Biogas Safety first!

Upgrading of biogas to biomethane
The relevant qualifications held by the responsible
operators and the personnel assigned to the work
must also meet national requirements. The same
applies to specialised companies involved in the
planning, construction, operation and maintenance
of the plants. Regular training measures should be
obligatory in order to keep technical knowledge upto-date
with the latest findings and technical requirements.
For organisational reasons it is advisable to
draw up a plan of the organisational structure for the
plant as a whole.
In addition, a plan of organisational procedures
should be drawn up (recording of faults: checking,
causes etc.) along with operational documentation
(briefings, inspections, tests, incidents, work instructions
etc.).
To be documented:
briefings and instruction sessions held
inspections
and tests
incidents
work instructions
Technical protective measures
The odorisation (addition of an odorous substance as
a warning) of natural gas/biomethane is an important
safety measure because purified natural gas/biomethane
is almost odourless. In order to ensure that leaks
in pipes or parts of the indoor gas installations are noticed
promptly, for safety reasons specific prescribed
warning odours are added to the natural gas/biomethane.
The smell of the odorised gas must therefore
not be familiar to people from their everyday lives, for
example from kitchens or a domestic setting.
The upgraded biomethane must be adapted in accordance
with the odorisation requirements of the
gas grid into which it is to be injected. This usually
involves the use of highly volatile, typical-smelling
organic sulphur compounds such as tetrahydrothiophene
(THT), which smells like rotten eggs, and mercaptan
mixtures.
National regulations must be observed in the planning,
construction and maintenance of pipework in
biomethane plants and external areas, and in the selection
of materials. All such work must always be
carried out by specially trained personnel.
The choice of plant components should be made according
to practical requirements at the plant (gas
quality, corrosive constituents of the gas, internal
pressure, climate, geographical location). Potential
deformation, deflection and linear expansion must
be taken into consideration when installing the
pipes, in accordance with site-specific regulations. If
it is expected that condensate will be formed (mainly
applicable to biogas pipes), the pipes should be laid
on a gradient and fitted with condensate separators
at the low points of the installation.
It is particularly important that building entry points
for gas pipes are corrosion-resistant and strain-free.
Pipes carrying gas must always have corrosion protection,
ignition protection and equipotential bonding,
and they must be clearly identified by colourcoding
or labelling.
If gas pipes are potentially exposed to mechanical
damage (for example from vehicles or other traffic),
they must be protected accordingly by collision impact
protection guards. If gas pipes are laid on land
belonging to a third party or public property, permissions/concessions
for crossing the land (e.g. roads
and railway lines) and laying the pipes must be taken
into consideration.
Gas pipes must be checked to ensure they are in
faultless condition prior to installation. National
guidelines regarding pipe covering, pipe routing and
filling of the pipe trench (e.g. in sloping locations)
must be observed.
Gas pipes must be subjected to a pressure test after initial
installation and after any significant changes, with
due consideration for the relevant regulations (test
procedure, test duration, test medium, test pressure,
person permitted to perform the test etc.). If the operating
pressure changes during use, any regulations
relevant in such circumstances must be observed.
Documentation for pipes:
details of the design of the gas pipes
(pressure, nominal diameter ...)
structural analysis records
certificate of competence from the
executing companies
up-to-date working drawings and
plans of present inventory of facilities
and equipment
pipe book (documentation of welding
work, verification of quality
requirements)
test reports / acceptance certificate
56