn upside down.
Which of the following is not commonly installed on a floating roof
Drains
Grounding Connections
Guides
Cathodic Protection–
During an outage, the floating roof drain lines should initially be pressure tested for 1/2 hour. The test should normally be conducted at
30 psig
If a drain line contains a swing joint, a second 1/2 hour pressure test should be conducted at
5 psig
What is the reason for a 2nd pressure test of a drain that has a swing joint?
The joint may be self sealing at high pressures, but leaks at low pressures
When walking on an aluminum internal floating roof:
it’s best to add planking prior to walking on the tank
Aluminum floating roof legs must be:
Electrically isolated from carbon steel to prevent galvanic corrosion
Normally internal tank corrosion is least likely to occur
On the bottom
At the liquid-level line
In the vapor space
inside nozzles –
Pyrophoric material tends to collect on the
Floor and top side of the rafters
Pyrophoric material should be
kept moist until removed
In sour services, corrosive vapors are formed when moisture and air mixes with
Hydrogen sulfide
In a 98% sulfuric acid tank, corrosion often occurs in the
Vapor-liquid interface
In a 98% sulfuric acid tank, corrosion occurs in the vapor-liquid interface, this is because the
water on top of the acid that creates a weaker acid
In tanks that are rarely used, like pipeline breakout tanks, corrosion often occurs
behind the tank seal
Some incomplete penetration on circ shell welds
was allowed in API 650 prior to the 7th edition
Which of the following carbon steels are the most susceptible to hydrogen blistering?
Those with laminations and slag inclusions
A statistical method is used to determine the probable minimum remaining thickness of a tank bottom. Typically how much of the bottom is scanned to gather info for the statistical analysis?
0.2-10%
A statistical method is used to determine the probably minimum remaining bottom thickness. What part of the floor should be included in the statistical analysis
Outer circumference by the shell
When is a statistical analysis of a tank floor effective?
Tanks on pads that have uniform consistency
MFL Scanning equipment is useful for finding
Both top-side & bottom-side corrosion on coated & non-coated floors
MFL scanning equipment may miss
Sharp small diameter isolated pits
On the tank bottom, removing a coupon is an effective method for
determining root cause of soil-side corrosion
A method to use when checking for shell cracks is to put penetrant on one side of a the shell and developer on the other. How long might it take to detect a crack?
24 hours
What type of lined tanks should be painted on the outside with a unique color or a warning stenciled, that indicates this tank has a special lining?
Glass-lined
Steam heating coils should be inspected using either RT or UT to detect:
Condensate Grooving
A hydrotest is performed on a tank of high alloy. What is one major concern?
Chloride stress corrosion cracking
An air-test is substituted for a tank hydro. The air pressure should not exceed:
2 inches of water
Vacuum box testing is being performed on the roof welds. What types of leaks might be missed?
Very small leaks and large leaks.
