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Straight Through Diaphragm Valves - Flow Coefficients

Flow coefficients - C_v - and flow factors - K_v - for straight through diaphragm valves.

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Typical flow coefficients - C_v - and flow factors - K_v - for diaphragm straight through flanged cast iron valves of "Saunders" type:

Valve Size		Unlined		Rubber Lined		Glass/Plastic Lined
DN	Inches	C_v	K_v	C_v	K_v	C_v	K_v
15	1/2	9	7			9	8
25	1	38	33	31	26	39	34
32	1 1/4	56	48	46	39	58	50
40	1 1/2	75	65	66	57	79	68
50	2	128	110	107	92	138	119
65	2 1/2	238	205	195	168	254	219
80	3	330	284	264	228	342	295
100	4	588	507	480	414	618	533
125	5	924	797	720	621	960	828
150	6	1 680	1 448	1 260	1 086	1 800	1 552
200	8	2 580	2 224	2 196	1 893	2 724	2 348
250	10	4 020	3 466	3 420	2 948	4 296	3 703
300	12	6 060	5 224	4 884	4 210
350	14	10 300	8 879	9 950	8 578

The opening and closing characteristic of the valves are close to positive linear:

closing a valve to 80% - reduces the flow coefficient to approximately 85%
closing a valve to 50% - reduces the flow coefficient to approximately 60%

This close to linear characteristic make the valves suited for adjustment and balancing operations. In addition the lined versions are able to resist wear and tear and rough environments and processes.

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