Primary & secondary seal gap measurements by circumferential position, mapped across surveyed roof levels
New here? Read the User Manual — set-up, field entry, limits and how to read the results.
◉ POSITION-BASED GAP SURVEY · EIL 6-13-0053 REV. 6 PROFILE · NOT A REGULATORY SUBMISSION TOOL
⚠ Indicative tool only. This module records rim seal gap surveys and compares them against the limits in the Regulatory Profile, which stay editable.
US EPA figures are taken from the eCFR text of 40 CFR 60.113b (NSPS Kb) and 60.113c (NSPS Kc), checked Oct 2026.
India figures are Claude’s own translation of a Hindi-only MoEF Gazette notification (Nov 2012) — verify against the original before relying on them.
EIL 6-13-0053 (Rev. 6, July 2010, the copy on file; later revisions not compared) is a purchase specification, not a regulation: its Annexure-I gap limits and the ±13 mm roof gap tolerance of 10.2 are for handover of new tanks.
EU: EN 14015 Annex E and Directive 94/63/EC require rim seals but set no numeric gap limit, so that profile has no defaults — enter your permit or company limits.
Survey Setup
Point count = max(min points, ⌈π × diameter ÷ spacing⌉) — evenly spaced by degrees around the circumference. Spacing is a configurable survey-procedure value, not a hardcoded regulatory requirement — adjust to match your own inspection SOP.
Use the same 0° point and direction on every survey of this tank, or positions can’t be compared between surveys. Readings stay at the angle where they were measured: if the point count changes after you have entered data, those readings are kept as extra rows rather than moved.
A gap only counts if the probe passes freely between seal and shell — 40 CFR 60.113b(b)(2) uses a 0.32 cm (≈⅛ in) probe. Widths below the probe are struck through and left out. Readings are always saved in inches; the unit switch only changes what you type and see.
Research surveys stay private to you for practice/testing. Switch to Official once this is a real inspection your company should see in the shared history and heatmap.
Regulatory Profile
Values are editable and are filled in the regulation’s own units, then converted to the units you have selected. Leave a limit blank to skip compliance evaluation for that metric. These limits stay editable even after a survey is submitted — only the measured readings lock, since a reference standard shouldn't require reopening the record to correct.
Where the 200 ± 100 mm band comes from: API 650 does not fix a rim space. Its seal clause (H.4.4.3 in the 14th edition, August 2025, unchanged from earlier editions) requires peripheral seals to accommodate ±100 mm (±4 in) of local deviation between roof and shell, and a 200 mm (8 in) nominal rim space is common design practice — together these give the 100–300 mm band. It is filled automatically for the India profile on tanks over 30 m; that diameter threshold is your own practice figure, not a published clause we have found. Use 200 ± 100 mm on any tank, or enter the design rim space from the roof drawings, which is the better reference.
This survey is submitted and locked — this button updates only the regulatory limits above, without reopening the readings.
Gap Readings
Position is auto-spaced by point count above but is editable per row if a point needs to move. Areas compute automatically as length × width. Rim gap is optional — the physical shell-to-roof-rim clearance at that position, independent of either seal, useful for correlating seal gap severity against underlying shell fit/deformation. Blank means “not measured”; 0 means “measured, no gap”. A seal only reads as passing once every point has a width recorded. Gap length runs around the circumference, centred on the row’s position — if one gap is long enough to reach the next point, record it once, not at both points. Use “Add reading” for a gap that falls between survey points.
#
Position °
Rim Gap mm
Primary L in
Primary W in
Primary Area in²
Secondary L in
Secondary W in
Secondary Area in²
Note
Tips: Enter moves down the column. You can paste a block straight from Excel or a gauge log into the table — it fills from the cell you’re in, in the table’s column order. Readings are kept on this device as you type, so a dropped connection or closed tab doesn’t lose them. Ctrl/⌘+S saves a draft.
Seal & Fitting Condition Checks
Visual checks made at the same time as the gap measurement. Under NSPS Kb and Kc a failed check is an inspection failure, the same as a gap over the limit.
API 653 Seal Inspection & Repair Not used
API 653 5th edition (2014), Addendum 4 (July 2025): the floating roof seal items of the in-service checklist (Annex C, C.1.4.7) or the out-of-service checklist (C.2.9), the roof rim thickness for seal work (9.14.6.2) and the repairs 9.14 allows. These are inspection and maintenance findings; they do not change the regulatory gap verdict above. API 650 14th edition (2025) C.3.13.3: seals are installed to meet the jurisdiction’s gap requirements for new construction and the Purchaser’s.
Compliance Summary
Primary Seal Not evaluated
Total gap area—
Area per ft diameter—
Max single gap width—
Gaps counted—
Points recorded—
Secondary Seal Not evaluated
Total gap area—
Area per ft diameter—
Max single gap width—
Gaps counted—
Points recorded—
Rim Gap Informational
Expected range—
Min rim gap—
Max rim gap—
Average rim gap—
Outside expected range—
Readings logged—
Roof Centring & Shell Fit Needs rim gap readings
Fitted from the Rim Gap column. A roof sitting off-centre makes the gap swing once around the tank (tight on one side, wide opposite); an oval shell or roof makes it swing twice; anything left over is local — a dent, bulge or out-of-plumb shell at that spot. Needs at least 6 rim gap readings spread round the tank (no stretch over 120° without one); the oval term needs 8, no stretch over 90°.
Plan View
Looking down on the tank. Seal gaps are drawn on the shell at their measured position and length — thicker means wider, coloured against the limit. The inner line is the roof edge traced from the rim gap readings, stretched radially so its shape shows; the shaded ring is the expected rim gap range.
Gap Map — Position × Survey Level
The top row is the survey on screen (live, before saving); below it are saved surveys for this Company + Tank ID, most recent first, each colour-coded against its own regulatory profile. A position that runs hot across multiple rows points to localized shell deformation rather than a one-off seal issue. Your own "research" surveys always show here for you; colleagues only see surveys marked Official.
No survey history loaded yet for this tank. Fill in Company + Tank ID above, save at least one survey, then click "Load Survey History".
Gap within limitGap ≥ 70% of limitGap exceeds limitGap, no limit setMeasured — no gap (or below probe)Not measuredOlder survey: 0 could mean blank
Within that survey's expected rangeNear a range boundaryOutside expected rangeNo range set for that survey — shown on a relative scale insteadNot measured
Tighter ← survey average → widerNot measuredShows the shape of the gap even when every point is inside the expected range — an off-centre roof appears as a tight band on one side and a wide band opposite.
Each block is one reading, drawn at its true position and spanning halfway to its neighbours, so nothing is merged or hidden. White ticks mark the exact reading positions. Hover a block for its values.
Trend Across Surveys
Each survey’s results as a percentage of the limit it was assessed against, so surveys under different profiles still compare. Uses the surveys shown in the gap map (including this one while unsaved, drawn hollow).