Repair Design Check (API 653 Section 9)

Design check of a repair or alteration to an existing tank against API 653 Section 9: replacement shell plates and door sheets with the Figure 9.1 weld spacing, lapped patches on the shell (thickness by design with the 9.3 joint efficiencies, size, location), new or replacement shell penetrations (the 9.9.2 reinforcement thickness, stress relief, insert plates), welded-on bottom patches inside and outside the critical zone, and hot taps (Table 9.1, unknown toughness limits, spacing)

New here? Read the User Manual — the six repair types, the rule sets, a worked example for each and how the results tie to the radiograph count and the hydrotest decision.

◉ API 653 5TH ED. (2014) ADDENDUM 4 (JULY 2025) SECTION 9 · FIGURES 9.1, 9.13, 9.14 · TABLE 9.1 · API 650 14TH ED. 5.7.3, 5.7.4 · NOT A REGULATORY SUBMISSION TOOL

⚠ Indicative tool only. All repairs and alterations are approved before the work starts by an authorized inspector or a storage tank engineer (9.1.3), and the basis is API 650 equivalence (9.1.1). The tool checks the dimensions and limits Section 9 prints; the plate thickness for a replacement plate comes from the as-built standard (Shell Design), the full nozzle reinforcement and weld spacing from Nozzle Reinforcement, and nonmetallic repairs (9.4, Annex J) are not covered.

Identification

Company

Tank ID

Repair item

Location

Record Type

Units and rule set

API 653 prints each limit in both systems (1.1.3): the tool checks against the set you choose. Records are kept in SI.

Summary of checks

Choose the repair type and enter the tank.

1. Tank, Shell and Repair Type

Repair or alteration

Nominal diameter, D m

Maximum liquid level m

Highest specific gravity, G

Height of the repair above the bottom m · lowest point; centreline for a nozzle or hot tap

Shell construction

Shell toughness (Section 3)

Shell material group (API 650 Table 4.4)

Course at the repair

Nominal thickness of that course, t mm · bottom course for a bottom patch

Specified minimum yield, Y MPa · blank = unknown

Specified minimum tensile, T MPa · blank = unknown

2. Replacement Plate (9.2, Figure 9.1)

Plate

Replacement plate thickness mm

Greatest adjoining plate in the course mm · blank = t

Required by the as-built standard mm · from Shell Design

Width (or diameter) mm

Height mm

Corner radius mm

The adjoining plate is a thickened insert plate

New weld to the nearest vertical weld, V mm · toe to toe

To the nearest horizontal weld, H mm

Extension past the crossed horizontal seam mm

To the shell-to-bottom weld toe, B mm

New vertical weld to bottom plate welds, C mm

New seams to rivet seams mm

Crosses an existing horizontal seam

Extends to the shell-to-bottom joint at about 90°

Door sheet cut lines

Offset of the vertical welds above and below the seam mm

Door sheet reinstalled from

2. Lapped Patch on the Shell (9.3)

Purpose

Patch thickness mm

Nominal thickness of the adjacent shell plate mm · blank = t

Shell thickness at the patch perimeter mm · measured

Shell thickness away from the pits mm · 9.3.4.1

Joint efficiency for t_min, E blank = 1.0 (away from welds)

Height mm

Width mm

Corner radius mm · blank if circular

Patch on the

To other vertical welds or patches mm · toe to toe

To other horizontal welds or patches mm

To the shell-to-bottom weld mm · toe to toe

Overlap past the crossed seam mm

Hole, smallest dimension mm

Hole corner radius mm · blank if round

Overlap of the patch past the hole mm

Crosses a shell seam

Extends to the external shell-to-bottom joint

Lies over a lap or riveted seam, another patch, a distorted area or an unrepaired crack

A shell opening or its reinforcement is inside the patch

2. New or Replacement Shell Penetration (9.9)

Size

Vertical dimension of the hole cut in the shell mm

Allowable design stress, API 650 Table 5.2 MPa · blank = 138 MPa (20,000 lbf/in²), unknown

Joint efficiency, E blank = 1.0 (9.9.2, with 9.9.5)

Reinforcement area provided mm² · from Nozzle Reinforcement

Installed in

Insert plate thickness mm

Insert plate diameter, or least dimension mm

Opening in the insert, same direction mm

The shell plate meets the current design metal temperature criteria

Located on a shell joint (Purchaser accepted)

2. Welded-on Bottom Patch Plate (9.11.1, Figure 9.13)

Patch thickness mm

Existing bottom nominal thickness mm

Smallest dimension across the patch mm

Shape

Patch edge to the inside of the shell mm · blank = away from the shell

Corner radius mm

Extension past the corroded area mm

Edge parallel to a seam, or to another lap weld mm

Crosses a bottom lap seam

Covers a three-plate lap

Placed over an existing patch

Over a mechanical dent or local dishing

Angle at which it crosses the seam degrees

To the adjacent three-plate lap mm

Past the three-plate lap along the lap welds mm

Unsupported dimension over the dent mm

Annex M tank

Dimension along the shell mm

Bottom thickness under the perimeter mm

Operating temperature °C

Bottom material

To the next patch in the critical zone mm · blank = none

Smaller patch: dimension along the shell mm

New fillet welds to vertical shell welds mm

Butt-welded to an adjacent patch

2. Hot Tap (9.15, Figure 9.14)

Connection size

Liquid above the tap during the work m

Largest weld size, W mm · API 650 5.7.3

To the nearest nozzle mm · toe to toe

Shell thickness reading 1 mm

Reading 2 mm

Reading 3 mm

Reading 4 mm

Reinforcing plate to the nearest vertical weld mm

To the nearest horizontal weld mm

To the shell-to-bottom weld mm

Reinforcing plate thickness mm

Reinforcing plate diameter mm

Shell cutout diameter mm

Shell kept at or above the minimum design metal temperature

Reinforcing plate crosses a seam or reaches the shell-to-bottom weld

On the roof or in the vapour space

3. Work Record (Section 9, 12)

Tick each item once it is confirmed. Items that don’t apply to the chosen repair are hidden.

Save & Report

Inputs are kept on this device as you type and offered back if the page is closed before saving. Next steps: count the radiographs in Construction Checklists (API 653 Shell Radiograph Count) and decide the hydrostatic test in the Hydrostatic Test tool (existing-tank mode).

Tank Repair List

All repair items saved for this Tank ID, the latest save of each repair item reference, in one register and one report: failing checks, whether a hydrostatic test is needed, the plates to enter in the API 653 Shell Radiograph Count, hot tap tests and open record items. Give every item its own repair item reference (R-01, R-02 …) so later saves replace earlier ones.

Work order / contract

Contractor

Inspector