Single Mechanical Seals

Balanced and unbalanced single mechanical seals for water, utility and general process pumps — built to spec in SiC, carbon and tungsten carbide.

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Balanced & unbalancedCommon requests: Type 1 / 2 / 21SiC / Carbon / TCFFKM / EPDM / VitonCustom

Single-spring seal with ceramic seat

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.

Balanced & unbalancedfor low- and high-pressure duty

Proven designsType 1, 2, 21 and many other component seals

Any face pairSiC, carbon or tungsten carbide

Selection

When a single seal is the right call

Clean, non-hazardous media
For water, coolant and benign process fluids a single seal is the simplest, most economical choice.
Balanced for pressure
Balanced single seals take higher stuffing-box pressure without the heat and wear an unbalanced seal suffers.
Face pair matters
Carbon/SiC for clean duty, SiC/SiC for mild abrasives; the wrong pair is the usual cause of early failure.
Easy to standardize
Type 1, 2 and 21 are the workhorses; matching the original type keeps a fleet simple to maintain.

Hazardous or volatile duty instead? See when you need a double seal vs a single.

Range

What we supply

Unbalanced and balanced single seals, OEM-compatible or custom — at the quantities your operation actually orders.

Unbalanced single seals

Single-spring and multi-spring seals for low-pressure water and utility pumps, for example Type 1 and Type 2 equivalents.

Balanced single seals

Balanced designs for higher stuffing-box pressure and longer life on demanding duty.

OEM-compatible & custom

Drop-in equivalents to common single seals, or custom-machined to your shaft and stuffing-box dimensions.

Photographed in our shop

From our bench

Seals as they leave the shop. Faces, springs and elastomers vary with the duty.

Selection guide

Match the single seal to the duty

Type, face pair and elastomer follow the service. The table is a starting point; send the duty and we confirm.

Service	Type	Face pair	Elastomer
Clean water	Unbalanced (Type 1)	Carbon / Ceramic	NBR / EPDM
Hot water / utilities	Balanced	Carbon / SiC	EPDM / Viton
Mild chemical	Balanced	SiC / SiC	Viton / FFKM
High pressure	Balanced	SiC / SiC	FFKM

Once stuffing-box pressure climbs, a balanced seal runs cooler — see balanced vs unbalanced seals.

Go deeper: Balanced vs unbalanced · Single vs double.

From our catalog

Single-spring pusher seals in our catalog

Standard single-spring pusher seals from our catalog. For rubber bellows seals see rubber bellows seals; for multi-spring seals see multi-spring seals.

Model	Standard sizes (d1)	Pressure	Speed	Temperature
WM 103U	16 – 120 mm	≤ 0.8 MPa	≤ 13 m/s	-20 to +200 °C
WM 103B	16 – 120 mm	≤ 0.6-3.0 MPa	≤ 13 m/s	-20 to +200 °C
WM 104U	16 – 120 mm	≤ 0.8 MPa	≤ 13 m/s	-20 to +200 °C
WM 104B	16 – 120 mm	≤ 0.6-3.0 MPa	≤ 13 m/s	-20 to +200 °C
WM 1527	18 – 100 mm	≤ 1.0 MPa	≤ 10 m/s	-20 to +180 °C
WM 250	20 – 85 mm	≤ 1.2 MPa	≤ 16 m/s	-20 to +180 °C
WM 551	14 – 80 mm	≤ 1.0 MPa	≤ 15 m/s	-20 to +220 °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 103U

Pressure: ≤ 0.8 MPa
Speed: ≤ 13 m/s
Temperature: -20 to +200 °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)	d3	d4	d6	d7	d8	d0	l	l3	l4	l5	l6	l7	l8
WM103U-16	16	33	36	25	33	2	21	52	40	12	1.5	5.5	7.0	16
WM103U-18	18	35	38	28	36	2	23	56	44	12	1.5	5.5	7.0	16
WM103U-20	20	37	40	30	40	3	25	58	44	14	2.0	6.5	8.0	19
WM103U-22	22	39	42	32	42	3	27	62	48	14	2.0	6.5	8.0	19
WM103U-25	25	42	45	35	45	3	30	62	48	14	2.0	6.5	8.0	19
WM103U-28	28	45	48	38	48	3	33	64	50	14	2.0	6.5	8.0	19
WM103U-30	30	52	55	40	50	3	35	70	56	14	2.0	6.5	8.0	19
WM103U-35	35	57	60	45	55	3	40	74	60	14	2.0	6.5	8.0	19
WM103U-40	40	62	65	50	60	3	45	78	64	14	2.0	6.5	8.0	19
WM103U-45	45	67	70	55	65	3	50	85	71	14	2.0	6.5	8.0	19
WM103U-50	50	72	75	60	70	3	55	89	75	14	2.5	6.5	8.0	19
WM103U-55	55	77	80	65	75	3	60	91	77	14	2.5	6.5	8.0	19
WM103U-60	60	82	85	70	80	3	65	91	77	14	2.5	6.5	8.0	19
WM103U-65	65	92	95	80	90	3	73	106	89	17	2.5	6.5	8.0	22
WM103U-70	70	97	100	85	97	3	78	110	91	19	2.5	7.5	9.0	25
WM103U-75	75	102	105	90	102	3	83	110	91	19	2.5	7.5	9.0	25
WM103U-80	80	107	110	95	107	3	88	117	98	19	3.0	7.5	9.0	25
WM103U-85	85	112	115	100	112	3	93	119	100	19	3.0	7.5	9.0	25
WM103U-90	90	117	120	105	117	3	98	120	101	19	3.0	7.5	9.0	25
WM103U-95	95	122	125	110	122	3	103	120	101	19	3.0	7.5	9.0	25
WM103U-100	100	127	130	115	127	3	108	120	101	19	3.0	7.5	9.0	25
WM103U-110	110	141	145	130	142	3	120	147	126	21	3.0	8.0	9.0	27
WM103U-120	120	151	155	140	152	3	130	147	126	21	3.0	8.0	9.0	27

Catalog model

WM 103B

Pressure: ≤ 0.6-3.0 MPa
Speed: ≤ 13 m/s
Temperature: -20 to +200 °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)	d2	d3	d4	d6	d7	d8	d0	l	l2	l3	l4	l5	l6	l7	l8
WM103B-16	16	11	33	36	25	33	2	19	60	20	48	12	1.5	5.5	7.0	16
WM103B-18	18	13	35	38	28	36	2	22	64	20	52	12	1.5	5.5	7.0	16
WM103B-20	20	15	37	40	30	40	3	23	66	22	52	14	2.0	6.5	8.0	19
WM103B-22	22	17	39	42	32	42	3	26	70	22	56	14	2.0	6.5	8.0	19
WM103B-25	25	20	42	45	35	45	3	28	70	22	56	14	2.0	6.5	8.0	19
WM103B-28	28	22	45	48	38	48	3	31	72	22	58	14	2.0	6.5	8.0	19
WM103B-30	30	25	52	55	40	50	3	33	79	23	65	14	2.0	6.5	8.0	19
WM103B-35	35	28	57	60	45	55	3	37	84	24	70	14	2.0	6.5	8.0	19
WM103B-40	40	34	62	65	50	60	3	42	88	24	74	14	2.0	6.5	8.0	19
WM103B-45	45	38	67	70	55	65	3	47	95	24	81	14	2.0	6.5	8.0	19
WM103B-50	50	44	72	75	60	70	3	52	99	24	85	14	2.5	6.5	8.0	19
WM103B-55	55	48	77	80	65	75	3	57	101	24	87	14	2.5	6.5	8.0	19
WM103B-60	60	52	82	85	70	80	3	62	101	24	87	14	2.5	6.5	8.0	19
WM103B-65	65	58	92	95	80	90	3	70	113	27	96	17	2.5	6.5	8.0	22
WM103B-70	70	62	97	100	85	97	3	74	120	32	101	19	2.5	7.5	9.0	25
WM103B-75	75	66	102	105	90	102	3	79	120	32	101	19	2.5	7.5	9.0	25
WM103B-80	80	72	107	110	95	107	3	84	127	32	108	19	3.0	7.5	9.0	25
WM103B-85	85	76	112	115	100	112	3	89	129	32	110	19	3.0	7.5	9.0	25
WM103B-90	90	82	117	120	105	117	3	94	130	32	111	19	3.0	7.5	9.0	25
WM103B-95	95	85	122	125	110	122	3	99	130	32	111	19	3.0	7.5	9.0	25
WM103B-100	100	90	127	130	115	127	3	104	130	32	111	19	3.0	7.5	9.0	25
WM103B-110	110	100	141	145	130	142	3	116	159	36	138	21	3.0	8.0	9.0	27
WM103B-120	120	110	151	155	140	152	3	126	159	36	138	21	3.0	8.0	9.0	27

Catalog model

WM 104U

Pressure: ≤ 0.8 MPa
Speed: ≤ 13 m/s
Temperature: -20 to +200 °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)	d3	d4	d6	d7	d8	d0	l	l3	l4	l5	l6	l7	l8
WM104U-16	16	33	36	25	33	2	21	49	37	12	1.5	5.5	7.0	16
WM104U-18	18	35	38	28	36	2	23	52	40	12	1.5	5.5	7.0	16
WM104U-20	20	37	40	30	40	3	25	54	40	14	2.0	6.5	8.0	19
WM104U-22	22	39	42	32	42	3	27	57	43	14	2.0	6.5	8.0	19
WM104U-25	25	42	45	35	45	3	30	57	43	14	2.0	6.5	8.0	19
WM104U-28	28	45	48	38	48	3	33	58	44	14	2.0	6.5	8.0	19
WM104U-30	30	52	55	40	50	3	35	63	49	14	2.0	6.5	8.0	19
WM104U-35	35	57	60	45	55	3	40	65	51	14	2.0	6.5	8.0	19
WM104U-40	40	62	65	50	60	3	45	68	54	14	2.0	6.5	8.0	19
WM104U-45	45	67	70	55	65	3	50	74	60	14	2.0	6.5	8.0	19
WM104U-50	50	72	75	60	70	3	55	77	63	14	2.5	6.5	8.0	19
WM104U-55	55	77	80	65	75	3	60	79	65	14	2.5	6.5	8.0	19
WM104U-60	60	82	85	70	80	3	65	79	65	14	2.5	6.5	8.0	19
WM104U-65	65	92	95	80	90	3	73	91	74	17	2.5	6.5	8.0	22
WM104U-70	70	97	100	85	97	3	78	95	76	19	2.5	7.5	9.0	25
WM104U-75	75	102	105	90	102	3	83	95	76	19	2.5	7.5	9.0	25
WM104U-80	80	107	110	95	107	3	88	100	81	19	3.0	7.5	9.0	25
WM104U-85	85	112	115	100	112	3	93	101	82	19	3.0	7.5	9.0	25
WM104U-90	90	117	120	105	117	3	98	102	83	19	3.0	7.5	9.0	25
WM104U-95	95	122	125	110	122	3	103	102	83	19	3.0	7.5	9.0	25
WM104U-100	100	127	130	115	127	3	108	102	83	19	3.0	7.5	9.0	25
WM104U-110	110	141	145	130	142	3	120	126	105	21	3.0	8.0	9.0	27
WM104U-120	120	151	155	140	152	3	130	126	105	21	3.0	8.0	9.0	27

Catalog model

WM 104B

Pressure: ≤ 0.6-3.0 MPa
Speed: ≤ 13 m/s
Temperature: -20 to +200 °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)	d3	d4	d6	d7	d8	d0	l	l2	l3	l4	l5	l6	l7	l8
WM104B-16	16	33	36	25	33	2	19	57	20	45	12	1.5	5.5	7.0	16
WM104B-18	18	35	38	28	36	2	21	60	20	48	12	1.5	5.5	7.0	16
WM104B-20	20	37	40	30	40	3	23	62	22	48	14	2.0	6.5	8.0	19
WM104B-22	22	39	42	32	42	3	25	65	22	51	14	2.0	6.5	8.0	19
WM104B-25	25	42	45	35	45	3	28	65	22	51	14	2.0	6.5	8.0	19
WM104B-28	28	45	48	38	48	3	31	66	22	52	14	2.0	6.5	8.0	19
WM104B-30	30	52	55	40	50	3	33	72	23	58	14	2.0	6.5	8.0	19
WM104B-35	35	57	60	45	55	3	37	75	24	61	14	2.0	6.5	8.0	19
WM104B-40	40	62	65	50	60	3	42	78	24	64	14	2.0	6.5	8.0	19
WM104B-45	45	67	70	55	65	3	47	84	24	70	14	2.0	6.5	8.0	19
WM104B-50	50	72	75	60	70	3	52	87	24	73	14	2.5	6.5	8.0	19
WM104B-55	55	77	80	65	75	3	57	89	24	75	14	2.5	6.5	8.0	19
WM104B-60	60	82	85	70	80	3	62	89	24	75	14	2.5	6.5	8.0	19
WM104B-65	65	92	95	80	90	3	70	98	27	81	17	2.5	6.5	8.0	22
WM104B-70	70	97	100	85	97	3	74	105	32	86	19	2.5	7.5	9.0	25
WM104B-75	75	102	105	90	102	3	79	105	32	86	19	2.5	7.5	9.0	25
WM104B-80	80	107	110	95	107	3	84	110	32	91	19	3.0	7.5	9.0	25
WM104B-85	85	112	115	100	112	3	89	111	32	92	19	3.0	7.5	9.0	25
WM104B-90	90	117	120	105	117	3	94	112	32	93	19	3.0	7.5	9.0	25
WM104B-95	95	122	125	110	122	3	99	112	32	93	19	3.0	7.5	9.0	25
WM104B-100	100	127	130	115	127	3	104	112	32	93	19	3.0	7.5	9.0	25
WM104B-110	110	141	145	130	142	3	116	138	36	117	21	3.0	8.0	9.0	27
WM104B-120	120	151	155	140	152	3	126	138	36	117	21	3.0	8.0	9.0	27

Catalog model

WM 1527

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)	d3	d7	l3	l1
WM1527-18	18	32	33	10	35
WM1527-20	20	34	35	10	35
WM1527-22	22	36	37	10	35
WM1527-24	24	38	39	10	40
WM1527-25	25	39	40	10	40
WM1527-28	28	42	43	10	40
WM1527-30	30	44	45	10	40
WM1527-32	32	46	48	10	45
WM1527-33	33	47	48	10	45
WM1527-35	35	49	50	10	45
WM1527-38	38	54	56	11	44
WM1527-40	40	56	58	11	44
WM1527-43	43	59	61	11	49
WM1527-45	45	61	63	11	49
WM1527-48	48	64	66	11	49
WM1527-50	50	66	70	13	47
WM1527-53	53	69	73	13	57
WM1527-55	55	71	75	13	57
WM1527-58	58	78	78	13	57
WM1527-60	60	80	80	13	57
WM1527-63	63	83	83	13	57
WM1527-65	65	85	85	13	67
WM1527-68	68	88	90	15.3	64.7
WM1527-70	70	90	92	15.3	64.7
WM1527-75	75	99	97	15.3	64.7
WM1527-80	80	104	105	15.7	74.3
WM1527-85	85	109	110	15.7	74.3
WM1527-90	90	114	115	15.7	74.3
WM1527-95	95	119	120	15.7	74.3
WM1527-100	100	124	125	15.7	74.3

Catalog model

WM 250

Pressure: ≤ 1.2 MPa
Speed: ≤ 16 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)	d3	d7	l3	l1
WM250-20	20	34	35	13	41
WM250-22	22	36	37	13	41
WM250-24	24	38	39	13	43
WM250-25	25	39	40	13	43
WM250-28	28	42	43	13	45
WM250-30	30	44	45	13	45
WM250-33	33	47	48	13	45
WM250-35	35	49	50	13	49
WM250-38	38	54	56	13	53
WM250-40	40	56	58	13	55
WM250-43	43	59	61	13	55
WM250-45	45	61	63	13	55
WM250-48	48	64	66	13	55
WM250-50	50	66	68	13	60
WM250-53	53	69	71	13	61
WM250-55	55	71	73	13	61
WM250-58	58	76	79	16	63
WM250-60	60	78	81	16	63
WM250-63	63	81	84	16	63
WM250-65	65	83	86	16	67
WM250-70	70	90	92	16	68
WM250-75	75	95	97	16	72
WM250-80	80	100	105	16	72
WM250-85	85	105	110	16	77

Catalog model

WM 551

Pressure: ≤ 1.0 MPa
Speed: ≤ 15 m/s
Temperature: -20 to +220 °C

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

Model	d (mm)	d3	d1	d7	d6	d4	d12	l	l1	l3	l4	c	d10	dk
WM551-14	14	24	26	25	21	18	24.6	26.5	34	8.5	4	1.5	23.1	17
WM551-16	16	26	28	27	23	20	28	28	35.5	8.5	4	1.5	26.9	19
WM551-18	18	32	34	33	27	23	30	31	38.5	9	5	2	30.9	21
WM551-20	20	34	36	35	29	25	35	33.5	41	9	5	2	30.9	27
WM551-22	22	36	38	37	31	27	35	33	40.5	9	5	2	35.4	26
WM551-24	24	38	40	39	33	29	38	35	42.5	9	5	2	35.4	28
WM551-25	25	39	41	40	34	30	38	38	45.5	9	5	2	38.2	30
WM551-28	28	42	44	43	37	33	42	38	45.5	9	5	2	43.3	33
WM551-30	30	44	46	45	39	35	45	38	45.5	9	5	2	43.3	35
WM551-32	32	46	48	48	42	38	48	40	47.5	9	5	2	43.3	37
WM551-33	33	47	49	48	42	38	48	40	47.5	9	5	2	53.5	38
WM551-35	35	49	51	50	44	40	52	40	47.5	9	5	2	53.5	40
WM551-38	38	54	58	56	49	44	55	47.5	55.5	9	6	2	60.5	44
WM551-40	40	56	60	58	51	46	58	50	58	9	6	2	60.5	45
WM551-43	43	59	63	61	54	49	62	52.5	60.5	9	6	2	60.5	50
WM551-45	45	61	65	63	56	51	64	53.5	61.5	9	6	2	65.5	52
WM551-48	48	64	68	66	59	54	68.4	60	68	9	6	2	65.5	55
WM551-50	50	66	70	70	62	57	69.3	60	68	9	6	2.5	72.5	58
WM551-53	53	69	73	73	65	60	69.3	62	70	9	6	2.5	72.5	61
WM551-55	55	71	75	75	67	62	75.4	64	72	9	6	2.5	72.5	63
WM551-58	58	78	83	78	70	65	78.4	70	78	9	6.5	2.5	72.5	67
WM551-60	60	80	85	80	72	67	50.4	70	78	9	6.5	2.5	79.3	69
WM551-63	63	83	88	83	75	70	80.4	70	78	9	6.5	2.5	79.3	72
WM551-65	65	85	90	85	77	72	85.4	70	78	9	6.5	2.5	84.5	74
WM551-68	68	88	93	90	81	75	91.5	73	81	9	7	2.5	84.5	78
WM551-70	70	90	95	82	83	77	92	75	83	9	7	2.5	89.5	80
WM551-75	75	98	104	97	88	72	99	80	88	9	7	2.5	94.5	86
WM551-80	80	103	109	105	95	89	104	80	88	9	7	3	99.5	91

FAQ

Single Mechanical Seal FAQ

Balanced or unbalanced?

Unbalanced single seals suit low stuffing-box pressure; once pressure climbs a balanced seal runs cooler and lasts longer. We size it to your conditions.

Single or double seal?

Single seals are for clean, non-hazardous media. Hazardous, toxic or volatile duty needs a double seal.

Will it fit my pump?

We build to your shaft and stuffing-box dimensions and to Type 1, 2 and 21 envelopes — send the seal drawing, the seal’s model or part number, or a sample of the old seal.

What face materials?

Carbon/ceramic for clean water, carbon/SiC for utilities, SiC/SiC for mild abrasives and chemicals.

Source Single Mechanical Seals At Scale

OEM-compatible, custom-machined and private-label single 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