Agenda Item: 653-219
Title:Temporary Repairs
Date:November 18, 2010
Contact:Domingo de Para
ExxonMobil Research & Engineering
281-834-4893
David Meaux
Fisher Tank Company
803-359-4173
Purpose:To provide definition oftemporary repairs, and to establish minimum requirements for their use.
Source:Inquiry TI 653-I-XX/07
Revision:2
Note: Based on the last ballot the following changes were made to Rev#1 in this ballot:
Para3.26 Temporary Repairs – The definition was wordsmith to incorporate comments given in the first ballot.
Para 9.2.1 General – Revised based on comments and gave STE and AI approval rights
Para 9.2.2 Non Welded repairs - Revised based on comments and abridged the description to better describe the repair. Incorporated non-metallic patch examples from API 575.
Para 9.2.3 Fillet-Welded Patches - Revised the entire section to reflect the comments from the first ballot. These include the addition of weld spacing restrictions.
Para 9.3 Added word "Permanent" to title of existing paragraph to make a distinction from temporary lap patches.
Para 13.2.4 – Added “weld procedure” and "visual inspection" to the specific details.
Impact:These provisions would permit a storage tank to remain in service if it can be repaired on a temporary basis to restore mechanical integrity until the tank can be scheduled for inspection and maintenance.
Rationale:Temporary repairs to storage tanks are a recognized practice used in industry to permit continued operations until a tank can be scheduled for permanent repairs. The current edition of API 653 makes no mention of temporary repairs, while similar inspection and repair documents such as API 570 (Piping Inspection Code)and API 510 (Pressure Vessels Inspection Code) include these provisions.
Proposal:
(Add) 3.26 Temporary Repairs:Repairs made to an in-servicestorage tank in order to restore sufficient integrity to continue safe operation until permanent repairs can be scheduled and accomplished within a time period acceptable to the authorized inspector and storage tank engineer.
Place between the current 9.1 General and 9.2 Removal and Replacement of Shell Plate Material:
9.2Temporary Repairs
9.2.1General
9.2.1.1Temporary repairs shall be evaluated and approved by the storage tank engineer and the authorized inspector.
9.2.1.2Temporary repairs shall be removed and replaced with suitable permanent repairs within the time period acceptable to the authorized inspector and the storage tank engineer.
9.2.2Non-Welded Repairs
9.2.2.1Non-welded repairs (patches) may be used to make temporary repairs to damaged, corroded, or eroded areas of the tank.
9.2.2.2Non-welded repairs (patches) may be made by installing a properly designed and applied clamp, wrap, patch or similardevice.Non-metallic patches can be made from a variety of materials including rubber, neoprene, glass cloth, asphalt, and mastic or epoxy sealing materials.
9.2.3Fillet Weld Patches
9.2.3.1Fillet welded patches which meet the requirements of this sectionmay be used to make temporary repairs to damaged, corroded, or eroded areas of the tank or tank component.
9.2.3.2Fillet-welded patches are not permitted to be installed on a fixed roof, a floating roof, or on the shell above the liquid level (gas/vapor space) of a tank which is in service.
9.2.3.3The material for the repair shall match the base metal unless approved by the storage tank engineer.
9.2.3.4Fillet-welded patches require special design consideration, especially related to weld joint efficiency. Fillet-welded patches may be applied to the external surfaces of tank shells or components, provided that, in the judgment of the engineer, either of the following is true:
a.The fillet-welded patches provide design safety equivalent to reinforced openings designed according to the as built Standard.
b.The fillet-welded patches are designed to absorb the membrane strain of the parts so that in accordance with the rules of the applicable construction code, the following result:
1.The allowable membrane stress is not exceeded in the shell or the patches.
2.The strain in the patches does not result in fillet-weld stresses that exceed allowable stresses for such welds.
9.2.3.5Fillet-welded patch plates shall be rolled to the radius of the part being patched and shall have rounded corners with a minimum radius of 2 in. (50 mm).
9.2.3.6The weld spacing requirements of Figure 9-1 shall be used as the basis for locating repair plates relative to butt-welded, fillet welded, and riveted seams and other repairs plates.
9.2.3.7The applicable requirements and restrictions given in 9.14 Hot Taps (existing paragraph) shall apply to temporary repairs using welded plates.
9.2.3.8Prior to the application of a fillet-welded patch shell repair, the area to be welded shall be ultrasonically inspected for plate defects and remaining thickness.
Change 9.2 to 9.4
Change 9.3 to read:
9.3 Permanent Shell Repairs Using Lap-welded Patch Plates
Change 12.1.8.2 to read:
12.1.8.2 The attachment welds of new or temporary lap-welded patches shall be visually examined, and shall be examined by either the magnetic particle or liquid penetration methods.
Add to Section 13
13.2.4Documentation of temporary repairs as described in 9.2 shall include:
a)Drawing showing location of temporary repairs
b)Specific details about the repair, e.g., material of construction, thickness, size of repair, weld procedure andNDE performed.
c)Details of analysis performed, including engineering calculations.
d)Requirements for future inspections, including monitoring
e)Due date for installing permanent repairs.
The inspection plans shall include visualmonitoring the integrity of the temporary repair until permanent repairs are complete.