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API 653 Repairs EXAM
Where to find joint types table - answer - Api sec. 4, table 4. Where to find joint efficiency table - answer - Api 653 sec. 4, table 4. Where to find table for type and extent of radiography performed - answer - Api 653 sec. 4, table 4.2 and Api 650 sec. .8.1, fig 8- 1 What is the equation for Tmin or max fill height for localized corrosion? Where is it found? - answer - Api 653 sec.4. H=(SETmin)/(2.6DG) What is the equation for Tmin or max fill height for entire shell? Where is it found? - answer - Api 653, sec. H=(SETmin)/(2.6DG)+ Lap patch shell repairs are acceptable for what types of tank shells? - answer - Butt weld, lap weld, and riveted tank shells Lap patch repairs are considered permanent and are subject to what? - answer - Ongoing inspections
Lap patch material shall comply with what requirements? - answer - The requirements of current applicable standards of construction and API 653 Lap patch repairs shall not be used on any shell course of what thickness? Nor is it to replace what on the shell? - answer - Shall not be used on shell course thicker than 1/2" or to replace door sheets or shell plates Except as permitted by 9.3.3.2 and 9.3.4.3, what thickness material shall a lap patch be? - answer - Shall be less than 1/2" or thickness of the shell plate, but not less than 3/16" What shape can lap patch be? - answer - Circular, oblong, square, or rectangular. All corners shall be rounded to a minimum 2" radius. Nozzle reinforcement shapes of API650 figure 5.8 are also acceptable Can lap patch plate cross butt welded vertical or horizontal shell seams? - answer - Yes. Seam welds shall be ground flush and lap patch welds must overlap a minimum of 6" beyond seam. Weld spacing requirements of figure 9-1 shall be used as a basis for what? - answer - Locating repair plates relative to butt welds, fillet welds, or riveted seams. Can lap patch plates intersect with shell to bottom weld? - answer - Yes. Vertical sides of lap patch must intersect shell to bottom weld at 90* angle and shell to bottom weld is in compliance with figure 9. Can lap patches on interior of tank shell intersect with shell to bottom weld? - answer - No. Patch shall be located a minimum 6" away from shell to bottom weld
For a shell lap patch covering a hole, how much thicker may the plate be than the adjacent shell plate to the repair? - answer - It shall not be thicker than the adjacent shell plate. Shell lap patch repairs may be used to reinforce what areas? - answer - May be used to reinforce severely corroded areas that are not able to retain service loads of the tank and also for shell plates that are below minimum thickness. Lap patch repairs that are used for reinforcement shall select plate thickness using what criteria? - answer - Thickness shall be designed using as-built standard and API 653, with a joint efficiency of no higher than .35 with a continuous perimeter fillet weld Lap patch repair used for reinforcement shall not exceed what thickness? - answer - Shall not exceed shell plate thickness at perimeter of repair plate be greater than 1/3, but n more than 1/8". Repair plate thickness shall not exceed 1/2" When using a lap patch repair for reinforcement, can remaining covered plate be considered reinforcement? - answer - No. deteriorated plate shall not be considered effective in carrying calculated service or hydro pressure. May shell lap patches be used to repair small shell leaks? - answer - Yes. Shell lap patches may be used to repair small leaks or minimize the potential for leaks from severely isolated or widely scattered pitting If a shell lap patch is used to repair a small leak, what thickness must shell plate meet? - answer - Shell plate must meet minimum required thinckness A shell lap patch used to repair a small hole shall be designed to withstand what?
- answer - plate shall be designed to withstand hydro-static pressure load between plate and shell assuming hole exists in shell, with a joint efficiency of .
A shell lap patch used to repair a small hole may not exceed what thickness? - answer - Plate thickness shall not exceed shell plate thickness at perimeter of plate by 1/3, but no more than 1/8", with a continuous perimeter weld. A shell lap patch used to cover a small hole shall not be used when exposure of fillet weld to product can produce what? - answer - Crevice corrosion or if corrosion between shell and plate is likely. A shell lap patch used to repair a small hole is not be used if presence of product between shell and plate will prevent gas freeing from the tank to perform what?
- answer - hotwork A shell lap patch used to repair a small hole will require what of the shell plate below it? - answer - Existing shell plate below repair plate shall be evaluated at each future inspection to insure it satisfies the requirements of 9.3.4.1 or repair in accordance with 9.2 or 9.3. When is it permissible to grind surface irregularities on shell plate to a smooth contour? - answer - In areas where the shell plate thickness exceeds the required by design thickness and after grinding remaining thickness is adequate What may be done to shell plate when grinding irregularities to a smooth contoured surface results in unacceptable shell plate thickness? - answer - Shell plate may be repaired be deposition of weld metal. Can tank shells be modified to make the tank taller? - answer - Yes, new plate material may be added to increase the height of the tank shell and shall be in accordance with requirements of current applicable code and shall take into consideration of wind and seismic loading. What shall repairs to existing shell penetrations be in compliance of? - answer - API 650, Section 5.
When may weld on plate be placed on bottom area over a mechanical dent or local dishing? - answer - If areas unsupported dimension does not exceed 12" in any direction; it is at least 1/4" thick; it is at least as thick as existing bottom; does not overlap seams or existing patches, except for tanks designed in accordance with API 650 annex M, which shall have patch plates at least 3/8" thick. Are weld on patch plates attached to tank bottom considered permanent repairs?
- answer - Yes, and they are subject to ongoing inspection and maintenance program. Are weld on patch plate repairs allowed within the critical zone of the tank bottom? - answer - Yes, provided the requirements of 9.10.1.1 and 9.10.1.2 are followed. What is the max thickness of weld on patch plate within critical zone of tank bottom? - answer - 1/4" thick and must meet toughness requirements of API 650, Section 4.2. What shall be done if weld on plate within the critical zone of tank bottom is within 6" of shell to bottom weld? - answer - Patch plate shall be made into tombstone shape and intersect shell to bottom weld at approximately 90*. What weld on patch plate repairs shall have a minimum of two weld passes on perimeter welds and examined per API 653, Sections 12.1.1.3 and 12.1.7.2? - answer - Weld on patch plates installed within the critical zone of tank bottoms Is installation of weld on patch plate by butt welding to and existing patch plate allowed within the critical zone of a tank bottom? - answer - No. What thickness shall the bottom plate below weld on patch plate installed in critical zone be? - answer - Bottom plate thickness must meet thickness requirements in API 653, Section 4.4.
For tanks with unknown origin, what spacing requirements shall be followed for fillet welds utilized to install tombstone weld on patch plates in critical zone of tank bottom? - answer - Fillet welds shall be spaced at least the greater of 3" or 5T from existing vertical weld joints in the bottom shell course, where T is the thickness of bottom shell course, in inches. What is the minimum dimension between 2 weld on patch plates in the critical zone of a tank bottom? - answer - Minimum dimension shall be 1/2 of the dimension parallel to shell of small patch. What is the maximum dimension along the shell for a weld on patch plate in the critical zone of a tank bottom? - answer - 24" Do the dimensions to vertical shell welds apply to shells of unknown toughness?
- answer - yes What thickness must the bottom plate be before welding the weld on patch plate to bottom plate? - answer - bottom plate must be at least .1". Refer to API 2207 No welding or weld overlays are permitted in critical zone of tank bottom, with what exceptions? - answer - widely scattered pits, the shell to bottom weld, welded or patch plates, or where the bottom plate welded to the shell is being replaced. Can a weld on patch plate be used in the critical zone if the covered bottom plate is projected to be below the required minimum thickness at the next internal inspection? - answer - no What temperatures are not to be exceeded in order to use weld on patch plates in the critical zone of tank bottoms? - answer - 20 0f for carbon steel tanks, 100f for Stainless Steel tanks
Where are the requirements for replacing tank bottoms over existing tank bottom found? - answer - API 653 9.10.2.1.1-9.10.2.1. When replacing new tank bottom over existing tank bottom what shall be placed in between old and new plates? - answer - A suitable non-corrosive cushion material such as sand, gravel, or concrete When replacing bottom over existing bottom, how shall the bottom be attached to tank shell? - answer - Shell shall be slotted with uniform cut made parallel to the tank bottom. The new bottom, plate shall extend outside the shell as required by API 650, Section 5.4.2. All rules for weld spacing shall be followed. When replacing tank bottom above existing bottom, what shall be done to any voids below existing tank bottom? - answer - voids below existing tank bottom shall be filled with sand, crushed limestone, grout, or concrete. When replacing tank bottom above existing tank bottom, what shall be done to existing shell penetrations? - answer - Except as permitted by API 653, Section 9.10.2.7, Existing shell penetrations shall be raised or their reinforcement plates modified if the elevation of new bottom plates results in inadequate nozzle reinforcement details or if weld spacing requirements given in API 650, Section 5.7.3 are not met. When replacing tank bottom over existing tank bottom on tanks with floating roofs, what must be kept on tank bottom? - answer - New tank bottom profile must keep roof level when it is resting on its support legs. Support legs for roof can remain the same length as before the new tank bottom was installed or adjusted in length, as needed. When replacing tank bottom plates, what shall be installed for fixed roof support columns? - answer - New bearing plates must be installed for fixed roof support columns. For steel floating roofs, steel pads or other means shall be used to distribute the loads on bottom plates and provide a wear surface. If pads are used, they shall be seal welded to the bottom plate.
When removing a tank bottom, how shall the bottom plates by separated from the shell? - answer - A) Cutting shell parallel to tank bottom a minimum of 1/2" above weld B) Removing entire shell to bottom weld, including any penetration and HAZ by suitable methods, such as gouging or grinding. When removing shell to bottom weld during bottom plate replacement, what NDE shall be required if using arc gouging to remove shell to bottom weld? - answer - MT examination shall be performed on areas arc gouging is used and defective ares found repaired or re-examined. What requirements shall be met during installation of new tank bottom? - answer - Installation of new tank bottom shall meet all requirements of the API 650 What requirements shall be considered when replacing bottom plates with cathodic protection? - answer - A) For tanks with Cathodic protection installed below tank bottom, removal of entire bottom and unused dead shell shall be considered to prevent shielding of cathodic protection current to new bottom. Removal of old bottom is also important to prevent galvanic corrosion. Where this is possible, removal of entire old bottom, except the unused dead shell and not more than 18" of bottom amulus attached to the shell, shall be considered. B) Consideration shall be given to installing an under bottom leak detection system at this time (such as RPB) to contain any bottom leak to a location where it can be easily observed from outside the tank. Roof repairs involving tank venting shall be made such that normal and emergency venting meet what requirements? - answer - API 650, Section 5.8. Roof repairs involving modification of roof structure and the frangible joint (if applicable) shall be in compliance with what requirements? - answer - API 650, Section 5.
When removing, repairing, or replacing rim mounted primary seals or toroidal systems, what is done to limit evaporation losses and potential hazard to workers? - answer - No more than 1/4 of roof seal system should be out of an in- service tank at one time. When removing, repairing, or replacing rim mounted primary seals or toroidal systems of floating roof perimeter seals, should spacers be used to keep the roof centered during repairs? - answer - No, spacers shall be used. When primary seal systems on floating roof perimeter seals are located partially or fully below the bolting bar or top of the rim and cannot be reached to allow in-service removal, what is to be done? - answer - In-service repairs are limited to replacement of the primary seal fabric. Are secondary seals possible to install, repair, or replace while tank is in-service on floating roof perimeter seals? - answer - Yes, secondary seals, rim mounted and shoe mounted, may be readily installed while the tank is in service. What repairs and other corrective actions are required to be performed to maintain seal to shell gap on floating roof perimeter seals? - answer - A) Adjusting the hanger system on primary shoe seals, and adding foam filler to toroidal seals B) Increasing the length of rim mounted secondary seals in the problem area C) replacing all or part of the primary seal system along with possible installation of a rim extension for a secondary seal system. This step should be taken only after checking the annular space variation at several levels from low pump out to high liquid level. What shall be done when mechanical damage is discovered on floating roof perimeter seals? - answer - Damages parts shall be replaced. Before replacing parts, the cause of damage shall be identified and corrected. Buckled parts are to be replaced, not straightened. Torn seal fabric shall be replaced.
What causes the deterioration of seal material on floating roof perimeter seal? - answer - Material deterioration results from wear and corrosion on metallic elements, and chemical and weather deterioration on fabric components.Service life and inspection information shall be used to determine whether a change of material is warranted. How shall the replacement or addition of primary or secondary seals be installed on floating roof perimeter seals? - answer - It shall be in accordance with seal manufacturer's recommendations. If the roof rim on a floating roof perimeter seal has a thickness of less than .10", what shall be done? - answer - Rim shall be replaced with a new rim of a minimum thickness of 3/16". When are hot taps not permitted on in-service tanks? - answer - When tank shell requires PWHT. What are the requirements for radial hot tap connections on existing in-service tanks with shell plate of a known toughness? - answer - For shell plates of known toughness, the connection size and shell thickness limitations are shown in Table
What are the requirements for radial hot tap connections on existing in-service tanks with shell plate of a unknown toughness? - answer - For shell plate of unknown toughness, the following limitations apply:
- nozzles are limited to NPS 4
- shell plate shall be above MDMT for entire hot tapping operation
- All nozzles shall be reinforced, calculated by API 650, Section 5.7.2, with a minimum thickness of the reinforcement plate equal to shell plate thickness. Minimum diameter of reinforcement plate shall not be less than the diameter of the shell cut out plus 2"
How shall the pipe nozzle be installed for the hot tap? - answer - Pipe nozzle shall be cut to the contour of the shell and beveled from the outside for full penetration weld. Nozzle neck to shell weld shall be examined in accordance with 12.1.2.3. How shall the reinforcement pad be installed after nozzle installation on a hot tap? - answer - After pipe is welded, reinforcement pad shall be installed in either 1 piece or 2 pieces with a horizontal weld. Reinforcement plate to nozzle shall be installed with a full penetration. Catre shall be taken to limit the heat input to the welds. After reinforcement pad is welded to shell and NDE performed on a hot tap, What shall be performed? - answer - Reinforcement pad shall be pneumatically test be procedure described in API 650, Section 7.3.5. After valve is installed on flange, a pressure test of at least 1.5x the hydro-static head pressure shall be performed on nozzle prior to hot tap machine, which shall be bolted to valve. How shall the required pressure for a hot tap nozzle pressure be computed? - answer - P= 1.5H^2GY^w P= PSI H^2= Height of tank G= specific gravity of product stored, as specified by purchaser. Shall be no less than 1.0. Y^w= Density of water in pound force per cubic inch (lbf/in^3) Who shall operate hot tap machine? - answer - A qualified operator shall operate hot tap machine and cut hole in the tank following machine manufacturer's procedures.
