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) cut from an existing tank shell to create a temporary access opening. After planned work is completed, the door sheet(s) will be reinstalled or replaced.
Commentary: Insert a new section 9.2.4 to address door sheet installation and renumber the following sections.
9.2.4  Door Sheet Installation
This section describes the requirements for re-installation or replacement of a door sheet. The requirements of figure 9-1 and 9-2 shall be used to locate door sheets relative to existing seams.
9.2.4.1  General Requirements for Door Sheet Installation. Door sheet installation shall meet the requirements of section 9.2.1, 9.2.2, 9.2.3 and 12.2.1.6
9.2.4.2  Door Sheet Crossing an Existing Seam, Utilizing New Shell Material. When a door sheet crosses an existing seam the following additional requirements shall apply:
a) Butt-welded Tanks: The door sheet vertical cut line may cross an existing horizontal seam without offset, however, additional non destructive testing of the intersection is required. In addition to the requirements of 12.1.5.1, the back-gouged surface of the root pass and the final pass (each side) of the new weld shall be examined by magnetic particle or liquid penetrant methods.
If a door sheet vertical cut line crosses an existing horizontal seam with an offset, the minimum offset must equal dimension ‘V’ as shown in figure 9-5. Prior to welding the new vertical seams, cut existing shell-to-bottom weld for a minimum of 12 inches beyond the new vertical joints. Weld the horizontal seam last.
b) Lap- shown in welded and Riveted Seam Tanks: The replacement section shall be constructed of two separate plates, with the lower section butt-welded to adjacent shell course by means of full penetration, full fusion vertical welds. The upper section shall be lapped over the lower section and the upper plate shall be butt welded to the existing shell plate. After the butt welds are completed, the horizontal lap shall be fillet welded along both inside and outside edges. The upper section shall be offset from the lower section, such that the vertical seams of the upper section and the vertical seams of the lower section are offset by a minimum distance of 12 inches. The vertical seams in the upper ring may utilize the lower shell plate as back-up.
c) Additional Requirements for Riveted Tanks: New weld seams shall be located a minimum of 12 inches from existing rivet seams. The heat created by welding is likely to cause nearby rivets and rivet seams to leak. Rivets and existing lap rivet seams located within 12” of a weld may require sealing.
9.2.4.3  Door Sheet Crossing an Existing Seam Utilizing Removed Shell Plate.
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 junction between the door sheet vertical seam and the existing horizontal weld seam shall be examined by MT or PT.
Lap Welded and Riveted Seam Tanks: Reinstallation of an original plate section that crosses an existing seam is not permitted
Add New Figures 9-2, 9-3, 9-4 and 9-5 that illustrates installation details for door sheets in riveted shell seam, lapped shell seam and butt welded shell seam tanks. All subsequent figures in section 9 shall be renumbered. /

AGENDA ITEM 653-195

Sheet 1 of 5

Revision 3

April 27, 2009

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:
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 butt welded, 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: 27 Affirmative, 7 Negatives, 7 Affirmative with Comments.

Figure 9-2 – Acceptable Details for Door Sheets in Riveted Seam Tank

Notes:

1. When a door sheet crosses the horizontal joint between two courses, a replacement door sheet assembly shall be comprised of two separate plates. The upper door sheet thickness shall be the same as the higher shell course thickness. The lower door sheet thickness shall be the same as the lower shell course thickness.

2. Fillet Weld size shall be equal to thickness of thinner of two plates.

3. Rivets and existing lap rivet seams located within 12” of a weld may need to be sealed with caulk/coating or seal-welded to prevent product seepage.

4. Prior to welding new vertical seam which intersect the bottom plate, cut existing shell-to-bottom weld for a minimum of 12” beyond the new vertical weld seam. 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.

5. Plug weld all rivet holes in the shell plate where rivets are removed. Filler weld to full plate thickness and grind flush.

Figure 9-3 – Acceptable Details for Door Sheets in Lap Weld Seam Tank

Notes:

1. When a door sheet crosses the horizontal joint between two courses, a replacement door sheet assembly shall be comprised of two separate plates. The upper door sheet thickness shall be same as the higher shell course thickness. The lower door sheet thickness shall be the same as the lower shell course thickness.

2. Fillet Weld size shall be equal to thickness of thinner of two plates.

3. Prior to welding new vertical joints which intersect the bottom plate, cut existing shell-to-bottom weld for a minimum of 12” beyond the new vertical weld joint. 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.

Figure 9-4 –Door Sheet in Butt Weld Shell Seam Tank – No vertical seam offset

Notes:

1. See table in figure 9-1 for minimum weld spacing and dimensions H, R and V.

2. Prior to welding new vertical joints which intersect the bottom plate, cut existing shell-to-bottom weld for a minimum of 12” beyond the new vertical weld joint. 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.

Figure 9-5 –Door Sheet in Butt Weld Shell Seam Tank –Vertical Seam Offset

Notes:

1. See table in figure 9-1 for minimum weld spacing and dimensions H, R and V

2. Prior to welding new vertical joints, cut existing horizontal weld for a minimum of 12” beyond the new vertical weld seam. Weld the horizontal seam last.

3. Prior to welding new vertical joints which intersect the bottom plate, cut existing shell-to-bottom weld for a minimum of 12” beyond the new vertical weld joint. 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.4..