653 & 650 - P3 (50Q) Flashcards
Peaking shall not exceed ½” when measured with:
A horizontal sweep board 36” long and made to the true outside radius of the tank.
Routine in-service inspection includes:
Visually checking the exterior tank’s surface for leaks, shell distortions, signs of settlement, signs of corrosion, condition of foundation, condition of paint, condition of insulation system, and condition of appurtenances.
Corroded roof plates shall be repaired or replaced, when the:
Average thickness is less than 0.09” in a 100 square inch area.
Hydrostatic test stress for a new tank is based upon:
The lesser of ¾ the yield stress or 3/7 the minimum tensile stress of the tank’s material of construction.
If the number of elevation measurement points is determined by N = D/10, how many measurement points are necessary on a 50 feet diameter tank?
8
The joint between the new material of an insert plate and the old material of the existing tank shell plate shall be:
Butt welded.
It has been determined that L=32” in a corroded area of a tank 125’ in diameter and 40’ high. Sixteen UT readings are taken every 2” over the length of “L”. The readings are as follows: 0.42, 0.32, 0.38, 0.30, 0.28, 0.25, 0.26, 0.25, 0.23, 0.29, 0.26, 0.31, 0.37, 0.34, 0.33, and 0.39. Determine t1(tavg). Round to the nearest hundredth.
0.31”
The critical zone for repairs to tank bottoms is that portion of the bottom or annular plate within ______ of the inside edge of the shell, measured radially inward.
3”s
Two methods of quantifying the remaining thickness of tank bottoms are mentioned in API 653. One method uses the formula involving “MRT”. What is the name of the other method?
Probabilistic and Deterministic
What is the maximum out-of-plumbness allowed from the top of the shell to the bottom of the shell on a 48’ high tank?
5.00”
Due to strength requirements, the minimum thickness of an annular plate ring is usually greater than:
0.100”
The joint between the new material of an insert plate and the old material of the existing tank shell plate shall be:
Butt welded
A pressure test at least 1.5 times the __________ shall be performed on a nozzle installed by hot tapping after the valve has been installed on it and prior to mounting the hot tap machine.
Hydrostatic head
Cone roof storage tanks may be as large as ______ feet in diameter.
300’
The simplest type of floating roof is the:
Pan
An oxygen deficient atmosphere exists when a tank atmosphere has less than what percent oxygen by volume?
19.5%
Lead-in-Air analyzers must be designed to measure _______ Lead-in-Air concentrations.
Organic
Entry into a confined space is considered to have occurred as soon as:
A part of the entrant’s body breaks the plane of an opening into the space.
When repairs involve most of the tank bottom, it may be desirable to displace the flammable liquids beneath the tank by:
Water flooding
Tank surfaces that have been in contact with leaded gasoline should be scraped down to bare metal. On each side of a line that might be heated excessively by welding or other operations, an area of at least ______ should be scraped down to bare metal.
12”
What is the axis of a weld?
A line through the center of the weld, parallel with the sides of the weld
In monitoring the density limitations of radiographs, either a ________ or step wedge comparison film shall be used for judging film density.
Densitometer
During tank roof evaluations, roof plates corroded to an average thickness of less than ______ in any 100 square inch area shall be repaired or replaced.
0.09”
API 653 covers minimum requirements for maintaining the integrity of above ground storage tanks.
After placed in service
In the evaluation of fixed roofs for continued service, particular attention must be given to:
The possibility of internal corrosion of pipe columns
In determining the lowest average thickness t avg (or t1) over a length of “L” of a tank shell plate, the inspector shall use at least _______ equally spaced measurements over the length of “L”.
5
To determine if a tank is suitable for continued operation, t1 shall be greater than or equal to t min subject to verification of all intended loadings and the value of t2 shall be greater than or equal to what percent of t min?
60%
Tanks with diameters greater than ______ feet shall be analyzed for acceptable shell plate thickness using the variable design point method in API 650.
200
In evaluating tank shell corrosion/pitting, widely scattered pits may be ignored provided that pits meet API 653 depth acceptability criteria and the length of each pitted area does not exceed __ inches in an examined length of __ inches.
2,8
Atmospheric pressure when used to describe the design pressure of a tank refers to internal pressure up to but not exceeding:
2.5 pounds per in2 gage.
If a tank shell has a thickness no greater than _____, the risk of failure due to brittle fracture is minimal, provided that an evaluation for suitability of service per section 2 of API 653 has been performed.
0.500”
All tanks shall be given a visual external inspection by an inspector qualified in accordance with API 653 at least every _____ years or RCA / 4N years, whichever is less.
5
Where concrete ringwalls are provided under the shell, the top of the ring shall be level within _____ in any 30 feet of the circumference measured from the average elevation.
Plus or minus 1/8”
If a tank is designed to have a leak detection and containment system, the minimum thickness of the bottom plates at the next inspection can be:
0.05”
The maximum vertical and horizontal dimension of a lapped patch repair plate is _____ inches and _____ inches respectively.
48,72
When gouging or grinding welds to remove defects, cavities often result. These cavities must be examined visually and by:
MT or PT
Completed welds of stress relieved assemblies of shell penetrations shall be examined by visual and magnetic particle or liquid Penetrant methods:
After stress relief and before hydrostatic test
Corrosion that occurs when two metals with different compositions (thus different electrolyte potentials) are connected in an electrolyte (usually oil) is called:
Galvanic corrosion
What are two systems of cathodic protection normally used for corrosion control?
Galvanic and impressed current
When calculating the critical length “L” and determining the least minimum thickness “t2” of an area of a tank shell, the critical length cannot be more than:
40”
The simplest type of atmospheric storage tank is the:
Cone roof
Corrosion on the underside of tank bottoms that rest on pads or on the soil cannot be inspected readily from the outside. If it becomes necessary to make an external inspection of the bottom located near the edge of the tank, the following method can be used when the tank is out of service.
Tunneling method
During an external inspection of an in-service aboveground storage tank, crevices associated with structural steel ladders, stair treads, and platforms plates, etc., where water can collect, should be closely checked by:
Picking with a scraper or knife
Tank bottoms should be checked thoroughly for thickness over its entire area. UT measurements are usually the first choice. If an UT instrument is not available, what other alternate non-destructive method could be used for quickly checking the condition of the bottom?
Hammer testing
The internal tank shell should be inspected for corrosion. Two likely corrosion areas are the:
Vapor space and liquid level line.
Two of the best tools for visually inspecting inside a tank for cracks is a:
Strong light and a magnifying glass
If evidence of cracking is found during the internal inspection of a tank, a thorough investigation should be made using:
MT, PT, or RT or UT shear wave testing
_______ is an electrode of an electrochemical cell where oxidation (corrosion) occurs.
An anode
_______ is an electrode of an electrochemical cell at which a reduction reaction occurs.
A cathode
Radiographs for an evaluated, repaired, or reconstructed tank shall be retained for:
1 year
