Double Mechanical Seals
Back-to-back, face-to-face and tandem double seals to API 682 — barrier and buffer-fluid arrangements for hazardous, toxic and volatile duty.
API 682 Arr. 2 & 3 · pressurized & unpressurized · SiC/SiC · FFKM / PTFE · Custom
We are the manufacturer, not a reseller — we build in-house and supply at quantities that work for a distributor, an OEM or a maintenance department.
API 682
Arrangement 2 and 3 to the process standard
Barrier / buffer
pressurized and unpressurized configurations
Zero emissions
keeps hazardous media off the atmosphere
Why a double seal, and when
- Hazardous, toxic or flammable media — a single seal leaks process to atmosphere; a double seal keeps it contained.
- Poor lubricity or flashing fluids — the barrier or buffer fluid, not the process, lubricates the inboard faces.
- Environmental and safety limits — a reservoir gives early warning before a release becomes a reportable event.
- Valuable product — containment pays for itself when the leaked fluid is expensive.
New to the choice? Read double vs single mechanical seal.
What we supply
Pressurized and unpressurized double cartridges, OEM-compatible or fully custom — at the quantities your operation actually orders.
Back-to-back (pressurized)
Arrangement 3 double seals with a pressurized barrier fluid for the most hazardous duty — process never contacts atmosphere.
Tandem (unpressurized)
Arrangement 2 with an unpressurized buffer fluid and reservoir — redundancy plus leak detection for volatile service.
OEM-compatible & custom
Built to your pump envelope, or as a drop-in for common double-seal cartridges and machined to spec for non-standard pumps.
Match the arrangement to the duty
Arrangement and barrier system follow the media and the risk. Use the table as a starting point and send the service to confirm.
| Duty | Arrangement | Barrier / buffer | Typical plan |
|---|---|---|---|
| Toxic / hazardous | Pressurized (Arr. 3) | Barrier fluid | Plan 53A/B/C |
| Volatile / flashing | Unpressurized (Arr. 2) | Buffer fluid | Plan 52 |
| Abrasive slurry | Pressurized (Arr. 3) | Clean barrier | Plan 53 / 54 |
| Polymerizing | Pressurized (Arr. 3) | Barrier fluid | Plan 53 + 62 |
Go deeper: Double seal arrangements · Plan 53A vs 53B vs 53C.
Double Mechanical Seal FAQ
Barrier or buffer fluid — what is the difference?
A barrier fluid is held above process pressure (pressurized, Arrangement 3) so any leakage is barrier into process; a buffer fluid sits below process pressure (unpressurized, Arrangement 2) for redundancy and detection. More in our buffer and barrier fluids guide.
Back-to-back, face-to-face or tandem?
Back-to-back suits abrasive and pressurized-barrier duty; tandem (in series) suits volatile media on a buffer; face-to-face fits tight axial space. We size it to your service.
Do you build to API 682?
Yes — Arrangement 2 and 3 double cartridges to the standard’s piping-plan and configuration requirements, sized to your pump.
Single or double for my pump?
If the media is hazardous, toxic, volatile or valuable, run a double. See double vs single.
Source Double Mechanical Seals At Scale
OEM-compatible, custom-machined and private-label double seals built in-house to your spec, at low minimums. Send a pump model, a duty sheet or a sample and we’ll quote.