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Replacement shell plate may be circular,oblong,square with rounded corners or rectangular with rounded corners except when: โโan entire shell plate is replaced
Shell replacement patch plates shall be welded with butt joints with complete penetration and complete fusion, except as: โโpermitted for lapped patch shell repairs
Joints in lap-welded shell tanks: โโmay be repaired according to the as-built standard of construction
A 7/8 thick inch circular butt welded repair plate is installed in the 0.875" thick lower course of a tank. What is the minimum weld spacing required from the vertical and horizontal plate welds of the lower course? โโ10"&10"
Lapped patch shell repairs are: โโan acceptable form or repairs for butt-welded,lap-welded, and riveted tank shells only when specified by the owner.
Lapped patch shell repairs shall not be used on any shell course thickness (original construction) that exceeds____ inch. โโ0.
Lapped patch shell repairs shall not be used to replace : โโdoor sheets or shell plates
Lapped patch plates shall not have a thickness less than: โโ0.1875 inches
If a lapped patch plate is installed on a tank,what corner(s) may be exempt from being rounded to a minimum radius? โโThe joint at the shell to bottom intersection
A lapped repair plate is installed across a butt-welded vertical seam.The seam is ground flush and checked by ultrasonics.The inspector must specify the minimum overlap of the patch plate.What minimum distance is selected? โโ6 inches beyond the shell seam.
Lapped repair plates positioned on the tank shell interior shall be located such that the toe-to-toe weld clearances are a minimum of _____ to the shell-to-bottom weld. โโ6 inches
The maximum vertical and horizontal dimension of a lapped patch repair plate is: โโ48 inches and 72 inches respectively
A NPS 3 nozzle is removed from the 0.325" thick third course of an AST. The reinforcing pad is removed from around the nozzle and welds are ground smooth. The hole left by removing the NPS 3 nozzle is 3.75" in diameter. You are required to only have the minimum overlap over the hole by the lapped repair plate as required by API 653. What is the minimum diameter of the lapped repair plate? โโ5.75 inches
What maximum joint efficiency may be used for a lapped patch repair plate with a full fillet perimeter weld that is used to. repair a thin area of a tank shell? โโ0.
An AST has a thin area caused by external corrosion on the third shel course.The original thickness of the shell course was 3/8 inch. It has thinned to 0.06 inch in a 13" by 17" rectangular area. The lap patch is to be installed over the area to a point where the shell thickness is at original thickness. what is the maximum thickness lap patch that you could use to repair this thinned spot? โโ1/2"
The area of metal on the tank shell that has thinned and been repaired by using a lapped patch : โโshall not be considered as effective in carrying the calculated service or hydrotest loads.
Lapped patch repair plates may be used to repair small. shell leaks. The repair plate must be designed to withstand hydrostatic pressure load between the repair plate and the shell. The joint efficiency used for this calculation is: โโ0.
If a lapped patch repair patch is used to repair a small shell leak on an AST, what are the maximum and minimum thicknesses of the repair plate โโ1/2" & 3/16"
Which of the conditions listed below would be unacceptable as an application of a lapped patch repair plate to repair a small shell leak? โโIf exposure of the fillet welds to the product will produce crevice corrosion then this repair method shall not be used.
When repairing a defective shell weld,cracks,lack of fusion, and rejectable slag and porosity โโshall be removed completely by gouging and/or grinding and properly welding.
While inspecting a tank an inspector finds a NPS 12 nozzle that has no reinforcement pad.What should he do? โโA reinforcing plate may be added when deemed appropriate.
A new nozzle is to be installed in an existing atmospheric storage tank. The nozzle is an integral reinforced design. The insert plate thickness is 1 -1/2 inch. The tank shell is. 3/4 inch thick at the
What is the minimum dimension of a welded - on patch plate that overlaps a bottom is considered,which of the following statements is true. โโWelded-on patch plates must extend at least 2" beyond the corroded area.
What is the maximum thickness of a welded-on patch plate that is used to make a bottom repair within the critical zone? โโ1/4 inch
An AST has no means for detection and containment of a bottom leak. What is the minimum acceptable thickness of the bottom if a welded- on patch plate in the critical zone is to be used? โโ0.1 inch
Welded-on patch plates are not permitted in the critical zone on a stainless steel tank bottom if: โโthe operating temperature exceeds 100F
A corroded area in the critical zone of an atmospheric storage tank(AST)bottom extends 30" around the periphery of the tank. The inspector notes that this area is too large for a bottom lap patch.The shell to bottom weld is removed in preparation for installing a new bottom to replace the corroded area. How much of the shell to bottom weld should be removed? โโ4.5 ft
A corroded area in the critical zone of an AST bottom extends 40" around the periphery of the tank.The inspector notes that a bottom lap patch in this area is not the correct repair. Why does he make this decision? โโThe corroded area is greater than the area allowed for a bottom lap patch.
When a welded-on parch plate, smaller than 12" diameter,on a tank bottom is considered, which of the following statements is true. โโWelded-on patch plates must extend at least 2" beyond the corroded area.
What are some examples of a suitable non-corrosive material cushion that shall be used between an old and new tank bottom? โโconcrete or sand.
An existing AST that has shell plates of unknown toughness (0.80 inch thick and operates at 40F) has a bottom sketch plate weld joint located near a vertical shell weld. How close to the vertical weld can you locate the bottom weld joint when replacing floor plates? โโ4 inches
The minimum thickness of new roof plates for a supported cone roof shall be ________ plus any corrosion allowance. โโ3/16inch
An owner / user of an existing AST that was constructed with material of known toughness requests that a hot tapped NPS 3 nozzle be installed in the third course of his tank. What minimum thickness must the shell plate be in order to install the nozzle? โโ1/8 inch
A NPS 4 Schedule X- Strong nozzle is installed in a tank shell 5/8" thick. The hot tap drill is 4 inches in diameter. The shell plates are of known toughness. what is the reinforcing plate outside diameter? โโ12 inches.
The minimum height of tank liquid above the hot tap location shall be at least ________ during the hot tapping operation. โโ3 feet
Hot taps are not permitted : โโall of the above
A hot tap nozzle is to be installed near an existing nozzle on a 117 feet diameter tank ( shell thickness of 0.625 inch). Using the requirements of API Standard 653, paragraph 9.14.3.1, determine the minimum spacing between the nozzles. โโ20.95 inches
After the valve has been installed on a welded hot tapped nozzle, what type pressure test is required prior to mounting the hot tap machine? โโA pressure test at least 1.5 times the hydrostatic head that will be placed on the nozzle shall be performed.
