Secondary pressure ranges higher than 1,6 MPa and lower than 0,05 MPa on request available.

Capacity Chart

Tables of calculation for steam
RE20 (REH20, REC20)
RE20L (REH20L, REC20L)

How to select the size of a PRV correctly?

Check the operating data:

• Inlet pressure p₁
• Requested downstream pressure p₂
• Requested steam flow

Check the requested steam flow in the capacity chart on page 15. Select the necessary size of the PRV. Table 1 shows the maximum available steam flow in kg/h at a given inlet pressure, if the ratio between the requested downstream pressure p₂ and the inlet pressure p₁ is lower than 0.577 (critical flow). Pay attention that the steam pressure is shown as bar_abs!

If the ratio between the downstream pressure p₂ and the inlet pressure p₁ is larger than 0.577 (non-critical flow), the available steam flow amount on the downstream side will be reduced. To get the maximum available downstream flow amount, the maximum steam flow from Table 1 must be multiplied with the calculation factor A. To get the Factor A see the Diagram 1.

Check if the requested steam flow matches the downstream side using Table 2 (page 16) for flows under 40 m/s. Choose the size based on barg pressure. If downstream piping is 1–2 sizes larger than the PRV inlet, you’re good. If the size difference is over 2, increase the PRV size. Keep the difference within 2 sizes!

Example of calculation

Operating data:

• p₁ = 9 barg = 10 bar_abs
  p₂ = 6 barg = 7 bar_abs
  Steam flow G = 1,100 kg/h

Search for the necessary size of the PRV in accordance with p₁.

• Table 1 shows 1,312 kg/h for size DN40 (1½”).
• bar_abs = 0.7 (i.e., larger than 0.577)
• Factor A acc. to Diagram 1 = 0.96
• Max. available steam flow G = 1,312 kg/h × 0.96 = 1,259 kg/h.

Steam flow in accordance with Table 2 at 6 barg = 1,720 kg/h for DN65.

Conclusion:
The PRV with an inlet size of DN40 and increase of the pipe size to DN65 at the downstream side will be suitable for a flow amount of 1,100 kg/h at the given pressures.

Capacity Chart
The Table 1 shows the maximum available steam flow amount of the pressure reducing valve at a given inlet pressure, if the ratio between the downstream pressure p₂ and the inlet pressure p₁ is lower than 0.577 (critical flow). Pay attention that the inlet steam pressure p₁ is shown as bar_abs.

Table 1

P1	Steam Flow per DN in kg/h
(bar abs)	15	20	25	32	40	50	65	80	100	125	150	200
1,1	21	38	59	94	154	238	405	607	952	1.545	2.14	3.81
1,2	23	41	64	101	167	257	437	655	1.028	1.67	2.313	4.112
1,3	25	44	70	110	181	279	474	711	1.116	1.813	2.511	4.464
1,4	27	48	75	119	195	300	510	765	1.2	1.951	2.702	4.803
1,5	29	51	80	127	208	320	545	818	1.283	2.085	2.887	5.133
1,6	30	54	85	135	222	342	581	871	1.366	2.22	3.074	5.466
1,7	32	58	91	143	236	363	617	926	1.452	2.36	3.267	5.808
1,8	34	61	95	151	248	382	649	973	1.526	2.48	3.434	6.105
1,9	36	64	101	159	262	402	684	1.026	1.61	2.616	3.622	6.438
2,0	38	68	106	167	275	424	720	1.081	1.695	2.755	3.814	6.781
2,2	42	74	116	184	302	465	790	1.185	1.859	3.021	4.183	7.437
2,4	45	81	126	200	329	506	860	1.289	2.022	3.286	4.55	8.09
2,6	49	87	136	215	354	545	926	1.389	2.179	3.541	4.903	8.717
2,8	52	92	144	227	373	575	977	1.465	2.298	3.735	5.171	9.194
3,0	56	101	157	248	409	629	1.069	1.603	2.514	4.086	5.657	10.058
3,5	65	116	182	287	472	727	1.236	1.854	2.908	4.726	6.543	11.632
4,0	75	133	207	328	539	830	1.411	2.116	3.319	5.394	7.468	13.277
4,5	84	149	232	367	604	929	1.58	2.369	3.717	6.04	8.367	14.867
5,0	93	165	258	408	671	1.032	1.755	2.632	4.129	6.709	9.29	16.515
5,5	99	176	274	433	714	1.097	1.865	2.798	4.389	7.132	9.875	17.555
6,0	111	197	308	486	800	1.23	2.092	3.138	4.922	7.998	11.074	19.686
6,5	119	213	332	525	864	1.329	2.259	3.388	5.315	8.637	11.959	21.261
7,0	129	229	358	565	930	1.431	2.433	3.649	5.724	9.302	12.879	22.896
7,5	138	245	382	604	994	1.529	2.599	3.899	6.116	9.939	13.761	24.464
8,0	146	260	407	643	1.058	1.628	2.767	4.15	6.51	10.579	14.648	26.042
8,5	155	277	432	683	1.124	1.729	2.94	4.409	6.917	11.24	15.563	27.667
9,0	164	292	456	720	1.185	1.823	3.098	4.648	7.29	11.847	16.403	29.162
9,5	173	307	480	759	1.249	1.921	3.266	4.899	7.684	12.487	17.289	30.736
10,0	182	323	505	798	1.312	2.019	3.433	5.149	8.077	13.125	18.173	32.307
10,5	191	339	530	837	1.378	2.12	3.604	5.406	8.48	13.78	19.08	33.92
11,0	200	355	555	877	1.443	2.22	3.774	5.661	8.88	14.43	19.98	35.52
12,0	218	387	605	956	1.573	2.42	4.115	6.172	9.682	15.733	21.784	38.726
13,0	235	417	652	1.03	1.695	2.608	4.434	6.651	10.433	16.953	23.474	41.731
14,0	252	449	701	1.108	1.822	2.804	4.766	7.15	11.215	18.225	25.234	44.861
15,0	270	481	751	1.187	1.954	3.006	5.11	7.665	12.023	19.538	27.052	48.093
16,0	288	513	801	1.266	2.083	3.204	5.447	8.17	12.816	20.826	28.836	51.264
17,0	306	545	850	1.343	2.21	3.4	5.78	8.671	13.601	22.101	30.602	54.403
18,0	324	575	899	1.42	2.336	3.595	6.111	9.166	14.378	23.365	32.351	57.514
19,0	342	607	949	1.499	2.466	3.795	6.451	9.676	15.178	24.665	34.151	60.714
20,0	357	635	993	1.568	2.581	3.971	6.75	10.126	15.883	25.81	35.737	63.533
21,0	376	669	1.046	1.653	2.719	4.184	7.112	10.669	16.735	27.195	37.654	66.941
23,0	413	735	1.148	1.814	2.985	4.592	7.807	11.71	18.369	29.849	41.33	73.475
25,0	449	798	1.247	1.969	3.241	4.986	8.476	12.714	19.944	32.409	44.874	79.776
27,0	484	861	1.346	2.126	3.498	5.382	9.149	13.724	21.528	34.983	48.438	86.112
29,0	520	924	1.444	2.282	3.755	5.777	9.82	14.73	23.106	37.548	51.989	92.426
30,0	538	957	1.496	2.363	3.889	5.983	10.17	15.256	23.93	38.887	53.843	95.722
33,0	590	1.05	1.64	2.592	4.265	6.561	11.153	16.73	26.243	42.645	59.047	104.973
Kvs	1,8	3,2	5,0	7,9	13	20	34	51	80	130	180	320

Capacity Chart
The Table 2 shows the maximum available downstream steam flow amount of the pressure reducing valve at the requested downstream pressure p₂. Pay attention that the steam pressure p₂ is shown as barg.

Table 2

P2	Steam Flow per DN in kg/h
p2 (barg)	15	20	25	32	40	50	65	80	100	125	150	200
0,1	16	29	45	73	115	179	303	460	715	1120	1610	2870
0,2	18	31	48	79	124	194	328	498	775	1215	1750	3110
0,3	19	34	52	85	134	209	353	535	835	1310	1880	3350
0,4	20	36	56	92	144	224	380	575	895	1405	2020	3590
0,5	22	39	60	99	154	239	405	615	955	1500	2170	3820
0,6	22	41	64	105	163	254	430	650	1015	1590	2290	4060
0,7	24	43	68	110	173	269	455	690	1075	1680	2420	4300
0,8	26	46	72	116	182	284	480	725	1135	1770	2550	4540
0,9	27	48	75	122	191	299	505	765	1195	1660	2680	4780
1,0	28	50	78	128	200	314	530	800	1250	1950	2820	5020
1,2	31	55	86	140	219	343	580	880	1360	2140	3080	5500
1,4	34	60	93	152	238	377	625	950	1480	2320	3350	5950
1,6	36	65	100	164	257	401	675	1025	1600	2500	3600	6420
1,8	39	69	107	176	275	430	725	1100	1720	2680	3850	6890
2,0	42	74	115	188	294	460	775	1180	1840	2870	4125	7360
2,5	48	84	132	217	338	530	890	1355	2120	3300	4750	8450
3,0	54	96	150	246	385	600	1010	1540	2400	3750	5400	9650
3,5	60	108	168	275	430	670	1130	1720	2680	4200	6050	10700
4,0	67	119	185	305	475	740	1250	1900	2960	4650	6650	11800
4,5	73	130	202	335	520	810	1370	2080	3240	5075	7300	13050
5,0	79	141	220	365	565	880	1490	2250	3520	5500	7900	14100
5,5	85	152	237	395	605	950	1600	2430	3800	5925	8500	15150
6,0	92	163	254	420	655	1020	1720	2610	4080	6350	9125	16300
6,5	98	174	271	445	695	1085	1840	2790	4360	6775	9750	17400
7,0	104	185	288	475	740	1160	1960	2970	4640	7200	10375	18500
7,5	110	196	305	500	785	1220	2070	3140	4900	7650	11000	19600
8,0	117	207	323	530	830	1290	2180	3320	5180	8100	11625	20700
8,5	123	218	341	560	875	1365	2300	3500	5450	8550	12250	21800
9,0	129	229	358	585	915	1430	2410	3670	5720	8975	12875	22900
9,5	135	240	375	615	960	1500	2530	3840	6000	9400	13500	24000
10,0	141	252	392	645	1000	1570	2650	4020	6270	9825	14125	25100
11,0	154	273	427	700	1090	1710	2880	4380	6800	10700	15300	27300
12,0	166	294	461	750	1180	1840	3100	4730	7300	11550	16500	29400
13,0	178	316	495	810	1270	1980	3340	5080	7850	12400	17750	31600
14,0	190	338	530	870	1355	2120	3570	5400	8400	13200	19000	33800
15,0	202	360	565	925	1440	2250	3800	5750	8950	14100	20300	36000
16,0	215	382	600	980	1530	2390	4030	6100	9550	15000	21600	38200
17,0	227	404	630	1020	1620	2530	4270	6450	10100	15900	22800	40400
18,0	240	427	665	1090	1710	2670	4500	6800	10650	16750	24000	42600
19,0	252	450	700	1145	1790	2800	4740	7150	11200	17600	25200	44800
20,0	263	473	730	1200	1870	2930	4950	7500	11750	18400	26500	47000
22,0	288	510	800	1310	2050	3200	5400	8200	12800	20000	28800	51000
24,0	312	555	870	1420	2220	3470	5850	8900	13900	21700	31200	55200
26,0	337	600	940	1530	2400	3750	6300	9600	15000	23400	33700	60400
28,0	362	645	1010	1650	2580	4020	6800	10300	16100	25100	36200	64600
30,0	387	690	1080	1770	2750	4300	7250	11000	17200	26900	38700	68800
32,0	413	735	1150	1890	2950	4600	7750	11800	18300	28800	41300	73500