Steam Flow Rate Pipes

Reference data and engineering information about steam flow rate pipes for fluid mechanics applications.

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Overview

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Steam flow rate data for Schedule 40 steel pipes, based on allowable pressure drops ranging from 1/16 to 2 psi per 100 ft of pipe. These values apply to saturated steam at low pressures (3–5 psig) and are used for sizing steam distribution piping in heating and process systems.

Selecting the right pipe size balances installation cost against acceptable pressure loss. Smaller pipes are cheaper but create higher pressure drops, while oversized pipes waste material and increase heat loss.

Original Source Scope

The source page title is Steam Flow Rate vs. Pressure Drop - Schedule 40 Pipe and its subtitle states that the data is flow rate (lb/h) and pressure drop per 100 feet of pipe. The original article text says that steam flow rates in Schedule 40 steel pipes are tabulated for pressure drops from 1/16 psi to 2 psi, and that wider screens show the full table with the higher pressure-drop columns.

Steam flow rates in schedule 40 steel pipes with pressure drops ranging 1/16 to 2 psi:

For full table with higher pressure drops - rotate the screen!

The source also includes three unit notes: 1 in = 25.4 mm, 1 ft = 0.3048 m, and 1 psi = 6895 Pa = 0.069 bar. Shared site navigation/search tables from the source extraction are intentionally excluded because they are not engineering data; the complete engineering data table is preserved below.

Key Formulas

The underlying flow relationship comes from the Darcy-Weisbach equation for pressure drop in straight pipe:

$\Delta P = f \cdot \frac{L}{D} \cdot \frac{\rho v^2}{2}$

For sizing purposes, velocity can also be expressed through mass flow:

$\dot{m} = \rho \cdot A \cdot v = \rho \cdot \frac{\pi D^2}{4} \cdot v$

Typical steam velocities in distribution mains range from 4,000 to 6,000 ft/min (20–30 m/s), depending on operating pressure and pipe length.

Variables

Symbol	Description	Unit
$\Delta P$	Pressure drop	psi
$f$	Darcy friction factor	—
$L$	Pipe length	ft
$D$	Inside pipe diameter	ft or in
$\rho$	Steam density	lb/ft³
$v$	Flow velocity	ft/min
$\dot{m}$	Mass flow rate	lb/h
$A$	Cross-sectional area	ft²

Restored Original Source Tables

The following tables are restored from the original source page to preserve the complete reference data.

Original Source Layout/Search Table

2 rows

Original source layout/search table
Column 1	Column 2	Column 3	Column 4	Column 5
×		×	検索
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Source: engineeringtoolbox.com

Steam Flow Rate vs. Pressure Drop - Schedule 40 Pipe

17 rows

Steam Flow Rate vs. Pressure Drop - Schedule 40 Pipe
Pressure drop per 100 ft of pipe length	Pressure drop per 100 ft of pipe length	Pressure drop per 100 ft of pipe length	Pressure drop per 100 ft of pipe length	Pressure drop per 100 ft of pipe length	Pressure drop per 100 ft of pipe length	Pressure drop per 100 ft of pipe length	Pressure drop per 100 ft of pipe length	Pressure drop per 100 ft of pipe length	Pressure drop per 100 ft of pipe length	Pressure drop per 100 ft of pipe length	Pressure drop per 100 ft of pipe length	Pressure drop per 100 ft of pipe length	Pressure drop per 100 ft of pipe length	Flow Rate (lb/h)
1/16 psi (1 oz/in2)	1/16 psi (1 oz/in2)	1/8 psi (2 oz/in2)	1/8 psi (2 oz/in2)	1/4 psi (4 oz/in2)	1/4 psi (4 oz/in2)	1/2 psi (8 oz/in2)	1/2 psi (8 oz/in2)	3/4 psi (12 oz/in2)	3/4 psi (12 oz/in2)	1 psi	1 psi	2 psi	2 psi
Saturated Pressure (psig)	Saturated Pressure (psig)	Saturated Pressure (psig)	Saturated Pressure (psig)	Saturated Pressure (psig)	Saturated Pressure (psig)	Saturated Pressure (psig)	Saturated Pressure (psig)	Saturated Pressure (psig)	Saturated Pressure (psig)	Saturated Pressure (psig)	Saturated Pressure (psig)	Saturated Pressure (psig)	Saturated Pressure (psig)
3.5	12	3.5	12	3.5	12	3.5	12	3.5	12	3.5	12	3.5	12
3/4	9	11	14	16	20	24	29	35	36	43	42	50	60	73
1	17	21	26	31	37	46	54	66	68	82	81	93	114	137
1 1/4	36	45	53	66	78	96	111	138	140	170	162	200	232	280
1 1/2	56	70	84	100	120	147	174	210	218	260	246	304	360	430
2	108	134	162	194	234	285	336	410	420	510	480	590	710	850
2 1/2	174	215	258	310	378	460	540	660	680	820	780	950	1150	1370
3	318	380	465	550	660	810	960	1160	1190	1430	1380	1670	1950	2400
3 1/2	462	550	670	800	990	1218	1410	1700	1740	2100	2000	2420	2950	3450
4	640	800	950	1160	1410	1690	1980	2400	2450	3000	2880	3460	4200	4900
5	1200	1430	1680	2100	2440	3000	3570	4250	4380	5250	5100	6100	7500	8600
6	1920	2300	2820	3350	3960	4850	5700	6800	7000	8600	8400	10000	11900	14200
8	3900	4800	5570	7000	8100	10000	11400	14300	14500	17700	16500	20500	24000	29500
10	7200	8800	10200	12600	15000	18200	21000	26000	26200	32000	30000	37000	42700	52000
12	11400	13700	16500	19500	23400	28400	33000	40000	41000	49500	48000	57500	67800	81000

Source: engineeringtoolbox.com

Engineering Notes

Steam Flow Unit Converter

Steam flow(lb/h)

Steam specific volume(ft3/lb)

Pressure drop(psi / 100 ft)

Pipe length(ft)

Pressure drop basis. Values are per 100 ft of straight pipe. For longer runs, scale linearly or use the Darcy-Weisbach equation with appropriate friction factors.
Higher pressures. At 5 psig saturated pressure, capacities increase roughly 20–25% compared to 3.5 psig for the same pipe size and pressure drop allowance.
Fittings and valves. Add equivalent lengths of pipe for elbows, tees, and valves. A common rule is 50–75% additional length for typical distribution systems.
Noise and erosion. Velocities above 6,000 ft/min (30 m/s) can cause noise, water hammer, and pipe erosion. Keep velocities within recommended limits for the operating pressure.
Condensate. Steam pipes must be pitched to drain condensate. Undrained condensate causes water hammer and reduces effective capacity.
Insulation. All steam pipes should be insulated to minimize heat loss and maintain steam quality at the point of use.

References

Engineering ToolBox – Steam Flow Rate Pipes

Source: engineeringtoolbox.com