Pressure drop by safety devices conforming to EN ISO 5175-1

  • Every flashback arrestor clogs up at the sintered element with the passage of time.
  • An increase in impurities in the arrestor reduces the flow rate.
  • The better the performance of an arrestor, the longer its life.

mehrloch anwaermbrenner

This multiple-hole burner has high gas consumption. If the flashback arrestor is too small for the application, high pressure drops may occur.

For explanation purposes, a manual heating burner during operation is illustrated. First, the Oxygen side is protected by a torch-mounted flashback arrestor type GG. In the second picture, the Oxygen side is protected by a flashback arrestor type DG91UA.

fba pressure drop

The same burner, but with different safety devices.

pressure drop GG
Model GG
Inlet pressure 5,2 bar
Outlet pressure 4,0 bar
A pressure loss of 1,2 bar is visible.
pressure drop DG91UA
Model DG91UA
Inlet pressure 4,2 bar
Outlet pressure 4,0 bar
A pressure loss of only 0,2 bar is visible.

Inlet pressure 
(P1) bar

Outlet pressure
(P2) bar
Airflow in Nm³/h
Inlet pressure
(P2) bar
Airflow in Nm³/h
Δp=0,3 bar
Outlet pressure
(P2) bar
Airflow in Nm³/h
Δp=0,6 bar
0,0 0,0 0,0        
0,3 0,0 3,9 0,0 3,9    
0,6 0,0 8,3 0,3 4,8 0,0 8,3
0,9 0,0 12,6 0,6 5,7 0,3 9,9
1,2 0,0 16,6 0,9 6,3 0,6 11,4
1,5 0,0 20,5 1,2 6,8 0,9 12,8

Δ = delta = difference, Δp = inlet pressure minus outlet pressure, outlet pressure = inlet pressure minus Δp
Nm³/h = standard cubic meter per hour, bar = pressure measurement

Three curves with different pressure losses are recorded. The higher the difference Δp between the inlet pressure and the outlet pressure, the higher the flow rate (P1 – P2 = Δp).

In order to achieve the necessary flow rate of approx. 10 Nm³/h with a required working pressure of 0,3 bar, the pressure regulator must be set to 0,9 bar.


The flow curves are mostly measured with air. For other gases there are calculation factors available.

Gas type Chemical formula Conversion factor
Air   1,00
Acetylene C2H2 1,20
Butane C4H10 0,86
Natural gas   1,25
Methane C2H4 1,40
Propane C3H8 0,90
Oxygen O2 0,95
Hydrogen H2 2,50
Ethene CH4 1,02
Industrial gas   1,55