Proposed Change: Notes: Insert new item 10 in section 3 to define door sheet as follows: 10 Door Sheet




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Proposed Change:
Notes: Insert new item 3.10 in section 3 to define DOOR SHEET as follows:
3.10 Door Sheet: A plate (or plates) that is cut from an existing tank shell to create a temporary access opening and which is subsequently reinstalled or replaced.

Commentary: Insert a new section 9.2.4 to address door sheet installation and renumber the following sections.




      1. Door Sheet Installation

This section describes the requirements for re-installation or replacement of a door sheet in the tank shell. The weld spacing requirements of figure 9-1 and 9-2 shall be used as a basis for locating door sheets relative to existing seams.



        1. Door Sheet That Does Not Cross an Existing Seam. If a door sheet does not cross a vertical or horizontal seam then the requirements specified in section 9.2.1, 9.2.2 and 9.2.3 shall be met. If a door sheet reutilizes the removed material then the requirements of 11.1.2 shall also be met.

        2. Door Sheet Crossing an Existing Seam, Utilizing New Shell Material. When a door sheet crosses an existing seam the following additional requirements shall apply:

          1. Butt-welded Tanks: No additional requirements are required.

          2. Lap-welded Tanks: If new shell plate material is utilized for the door sheet, and the replacement section extends above the first horizontal weld seam, the replacement section must be constructed of two separate plates, with the lower section butt-welded to adjacent first course by means of full penetration vertical welds, then the upper section shall be lapped over the lower section and the vertical welds butt welded to existing second course shell. The horizontal weld joining the first shell course to the second course shall be a full fillet weld on each side. The upper section shall be 24” longer or shorter than the lower section, such that the vertical seams of the upper section offset the vertical seams of the lower section by 12". The vertical seams in the second ring may utilize the lower shell plate as back-up.

          3. Riveted Tanks: If new shell plate material is utilized for the door sheet, the replacement door sheet must be constructed of two separate sections of plate, with the lower section butt-welded to adjacent first course by means of full penetration vertical welds, then the upper section shall be lapped over the lower section and the vertical welds butt welded to existing second course shell. The first shell course shall be joined to the second course by means of a full fillet weld on each side. The upper section shall be 24” longer or shorter than the lower section, such that the vertical seams of the upper section offset the vertical seams of the lower section by 12". The vertical seams in the second ring may utilize the lower shell plate as back-up. New weld seams shall be located a minimum of 12” from existing rivet seams. The heat created by welding is likely to cause nearby rivets and rivet seams to leak. Therefore sealing of rivets and rivet seams by some means within 12” of the door sheet welds shall be required.

        3. Door Sheet Crossing an Existing Seam Utilizing Removed Shell Plate.

          1. Butt Welded Tanks: The removed shell plate section may be re-installed in its original location utilizing joints with complete penetration and complete fusion. The existing horizontal welds adjacent to the newly welded vertical seams shall be cut for a minimum distance of 12 inches beyond the new vertical joints. The vertical joints shall be welded prior to welding the horizontal joints.

          2. Lap Welded Tanks: Reinstallation of original plate section is not permitted when it extends beyond a vertical or horizontal lap weld seam.

          3. Riveted Tanks: Reinstallation of original plate section that is not permitted when it extends beyond a vertical or horizontal rivet seam.



Add New Figure 9-2 that illustrates installation details for door sheets in riveted seam and lapped seam tanks. All subsequent figures in section 9 shall be renumbered.

AGENDA ITEM 653-195




Sheet 1 of 3

Revision 1

October 31, 2006

Title: Alignment of Vertical Welds for door sheets

Source: Inquiry 653-I-10/03

Purpose: To clarify the requirements for installing a door sheet.

Contact: John Farrell


BP

Phone: 630 836-3543

Fax: 630 836-3587

Email: farrelje@bp.com



Background: This agenda item is in response to an inquiry that asked if vertical weld seams of door sheets needed to be offset if they pass from one course to another. During the inquiry discussion, it was noted that the 653 standard doesn’t give sufficient guidance on door sheet installations, and that it would be particularly helpful to address door sheet installations in riveted & lap welded tanks.
Technical Justification: Providing specific guidance in the installation of door sheets will improve the quality, consistency and integrity of storage tanks that require door sheets for access.
Cost Effects: There will be some small cost impact on tanks that utilize door sheets, but not substantial.
Last Ballot Results: 5 Negatives, 13 Affirmative with Comments.



Figure 9-2 – Acceptable Details for Door Sheets in Lap Seam or Riveted Seam Tanks.

Notes:


1. All weld seams where replacement door assembly butts up to existing shell shall be full penetration and full fusion.

2. Fillet Weld size on both near and far sides of lap seams to be equal to thickness of thinner of two lower and upper plates.

3. Replacement Door assembly shall be comprised of two separate plates. The upper thickness shall be same as 2nd shell course. The lower plate shall be same thickness as 1st shell course.

4. Rivets and existing lap rivet seams located within 12” of a weld shall be sealed to prevent product seepage.

5. All weld seam intersections shall be at approximately 90 degrees.

6. Prior to welding new vertical joints, cut existing shell-to-bottom weld for a minimum of 12” beyond the new vertical joints. The cut shall extend past or stop short of existing bottom plate welds by at least 3” or 5t. Weld the shell-to-bottom weld last.



7. Height of second course plate shall be a minimum of 6”, but no less than the corner radius.

8. Shown for Riveted Seam Tank, but also applies to Lap seam Tank.


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