30
Rev. 09/2022
6.1
Start-up
Explosion hazard!
If the system is not entirely tight and sealed, the combustible gas mixture
may escape and result in an explosion hazard. Always check the tightness
of the system before start-up. Upon completion of your works, make sure
that you close the gauge port on the VariFuel3.
Operational safety!
Contaminated gas can lead to blocking of the fuel ring and thus can cause
the gas engine to stop. Examine the VariFuel3 regularly for contamination
as a part of the regular maintenance intervals customary for your system.
Use clean gas preferably.
Basic Settings of the System
With an ideal design, the VariFuel3 gas mixer is operated in a range between 15 % and 80 % of
the fuel ring’s opening. In this way the prescribed emission values should be complied with at
nominal load. For the engine start, additionally specify a suitable start position in the master
control.
The VariFuel3 gas mixer is a Venturi mixer. For optimum performance according to its design, it
is important that air pressure and gas pressure are equal, so that the gas is sucked in by the
Venturi effect alone. Therefore, operate the VariFuel3 gas mixer solely with a balance or zero
pressure regulator connected to the air inlet of the VariFuel3 via the impulse line connection of
the VariFuel3. Also, adjust the balance/zero pressure regulator in such a way that the balance/
zero pressure regulator equalizes the gas pressure with the air pressure. Otherwise, if the con-
nection or adjustment is incorrect, the gas will be forced into the gas mixer and not sucked in
alone, which can lead to a performance loss.
Problems When Starting
Often the gas engine's problem is its starting performance. With the starting speed the air speed
in the gas mixer is very low, which will cause very low suction pressure at the gas inlet. This can
lead to not enough gas being sucked into the engine to make the mixture ignite. The following
procedures may be helpful:
–
MOTORTECH recommends to start with an opening of the fuel ring of 30 % to 35 %. If the
engine does not start, open the fuel ring in steps of 1 to 2 %.
–
For gases with low fuel value, it may be necessary to set the balance/zero pressure regulator
to a slight overpressure (max. 5 mbar for starter speed) for the engine start phase. Do not
set the overpressure too high, because too much gas content in the engine can lead to start
problems. As soon as the engine is running, set the balance/zero pressure regulator back to
pressure balance in idle at nominal speed. This setting guarantees that adequate suction
pressure exists at the gas inlet at engine start.
6 Operation