Metal Bellows Mechanical Seals

Edge-welded metal bellows seals for high-temperature, cryogenic and chemical duty — no elastomer secondary to harden, swell or hang up.

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At a glance

01Edge-welded & formed
02AM350 / Inconel / Hastelloy
03API 682 Type B/C
04−200 to 400°C+
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.

No elastomerthe secondary seal cannot harden or swell

High & low temphot oil, steam and cryogenic service

Hang-up freeno dynamic O-ring to stick on the shaft

Selection

Why metal bellows instead of a pusher seal

Extreme temperature
There is no elastomer to harden, soften or take a set; the metal bellows is the spring and the secondary seal in one.
No fretting, no hang-up
A pusher seal’s dynamic O-ring can stick or fret the sleeve; a bellows has no sliding secondary.
Aggressive or polymerizing media
Fewer soft parts to attack, and the bellows flexes through deposits that jam a pusher.
Cryogenic and hot-oil duty
Bellows alloys hold their spring rate where rubber simply fails.

New to the choice? Read pusher vs bellows seals.

Range

What we supply

Edge-welded and formed bellows units, OEM-compatible or fully custom — at the quantities your operation actually orders.

Edge-welded bellows

Thin-leaf welded bellows for the widest temperature range and tightest axial response — the high-performance choice.

Formed bellows

Cost-effective formed bellows for moderate temperature and general high-temp water and oil service.

OEM-compatible & custom

Alloy and convolution selection (AM350, Inconel 718, Hastelloy C) machined to your pump and service, including obsolete designs.

Selection guide

Match the bellows to the duty

Construction and alloy follow temperature and media. The table is a starting point; send the service and we confirm the spec.

Service	Construction	Alloy	Faces
Hot oil / thermal	Edge-welded	Inconel 718	Carbon / SiC
Steam / condensate	Edge-welded	AM350	SiC / SiC
Cryogenic	Edge-welded	Inconel	Carbon / SiC
Aggressive chemical	Edge-welded	Hastelloy C	SiC / SiC

Edge-welded bellows handle the widest temperature range; formed bellows cover moderate duty at lower cost. See welded vs formed bellows.

Go deeper: How bellows seals work · Selecting welded bellows seals.

From our catalog

Metal bellows seals in our catalog

Standard metal bellows seals from our catalog. Other sizes and bellows materials are built from a drawing, a part number or the old seal.

Model	Standard sizes (d1)	Pressure	Speed	Temperature
WM 785	16 – 100 mm	≤ 2.0 MPa	≤ 23 m/s	-20 to +200 °C
WM 780	16 – 100 mm	≤ 2.0 MPa	≤ 23 m/s	-20 to +200 °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 785

Pressure: ≤ 2.0 MPa
Speed: ≤ 23 m/s
Temperature: -20 to +200 °C

Stationary ring: SiC, tungsten carbide
Rotary ring: Carbon, SiC, tungsten carbide
Secondary seals: NBR, EPDM, Viton
Bellows: AM350, Inconel 718
Metal parts: 304 stainless, 316 stainless

Model	d1 (mm)	d3	d7	l3	l1
WM785-16	16	30	27	10	32.7
WM785-18	18	32	33	7	30.7
WM785-20	20	33.5	35	7	30.7
WM785-22	22	36.5	37	7	30.7
WM785-24	24	39	39	11.5	28.7
WM785-25	25	39.6	40	11.5	28.7
WM785-28	28	42.8	43	11.5	31.2
WM785-30	30	45	45	11.5	31.2
WM785-32	32	46	48	11.5	31.2
WM785-33	33	48	48	11.5	31.2
WM785-35	35	49.2	50	11.5	31.2
WM785-38	38	52.3	56	14	31.2
WM785-40	40	55.5	58	14	31.2
WM785-43	43	57.5	61	14	31.2
WM785-45	45	58.7	63	14	31.2
WM785-48	48	61.9	66	14	31.2
WM785-50	50	65	70	15	32.7
WM785-53	53	68.2	73	15	32.7
WM785-55	55	70	75	15	32.7
WM785-58	58	71.7	78	15	37.7
WM785-60	60	74.6	80	15	37.7
WM785-63	63	79	83	15	37.7
WM785-65	65	84.1	85	15	37.7
WM785-68	68	87.3	90	18	34.7
WM785-70	70	87.3	92	18	42.2
WM785-75	75	95	97	18	42.2
WM785-80	80	98.4	105	18.2	42
WM785-85	85	104.7	110	18.2	42
WM785-90	90	111	115	18.2	47
WM785-95	95	114	120	17.2	48
WM785-100	100	117.4	125	17.2	48

Catalog model

WM 780

Pressure: ≤ 2.0 MPa
Speed: ≤ 23 m/s
Temperature: -20 to +200 °C

Stationary ring: SiC, tungsten carbide
Rotary ring: Carbon, SiC, tungsten carbide
Secondary seals: NBR, EPDM, Viton
Bellows: AM350, Inconel 718
Metal parts: 304 stainless, 316 stainless

Model	d1 (mm)	d3	d7	l3	l1
WM780-16	16	38	35	11.5	46.7
WM780-18	18	40	37	11.5	46.7
WM780-20	20	42	40	11.5	46.7
WM780-22	22	44	43	11.5	46.7
WM780-24	24	46	43	11.5	46.7
WM780-25	25	47	45	11.5	46.7
WM780-28	28	50	48	11.5	46.7
WM780-30	30	52	50	11.5	46.7
WM780-32	32	54	56	14	46.7
WM780-33	33	55	56	14	46.7
WM780-35	35	57	58	14	46.7
WM780-38	38	60	61	14	46.7
WM780-40	40	66	63	14	47.7
WM780-43	43	69	66	14	47.7
WM780-45	45	71	70	15	47.7
WM780-48	48	74	73	15	47.7
WM780-50	50	76	75	15	47.7
WM780-53	53	79	78	15	47.7
WM780-55	55	81	80	15	47.7
WM780-58	58	85	83	15	53.2
WM780-60	60	87	85	15	53.2
WM780-63	63	90	90	18	53.2
WM780-65	65	92	92	18	53.2
WM780-68	68	95	97	18	53.2
WM780-70	70	97	97	18	53.2
WM780-75	75	102	105	18.2	53
WM780-80	80	107	110	18.2	53
WM780-85	85	112	115	18.2	53
WM780-90	90	117	120	17.2	54
WM780-95	95	122	125	17.2	54
WM780-100	100	127	134.3	20	54.2

FAQ

Metal Bellows Seal FAQ

Edge-welded or formed bellows?

Edge-welded (thin welded leaves) give the widest temperature range and best axial response; formed bellows are more economical for moderate high-temp duty. We match it to your temperature and budget.

What temperature can bellows seals handle?

With the right alloy and faces, metal bellows run from cryogenic (around −200°C) to well above 400°C — far beyond any elastomer secondary.

Which alloy do I need?

AM350 for general high-temp, Inconel 718 for hot oil and higher stress, Hastelloy C for aggressive chemicals. We select it from your media and temperature.

Do you build to API 682?

Yes — Type B and Type C metal bellows cartridge seals to the standard, sized to your pump and service.

Source Metal Bellows Seals At Scale

OEM-compatible, custom-machined and private-label metal bellows 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