Steam System Losses Reference

Typical heat loss, condensate-loss, and trap-failure rates for steam distribution headers, traps, and pipe insulation.

Trap Losses

Steam Trap Failure-Open Losses (Napier / DOE Tip Sheet #1) · Source: DOE Steam Tip Sheet #1 (2012); Napier eqn per Spirax Sarco · Napier: steam loss (lb/hr) ≈ 24.24 x P_abs(psia) x D_orifice(in)² · Trap orifice equivalent: 1/32" ≈ 0.031" | 1/16" ≈ 0.0625" | 3/32" ≈ 0.094" | 1/8" ≈ 0.125"

Orifice	Steam P (psig)	Leak rate (lb/hr)	Annual loss (klb/yr, 8760hr)	Fuel cost @$6/MMBtu (annual $)	Comments
1/32"	15	0.7	6.2	37	Napier
1/32"	50	1.53	13.4	80	Napier
1/32"	100	2.72	23.8	143	Napier
1/32"	150	3.9	34.2	205	Napier
1/32"	250	6.27	54.9	329	Napier
1/32"	600	14.55	127.5	765	Napier
1/16"	15	2.81	24.6	148	Napier
1/16"	50	6.13	53.7	322	Napier
1/16"	100	10.86	95.1	571	Napier
1/16"	150	15.59	136.6	820	Napier
1/16"	250	25.06	219.6	1317	Napier
1/16"	600	58.2	509.9	3059	Napier
3/32"	15	6.33	55.4	333	Napier
3/32"	50	13.78	120.7	724	Napier
3/32"	100	24.44	214.1	1284	Napier
3/32"	150	35.09	307.4	1844	Napier
3/32"	250	56.39	494	2964	Napier
3/32"	600	130.96	1147.2	6883	Napier
1/8"	15	11.25	98.5	591	Napier
1/8"	50	24.5	214.7	1288	Napier
1/8"	100	43.44	380.5	2283	Napier
1/8"	150	62.38	546.4	3279	Napier
1/8"	250	100.25	878.2	5269	Napier
1/8"	600	232.82	2039.5	12237	Napier
3/16"	15	25.31	221.7	1330	Napier
3/16"	50	55.13	483	2898	Napier
3/16"	100	97.74	856.2	5137	Napier
3/16"	150	140.35	1229.5	7377	Napier
3/16"	250	225.57	1976	11856	Napier
3/16"	600	523.84	4588.8	27533	Napier
1/4"	15	44.99	394.1	2365	Napier
1/4"	50	98.01	858.6	5152	Napier
1/4"	100	173.76	1522.2	9133	Napier
1/4"	150	249.51	2185.7	13114	Napier
1/4"	250	401.01	3512.9	21077	Napier
1/4"	600	931.26	8157.9	48947	Napier

Insulation Loss

Bare Pipe & Insulation Heat Loss (DOE Steam Tip Sheet #2) · Source: DOE Steam Tip #2; NAIMA 3E Plus program verified

Pipe NPS	Steam T (°F)	Bare loss (Btu/hr·ft)	1" insul loss	2" insul loss	3" insul loss
1"	250	240	35	25	20
1"	350	450	55	40	33
1"	450	710	78	57	47
2"	250	380	45	32	26
2"	350	710	72	51	42
2"	450	1120	102	75	60
4"	250	620	65	46	37
4"	350	1160	104	74	60
4"	450	1830	148	107	86
6"	250	840	80	58	47
6"	350	1575	127	92	74
6"	450	2485	181	133	107
8"	250	1050	96	70	56
8"	350	1970	153	112	90
8"	450	3110	219	161	130
12"	250	1490	130	96	78
12"	350	2790	208	154	124
12"	450	4400	298	220	178
Notes: Mineral wool k≈0.27 Btu·in/hr·ft²·°F at 200°F mean; ambient 65°F; wind 0 mph;
pipe emissivity 0.9 bare / 0.1 jacketed. ASTM C585-10 insulation thickness.

Flash Steam

Flash Steam Generation from Condensate (Spirax) · % flash = (h_f_high - h_f_low) / h_fg_low × 100

HP condensate P (psig)	LP flash P (psig)	% flash by mass	Flash T (°F)
150	0	13	212
150	15	10.1	250
150	50	6.5	298
300	0	18.7	212
300	15	15.9	250
300	50	12.4	298
300	150	5	366
600	50	20.7	298
600	150	13.9	366
600	300	7.4	417
Typical recovery: deaerator flash, LP header augmentation, hot water preheat.
Flash tank sizing: t_residence ≥ 30 s, V_liq ≥ 10% of hourly condensate volume.

Pipe Leaks

Plume / Audible Steam Leak Estimation Guide · Source: Spirax Sarco Module 3.10 (2011) + DOE Tip #9

Plume length (ft)	Approx leak rate (lb/hr @150 psig)	Annual cost @$6/MMBtu	Field signature
< 2 ft	6	315	Small hiss; hard to detect w/o thermal cam
2-5 ft	20	1050	Clearly audible; small visible plume
5-10 ft	45	2365	Loud; significant visible plume
10-20 ft	95	4994	Can be heard across unit; large plume
> 20 ft	180	9460	Hazard; stop work & tag for repair

Source: Steam_System_Losses_Reference_v1.xlsx

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