Fig 542 Safety Relief Valve

Features

Pipe Connections

Threaded female inlet and outlet connections. inlet and outlet connections are of equal size. Threaded connections are Rp (BSP) parallel to BS EN 10226-1 NPT connections are available upon request.

Testing

All valves are shell and seat tested (to confirm set pressure) before leaving the factory and all valves are supplied pre-set with a tamper proof seal. Pressure Test Certificate and Letters of Conformity available on request.

Product Extras

Available with Viton seat design
Padlock available
Pressure setting locked and sealed
Drain plug fitted on sizes DN40 and above allows fitting of a pressure gauge

Fig 542 Dimensional Drawing

Dimensions & Weights

SIZE DN	Rp BSP Inlet & Outlet	A (mm)	B (mm)	C (mm)	Weight (Kg)
15	1/2″	30	23	113	0.35
20	3/4″	34	23	118	0.53
25	1″	39	27	132	0.80
32	1 1/4″	46	33	153	1.33
40	1 1/2″	54	38	198	2.30
50	2″	64	46	236	4.20
65	2 1/2″	76	55	275	7.80
80	3″	90	65	335	12.50

Materials

Ref No	Name of Part	Material
1	Thrust Washer	Brass, BS EN 12164 CW609N
2	Grubscrew	Steel
3	Test Lever	Brass, BS EN 1982 CC754S
4	Spring	Chrome Vandium Alloy Steel, BS 2803 735 A50 HS (Stainless Steel, BS 2056 302S26 Opt)
5	Label	Yellow kapton
6	Spring Cover	Bronze, BS EN 1982 CC491K
7	Piston	Brass, BS EN 12164 CW609N
8	Diaphragm	Silicon Rubber
9	Seat Seal Holder	Bronze, BS EN 1982 CC491K / Brass BS EN 12164 CW602N (DZR)
10	Seat Seal	PTFE (Viton Opt)
11	Starlock Washer	Stainless Steel
12	Body	Bronze, BS EN 1982 CC491K
13	Lever Pin	Steel
14	Lead Seal (Not shown)	Lead
15	Adjusting Screw	Brass, BS EN 12164 CW609N
16	Spring Plate	Brass, BS EN 12164 CW609N
17	Spindle	Brass, BS EN 12164 CW721R
18	Seat Seal Retaining Plate	Bronze, BS EN 1982 CC491K / Brass BS EN 12164 CW602N (DZR)
19	O-Ring	Viton

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Discharge

Discharge Capabilities

The discharge capacity of a safety valve must be equal to or greater than the output of the boiler or system it is protecting. To ensure that the correct method of sizing is used, reference should be made to the relevant BS specification for the design of the boiler or system. Fig 542 capacities are tabulated below to assist selection.

Fig 542 – Air Capacity – 10% Overpressure (BS EN 4126-1)Click to View +

std. litres/sec (Kdr=0.19)

Set Pressure Bar	15	20	25	32	40	50	65	80
1.00	14	24	38	62	97	151	256	387
1.25	15	27	43	70	109	171	289	438
1.50	17	31	48	78	122	191	322	488
1.75	19	34	53	86	135	211	356	539
2.00	21	37	58	94	148	230	389	590
2.25	23	40	63	102	160	250	423	640
2.50	24	43	68	111	173	270	456	691
2.75	26	46	72	119	186	290	490	742
3.00	28	50	77	127	198	310	523	793
3.25	30	53	82	135	211	329	557	843
3.50	31	56	87	143	224	349	590	894
3.75	33	59	92	151	236	369	624	945
4.00	35	62	97	159	249	389	657	995
4.25	37	65	102	167	262	409	690	1046
4.50	39	69	107	175	274	428	724	1097
4.75	40	72	112	184	287	448	757	1147
5.00	42	75	117	192	300	468	791	1198
5.25	44	78	122	200	312	488	824	1249
5.50	46	81	127	208	325	507	858	1299
5.75	48	84	132	216	338	527	891	1350
6.00	49	88	137	224	350	547	925	1401
6.25	51	91	142	232	363	567	958	1451
6.50	53	94	147	240	376	587	992	1502
6.75	55	97	152	248	388	606	1025	1553
7.00	56	100	157	256	401	626	1059	1603
7.25	58	103	162	265	414	646	1092	1654
7.50	60	107	167	273	426	666	1125	1705
7.75	62	110	171	281	439	686	1159	1755
8.00	64	113	176	289	452	705	1192	1806
8.25	65	116	181	297	464	725	1226	1857
8.50	67	119	186	305	477	745	1259	1908
8.75	69	122	191	313	490	765	1293	1958
9.00	71	126	196	321	502	785	1326	2009
9.25	73	129	201	329	515	804	1360	2060
9.50	74	132	206	338	528	824	1393	2110
9.75	76	135	211	346	540	844	1427	2161
10.00	78	138	216	354	553	864	1460	2212
10.25	80	141	221	362	566	884	1494	2262
10.50	81	145	226	370	578	903	1527	2313

To convert to ft3/min multiply by 2.1.

Fig 542 – Steam Capacity – 10% Overpressure (BS 6759)Click to View +

Kg/hr (Kdr=0.19)

Set Pressure Bar	15	20	25	32	40	50	65	80
1.00	37	66	103	168	263	411	695	1053
1.25	42	74	116	190	298	465	786	1191
1.50	47	83	130	213	332	519	877	1329
1.75	52	92	143	235	367	573	968	1466
2.00	56	100	157	257	401	627	1059	1604
2.25	61	109	170	279	436	680	1150	1742
2.50	66	117	184	301	470	734	1241	1880
2.75	71	126	197	323	505	788	1332	2018
3.00	76	135	211	345	539	842	1423	2156
3.25	81	143	224	367	574	896	1514	2294
3.50	86	152	238	389	608	950	1605	2432
3.75	90	161	251	411	643	1004	1696	2569
4.00	95	169	264	433	677	1057	1787	2707
4.25	100	178	278	455	712	1111	1878	2845
4.50	105	186	291	477	746	1165	1969	2983
4.75	110	195	305	499	781	1219	2060	3121
5.00	115	204	318	521	815	1273	2151	3259
5.25	120	212	332	543	849	1327	2242	3397
5.50	124	221	345	565	884	1380	2333	3534
5.75	129	229	359	587	918	1434	2424	3672
6.00	134	238	372	610	953	1488	2515	3810
6.25	139	247	386	632	987	1542	2606	3948
6.50	144	255	399	654	1022	1596	2697	4086
6.75	149	264	413	676	1056	1650	2788	4224
7.00	154	272	426	698	1091	1704	2879	4362
7.25	158	281	440	720	1125	1757	2970	4500
7.50	163	290	453	742	1160	1811	3061	4637
7.75	168	298	467	764	1194	1865	3152	4775
8.00	173	307	480	786	1229	1919	3244	4913
8.25	178	316	493	808	1263	1973	3335	5051
8.50	183	324	507	830	1298	2027	3426	5189
8.75	188	333	520	852	1332	2080	3517	5327
9.00	192	341	534	874	1367	2134	3608	5465
9.25	197	350	547	896	1401	2188	3699	5603
9.50	202	359	561	918	1436	2242	3790	5740
9.75	207	367	574	940	1470	2296	3881	5878
10.00	212	376	588	962	1505	2350	3972	6016
10.25	217	384	601	984	1539	2404	4063	6154
10.50	222	393	615	1006	1574	2457	4154	6292

To convert to lb/hr multiply by 2.2.
*The minimum bore size permitted by BS specifications for steam and hot water boilers is 20mm.
Capacities given for DN15 size in the tables are for applications outside the scope of these standards.

Fig 542 – Water Capacity – Unvented System – 10% Overpressure (BS EN 4126-1)Click to View +

kg/min water (Kdr=0.19)

Set Pressure Bar	15	20	25	32	40	50	65	80
1.00	30	53	83	136	213	332	561	850
1.25	33	59	93	152	238	371	627	950
1.50	37	65	102	167	260	407	687	1041
1.75	40	70	110	180	281	439	742	1124
2.00	42	75	117	192	301	469	793	1202
2.25	45	80	125	204	319	498	842	1275
2.50	47	84	131	215	336	525	887	1344
2.75	50	88	138	225	352	550	930	1409
3.00	52	92	144	235	368	575	972	1472
3.25	54	96	150	245	383	598	1011	1532
3.50	56	99	155	254	398	621	1050	1590
3.75	58	103	161	263	412	643	1086	1646
4.00	60	106	166	272	425	664	1122	1700
4.25	62	109	171	280	438	684	1157	1752
4.50	63	113	176	288	451	704	1190	1803
4.75	65	116	181	296	463	723	1223	1852
5.00	67	119	186	304	475	742	1255	1900
5.25	69	122	190	312	487	761	1286	1947
5.50	70	125	195	319	498	778	1316	1993
5.75	72	127	199	326	510	796	1345	2038
6.00	73	130	203	333	521	813	1374	2082
6.25	75	133	208	340	531	830	1403	2125
6.50	76	135	212	347	542	846	1430	2167
6.75	78	138	216	353	552	862	1458	2208
7.00	79	140	220	360	562	878	1484	2249
7.25	81	143	224	366	572	894	1511	2288
7.50	82	145	227	372	582	909	1536	2327
7.75	83	148	231	378	592	924	1562	2366
8.00	85	150	235	385	601	939	1587	2404
8.25	86	153	238	390	611	953	1611	2441
8.50	87	155	242	396	620	968	1636	2478
8.75	89	157	246	402	629	982	1660	2514
9.00	90	159	249	408	638	996	1683	2550
9.25	91	161	253	413	646	1010	1706	2585
9.50	92	164	256	419	655	1023	1729	2619
9.75	93	166	259	425	664	1036	1752	2654
10.00	95	168	263	430	672	1050	1774	2687
10.25	96	170	266	435	680	1063	1796	2721
10.50	97	172	269	441	689	1076	1818	2754

In the above tables, discharge capacities have been calculated in accordance with BS EN 4126-1 & BS 6759, using a derated coefficient of discharge (Kdr) 0.19, approved by AOTC.

Fig 542 – Hot Water Capacity – Unvented System – 10% Overpressure (BS EN 4126-1)Click to View +

kW (Kdr=0.19)

Pressure Set Bar	15	20	25	32	40	50	65	80
1.00	23	41	64	106	165	258	436	660
1.25	26	47	73	119	187	291	493	746
1.50	29	52	81	133	208	325	550	833
1.75	32	57	90	147	230	359	607	919
2.00	35	63	98	161	251	393	664	1005
2.25	38	68	107	175	273	426	721	1092
2.50	41	74	115	188	295	460	778	1178
2.75	45	79	124	202	316	494	835	1265
3.00	48	84	132	216	338	528	892	1351
3.25	51	90	140	230	359	561	949	1437
3.50	54	95	149	244	381	595	1006	1524
3.75	57	101	157	258	403	629	1063	1610
4.00	60	106	166	271	424	663	1120	1697
4.25	63	111	174	285	446	696	1177	1783
4.50	66	117	183	299	468	730	1234	1869
4.75	69	122	191	313	489	764	1291	1956
5.00	72	128	200	327	511	798	1348	2042
5.25	75	133	208	340	532	831	1405	2129
5.50	78	138	216	354	554	865	1462	2215
5.75	81	144	225	368	576	899	1519	2301
6.00	84	149	233	382	597	933	1576	2388
6.25	87	155	242	396	619	966	1633	2474
6.50	90	160	250	410	640	1000	1690	2561
6.75	93	165	259	423	662	1034	1747	2647
7.00	96	171	267	437	684	1068	1804	2733
7.25	99	176	275	451	705	1101	1861	2820
7.50	102	182	284	465	727	1135	1919	2906
7.75	105	187	292	479	748	1169	1976	2993
8.00	108	192	301	493	770	1203	2033	3079
8.25	111	198	309	506	792	1236	2090	3165
8.50	115	203	318	520	813	1270	2147	3252
8.75	118	209	326	534	835	1304	2204	3338
9.00	121	214	335	548	856	1338	2261	3425
9.25	124	219	343	562	878	1371	2318	3511
9.50	127	225	351	575	900	1405	2375	3597
9.75	130	230	360	589	921	1439	2432	3684
10.00	133	236	368	603	943	1472	2489	3770
10.25	136	241	377	617	965	1506	2546	3857
10.50	139	246	385	631	986	1540	2603	3943

To convert to Btu/hr multiply by 3400.

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