The 4th edition of API 682 runs to roughly 250 pages. Yet the seal Types (A, B, C) and Arrangements (1, 2, 3) you already write into datasheets carry over from the 3rd edition almost untouched.
What forces a rewrite sits elsewhere — re-scoped defaults, a 28-day rule for seal-support reservoirs, new leakage-detection piping plans, and a move from switches to transmitters.
Published in May 2014, the 4th edition supersedes the September 2004 3rd edition and remains the current version. The trap I see most often is a specifier rubber-stamping a 3rd-edition Category 2 datasheet as still compliant, missing that the 4th edition pushed Category 3 features onto every Category 2 seal.
The seal geometry barely moved. The obligations wrapped around it did.
Is the 4th Edition the Latest API 682 Standard?
The 4th edition, published in May 2014, is still the current published edition of API 682 as of 2026, and it superseded the September 2004 3rd edition.
A task force has worked on the 5th edition since 2017, aiming to add a Category 4 for pipeline pressures up to 1440 psig. Until it publishes, every datasheet you issue is still written to the 4th edition.
API 682 has moved through four published editions:
- 1st edition — October 1994
- 2nd edition — 2002
- 3rd edition — September 2004 (issued as ISO 21049:2004)
- 4th edition — May 2014 (current)
One change reaches anyone whose spec still cites the ISO number. The 3rd edition shipped jointly with ISO 21049 as its international twin, but the 4th edition is issued as API 682 only.
A spec that still calls out the ISO number points at 3rd-edition text, not the current standard.
How the 4th Edition Changed Seal Selection and Categories
The 4th edition rewrote seal selection from “standard” designs to “default” designs — the same recommended configurations, but now explicitly optional where the 3rd edition implied they were mandatory.
The most consequential change reaches every Category 2 seal. Both a distributed flush arrangement and a floating carbon throttle bushing — features the 3rd edition reserved for Category 3 — are now mandatory on Category 2.
A Category 2 datasheet written to the 3rd edition is therefore under-specified against the 4th. The only real differences left between Categories 2 and 3 are now testing, qualification, and documentation.
Category 2 and 3 seal chambers follow API 610, while Category 1 uses the lighter ASME B73 chemical-process envelope.
| Attribute | Category 1 | Category 2 | Category 3 |
|---|---|---|---|
| Seal chamber | ASME B73.1/B73.2 | API 610 | API 610 |
| Max temperature | 260 °C (500 °F) | 400 °C (750 °F) | 400 °C (750 °F) |
| Max pressure | 20 bar (315 psi) | 40 bar (615 psi) | 40 bar (615 psi) |
| Throttle bushing | Fixed carbon | Floating carbon | Floating carbon |
| Distributed flush | Optional | Required | Required |
The seal Types themselves — A, B, and C — carry over, but the 4th edition loosened their definitions. Rotating and stationary flexible elements now count as technically equivalent across all three types.
A dual seal may even mix them, pairing a Type C inner with a Type A outer.
Face-material defaults unified across all categories — premium blister-resistant carbon against silicon carbide — dropping the 3rd edition’s per-category split.
New Requirements for Piping Plans and Support Systems
The 4th edition reworked API 682’s seal-support requirements around a single target — unattended run time. Plans 52, 53A, 53B, and 53C must now hold enough buffer or barrier fluid for at least 28 days of operation without a refill.
That replaces the 3rd edition’s fixed 3-gallon and 5-gallon reservoir basis. The rule applies whether the fluid is an unpressurized buffer (Plan 52) or a barrier held above process pressure (Plans 53A/B/C).
The 28-day basis drives accumulator sizing. A 53B bladder accumulator now runs 20 to 35 litres by shaft size, and a 53C piston accumulator is capped near 2.8 to 5.1 litres.
A reservoir sized to the old gallon basis will not qualify.
Leakage detection expanded with new and split plans:
- Plan 65 split into 65A (detects excessive leakage flow rate) and 65B (detects cumulative leakage)
- Plans 66A and 66B are new, detecting and restricting excessive leakage after an Arrangement 1 seal fails
- Plans 03, 55, and 99 were newly added to the schedule
Instrumentation shifted from switches to transmitters. The default device for monitoring pressure, temperature, flow, and level is now a transmitter with a local indicator, not a bare switch.
The transmitter default is the most visible instrumentation change in the edition, and end users pushed for it for a reason. A switch tells you a limit was crossed; a transmitter shows the trend before it gets there.
Qualification Testing and Documentation Changes
Qualification testing and documentation carry most of the remaining changes, and a 3rd-edition spec is where they most often slip through unnoticed.
The full test protocol moved to Annex I. The 4th edition also defines “core seal components” — the seal ring and mating ring — so a qualified core reuses across designs without a repeat test.
With roughly 4,000 possible parameter combinations, no manufacturer has tested every one. The 4th edition puts the burden on the buyer to confirm the specific seal, fluid, and face pair was actually qualified for the service.
“API 682 compliant” is not the same as “tested for my application” — that is the line the spec sheet never draws for you.
A cartridge already built to the 4th-edition defaults — distributed flush, a floating throttle bushing, unified face materials — narrows that verification. The seal you receive matches the configuration the qualification tests were run against.
The documentation rules also changed how a seal is coded and shipped:
- The seal code expanded to eight fields, now carrying the material selection and shaft diameter the 3rd edition left out
- Elastomer secondary seals need a proven track record — two installations with a year of service — tied to qualification testing
- The metal-plug-all-ports rule is gone; seals ship with red plastic plugs, a yellow multilingual warning tag, and a bag of the correct metal plugs, after the old rule damaged threads and contaminated faces
What This Means for Your 3rd-Edition Datasheets
Treat every 3rd-edition datasheet as needing reconciliation, not renewal. Walk each field against the changed defaults — the Category 2 flush and throttle bushing, the 28-day reservoir volume, the split piping-plan numbers, the transmitter instrumentation, and the eight-field seal code.
Most of the seal geometry you specified in 2004 still holds; what changed is nearly everything wrapped around it. A purchase order that names “API 682” without checking those clauses buys the current standard’s title and the old standard’s substance.
The 5th edition will eventually raise the pressure ceiling for pipeline service, but until it publishes, the 4th edition is the only text your procurement documents should name.
