Piping Systems
The piping system connects the biogas plant with the gas appliances. It has to be safe,
economic and should allow the required gas-flow for the specific gas appliance. Galvanized
steel (G.I.) pipes or PVC-pipes are most commonly used for this purpose. Most prominently,
the piping system has to be reliably gas-tight during the life-span of the biogas unit. In the
past, faulty piping systems were the most frequent reason for gas losses in biogas units.
PVC piping
PVC pipes and fittings have a relatively low price and can be easily installed. They are
available in different qualities with adhesive joints or screw couplings (pressure water pipes).
PVC pipes are susceptible to UV radiation and can easily be damaged by playing children.
Wherever possible, PVC pipes should be placed underground.
Figure 26: Final touches on a piping system with PVC pipes
Photo: Krämer (TBW)
Galvanized steel piping
Galvanized steel pipes are reliable and durable alternatives to PVC pipes. They can be
disconnected and reused if necessary. They resist shocks and other mechanical impacts.
However, galvanized steel pipes are costly and the installation is labor intensive, therefore
they are only suitable for places where PVC is unavailable or should not be used.
Pipe diameters
The necessary pipe diameter depends on the required flow-rate of biogas through the pipe
and the distance between biogas digester and gas appliances. Long distances and high flow-
rates lead to a decrease of the gas pressure. The longer the distance and the higher the flow
rate, the higher the pressure drops due to friction. Bends and fittings increase the pressure
losses. G.1. pipes show higher pressure losses than PVC pipes. The table below gives some
values for appropriate pipe diameters. Using these pipe diameters for the specified length
and flow rate, the pressure losses will not exceed 5 mbar.
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