Cast steel
GP240GH
(GS-C25,1.0619)

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. The 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.

Now, check if the requested steam flow is available on the downstream side. Use the capacity chart (Table 2) on page 16 to find the maximum downstream steam flow in kg/h, assuming a steam velocity of up to 40 m/s. The steam pressure is listed in barg, so choose the corresponding size. If the steam piping on the downstream side is 1–2 sizes larger than the PRV inlet size, the selection is correct. However, if the inlet size from Table 1 (page 15) differs from the downstream size in Table 2 by more than 2 sizes, increase the PRV inlet size. Keep the size difference between the inlet and downstream piping 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	1.245	1.14	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