Api 650 welded steel tanks for oil storage inquiries

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Api 650 welded steel tanks for oil storage inquiries

  1. 1. API Standard 650 - Welded Steel Tanks for Oil Storage Last update: November 27, 2004 Standard Edition Section Inquiry # Question Reply 650 9th - May General 650-I-02/98 Does API 650 include the applicable requirements for tanks that are API 650 makes no attempt to address federal requirements, nor 1993 either stated in pertinent Code of Federal Regulations? those of any other jurisdiction. Compliance with the various jurisdictions is a contractual matter between the tank manufacturer and the purchaser. 650 9th - May General What is the appropriate ratio of tank diameter to tank height to avoid The determination of anchorage requirements is adequately 1993 anchorage? covered in API 650. Many factors are included in determining if anchors are required and the number of anchors. This is a specific design condition and should be considered in completing the detailed design of a tank. 650 10th - Nov. General Background: Many times small tanks with diameters less than 10 ft. No. 1998 are specified for construction in accordance with API 650. A review of API 650, Section 3.6.1.1, shows the minimum thickness to be 3/16 in. and 3.6.1.2 indicates that the minimum shell plate width is 72 in. Appendix J states that the maximum tank diameter of a tank constructed to API 650 is 20 ft. Question: Is there a minimum diameter or height or volume for which new tanks constructed to API 650 apply? 650 10th - Nov. 1.1 650-I-03/00 Question 1: Regarding the use of SI units, does API 650 allow either of Reply 1: Yes, both are allowed. 1998 the following? (1) Use of SI units throughout the design process. (2) Use the original U.S. Customary units with a hard conversion to SI units as a final step to the design process. Question 2: Does the wording of the Foreword to API 650 to require a Reply 2: No. separate check of the U.S. Customary results when SI unit are specified and after making such a check using the U.S. Customary results if more restrictive? Question 3: When SI units are used does API 650 require a change in Reply 3: Yes. the thickness minimums and maximums? 650 10th - Nov. 1.1 650-I-36/00 Whenever more than one of the appendices with status Yes. 1998 Table 1-1 “Requirements” in Table 1 1 is specified, and it is determined that these requirements do not agree, is the more restrictive requirement to be applied? 650 10th - Nov. 2 Do the current rules in API 650 allow for a carbon steel tank to No. For a carbon steel tank, API 650 does not allow the use of 1998 incorporate stainless steel components such as nozzles or an entire materials that do not comply with the specifications listed in shell ring, provided all requirements of API 650 are followed for each of Section 2. the particular material types (CS or SS) used in the structure? 650 9th - May 2.1 Does API 650 permit the substitution of Charpy impact testing in lieu of No. 1993 meeting specified chemistry requirements? 650 9th - May 2.1.1 Does API 650 permit the use of SA 36 for shell plate? Yes, if the material is also certified by the mill as complying with A 1993 36, and is acceptable to the Purchaser. See Section 2.1.1. 650 9th - May 2.1.1 A 36 can be a Group I or Group II material, if it complies with the What API group number is A 36? 1993 respective footnotes in Table 2-3 of API 650 650 10th - Nov. 2.2 650-I-06/04 Question 1: Does the 0.01 in. thickness tolerance specified for plate in Reply 1: Yes. All requirements of the base document apply to an 1998 API 650, 2.2.1.2.3 apply to carbon and stainless coil product? Appendix S tank unless specifically changed or waived by a statement in Appendix S. Refer to S.1.5. Question 2: When purchasing hot-rolled coil-processed steel for use as roof, shell, and/or bottom plate on a stainless tank, does the ASTM Reply 2: The minimum of the ASTM tolerance or as specified in under-run tolerance apply? API 650, Sections 2.2.1.1, 2.2.1.2, or 2.2.1.3, shall apply. 1 of 26
  2. 2. Standard Edition Section Inquiry # Question Reply 650 9th - May 2.2.2a Referring to API 650, does A 36 plate material meet the requirements of Yes. However, the use of A 36 material also requires that other 1993 Section 2.2.2.a? conditions, such as those described in Figure 2-1 and Table 2-3, and their notes, are met. 650 9th - May 2.2.2c Does the thickness limitation of 1 in. for A 283 Grade C plates specified Yes. 1993 in Section 2.2.2.c of API 650 apply to the type of plates used in construction of a tank, such as the thickness of the bottom reinforcing plate and bolting flange and cover plate for flush-type cleanout fittings in Table 3-12? 650 9th - May 2.2.9 Referring to Section 2.2.9.3, does the phrase "experience or special No. The Section is referring to variations in local climatic 1993 local conditions justify another assumption" mean that a tank is conditions that might not show up on the isothermal charts. permitted to be designed for temperatures higher than the specified However, the document does not yet provide data for locations 15°F above the lowest one-day mean ambient temperature of the not covered in Figure 2-2, such as Alaska and Hawaii. locality if the stored product was "normally warmer" than this specified temperature? 650 9th - May 2.2.9 Is it permissible to use Group 1 plates for a tank bottom, except for API 650 only addresses toughness of bottom plates welded to the 1993 plates welded to the shell, for tanks with a -50°F design metal shell, per Section 2.2.9 or 2.2.10. temperature? 650 9th - May 2.2.9 Does API 650 permit the use of fabricated A 53 pipe, for use in sizes No. All fabricated pipe must comply with A 671, or be fabricated 1993 about 20"? from plate per Section 2.2.9.1, as described in Section 2.5.2. 650 9th - May 2.2.9 What is meant by the minimum design metal temperature in API 650? This is the minimum temperature that a given material can be 1993 used in tank shells without impact testing, per Figure 2-1. This value is to be compared against the design metal temperature, which is defined in Section 2.2.9.3. 650 10th - Nov. 2.2.9 650-I-11/01 Does API 650 require that the material used for the tank shell is of the No, see Section 2.2.9.4. 1998 same group that the material used for manhole reinforcement plates? 650 10th - Nov. 2.2.9 650-I-33/03 Are roof materials required to meet the toughness requirements in No. Refer to 2.2.9.1. 1998 2.2.9? 650 10th - Nov. 2.2.9 650-I-44/03 Question: Does API 650 require manganese content between 0.8% and Yes. Refer to Table 2-3b, Note 6. Otherwise, the plate would be 1998 1.2% for A 36 plate less than 0.75 in. to be classified as a Group II classified as Group I. material? 650 9th - May 2.3.3 Should the M.3.2 yield strength reduction factor also be applied to the Yes 1993 0.426T and 0.472T terms of Section 2.3.3.1 when determining the allowable stress S? 650 10th - Nov. 2.5.2 650-I-15/00 Question 1: For nozzles made from pipe materials, does API 650, Reply 1: Yes, unless ASTM A 671 pipe is used. 1998 Section 2.5.2 require that seamless pipe be used for nozzles in shells made from Group I, II, III, or IIIA materials? Qustion 2: Does API 650, Section. 2.5.2 preclude the use of electric- Reply 2: Yes. resistance welded pipe meeting ASTM A 53, or electric-welded pipe meeting API 5L, for nozzles in shells made from Group IV, IVA, V, or VI materials, but allow use of electric-fusion-welded pipe nozzles made from ASTM A 671? 650 9th - May 2.7 Referring to API 650, Section 2.7, are bolt heads required to be marked No. Refer to the applicable ASTM bolt specification, which may or 1993 according to ASME Section II, Part A for bolting? may not be identical to the parallel ASME bolt specification. 650 9th - May Table 2-3 Does Table 2-3 only relate to plates that are to be heat-treated? No. 1993 650 9th - May Table 2-3 Does API 650 require that all A 36 material be killed or semi-killed? Yes, see Table 2-3, Note 2. 1993 650 10th - Nov. Table 2-3 650-I-09/01 For plate material certified by the manufacturer to meet more than one Dual certification of material is not addressed in API 650, except 1998 specification, such as A 516 Grade 60 and A 516 Grade 70, which in Appendix S. specification should be used when applying the rules in Table 2-3, Figure 2-1, and Section 2.2.9 of API 650? 2 of 26
  3. 3. Standard Edition Section Inquiry # Question Reply 650 9th - May 3 Please furnish details on the maximum allowable tank diameter and The appropriate combination of tank diameter and height is a 1993 height for tanks built in accordance with API 650. design consideration. There are several factors which influence this. API 650 does not cover an explanation of these factors. Please note the thickness limitations given in Section 2.2.2. 650 10th - Nov. 3.1.3.5 650-I-37/03 Is it the intent of 3.1.3.5 to limit the maximum lap of a double welded lap No. 1998 joint to 2 in. and a single welded lap joint to 1 in. If not, is there a maximum lap requirement for single welded lap joint bottoms and roofs? Would this constraint, if any, also apply to bottom or roof repair or replacements governed by API 653. 650 10th - Nov. 3.1.3.5 650-I-49/03 Question 1: Section 3.1.3.5 of API 650 specifies minimum lap joint Reply 1: API Standard 650 does not address maximum lap. 1998 dimensions. Is there any limit on the maximum width of a lap joint? Question 2: Can a lap joint consisting of two (2) ¼ in. plates be lapped 3 in.? Reply 2: Yes. Any lap that exceeds the minimum is acceptable. Refer to 3.1.3.5. 650 9th - May 3.1.5 What is the distance between vertical welds? Please refer to API 650, Section 3.1.5.2.b and Section 3.7.3. 1993 650 9th - May 3.1.5 & Figure 650-I-24/98 Referring to API 650, Section 3.1.5 and Figure 3-3a, is it permissible to Yes, the details shown represent the typical or most common 1993 3-3a lap roof plates with the inner (upper) plate lapping under the lower details, but other details are also permitted. (outer) plate, to protect against the tank contents condensing in the lap joint on the underside of the roof? 650 9th - May 3.1.5.4 Referring to API 650, Section 3.1.5.4, is it required to make a full fillet Yes. 1993 lap seam weld (top side only) under the tank shell? 650 10th - Nov. 3.1.5.8 650-I-02/04 Question 1: Referring to API Standard 650 3.1.5.8 (b) and Figure 3-20, Reply 1: This is a purchaser specified option for details a, b, c 1998 is it mandatory to provide welding between the bottom-side of a wind and e of Figure 3-20. It is required for detail d of Figure 3-20. girder plate/section and the tank shell if not specified by the purchaser? Question 2: Is it mandatory to seal-weld the bottom of the weld joints Reply 2: Section 3.1.5.8 (a) requires this to be a full-penetration joining ring sections of the wind girder? butt-weld. 650 10th - Nov. 3.1.5.9 650-I-11/02 Is there any allowance or provision to omit the top angle as required by No. 1998 API 650, 3.1.5.9e and 3.1.5.9f if we can show by calculation that the top compression area is sufficient. 650 9th - May 3.2.4 Does API 650 cover the design of a tank for a design vacuum condition No. Per API 650 Section 3.2.4, the tank is limited to one in. of 1993 of 50 mm of water? water vacuum (roughly 25 mm). If the tank must be designed for 50 mm water vacuum, then this is a special design which is not covered by API 650. 650 9th - May 3.2.4 Should the vacuum relief system set pressure be 25 mm of water if the API 650 does not cover the required setting for vacuum relieving 1993 required design vacuum condition is 50 mm of water? systems. The vacuum relieving systems should be adequately sized to limit the partial vacuum to 1 in. of water vacuum (roughly 25 mm of water). Refer to API Std. 2000, Section 3.6.1.2. 650 10th - Nov. 3.2.4 650-I-20/03 Can tanks that are designed to exceed 1 in. external pressure have an Yes. API 650 does not contain design rules covering external 1998 API nameplate? pressure exceeding 1 in. water column. 650 9th - May 3.4 Is a repad allowed to go to the tank bottom and intersect the bottom at Yes. 1993 90 degrees to the bottom? 650 10th - Nov. 3.4 Is it acceptable for the primary (upper) bottom, of an API 650 Appendix No. API 650, Section 3.4.2 requires the bottom plate project at 1998 I double-bottom tank to not project through the shell and to be attached least 25 mm (1 in.) outside the toe of the outer shell-to-bottom only to the inside of the shell? weld. Section 3.5.2 requires the annular plate project at least 50 mm (2 in.) outside the shell. Furthermore, Section 3.1.5.7 requires the bottom be welded to the shell on both sides of the shell. The only way this can be accomplished is with a shell projection. Figure I-4 illustrates an acceptable double-bottom installation. 3 of 26
  4. 4. Standard Edition Section Inquiry # Question Reply 650 10th - Nov. 3.4.1 Can a bottom rectangular plate, as described in API 650, Section 3.4.1, Yes, if the purchaser agrees to the reduced width. There is no 1998 be smaller than 72 in. x 72 in.? requirement that the length be at least 72 in. 650 10th - Nov. 3.4.1 650-I-38/02 API 650 3.4.2 requires a 1 in. projection of bottom plates beyond the toe The API committee responsible for this standard has issued an 1998 of the fillet weld attaching the shell to the bottom. Does this 1 in. agenda item to study this issue further to determine if a change in projection apply to the toe of the fillet weld attaching a thickened insert the standard is required. Any changes resulting from this agenda or reinforcement plate to the bottom plate? item will appear in a future edition or addendum to API 650. 650 9th - May 3.5 Does API 650 require that tank annular plates be the same material as No. However, the annular plate material must meet the toughness 1993 the bottom shell course? requirement of Section 2.2.9. See Section 2.2.9 1 and Figure 2-1. 650 9th - May 3.5 Does API require an annular plate to be used if (1) bottom plates (1/2 in. The requirement to provide an annular plate depends upon the 1993 nominal thickness) are butt welded and 100% radiographed, and (2) the material group and the stress levels in the bottom shelf course. bottom shell course material falls under Group IV or V, and (3) the Refer to Section 3.5.1. The question cannot be answered without materials are not Charpy tested? more information being provided. Bottom plate thickness, the NDE applied, and the material toughness are not factors in the decision. 650 9th - May 3.5 Does API 650 prohibit installing the bottom annular plates on top of the Except for the flush-type cleanout connections (see Figures 3-11 1993 ¼ in. bottom plates? If allowed, this option would eliminate an area for and 3-12), there is no requirement that the bottom plate must lap water to collect causing corrosion. above, or must lap under the annular plate. 650 10th - Nov. 3.5.2 650-I-22/03 Section 3.5.2 states the annular bottom plates shall have at least a 50 The reference point is on the outside diameter of the shell plate, 1998 mm projection outside the shell. Is the reference point to calculate the as stated in 3.5.2. projection located on the outside or inside diameter of the shell? 650 9th - May 3.6 Is the joint efficiency in equations of Section 3.6 assumed to be 1.0? Yes. API does not provide the rationale behind the requirements 1993 Why? in its standards. These requirements are based on consideration of technical data and the judgment and expertise of engineers and technical personnel, representing both users and manufacturers, who serve on API’s standards developing committees. We can only provide interpretations of API 650 requirements or consider revisions to the standard based on new data or technology. All API standards- development meetings are open to the public. The API Subcommittee on Pressure Vessels & Tanks is responsible for API 650 and meets at API’s Spring and Fall Refining Meeting. Information on these meetings can be found at http://api-ep.api.org under "Meetings and Training". 650 9th - May 3.6.1 If the calculated shell thickness is 1/8 in. and the specified corrosion The minimum thickness requirements of Section 3.6.1.1 are 1993 allowance is 1/8 in., must the shell thickness be obtained by adding the primarily for fabricability. The corrosion allowance may be added 1/8 in. to the minimum thicknesses required by Section 3.6.1.1, which to the computed shell minimum thickness, in this case, 1/4 in. would be 1/8 plus 3/16 in., or can it be determined by adding the total. corrosion allowance to the computed required minimum thickness, in this case 1/8 in. plus 1/8 in.? 650 10th - Nov. 3.6.1 650-I-50/00 Question 1: Referring to API 650, Section 3.6.1.2 and Section 3.1.5.2, is Reply 1: No. See 3.1.5.2b. 1998 it permissible for the tank manufacturer, with or without the purchaser’s consent, to seam weld two plates (circumferentially) then join the two with one vertical weld, thus intersecting the horizontal weld? Question 2: Is a shell course considered from one circumferential weld Reply 2: Yes. to the next circumferential weld, assuming 72 in. minimum width as stated in Section 3.6.1.2? 650 9th - May 3.6.3 Referring to Section 3.6.3.2, is it required to add the depth of undercut No, as long as the undercut does not exceed the limits of Section 1993 (vertical seam 1/64 in., or horizontal seam 1/32 in.) to the calculated 5.2.1.4. thickness? 650 9th - May 3.6.3 Does API 650 allow for overflows? Overflows limiting "H" as defined in Section 3.6.3 are permitted. 1993 650 9th - May 3.6.3 Does API 650 specify the maximum height to which a tank may be Yes. See definition of the term "H" in Section 3.6.3 and 5.3.5a. 1993 filled? 4 of 26
  5. 5. Standard Edition Section Inquiry # Question Reply 650 10th - Nov. 3.6.3.2 650-I-21/02 Question 1: In section 3.6.3.2, is the H for calculating tt the same value Reply 1: Yes. 1998 as H for the calculating td? Question 2: Is the value of H in 3.6.3.2 to be used for calculation of ts Reply 2: Yes. should be equal to the value of H for calculation of td? Question 3: Do the above mean that the value of H to be used for calculation of ts should be equal to the value of H for calculation of td? Reply 3: Yes. 650 10th - Nov. 3.6.4 Background: On one recent contract, corrosion allowance of 0.25 in. No. 1998 was specified only on first shell course. The tank is 250 ft. (diameter) by 53 ft. high, with a liquid height of 48 ft. 0"(external floater) and design specific gravity = 0.968. Detail design per the current edition API 650 (10th) shows that the second course thickness is controlled by hydrostatic test condition, which is incorrect. Investigation has proven that the current rules in API 650 for the variable design point method are not valid for variable corrosion allowance. The second course thickness calculated is more than the one-foot method will calculate, however, this is not stated in API 650. It is not unusual for a customer to specify variable corrosion allowance. The variable design point method is used only for large tanks and in some cases, as I have discovered, the second course will be calculated 1/16 in. thicker than needs to be when corrosion allowance is a significant percentage of first course. This extra thickness amounts to good some of money. Question: Is the variable design point method of shell design covered under API 650, Section 3.6.4, valid for tanks with variable corrosion allowance (i.e. different corrosion for each shell course)? 650 10th - Nov. 3.7 650-I-32/00 Are square or rectangular manways allowed per API 650? If no, what Yes. See Figure 3-14 for roof manway requirements. 1998 specific section limits them? 650 9th - May 3.7 Are shell openings for use as overflows a mandatory requirement No. 1993 according to API 650? 650 9th - May 3.7 In the expression "R/t" is "t" the sum of thickness of the shell plus the No, "t" is the shell thickness only at the location of the shell 1993 thickness of the reinforcing pad around the opening? opening. 650 9th - May 3.7 When the shell is reinforced, does the variable "2s" mean the diameter No, "2s" is the diameter of the opening rack. 1993 of the reinforcement pad at the opening in all the charts? 650 9th - May 3.7 Does API 650 allow the use of 90 degree elbows between shell nozzles No. Refer to Section 3.7.1.2 and 3.7.1.8 which indicate that the 1993 and the first flange? only alternate designs permitted are for nozzle reinforcing, with approval of the purchaser. These sections do not permit alternate designs in the basic nozzle configuration as proposed. 5 of 26
  6. 6. Standard Edition Section Inquiry # Question Reply 650 10th - Nov. 3.7 650-I-09/04 Question 1: Section 3.7.1.8 states "Reinforcement of shell openings Reply 1: No. 1998 that comply with API Standard 620 are acceptable alternatives". When using API 620 to calculate nozzle reinforcement does the entire API 620 standard apply? Question 2: API 620 limits the design temperature to 250º F. Can the Reply 2: Yes. rules for nozzle reinforcement be used for designing nozzle reinforcement for an API 650 Appendix M tank with a design temperature greater than 250º F? Question 3: Can the rules for nozzle reinforcement in API 620 be used Reply 3: Yes. for designing nozzle reinforcement for a stainless steel API 650 Appendix S tank? Question 4: When designing nozzle reinforcement for an API 650 tank Reply 4: Yes. using the rules of API 620, should the allowable stresses of API 650 be used? 650 9th - May 3.7.1 Is the ASME Code, Section VIII, Div. 1 an acceptable alternative for the No. 1993 reinforcement of shell openings per Section 3.7.1.8 650 10th - Nov. 3.7.1 650-I-38/02 Does note c of API 650 Table 3-6 allow the customer to locate nozzles No. 1998 Table 3-6 lower than allowed by the weld spacing requirements of 3.7.3? 650 10th - Nov. 3.7.1 650-I-38/02 Do notes 6 and 7 from API 650 Figure 3-4A require the use of nozzle The API committee responsible for this standard has issued an 1998 Fig. 3-4A flanges listed in Table 3-8 when substituting Table 3-6 nozzles for agenda item to study this issue further to determine if a change in manways? the standard is required. Any changes resulting from this agenda item will appear in a future edition or addendum to API 650. 650 10th - Nov. 3.7.1 650-I-37/00 May a shell nozzle or manhole that otherwise complies with Figure 3-4B Yes. 1998 Fig. 3-4B have its reinforcing plate welded to the nozzle neck with a full- penetration weld, in addition to the fillet weld in the same manner as API 620 Figure 3-8 Part 2 Panel m, if the purchaser has so approved as permitted by API 650 Section 3.7.1.8? 650 9th - May 3.7.2 Is a minimum repad required around all nozzles greater than 2" even if No, see Section 3.7.1.8. 1993 the area of the nozzle allowed as reinforcing (Section 3.7.2.3) is greater than the reinforcing required (Section 3.7.2.1)? 650 9th - May 3.7.2 May shell opening reinforcement be determined either in accordance No, Section 3.7.2.1 requires that Tables 3-8 and 3-9 be used. 1993 with Section 3.7.2.1 or, alternately, in accordance with Tables 3-8 and However, alternate details satisfying the reinforcement 3-9? requirements of Section 3.7.2.1 are allowed if the purchaser agrees to their use. 650 10th - Nov. 3.7.2 650-I-07/04 Regarding Section 3.7.2 as it applies to Appendix F, when calculating No. 1998 the required shell thickness at the nozzle location is it necessary to use the joint efficiency factor that was used for calculating the required tank shell thickness? 650 9th - May 3.7.3 Referring to API 650, Section 3.7.3, is it correct to conclude that the Question 1 is correct. Question 2 is incorrect. The requirement 1993 minimum distance between the periphery of a nozzle reinforcing plate for the case of shell plate greater than ½ in. with no stress relief is and the shell-to-bottom weld (measured as toe-to-toe) is as follows: 1) the greater of 10 inches or 8 times the weld size. For the case of For shell plate ½ in. or less, or for any stress-relieved shell plate shell plate greater than ½ in. with stress relief, the distance is 3 thickness, the required distance is the greater of 3 inches or 2.5 times inches or 2.5 times the shell thickness. the shell thickness? 2) For shell plate greater than ½ in., with or without stress relief, the required distance is 10 inches? 650 9th - May 3.7.3 Regarding reinforcement for shell openings, is the total area of Yes, the areas are measured vertically, along the diameter of the 1993 provided reinforcing equal to the sum of the reinforcing areas above opening, and must be within a distance above or below the and below the opening? horizontal centerline equal to the vertical dimension of the hole. 650 9th - May 3.7.3 Is the total area of required reinforcing equal to the product of the Yes, however, when calculations are made for the required 1993 vertical diameter of the hole and the nominal plate thickness? thickness considering all design and hydrostatic test load conditions, the required thickness may be used in lieu of the nominal thickness. 650 9th - May 3.7.3 What is the distance between vertical welds? Please refer to API 650, Section 3.1.5.2.b and Section 3.7.3. 1993 6 of 26
  7. 7. Standard Edition Section Inquiry # Question Reply 650 10th - Nov. 3.7.3 650-I-07/02 Given a 2 in. nominal bore non-reinforced nozzle in a non stress- Yes, for new tanks, see API 650, sections 3.7.3.1, 3.7.3.3, and 1998 relieved shell greater than 0.5 in. thickness. Are the minimum Figure 3-22. distances for: (1) the outer edge of nozzle attachment weld to center line of a shell butt weld, either vertical or horizontal, and (2) the toe-to- toe distance of the fillet to the shell-to-bottom weld, required to be 10 in. (or 8x weld thickness) and 3 in., respectively? 650 9th - May 3.7.3.1 Based on API 650, Section 3.7.3.1(b) (shells greater than ½ in. thick), is Yes, assuming there is also no stress-relieving in this case. 1993 the spacing dimension required to be the greater of 8x weld size or 6 inches from the toe or edge of welds in all cases shown in the attached figure? 650 10th - Nov. 3.7.3.2 650-I-19/99 API 650, Section 3.7.3.2 decreases the required minimum spacing from Section 3.7.3.2 does not define requirements for the distance 1998 the nozzle neck weld to the edge of reinforcing when stress-relieving of from the nozzle neck weld to the edge of reinforcement. The the periphery has been performed before welding the assembly to the spacing between the nozzle centerline and the edge of adjacent shell joint, by reducing the spacing to 6 inches from vertical reinforcement, which is also the shell-to-bottom for this assumed joints, or 3 inches from horizontal joints. Does this include the tombstone-type detail, must meet the limits in Table 3-6, Column distance from the penetration weld (nozzle neck) to the shell-to-bottom 9. weld if the reinforcing extends to the shell-to-bottom weld? 650 9th - May 3.7.3.2 650-I-19/99 Based on API 650, Section 3.7.3.2 (shells greater than ½ in. or less or Yes. 1993 stress-relieved), would all the spacing dimensions in the attached sketch be the same (the greater of 3 inches or 2 ½ times the shell thickness from edge or toe of welds)? 650 10th - Nov. 3.7.3.3 650-I-19/99 Referring to API 650, Section 3.7.3.3 and 3.7.3.1(a), if the thickened No, these sections do not define requirements for the distance 1998 insert or reinforcing plate is detailed to extend the reinforcing to the from the nozzle neck to the edge of reinforcing. However, the bottom-to-shell joint, does the distance from the toe of the weld around spacing between the nozzle centerline and the edge of the penetration (nozzle neck) to the shell-to-bottom weld still have to reinforcing, which is also the shell-to-bottom for this assumed meet the minimum spacing of 8t or 10 inches from any butt-welded tombstone-type detail, must meet the limits in Table 3-6, Column joint, including the bottom-to-corner weld? 9. 650 9th - May 3.7.3.4 Does API 650 allow for nozzles to be installed in circumferential seams? Yes, if the conditions specified in Section 3.7.3.4 are met, 1993 including purchaser and manufacturer agreement, and radiography requirements. 650 9th - May 3.7.4 Does API 650 require flush-type cleanout fittings to be stress-relieved Yes. The contractual arrangements are not a factor. 1993 as a complete assembly, when more than one manufacturer is involved in fabricating the components? 650 10th - Nov. 3.7.4 When stress-relieving the assembly defined in API 650 Sections 3.7.4.1, No, however, there is no rule against shortening the plate length 1998 3.7.4.2, and 3.7.4.3, is it permissible to perform a local heat treatment circumferentially, prior to installation of the fitting or connection. that includes part of a shell plate, instead of the whole shell plate, i.e., the portion around the connection at full width of shell plate? 650 10th - Nov. 3.7.4 650-I-20/00 Does API 650, Section 3.7.4, require that all flush-type cleanout fittings Yes, except as permitted by A.8.2. 1998 be stress-relieved? 650 9th - May 3.7.4.1 Does API 650, Section 3.7.4.1, require stress-relieving of flush-type No. Unless Appendix A applies, stress-relieving of flush-type 1993 cleanout fittings only if the entire tank is stress-relieved? cleanout fittings is required regardless of whether the entire tank is stress-relieved or not. 650 9th - May 3.7.4.1 Is there a conflict between API 650 Sections 3.7.4.1 and 3.7.4.3 and No. 3.7.4.1 and 3.7.4.3 cover the general rule; 3.7.7.3 and 1993 3.7.7.3 and 3.7.8.3 regarding stress-relieving of flush-type cleanout 3.7.8.3 cover a special situation that merits tighter stress-relieving fittings? requirements. Flush-type cleanout fittings are a complex weldment. 650 10th - Nov. 3.7.4.1 Referring to API 650, Section 3.7.4, must all flush-type cleanouts and Yes, see Section 3.7.4.1. 1998 flush-type shell connections be stress-relieved regardless of the material used, the nozzle diameter, or the thickness of the shell insert plate? 650 10th - Nov. 3.7.4.1 & 650-I-02/00 Question: Referring to API 650, Section 3.7.4.2 and 3.7.4.3, is the Reply 1: No, but the heat treatment must be performed prior to 1998 3.7.4.2 thermal stress relief required to be performed in an enclosed furnace? installation of the assembly into the shell. Question: Does API 650, Section 3.7.4.2 and 3.7.4.3, allow stress- relieving nozzles, as described therein, using locally applied heaters? Reply 2: Yes, however, the heat treatment has to be performed prior to installation into the tank. 7 of 26
  8. 8. Standard Edition Section Inquiry # Question Reply 650 10th - Nov. 3.7.4.2 650-I-53/99 Question 1: Per API 650, Section 3.7.4.2, for shell openings over NPS Reply 1: Yes. 1998 12, if insert plates are not used to reinforce the shell opening, is the shell thickness a factor in determining if PWHT of the assembly is required? Question 2: Regarding Section 3.7.4.2, is stress-relieving mandatory Reply 2: No. The requirement applies only to NPS 12 or larger for the prefabricated assembly when the thickness of the thickened connections. insert plate exceeds 1 in., irrespective of the shell opening size. 650 10th - Nov. 3.7.4.2 650-I-17/01 Does Section 3.7.4.2 of API 650, mean that stress-relieving of opening Stress-relieving of the opening connections meting the conditions 1998 connections after welding the shell joints is prohibited? specified in 3.7.4.2 is required prior to installation of the assembly into the shell. 650 9th - May 3.7.4.3 650-I-41/98 Question 1: Does API 650 require the stress-relieving of a pre- Reply 1: The entire assembly, not just the welds, must be heated 1993 fabricated clean-out fitting, or a reinforced opening in a tank shell, be to the required temperature. The method for accomplishing this is performed in one operation by enclosing the assembly in a furnace, or not specified in API 650. Refer to Section 3.7.4 of API 650. can the heat treatment be achieved by placing electric wire elements Clean-out fitting assemblies, but not other reinforced connections, just around the welded joints of the assembly and providing may alternatively be stress-relieved by heat treating the entire insulation? tank with the assembly installed in the tank. Reply 2: No. Clean-out openings are required to be stress- Question 2: Does API 650 allow stress-relieving reinforced shell relieved prior to installation in the tank or by heating the entire openings or clean-out shell fittings in position after installation using tank. Refer to Section 3.7.4. electric wire elements and insulation? 650 9th - May 3.7.4.3 Referring to API 650, Section 3.7.4.3, is it acceptable to perform the The entire assembly has to be heated uniformly, not just the 1993 required stress-relieving in a field fabrication shop, applying the heat welds. API 650 does not specify the technique to be used to locally? achieve this uniform heating, or where the stress-relieving is to be performed. 650 10th - Nov. 3.7.4.3 Referring to API 650, Section. 3.7.4.3, if the required reinforcing can all Yes. 1998 be placed in the nozzle neck, using internal and external projections as required, thereby eliminating any insert plate or reinforcing plate, is PWHT of the prefabricated opening connection assembly required? 650 10th - Nov. 3.7.4.3 650-I-01/00 Does API 650, Section 3.7.4.3, allow stress-relieving nozzles, as No. The heat treatment has to be performed prior to installation 1998 described therein, after installation in the shell, using locally applied in the tank. heaters? 650 9th - May 3.7.4.4 Does API 650, Section 3.7.4.4, require for the stated materials that the Yes, in addition, the nozzle-to-shell weld is to be stress-relieved 1993 weld attaching a nozzle reinforcing plate to a shell plate be stress- also. relieved? 650 9th - May 3.7.5 Does API 650 specify a minimum number and location for manholes No. 1993 and inspection openings in tanks? 650 10th - Nov. 3.7.6 Does API 650 allow nozzle-type clean out fittings that are half above No. 1998 floor level and half below floor level to be replaced in an old tank or installed in a new tank? If so, what section permits them to be replaced? 650 10th - Nov. 3.7.6.1 Does API-650, Section 3.7.6.1, permit making a hot tapping connection No. Refer to API 650, Section 3.8.3, for rules on installing a 1998 on a blind flange on a nozzle in a tank? nozzle in a cover plate in a new tank. Refer to API 653, Section 7.14, for rules and guidance on hot tapping in an in-service tank. 650 10th - Nov. 3.7.7 650-I-08/99 Does a flush-type cleanout built to API 650 require a machined surface No. 1998 on either the bolting flange or the cover plate? 650 10th - Nov. 3.7.7 650-I-01/04 Question 1: When installing a flush-type cleanout fitting, is it Reply 1: Yes. Refer to Figure 3-9, Note 2. 1998 mandatory to provide a bottom reinforcing plate width the as same as the annular plate width? Question 2: When an annular plate is provided, does API 650 permit Reply 2: No. Refer to Figure 3-9, Note 2. provision of bottom reinforcing plate having lesser width than that of annular plate? 650 10th - Nov. 3.7.7.6 650-I-56/02 Do the minimum thicknesses listed in Table 3-10, and calculated by the No. See Section 3.3.2. 1998 equations in section 3.7.7.6 have a corrosion allowance? 650 9th - May 3.7.8 Should the corrosion allowance used on the shell plate be included in No. A corrosion allowance for an external reinforcing pad is not 1993 the required thickness of the reinforcing pad? required unless specified by the purchaser. 8 of 26
  9. 9. Standard Edition Section Inquiry # Question Reply 650 10th - Nov. 3.7.8 650-I-14/02 Background: Section 3.8.3.2 states: "a cover plate with a nozzle 1998 attachment for product-mixing equipment shall have a thickness at least 1.4 times greater than the thickness required by Table 3-3." Section 3.8.3.3 also states that "when cover plates (or blind flanges) are required for shell nozzles, the minimum thickness shall be that given for flanges in Table 3-8". There seems to be a conflict between these two sections in that when the thickness specified by Table 3-3 (at max liquid level) is increased by 40%, it is still thinner than the thickness specified by Table 3-8. Question 1: In determining the thickness of a cover plate and bolting Reply 1: No. flange in which product mixing equipment is installed, is there a conflict between 3.8.3.2 and 3.8.3.3. Question 2: If we are to adhere to 3.8.3.3, how are we to compute the Reply 2: API does not provide consulting on specific engineering new thickness of a cover plate whose integrity has been compromised problems or on the general understanding of its standards. We by the addition of a hole into which a smaller adapter nozzle has been can only provide interpretations requirements that are stated in an placed. 3.8.3.3 only directs the reader to Table 3-8 to find the thickness API standard or consider revisions based on new data or of unadulterated cover plates. No mention is made in 3.8.3.3 regarding technology. how to compute the new thickness after a nozzle has been added. 650 10th - Nov. 3.8 650-I-50/00 Referring to API 650 Section 3.8, if the requirements of this section Yes. However, certain attachments (e.g. stiffening rings, per 1998 have been satisfied, is it permissible to make permanent attachments Section 3.9.4) are covered by specific rules that affect size, of any size, shape or thickness? shape, or thickness. 650 10th - Nov. 3.8.1 650-I-53/00 Referring to API 650, is magnetic particle testing applicable for No. See 3.8.1.2 and 5.2.3.5, in Addendum 1 to the 10th Edition of 1998 inspecting permanent attachments to the shell and at temporary API 650. attachment removal areas, when the material group is of Group I (A 283, Grade C)? 650 10th - Nov. 3.8.1 650-I-45/03 Does API 650 allow butt-welded connections without flanges outside Yes. Refer to section 1.2 d. 1998 the tank shell? 650 10th - Nov. 3.8.3.2 650-I-51/00 API 650, Section 3.8.3.2, requires mixer manway bolting flanges to be No. 1998 40% thicker than the values shown in Table 3-3. Footnote b under Table 3-4 requires the minimum manway neck thickness to be the lesser of the flange thickness or the shell plate. Is it therefore required that the minimum neck thickness on a mixer manway be the lesser of 140% of the flange thickness value in Table 3-3 or the shell thickness? 650 9th - May 3.8.7.2 Referring to API 650, Section 3.8.7.2, is the "as-ordered thickness" The "new condition". 1993 equal to the "new condition" or the "corroded condition"? 650 9th - May 3.8.10 Does API 650 require intermediate landings for spiral stairways? No. 1993 650 9th - May 3.9 Section 3.9 addresses the stiffening of open top tanks for wind loads. The top of a fixed roof tank does not require stiffening for wind 1993 Does this mean that fixed roof tanks, such as cone, dome, and loads, however, the tank shell must be checked to determine if an umbrella roof tanks, do not need to be stiffened for wind loads or intermediate wind girder per Section 3.9.7 is required. should the same procedure be used for designing fixed roof tanks? 650 9th - May 3.9 If more than one intermediate wind girder is required, is the section To determine the section modulus of the second intermediate 1993 modulus of the second intermediate wind girder based on the height wind girder, first determine the transformed shell height equal to between the second intermediate wind girder and the top wind girder, the distance between the fist wind girder and the top wind girder. or should H1 be based on 1/2 the distance between adjacent wind Subtract this value from the total transformed shell height girders/stiffeners where the bottom plate counts as the bottom determined in Section 3.9.7.2. The remaining shell is then stiffener? transposed to an actual shell height and this value is used for H1 in the formula in Section 3.9.7.6. 650 9th - May 3.9 Does Section 3.9 of API 650 require intermediate wind girders for Yes. Where required by 3.9.7, intermediate wind girders are 1993 closed top tanks where required by Section 3.9.7? required for closed top tanks as well as open top tanks. This requirement is not in conflict with Section 3.9.1 which deals only with the requirement for a top wind girder on open top tanks. 9 of 26
  10. 10. Standard Edition Section Inquiry # Question Reply 650 9th - May 3.9.1 Section 3.9.1 implies that the intermediate wind girders are not required Intermediate wind girders are required for fixed roof tanks if height 1993 for fixed roof tanks although the definition for H1 in Section 3.9.7.1 and of unstiffened shell exceeds H1 as calculated by Section 3.9.7.1. 3.9.7.6 implies otherwise? 650 9th - May 3.9.2 Is it permissible to construct the top wind girder as a circular ring Yes, provided the requirements of Section 3.9.2 are met. 1993 using flat plate components? 650 10th - Nov. 3.9.6 650-I-23/02 Is there any upper limit for the number of intermediate wind girders in No. 1998 API 650? 650 9th - May 3.9.6.1 In Section 3.9.6.1, the definition of H2 implies that the modulus of the Yes. 1993 top wind girder is not reduced by providing the intermediate wind girder. Is this correct? 650 9th - May 3.9.6.1 Reference 650 Section 3.9.6.1, is it permissible to use a double wind The top wind girder must meet the requirements of API 650 1993 girder in lieu of a top wind girder on an open top tank? Section 3.9.6. API does not restrict the details of construction. 650 9th - May 3.9.6.1 Is the conversion of design wind velocity of 100 mph to a peak 3 The American Petroleum Institute does not approve, recommend, 1993 second wind gust 50 m/s giving design wind pressure of 31 psf or 1.485 or endorse any proprietary or specific design; nor does it limit the kPa correct? method of design or form of construction that might be used to conform to an API Standard. Therefore, we cannot act on your inquiry. We suggest that you review the notes to Sections 3.9.6.1 and 3.9.7.1. 650 9th - May 3.9.7 Must corrosion allowance be subtracted from t in the formula of 3.9.7.1 No. 1993 and 3.9.7.2? 650 9th - May 3.9.7 Does API 650 require the tank supplier to meet the intermediate wind Yes. 1993 girder requirements of Section 3.9.7 for all fixed roof tanks? 650 9th - May 3.9.7 If more than one intermediate wind girder is required, is the section To determine the section modulus of the second intermediate 1993 modulus of the second intermediate wind girder based on the height wind girder, first determine the transformed shell height equal to between the second intermediate wind girder and the top wind girder, the distance between the fist wind girder and the top wind girder. or should H1 be based on 1/2 the distance between adjacent wind Subtract this value from the total transformed shell height girders/stiffeners where the bottom plate counts as the bottom determined in Section 3.9.7.2. The remaining shell is then stiffener? transposed to an actual shell height and this value is used for H1 in the formula in Section 3.9.7.6. 650 9th - May 3.9.7 Is it permissible per API 650 to design tanks for a vacuum higher than 1 No. API 650 does not provide rules for the external pressure 1993 in. water column by accounting for the same in Section 3.9.7, Footnote design of tanks and does not comment on specific design (a)? methods or rules not covered y the standards. The committee is presently considering rules for the external pressure design. Any changes resulting from this agenda item will appear in a future edition or addendum of API 650. 650 10th - Nov. 3.9.7.1 650-I-37/02 In Section 3.9.7.1, should footnote (a) be referred to when analyzing Yes. 1998 wind velocities other than 100 mph? 650 9th - May 3.9.7.2 Referring to API 650, Section 3.9.7.2, is the "as-ordered thickness" The "new condition." 1993 equal to the "new condition" or the "corroded condition?" 650 10th - Nov. 3.9.7.6 650-I-23/02 Question 1: Does Section 3.9.6 apply only to open top tanks and Reply 1: Yes. 1998 Appendix G tanks? Question 2: Is it correct to consider length of shell 1.47×(D×t)0.5 Reply 2: Yes. specified in 3.9.7.6.2 on each side of the shell-ring attachment, resulting a total shell length of [2×1.47×(D×t)0.5 + (width of wind girder in contact with shell)]? 650 9th - May 3.10 If the corrosion allowance plus the calculated thickness is less than No. 1993 3/16 in. thick, must the corrosion allowance be added to the 3/16 in. minimum nominal roof thickness? 650 9th - May 3.10 For loads exceeding the code-specified 25 psf live load, how can the This is outside the scope of API 650. The services of a 1993 design be modified to avoid damage to the roof? consultant and/or the tank manufacturer may be needed. 650 9th - May 3.10 What happens when the roof is flat? API 650 does not cover flat roofs. 1993 650 9th - May 3.10 Does a 2% slope for a supported cone roof tank meet the requirements No. 1993 of API 650? 650 9th - May 3.10 When designing a cone roof based on the formulas in API 650, are The necessary and appropriate factors of safety are included 1993 factors of safety included in the rules of API 650 or must they be inherently in the design rules of API 650. considered separately by the tank designer? 10 of 26
  11. 11. Standard Edition Section Inquiry # Question Reply 650 10th - Nov. 3.10 650-I-52/99 Is welding of the main roof support members to the roof plates allowed No, see API 650, Section 3.10.2.3, that states that roof plates of 1998 by the standard? supported cone roofs shall not be attached to the supporting members. 650 10th - Nov. 3.10 How do you size an emergency vent for a sulfuric acid storage tank? API can only provide interpretations of its standard and consider 1998 revisions based on new data or technology. API does not act as a consultant on specific engineering problems or on the general understanding or application of the standard. 650 10th - Nov. 3.10 650-I-10/00 Does API 650 provide a way to obtain a frangible roof connection on a No. The API Subcommittee on Pressure Vessels and Tanks is 1998 small tank describe as follows? - Diameter: 8 ft. - Height: 10 ft. - currently reviewing the design criteria for frangible roof joints. Cross sectional area of the roof-to-shell junction "A": larger than that You may wish to review Publication 937, Evaluation of Design allowed by the equation in Section 3.10. Criteria for Storage Tanks with Frangible Roof Joints. 650 10th - Nov. 3.10 Section 10.4.3 states "When considering dead loads only, including the API does not respond to questions seeking the rationale for 1998 weight of the rafters and the roof plates, the compression flange of the requirements in its standards. These requirements are based rafter shall be considered as receiving no lateral support from the roof upon consideration of technical data and the judgment and skill of plates and shall be laterally braced if necessary (see Section 3.10.4.2)." experienced engineering and technical personnel representing This statement, which is a fairly recent revision, imposes much more both users and manufacturers who serve on the standards-writing stringent requirements on the rafters than what was required in the committees. All technical meetings during which API earlier editions that allowed the assumption of lateral bracing from the requirements are considered are open to the public. The API friction with the roof plate. What was the basis for this change in Pressure Vessels & Tanks Subcommittee, which is responsible requirements? for this standard, meets twice per year at the Spring and Fall Refining Meetings. Information on these meetings can be found on the API website at www.api.org/events. 650 10th - Nov. 3.10 Regarding the same sentence in 3.10.4.3, I have assumed that all dead The committee currently has an agenda item to study this 1998 loads should be included and not just roof plates and rafter weight. We question. Any changes resulting from this agenda item will have a 5 lb/ft2 insulation dead load which we have included in our appear in a future addendum or edition to API 650. calculations. Is this correct? 650 10th - Nov. 3.10 When installing girders and rafters in an existing tank, do they need to Yes, refer to API Standard 653, Section 9.11.1.2. 1998 be installed in accordance with the latest edition of API Standard 650? 650 10th - Nov. 3.10 When not altering the roof rafters and framing of an existing tank, is it Refer to API Standard 653 Section 4.2.2 1998 necessary to upgrade it to the current edition of API Standard 650? 650 10th - Nov. 3.10.1 650-I-31/03 Referring to 3.10.1(a) and 3.10.2.3, is it permissible by the code to No, however, a committee agenda item has been approved that 1998 3.10.2.3 locate rafters outside the tank over the roof plates? The rafters would will change this requirement. Please refer to the next addendum hold the roof plates welded to its bottom flange instead of supporting of the standard. the plate. 650 10th - Nov. 3.10.2 650-I-15/03 Background: Section 3.10.2 states the roof structure shall be designed API 650 does not specifically address this issue for roofs in 1998 for uniform live load of 1.2 kPa with no mention of either a wind or 3.10.2. The committee has issued an agenda item to define roof seismic load. However, per Appendix G the roof structure shall be design loads for a future addendum or edition of the standard. designed not only for live loads, but also for wind and seismic loads. Question: Do the requirements for fixed roofs in 3.10.2 include wind and seismic loads in the design? 650 10th - Nov. 3.10.2.5 What does API 650, Section 3.10.2.5 mean by the term "top angle"? Angle refers to a steel angle structural shape - see the AISC 1998 "Manual of Steel Construction" or other similar publications. It is usually a 90 degree shape but can be other angles. The "top angle" is the structural angle, purchased or fabricated, that is located at the top of the shell - see Figure F-2 for examples. 650 10th - Nov. 3.10.2.5 Can the roof plate be attached to the top angle with a groove weld on No. 1998 top and a fillet weld on the inside? 650 10th - Nov. 3.10.2.5.1 Refer to API 650, Section 3.10.2.5.1 and Figure F-2. Is the area "A" the Yes. 1998 crosshatched area in Figure F-2? 650 10th - Nov. 3.10.2.5.3 650-I-15/02 Question 1: Is the "W" in 3.10.2.5.3 referring to the same "W" in F.4.2? Reply 1: Yes. 1998 Question 2: Is the "A" in 3.10.2.5.3 referring to the same "A" in F.4.1 and cross-hatched area shown in Figure F-1? Reply 2: Yes. 650 9th - May 3.10.2.7 Are roof support trusses which are welded to the shell acceptable? API doesn't provide design detail attachment of roof trusses to the 1993 shell. Please refer to Section 3.10.2.7. 11 of 26
  12. 12. Standard Edition Section Inquiry # Question Reply 650 9th - May 3.10.3.4 Reference Section 3.10.3.4 (d) and (e) -- Is the compressive stress in Yes, unless the formulas in Sections 3.10.2.4 (d) or (e) limited the 1993 fixed roof tank rafters which are non-symmetrical and deflecting in the compressive stress to a lower value. Please see Section 3.10.4.3 direction of the applied load limited to 20,000 psi? Addendum 3, dated December 1996. 650 9th - May 3.10.3.4 Can the allowable bending stress be increased by bracing the Yes, subject to the limitation developed through the formulas in 1993 compressor flange? Section 3.10.3.4 (d) and (e). Reference Section 3.10.3.4 of Addendum 3, dated December 1996. 650 9th - May 3.10.5 In section 3.10.5 for self-supporting roofs, may the corrosion allowance Yes. 1993 be added to the minimum calculated thickness given by tmin = D/400 sin Ø to arrive at a total minimum required thickness of 3/16 in. or greater? 650 9th - May 3.10.5 If a self-supporting roof is stiffened by sections or rafters, as per the No. 1993 notes in Sections 3.10.5 and 3.10.6, and is supported only at the periphery, is this roof to be classified as a supported cone roof as per the definition of Section 3.10.1(a) and meet the requirements of Section 3.10.4? 650 9th - May 3.10.5 650-I-51/99 Question 1: In API 650, Section 3.10.5, is the calculated minimum Reply 1: Yes, it is the minimum required thickness, exclusive of 1993 thickness the actual required thickness that takes into account the corrosion allowance, for the tank diameter and roof slope under span of unstiffened cone plates with a total load of 45 lbf/ft2? consideration. It should be noted that the maximum allowable roof plate thickness limits the tank diameter as a function of the roof slope. Question 2: How is the minimum thickness used? Reply 2: API does not act as a consultant on specific engineering problems or on the general understanding or application of its standards. API’s activities in regard to technical inquiries are limited strictly to interpretations of the standard and to the consideration of revisions to the present standard based on new data or technology. 650 10th - Nov. 3.10.5.2 650-I-38/00 Do the notes of Sections 3.10.5.2 and 3.10.6.2 include all the Yes, An agenda item has been established to review the meaning 1998 3.10.6.2 permissible participating area of the roof-to-shell junction of Figure F-2 of and need for the terminology “maximum cross sectional area of to be included in the term “maximum cross-sectional area of the top top angle.” angle”? 650 9th - May 3.10.6 Referring to Section 3.10.6.2, is the equation given in this section the Yes. 1993 required area of the top angle acting as a tension ring? 650 10th - Nov. 3.10.6 650-I-04/02 Does Section 3.10.6, require full penetration welds if a dome roof is This subject is not covered in API 650. 1998 butt-welded? 650 9th - May 3.11 For tanks with anchorage required by API 650, Section 3.11 No, the requirements of Section 3.11 are independent of those in 1993 (overturning stability), is the shell thickness limited to 1/2 in.? Section F.7. 650 9th - May 3.11 Are methods other than the one stated in Section 3.11 permitted to Yes, as long as the requirements of Section 3.11 are also met. 1993 calculate wind loads, when specified by the purchaser for example, ASCE 7 or local building codes? 650 9th - May 3.11 Do the formulas for the relationship between wind moment, internal Yes. 1993 design pressure, and deadload resisting moment, given in Appendix F, supersede those given in Section 3.11, when designing a tank for small internal pressure using that appendix? 650 9th - May 3.11 What is the appropriate ratio of tank diameter to tank height to avoid The determination of anchorage requirements is adequately 1993 anchorage? covered in API 650. Many factors are included in determining if anchors are required and the number of anchors. This is a specific design condition and should be considered in completing the detail design of the tank. 650 9th - May 3.11 In designing a tank per API 650, is the customer specified corrosion No, unless the purchaser states that the corrosion allowance also 1993 allowance applicable to the anchor chairs and associated welds? applies to external attachments. 650 10th - Nov. 3.11 650-I-06/01 Does API allow the use of ISO 4354 for determination of wind speed? No. The API committee responsible for this standard has issued 1998 an agenda item that will use ASCE 7 as the basis for determining wind loads. Any changes resulting from this agenda item will appear in a future edition or addendum to API 650. 12 of 26

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