Low Pressure Steam Safety Valves - Capacities

Sizing safety valves after boiler output power in low pressure systems (kW and Btu/hr). Determines the appropriate pipe size and safety valve capacity based on maximum boiler output.

Calculator

Inputs

Boiler Output (kW)

Measurement System

Results

Selected Boiler Output-- kW

Recommended Valve Size (DN)-- mm

Pipe Size (in)	DN (mm)	Capacity (kg/h)	Capacity (lb/h)	Max Boiler Output (kW)	Max Boiler Output (Btu/h)
1/2	15	38	86	23	81 270
3/4	20	82	185	50	174 825
1	25	145	324	89	306 180
1 1/4	32	249	557	152	526 365
1 1/2	40	360	807	220	762 615
2	50	536	1 199	328	1 133 055
2 1/2	65	901	2 012	551	1 901 340
3	80	1 244	2 779	761	2 626 155
4	100	2 397	5 355	1 465	5 060 475

Technical Notes

System Pressure: Low pressure steam at 100 kN/m² (1 bar) or 15 psi

Latent Heat: 2201 kJ/kg (945 Btu/lb) for saturated steam

Key Principles

Purpose: Safety valves prevent system pressure from exceeding certification pressure
Sizing Criterion: Valve capacity must equal or exceed maximum boiler vapor output at working pressure
Higher Pressure: Compressed steam requires smaller valve (less volume)
Lower Pressure: Expanded steam requires larger valve (more volume)

Important Notes

Always consult manufacturer documentation before final design
This table is specifically for low pressure steam systems
For high pressure steam, different sizing applies
Proper valve selection is critical for system safety, especially with high-temperature steam and significant latent heat energy