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.

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At a glance

01API 682 Arr. 2 & 3
02Pressurized & unpressurized
03SiC/SiC
04FFKM / PTFE
05Custom

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 682Arrangement 2 and 3 to the process standard

Barrier / bufferpressurized and unpressurized configurations

Zero emissionskeeps hazardous media off the atmosphere

Selection

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.

Range

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.

Selection guide

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

Pressurized (barrier) arrangements keep process off the atmosphere; unpressurized (buffer) arrangements add redundancy and detection. See our API flush plan guide.

Go deeper: Double seal arrangements · Plan 53A vs 53B vs 53C.

From our catalog

Double seals in our catalog

Standard double seals from our catalog. We build most other double seals and arrangements too, from a drawing, a part number or the old seal.

Model	Standard sizes (d1)	Pressure	Speed	Temperature
WM 560D	13 – 50 mm	≤ 0.3 MPa	≤ 10 m/s	-30 to +200 °C
WM 202	14 – 45 mm	≤ 1.2 MPa	≤ 10 m/s	-30 to +200 °C
WM 208	10 – 45 mm	≤ 1.2 MPa	≤ 10 m/s	-30 to +200 °C
WM 47D	16 – 55 mm	≤ 0.5 MPa	≤ 8 m/s	-20 to +100 °C
WM 50D	18 – 100 mm	≤ 1.0 MPa	≤ 10 m/s	-20 to +180 °C
WM 5ED	20 – 80 mm	≤ 1.0 MPa	≤ 13 m/s	-20 to +180 °C

Limits as printed in our catalog for each model; the real limit depends on the face pair, elastomer and fluid.

Drawings & dimensions

Drawings and dimension tables

Dimensions in mm unless a table says inches. Inch sizes are named by the nominal shaft size in inches; d1 gives the same size in mm. Letters match the section drawing. Standard sizes shown; other sizes are built from a drawing or the old seal.

Catalog model

WM 560D

Pressure: ≤ 0.3 MPa
Speed: ≤ 10 m/s
Temperature: -30 to +200 °C

Rotary ring: Plastic carbon, carbon, SiC, tungsten carbide
Stationary ring: Ceramic, SiC, tungsten carbide
Secondary seals: NBR, EPDM, Viton
Spring and metal parts: 304 stainless, 316 stainless

Model	d1 (mm)	d3	d7	l1	l2	l3
WM560D-13	13	25	25	36	5	5
WM560D-14	14	30	30	37	5	5
WM560D-15	15	30	30	37	5	5
WM560D-16	16	30	30	37	5	5
WM560D-18	18	35	38	49	7	10
WM560D-19	19	35	38	49	7	10
WM560D-20	20	38	44	49	7	7
WM560D-25	25	44	50	51	7	7
WM560D-30	30	50	57	59	9	8
WM560D-35	35	58	64	61	9	9
WM560D-40	40	64	70	64	11	9
WM560D-45	45	66	70	65	10	9
WM560D-50	50	72	80	69	10	9

Catalog model

WM 202

Pressure: ≤ 1.2 MPa
Speed: ≤ 10 m/s
Temperature: -30 to +200 °C

Rotary ring: Plastic carbon, carbon, SiC, tungsten carbide
Stationary ring: Ceramic, SiC, tungsten carbide
Secondary seals: NBR, EPDM, Viton
Spring and metal parts: 304 stainless, 316 stainless

Model	d1 (mm)	d7	l10	l6
WM202-14	14	26/28	35/38	5.0
WM202-16	16	28	38/45	5.0
WM202-17	17	34/35	38/48	5.0
WM202-18	18	34/35	38/48	5.0
WM202-20	20	361	40/48	5.0
WM202-22	22	38	45	5.5
WM202-25	25	41	51.0	7.0
WM202-30	30	46	51.0	7.0
WM202-35	35	51	51.0	7.0
WM202-40	40	60	61.0	8.0
WM202-45	45	65	61.0	8.0

Catalog model

WM 208

Pressure: ≤ 1.2 MPa
Speed: ≤ 10 m/s
Temperature: -30 to +200 °C

Rotary ring: Plastic carbon, carbon, SiC, tungsten carbide
Stationary ring: Ceramic, SiC, tungsten carbide
Secondary seals: NBR, EPDM, Viton
Spring and metal parts: 304 stainless, 316 stainless

Model	d1 (mm)	d7	l1	l3
WM208-10	10	21	30	5
WM208-12	12	23	30	5
WM208-14	14	26/28	38	6
WM208-16	16	28/30	38	5
WM208-18	18	33/35	38	5
WM208-20	20	35/36	40	5.5
WM208-25	25	40/41	48	8
WM208-30	30	45	51	8
WM208-35	35	50	51	8
WM208-40	40	58	58	9
WM208-45	45	63	58	9

Catalog model

WM 47D

Pressure: ≤ 0.5 MPa
Speed: ≤ 8 m/s
Temperature: -20 to +100 °C

Stationary ring: Ceramic, SiC, tungsten carbide
Rotary ring: Carbon, SiC, tungsten carbide
Secondary seals: NBR, EPDM, Viton
Spring and pressed parts: Steel

Model	d1 (mm)	d7	d7	l
WM47D-16	16	27	27	36
WM47D-18	18	33	33	36
WM47D-20	20	35	35	49
WM47D-22	22	37	37	49
WM47D-24	24	39	39	49
WM47D-25	25	40	40	51
WM47D-28	28	43	43	51
WM47D-30	30	45	45	59
WM47D-32	32	48	48	61
WM47D-33	33	48	48	61
WM47D-35	35	50	50	61
WM47D-38	38	56	56	61
WM47D-40	40	58	58	64.5
WM47D-43	43	61	61	65
WM47D-45	45	63	63	65
WM47D-48	48	66	66	65
WM47D-50	50	70	70	69.5
WM47D-53	53	73	73	69.5
WM47D-55	55	75	75	71

Catalog model

WM 50D

Pressure: ≤ 1.0 MPa
Speed: ≤ 10 m/s
Temperature: -20 to +180 °C

Stationary ring: Ceramic, SiC, tungsten carbide
Rotary ring: Carbon, SiC, tungsten carbide
Secondary seals: NBR, EPDM, Viton
Spring and pressed parts: Steel

Model	d1 (mm)	d7	d7	l1	l3
WM50D-18	18	33	33	11.5	38
WM50D-20	20	35	35	11.5	38
WM50D-22	22	37	37	11.5	38
WM50D-24	24	39	39	11.5	38
WM50D-25	25	40	40	11.5	38
WM50D-28	28	43	43	11.5	39
WM50D-30	30	45	45	11.5	39
WM50D-32	32	47	48	11.5	39
WM50D-33	33	48	48	11.5	39
WM50D-35	35	50	50	11.5	39
WM50D-38	38	55	56	14	41
WM50D-40	40	57	58	14	42
WM50D-43	43	60	61	14	42
WM50D-45	45	62	63	14	42
WM50D-48	48	65	66	14	42
WM50D-50	50	67	70	15	43
WM50D-53	53	70	73	15	43
WM50D-55	55	72	75	15	43
WM50D-58	58	79	78	15	56
WM50D-60	60	81	80	15	56
WM50D-63	63	84	83	15	55
WM50D-65	65	86	85	15	55
WM50D-68	68	89	90	18	55
WM50D-70	70	91	92	18	55
WM50D-75	75	99	97	18	56
WM50D-80	80	104	105	18.2	56
WM50D-85	85	109	110	18.2	56
WM50D-90	90	114	115	18.2	56
WM50D-95	95	119	120	17.2	56
WM50D-100	100	124	125	17.2	56

Catalog model

WM 5ED

Pressure: ≤ 1.0 MPa
Speed: ≤ 13 m/s
Temperature: -20 to +180 °C

Rotary ring: Carbon, SiC, tungsten carbide
Stationary ring: Ceramic, SiC, tungsten carbide
Secondary seals: NBR, EPDM, Viton
Spring and metal parts: 304 stainless, 316 stainless

Model	d1 (mm)	d7	d2	l1	l3
WM5ED-20	20	38	35	11.5	39
WM5ED-25	25	43	40	11.5	39
WM5ED-30	30	48	45	11.5	42
WM5ED-35	35	53	50	12	40
WM5ED-40	40	61	58	12	45
WM5ED-45	45	66	63	12	45
WM5ED-50	50	73	70	13	46
WM5ED-55	55	78	75	13	46
WM5ED-60	60	83	80	14	56
WM5ED-65	65	88	85	14	56
WM5ED-70	70	95	92	17	58
WM5ED-75	75	100	97	17	58
WM5ED-80	80	108	105	17	58

FAQ

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 the seal drawing, the seal model or a sample and we’ll quote.

Request a quote →All seal types