1
Revise A.1.1 as shown bold in italics.Correct A.8.1 and A.9 Editorially.
A.1.1 This appendix provides requirements for field-erected tanks of relatively small capacity in which the stressed components have a maximum nominal thickness of 12.5 mm (1/2 in.), including any corrosion allowance specified by the purchaser. The stressed components include the shell and reinforcing plates, bottom andshell reinforcing plates for flush-type cleanout fittings and flush-type shell connections, and bottom plates that are welded to the shell. but the stressed components do not include, other bottom plates, covers, and nozzle and manhole necks and their flanges.Maximum nominal thickness of 12.5mm (1/2”) does not apply to:
(1)bottom plates not welded to the shell,
(2) the bottom reinforcing plate of flush-type cleanouts and flush-type shell connections,
(3) flanges and cover platse of flush- type cleanouts,
(4)flush-type shell connections’s necks attached to shell
(5)nozzle and manhole necks, their flanges and cover plates.
A.2.4 Bottom reinforcing plates in flush-type cleanouts and flush-type shell connections, and flush-type fitting’s necks attached to shell shall conform to toughness requirements of 2.2.9 and Fig.2.1 at Design Metal Temperature( DMT).
A.8.1 The details and dimensions of flush-type cleanout fittings shall conform to 3.7.7, Figures 3-9 and 3-10, and Tables 3-113-9through 3-13 3-11.
A.8.2 The provisions for stress relief specified in 3.7.4 and 3.7.7.3 are not required unless they are specified by the purchaser or unless any plate in the unit has a thickness greater than 16 mm (5/8 in.).
A.9.1 Flush-Type Shell Connections
The details and dimensions of flush-type shell connections shall conform to 3.7.8, Figure 3-11, and Table 3-113-12.
A.9.2 The provisions for stress relief specified in 3.7.4 and 3.7.8.3 are not required unless they are specified by the purchaser or unless any plate in the unit has a thickness greater than 16 mm (5/8 in.). /
AGENDA ITEM 650-557 Rev.3
Sheet 1 of 3
Date: Sept.15, 2003
Title: Appendix-A, Flush Type Clean outs. Para. A.1.1, A.8.2 Conflict.Source: B. Mistry’s letter of May 17, 2002
Hello Bob and Phil,
Recently, I had the need to study Flush Type clean out requirements in Appendix-A tank and I discovered some conflict in Para. A.1.1and A.8.1, A.8.2.
Para. A.1.1 limits all stress components including components of flush type clean out assembly to 1/2". In other words, no components in flush type clean out can exceed 1/2". Para. A.8.2 allows flush type cleat out upto 5/8"thick without post weld treatment. It means that, Appendix-A tank can have flush type clean out with 5/8" stress components without PWHT. This conflicts with 1/2" thickness limitation in A.1.1.
It is quite possible that allowing 5/8" thickness for flush type clean out was deliberate. In earlier edition of API-650, shell plate and reinforcing plate containing flush type clean outhad to be at least 1/16" thicker but not to exceed 1/8". This requirement was eliminated not too long ago. In earlier edition, Appendix-A tank with 1/2" thick shell had to have shell and reinforcing plate, containing flush type clean out ,thicker than .5".
Reviewing Table 3-10 of API-650,1/2" thickness limit on bottom reinforcing plate willlimit clean out size to 24"x24" with shell height of 34' 0". This is quite restrictive. Allowing 5/8" thickness, one can have 24"x24" clean outin a tank upto 53' 0" high.
I suggest that we revise Para. A.1.1 to allow 5/8" thick components in Flush Type clean outs in Appendix-A tanks.
There is also Editorial correction required in A.8.1. Tables 3-11 through 3-13 should read Tables 3-9through 3-11. In A.9, Table 3-14 should read Table 3-12.
AGENDA ITEM 650-557 Rev.3
Sheet 2 of 3
Date: Sept.15, 2003Further research of past Edition revealed the following.
Appendix-A (as we know), included in recent Edition of API-650 did not exist prior to 7 th. Edition of API-650. What we call Appendix-A now was the Basic Tank Design, with stress values limited to 21000 psi.
(1) API-650, 1964
Maximum size of clean out 48"x48".
PWHT required if any component exceeds 5/8".
(2) API-650,1966, 1970,1973,1978
No change.
(3) API-650, 1980- 1988, 7Th. Edition
Appendix-A , as we know, isintroduced . Stress Components were restricted to 1/2". Flush Type components were excluded from 1/2" limitations.. PWHT is required if components exceeded 5/8".
(4)API-650 1988, 8Th. Edition.
Appendix-A restricts 1/2" to all stress components including Flush Type Clean out, as in current edition. However, it permits 5/8" components in flush type components without PWHT. In other words, contradiction in Appendix-A has been around since 8Th. Edition of API-650.
Purpose:
Correct and resolve conflict in para. A.1.1 and A.8.2. Permit components in Flush Type Clean outs over ½”. Clarify that flush type clean out with components not exceeding 5/8” can be used in Appendix-A tank without PWHT and over 5/8” thick can be used with PWHT.
AGENDA ITEM 650-557 Rev.3
Sheet 3 of 3
Contact: Bhana MistryTIW Steel Platework
Tel: 905-684-9421
Fax: 905-684-7310
Email:
Technical Justification:
Same as stated in Purpose above.
Cost Effects:
None.
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