Rendering: an engineer's workbench in a dim workshop — an open notebook with pencil sketches, a coupling and a laptop, the left side of frame left clean

Engineering notes · 4 posts · revision-tracked

Notes from the bench

Sizing, tolerances, leak testing, fluids — written the way we spec them.

Published notes 4 long-form

Clusters 4 sizing · blind-mate · testing · fluids

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No vendor fluff — every figure here is traceable to a specification or a published source.

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Corrections: when a number changes, the note is rewritten and the revision is dated in that article's footer.

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Four clusters

Sizing · blind-mate · testing · fluids

Sizing

Loop flow decides the size family; the recommended-flow ladder for the four UQD grades is read backwards from there. UQD02 vs UQD04 vs UQD06 vs UQD08: How to Choose Spec values + derived math

Blind-mate

Docking and tolerance: how rack squareness, rail play and mounting deflection share one allowance, and why float is the last line of defence. Designing a Blind-Mate Tolerance Budget for UQDB Tolerance chain

Testing

Measurement and bands: how a leak claim becomes a range with a unit, and the four questions to ask before comparing two of them. Helium Leak Testing Levels, Explained Sccm bands

Fluids

Fluid and seals: PG25 chemistry, the two temperature windows that get confused with each other, and validation compound by compound. PG25 Coolant Compatibility for Quick Disconnects Fluid chemistry

The notes

Four subjects · one claim each

Rendering: four couplings of increasing size laid in a row on a dark bench, each joined to a progressively thicker hose

UQD02 vs UQD04 vs UQD06 vs UQD08: How to Choose

Size the coupling from the loop's required flow, then check loss, life and the pressure basis.

Spec values + derived math Open the note

Rendering: a server tray sliding into a rack at the moment before contact, the blind-mate plug approaching its receptacle

Designing a Blind-Mate Tolerance Budget for UQDB

Float is the last line of defence, not the main budget. Every millimetre belongs to somebody.

Tolerance chain Open the note

Rendering: a dim lab leak-test station with one coupling sealed inside a small chamber and a mass-spectrometer unit beside it

Helium Leak Testing Levels, Explained

Translate “it does not leak” into a unit and a band — then ask for the band, not the verdict.

Sccm bands Open the note

Rendering: a service cart beside a rack carrying a coolant jug, one coupling and a length of clear hose laid out together

PG25 Coolant Compatibility for Quick Disconnects

Chemistry, two temperature windows and one validation discipline — compatibility is a programme.

Fluid chemistry Open the note

Cadence & corrections

Cadence · corrections · archive

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Corrections

A changed number means the note is rewritten and the change is dated in that article's footer — never a silent replacement of the old text.

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