Type OB Diaphragm

General Description

Type OB Diaphragm

This type of diaphragm has a rectangular bead molded inside the cylinder wall. This design requires the smallest hardware diameter of any diaphragm type. Since clamping and sealing in this style is against the inside wall of the cylinder, the stroke capability is restricted to the lower half of the diaphragm.

Dimensions and Tolerances

Type OB Figure 1

	Inches	mm	Inches	mm	Inches	mm	Inches	mm
Cylinder Diameter	1.00-2.50	25-64	2.51-4.00	64-102	4.01-8.00	102-205	8.01 & up	205 & up
Height	See available sizes table
Cylinder Diameter	Tolerances on Cylinder Diameter and Piston Diameter are ± 0.010 per inch (0.254 mm) of diameter but the tolerance will be no less than ± 0.010 (0.254 mm) or greater than ± 0.060 (1.52 mm)
Piston Diameter
Head & Flange Thickness	.017 ± .004	0.43 ± 0.10	.024 ± .004	0.61 ± 0.10	.035 ± .005	0.89 ± 0.13	.045 ± .007	1.14 ± 0.18
Wall Gauge	.017 ± .003	0.43 ± 0.08	.024 ± .004	0.61 ± 0.10	.035 ± .005	0.89 ± 0.13	.045 ± .007	1.14 ± 0.18
Flash Projection	.025 Max.	0.64 Max.	.035 Max.	0.89 Max.	.040 Max.	1.02 Max.	.056 Max.	1.42 Max.
Flash Thickness	.025 Max.	0.64 Max.	.035 Max.	0.89 Max.	.040 Max.	1.02 Max.	.056 Max.	1.42 Max.
Flange Radius	.031	0.79	.047	1.19	.063	1.60	.063	1.60
Bead Width	.080 ± .003	2.03 ± 0.08	.100 ± .003	2.51 ± 0.08	.120 ± .003	3.05 ± 0.08	.160 ± .003	4.06 ± 0.08
Bead Height	.150 ± .005	3.81 ± 0.13	.200 ± .005	5.08 ± 0.13	.260 ± .005	6.60 ± 0.13	.300 ± .007	7.62 ± 0.18

Hardware Recommendations

Stamped Retainer Plate Sealing Via Axial Compression		Cast Machined Retainer Plate Sealing Via Radial Compression

Cylinder Diameter		Bead Groove Width = W		Bead Groove Height = H		Lip Radius = R1		Piston Corner Radius = R2		Lip Clearance = C
(Inches)	(mm)	(Inches)	(mm)	(Inches)	(mm)	(Inches)	(mm)	(Inches)	(mm)	Sidewall Thickness + .003
1.00-2.50	25-64	.080	2.03	1.50	3.81	.030	0.76	.063	1.60
2.51-4.00	64-102	.100	2.45	.200	5.08	.040	1.02	.094	2.39
4.01-8.00	102-205	.120	3.05	.260	6.60	.050	1.27	.125	3.18
8.01 and up	205 and up	.160	4.06	.300	7.62	.060	1.52	.188	4.78

Available Sizes

Dia•Com Part No,	Cylinder Diameter		Piston Diameter		Height		Gauge Approx.		Convolution Width		Effective Pressure Area		Maximum Half-Stroke
Dia•Com Part No,	(Inches)	(mm)	(Inches)	(mm)	(Inches)	(mm)	(Inches)	(mm)	(Inches)	(mm)	(Inches)	*	(Inches)	(mm)
OB-250-178	2.50	64	2.13	54	1.78	45	.035	0.89	.185	4.7	4.21	27.1	1.39	35.3
OB-250-225	2.50	64	2.13	54	2.25	57	.035	0.89	.185	4.7	4.21	27.1	1.86	47.2
OB-250-258	2.50	64	2.06	52	2.58	66	.035	0.89	.220	5.6	4.08	26.3	2.14	54.4
OB-300-284	3.00	76	2.56	65	2.84	72	.035	0.89	.220	5.6	6.07	39.1	2.39	60.7
OB-300-284	3.00	76	2.63	67	2.84	72	.035	0.89	.185	4.7	6.22	40.1	2.45	62.2
OB-306-338	3.06	78	2.63	67	3.38	86	.035	0.89	.215	5.5	6.35	41.0	2.95	74.9
OB-362-340	3.62	92	3.12	79	3.40	86	.035	0.89	.250	6.4	8.92	57.5	2.33	59.2
OB-362-351	3.62	92	3.12	79	3.51	89	.035	0.89	.250	6.4	8.92	57.5	2.44	62.0
OB-363-406	3.62	92	3.12	79	4.06	103	.035	0.89	.250	6.4	8.92	57.5	3.09	78.5
OB-388-406	3.88	99	3.38	86	4.06	103	.035	0.89	.250	6.4	10.34	66.7	3.09	78.5
OB-388-413	3.88	99	3.33	85	4.13	105	.035	0.89	.275	7.0	10.20	65.8	3.12	79.2
OB-416-195	4.16	106	3.66	93	1.95	50	.035	0.89	.250	6.4	12.00	77.4	0.95	24.1
OB-416-353	4.16	106	3.66	93	3.53	90	.035	0.89	.250	6.4	12.00	77.4	2.53	64.3
OB-416-481	4.16	106	3.66	93	4.81	122	.035	0.89	.250	6.4	12.00	77.4	3.81	96.8
OB-475-374	4.75	121	4.25	108	3.74	95	.035	0.89	.250	6.4	15.90	102.6	2.61	66.3
OB-475-541	4.75	121	4.25	108	5.41	137	.035	0.89	.250	6.4	15.90	102.6	4.28	108.7
OB-700-414	7.00	178	6.50	165	4.14	105	.040	1.02	.250	6.4	35.77	230.8	3.01	76.5
*Metric effective pressure area shown in square centimeters.

Dia•Com is a leading international provider of innovative, cost-effective molded diaphragm solutions critical to the operation of essential systems and equipment in industrial, automotive, aerospace, medical instrumentation, and food and water processing applications. The company's reputation for excellence is based on superior quality in the design, manufacture and application of its high-performance, state-of-the-art, fabric-reinforced and homogeneous elastomeric rubber seals. Our custom engineered solutions are found in many products today, including diaphragm pumps, rubber seals, pneumatic diaphragm pumps, high pressure diaphragm pumps, viton gaskets, diaphragm carburetor, diaphragm pressure gauges, diaphragm vacuum pumps, diaphragm air compressors, diaphgram fuel pumps and diaphragm metering pumps.