Delta-Elektrogas RAGH Air differential / Gas ratio regulators

The RAGH type regulator has been designed for burner with preheated air. It is able to maintain
a constant ratio between air and gas flow during the different phases of burner working. In a
regenerative or recuperative burner with the same air inlet pressure, the air flow changes during
burner working and aging. Air flow depends on air preheating grade and the presence of dirty
on recuperator or regenerator. RAGH is able to supply a gas pressure proportional to Air
differential pressure, which is directly linked with air flow.


The regulators are made of aluminum alloy die-cast, with a range for inlet/outlet connections
from 1/2” up to 2”.
Gas inlet pressure up to 500 mbar, air control differential pressure up to 35 mbar.
They are equipped with an adjustable spring, so that gas outlet pressure is equal to air control
differential pressure, with a ratio 1:4 and an adjustable offset of +/-3mbar.
RAGH regulators can be used also with modulating burner with preheating, they have been
designed for a flow regulation range equal to 4:1. Design is optimized to generate low pressure
The controls are equipped with inlet pressure compensating diaphragm for precise regulation
A metallic mesh filter protects the regulator seat from dirt contamination (filtration grade <1mm).
The impulse line is integrated inside the regulator. Special versions with external impulse line
are available on request.
Provided with pressure test points in gas inlet, outlet and air control chamber to connect
manometers, pressure switches or other equipments. On request pressure test points can be
provided with nipples Ø9 for fast connection of measuring instruments.
It is possible to provide RAGH with a bypass adjustable on-site. Bypass is useful in low fire state
when a constant low gas flow is necessary.
Pipe connections meet group 2.
Suitable for use with non-aggressive gases included in the 1, 2 and 3 families (EN 437).
Special versions for aggressive gases (e.g. biogas).
All components are designed to withstand any mechanical, chemical and thermal condition
occurring during typical service. Effective impregnation and surface treatments have been used
to improve mechanical sturdiness, sealing and resistance to corrosion of the components.
Regulators are 100% tested and fully warranted.


In fig. 1 it is described the working of
regeneratives burners: when a burner
ignites the heat exchanger is very hot, so air
warms, expands and its flow is lower.
During burner working, heat exchanger
cools and air flow increase.

In fig. 2 it is sketched a recuperative burner: when it ignites the
recuperator is cold, so air flow is higher, after some time recuperator
warms, air warms and its flow decrease. If recuperative burner are
used with pulse firing control, air flow is always changing, so a correct
gas flow is very important for an efficient combustion.
Furthermore air flow can change due to dirty accumulation on heat
exchanger: dirty reduce heat exchange and reduce air flow.

In RAGH outlet gas pressure pushes gas
diaphragm and air differential pushes the two sides
of air diaphragm. The two diaphragm are coupled
so a change in air differential pressure results in a
change of gas outlet pressure.
Figure 4 shows an example of installation in
combination with other Elektrogas devices.


Connections Gas threaded f/f ISO 7-1 from Rp1/2 to Rp2
Ambient temperature -15°C … +60°C
Gas Inlet pressure Max 500 mbar (50 kPa) or P out + 2.5 mbar for gas
P1 Differential pressure between the inlet and outlet pressure less than 100 mbar is advisable.
Air control pressure 0.5-120 mbar
P3 Gas inlet pressure has to be always higher than air control pressure
Gas Outlet pressure Air control pressure +/- 3 mbar (adjustable offset)
Accuracy ±1mbar or ±15% of air control pressure (plus offset)
Max testing pressure M Max 750 mbar at inlet chamber – max 200 mbar at air control chamber
Flow capacity See Datasheet
Bypass flow can be set from 0 to max flow (fig.7)
Filtration grade with metallic filter <1mm
Installation Horizontal (with adjustable spring downwards) or vertical pipeline.
Gas type Natural gas, town gas, LPG (gaseous) of families 1,2,3 (EN437).
On request special version for biologically produced methane without non-ferrous material and special seals.
Materials in contact with gas Aluminum alloy, Brass, Stainless steel, plated steel, Polyamide, Anaerobic adhesive, Nitrile rubber (NBR), Fluoroelastomer (FPM), Polytetrafluoroethylene (PTFE)


Datasheet : Delta-Elektrogas RAGH Air differential Gas ratio regulators

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