OCP UQD standard, explained.
The Universal Quick Disconnect specification is the reason a coupling from one vendor mates a manifold from another — and the reason your rack does not need a drain to swap a cold plate. This brief unpacks Rev 1.0: the four size tiers from UQD02 to UQD08, the performance floors (0.55–4.7 GPM, 100/300 psi, 5000 cycles), the terminations it prescribes, and the choices it leaves entirely to you.
DL-001 · Published 2026-09-06 · 9 min read
Before this specification existed, every flat-face quick disconnect on the market was proprietary. A coupling mated only its own socket, a rack qualified to one vendor's parts could not second-source, and a cold-plate swap meant draining the loop. The Open Compute Project fixed that by publishing a common hardware envelope instead of a reference design — so any compliant plug seats any compliant socket, across roughly twenty vendors shipping UQD-class parts today.
The document itself is short and unusually concrete: UQD Specification Rev 1.0, published through OCP in September 2020, authored by Mark Sprenger of Intel, with contributions from AVIC Jonhon Optronic, CPC, Fujikura, Lawrence Berkeley National Laboratory, Parker Hannifin's QCD division and Stäubli. That supplier list matters — it is effectively the audit list of companies that helped set the floors every compliant part is gauged against.
What Rev 1.0 locks in — for every size.
The specification works with minimums and maximums, not marketing classes. These are the numbers a compliant part must meet, and the numbers worth copying straight onto your RFQ.
- Four sizes, one interface logic — UQD02 / 04 / 06 / 08 on nominal 1/8", 1/4", 3/8" and 1/2" interfaces, with minimum flow bores of 3.63 / 7.14 / 9.47 / 10.75 mm.
- Flow floors — minimum Cv of 0.25 / 0.80 / 1.60 / 2.50 and rated flow of 0.55 / 1.7 / 3.0 / 4.7 GPM, from the smallest tier to the largest.
- Dry-break spillage caps — maximum 0.020 / 0.025 / 0.035 / 0.070 ml per disconnect at 0 psi, so a hot service action leaves drops, not puddles.
- Endurance — 5000 mate/disconnect cycles minimum, with 15 years of storage life and 20 years of service life.
- Rack packaging discipline — height envelope sized to a 1U slot on the 44.45 mm EIA pitch, ball contact surfaces at 24 HRC minimum, red/blue color coding for hot supply and cool return, and "UQD + size" marking on the body.
- Terminations and media — plug ends on ORB threads per ISO 11926-3, socket ends with barbs for 1/4"–5/8" reinforced EPDM hose; wetted materials qualified against glycol coolants such as DOWFROST LC 25 and JEFFCOOL ISF-25, with safety framed by IEC 62368-1 Annex G.15.
Temperature is bounded too: the operating window is 17–65 °C with transport and storage from −40 to +75 °C. That window surprises people the first time — it is set by the seal compounds common to the whole ecosystem, which is exactly why seal selection is one of the things the standard leaves open.
UQD02 to UQD08 at a glance.
One table, straight from the specification, ready to paste into a sourcing file.
| Parameter | UQD02 | UQD04 | UQD06 | UQD08 |
|---|---|---|---|---|
| Nominal interface | 1/8" | 1/4" | 3/8" | 1/2" |
| Min. flow bore ØN (plug) | 3.63 mm | 7.14 mm | 9.47 mm | 10.75 mm |
| Max. plug OD ØG | 11.0 mm | 15.4 mm | 18.6 mm | 21.8 mm |
| Max. socket OD ØA | 11.25 mm | 15.65 mm | 18.85 mm | 22.05 mm |
| Minimum Cv | 0.25 | 0.80 | 1.60 | 2.50 |
| Rated flow | 0.55 GPM | 1.7 GPM | 3.0 GPM | 4.7 GPM |
| Max. spillage @0 psi | 0.020 ml | 0.025 ml | 0.035 ml | 0.070 ml |
| Max. working pressure | 100 psi — all sizes (OCP floor) | |||
| Min. burst pressure | 300 psi — all sizes (OCP floor) | |||
| Mate-cycle endurance | 5000 cycles — all sizes (OCP floor) | |||
| Operating temperature | 17 to +65 °C · transport/storage −40 to +75 °C | |||
| Height envelope | 1U · 44.45 mm EIA pitch — all sizes | |||
| Ball contact hardness | 24 HRC minimum — all sizes | |||
| Color code / marking | red hot supply · blue cool return · "UQD + size" | |||
| Plug termination | ORB thread per ISO 11926-3 (−04/−06/−08/−10 stud ends) | |||
| Socket termination | min. barbed end for 1/4"–5/8" reinforced EPDM hose | |||
Source: OCP Universal Quick Disconnect Specification, Rev 1.0, September 2020. Order-specific certified drawings govern production.
What the standard deliberately leaves to you.
Rev 1.0 fixes the interface, not the part. Three decisions move cost and reliability more than any other — and all three sit on the buyer's side of the table.
1. Pressure class above the floor
The OCP floor is 100 psi working and 300 psi burst. Published UQDB-class parts run substantially above it: up to 20 bar (290 psi) working with 60 bar (870 psi) burst in the small sizes, and 16 bar working / 48 bar burst at the dash-04 tier. If your pump curve can dead-head above 10 bar, order above the floor — the price difference is in the machining and the test record, not in heroics.
2. Seal compound beyond EPDM
EPDM is the ecosystem default and covers water/glycol from −40 to +120 °C. But the standard does not forbid alternatives, and the published selection ladder is worth knowing: FKM for −15 to +200 °C warm-process loops, FVMQ down to −55 °C for cold starts, NBR to +80 °C for budget builds, HNBR to +150 °C. Match the compound to your coolant and your coldest aisle, not to the brochure.
3. Interchangeability you can audit
Because UQD is an open interface, cross-brand mating is a property of the envelope — and an Intel-led interchangeability consortium now standardizes cross-vendor mating durability on top of it. The practical move: ask any supplier to gauge parts against the Rev 1.0 envelope dimensions in the table above and to ship the leak and cycle record with the batch. A part that cannot show both numbers is not a UQD; it is a fitting with ambitions.
Three questions this brief answers most.
Is UQDB the same as UQD?
Does UQ04 mean a different standard?
What pressures does the standard actually require?
Specifying to Rev 1.0? We gauge every batch against it.
DryLink UQD and UQDB sets ship with the envelope check, helium leak record and cycle data in the carton. Send your tier and flow — quoted within 48 hours, MOQ from 50 pieces.