Biogas Safety first!

Specific requirements
Ensure gas production, e.g. by regular
feedstock input
Ensure that the enclosure is leak-tight
and stable
Monitor the fill level of the substrate and if
necessary shut off withdrawal from the liquid
phase (gas isolation point)
Ensure operation with positive pressure even
in the event of a sudden drop in temperature,
e.g. by means of
i. suitable gas displacement with respect
to the gas storage tank(s)
ii. constant monitoring of gas overpressure
in the interior and gas withdrawal
iii. sufficiently variable volume of the gas
storage tank
In addition, where inflatable double layer roofs
are used: ensure that the supporting air pressure
is lower than the pressure in the gas storage
tank, and ensure that the inner membrane is
leak-tight and stable.
No zoning necessary, unless the manufacturer’s
instructions specify different classification of
zones.
In the event that the above-mentioned requirements
are in place without all measures to monitor and
safeguard positive gas pressure being implemented,
the following conditions apply:
The occurrence of potentially explosive atmospheres
is identified, and measures are taken to
ensure that such atmospheres occur only rarely
and for short periods.
Zone 2: above the surface of the substrate in
the interior
Foreseeable disruptions or process-related operating
states that occur occasionally can allow air to
enter the interior of the digester, resulting in concentrations
falling below the UEL.
The occurrence of potentially explosive atmospheres
is occasionally possible.
Zone 1: above the surface of the substrate in
the interior
Agitators and ducts for agitator shafts and adjusters
for agitators, e.g. cable mechanisms
Submersible-motor agitators and submersiblemotor
pumps should comply with degree of protection
IP 68 according to DIN EN 60529. Material
requirements relating to corrosion, shear forces and
thermal stability should be taken into account when
selecting the agitators.
Ducts, technically leak-tight, in combination
with regular checks and maintenance, or the
agitator penetration below the surface of the
liquid/substrate.
No zoning necessary.
Ducts, technically leak-tight and above the
surface of the liquid/substrate.
Zone 2: 1 m around penetration.
Overflow aid
Overflow aid with screw conveyor.
Zone: as in downstream gas space.
Pressure surge overflow aid with physical limitation
of the injected air (volume limitation and
flow rate limitation).
Zone 0: in the pipe and in the vicinity of the
overflow.
Pressure surge overflow aid without physical
limitation of the injected air.
Zone 0: in the pipe and in the digester.
Surroundings of sight glasses in inside spaces
Bull’s eyes and observation windows must be
fitted in a leak-tight mounting in the digester
and permanently technically leak-tight according
to manufacturer’s declaration.
No zone.
Sight glass technically leak-tight, routine leak
checks in accordance with manufacturer’s
instructions.
No zone.
Sight glass technically leak-tight, but no routine
leak checks.
Zone 1: immediate vicinity.
Zone 2: remaining area.
Digestate storage with connection to gas system
Prevent air entering the gas system in the following
ways:
Ensure operation with positive pressure even
during removal of digestion products, e.g. by
constant monitoring of gas overpressure in the
interior and shutting off gas extraction pipes and
extraction points from the liquid phase;
Planned, monitored removal of digestion products,
especially by
ZZ
ensuring gas supply,
ZZ
visual inspection for ethylene propylene diene
monomer (EPDM) rubber membranes or gas
fill level monitoring for double membrane
systems or rigid gas storage tanks,
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