Steam Pipe Sizing for Large Steam Mains and Superheated Steam

How to use the Steam Pipe Sizing Chart

Example:
Required to size a pipe to handle 20 tonnes of steam per hour at a pressure of 14 bar gauge and a temperature of 340°C.
The length of the line is 300 metres and the permissable pressure drop over this length is 0.675 bar.

Note that the chart is in absolute pressure and for an exercise of this kind it is reasonable to assume that 14 bar gauge equals 15 bar absolute.

First find the pressure drop ratio

RATIO = PRESSURE DROP / INLET PRESSURE (ab.)
= 0.675 / 15
= 0.045

From this point on the left hand scale read horizontally to the right and at the intersection with the curved line read vertically upwards to meet the length line of 300 metres. At this point extend a horizontal line h1 h2 across the chart.
Now from the base temperature line at 340ºC extend upwards to meet the 15 bar abs. pressure line.

Read horizontally to the right to meet the capacity line of 20 tonnes/h and from this point extend a line vertically upwards. Where this intersects the line h1 h2 indicates the pipe size required.
Where this intersection comes between two pipe sizes, the larger should be used. The procedure can of course be reversed to find the pressure drop in a known pipe size.

Warm-up Load in Kilograms of Steam per 100 M of Steam Mains

Ambient Temperature 21ºC

Steam Pressure bar	50 mm	65 mm	80 mm	100 mm	125 mm	150 mm	Main size		300 mm	350 mm	400 mm	450 mm	500 mm	600 mm	-18C Correction
							200 mm	250 mm							-18C Correction
							200 mm	250 mm							Factor
0.00	9.2	14.4	19.0	27	37	47	71	101	134	159	208	262	308	309	1.50
0.35	10.0	15.9	20.8	29	40	52	69	112	146	174	227	287	338	470	1.45
0.70	11.3	17.8	23.4	33	45	58	88	125	165	196	255	322	379	529	1.41
1.00	12.2	19.5	25.4	36	50	64	96	135	179	212	277	350	412	575	1.39
2.50	13.4	21.3	27.8	39	53	70	105	148	195	232	303	383	450	627	1.33
4.00	15.8	25.2	33.0	47	63	82	123	175	233	276	360	454	535	745	1.30
5.50	17.8	28.0	37.0	52	71	92	138	196	260	308	402	507	598	832	1.28
7.00	19.3	30.6	40.0	57	77	100	151	214	284	335	438	553	651	906	1.26
8.50	20.1	31.8	42.0	59	80	104	157	223	293	349	455	574	676	942	1.25
10.00	20.8	33.1	43.0	62	83	108	162	230	305	361	472	595	700	997	1.24
12.00	22.6	35.8	47.0	67	90	117	176	250	331	392	513	646	760	1059	1.23
14.00	24.2	38.2	50.0	71	96	125	189	267	353	418	546	689	811	1130	1.22
16 00	28.1	45.0	58.0	83	113	146	219	312	412	489	638	805	947	1320	1.21
20.00	36.0	55.0	74.0	108	150	205	312	463	637	764	981	1228	1503	1700	1.20
25.00	39.0	59.0	80.0	117	162	222	338	502	692	828	1065	1362	1631	2315	1.19
30.00	41.5	64.0	85.0	124	173	237	360	534	735	882	1134	1420	1735	2464	1.18
40.00	44.3	68.0	91.0	132	184	253	385	570	784	940	1210	1514	1852	2627	1.17

* For outdoor temperature of -18ºC, multiply load value in table for each main size by correction factor shown.

Steam Pipe Sizing for Large Steam Mains and Superheated Steam

How to use the Steam Pipe Sizing Chart

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