The over-pressure, under-pressure valve is connected with flanges to the gas system. It has top and bottom a connecting flange to the gas line, so that it can be connected to either the top or the bottom (see figures in the sections gas supply in series (in-line) and gas flow in parallel) The gas supply can be effected through the under-pressure valve (inline), or parallel to the valve.
In the case of in-line operation a second gas pipe should always be available to the container in order to allow outflow even during maintenance work on the over-pressure, under-pressure valve.
Furthermore, the gas should not be sucked by means of a compressor through the valve, resulting in under-pressure even at normal operation. This applies particularly for membrane covers without supporting air pressure.
By connecting gas pipes there must be no strain or compressive forces acting on the valve, for example due to temperature expansion, subsidence, weight of the line or vibrations. Expansion joints should be used if needed.
Inline gas flow
When connected in series with the gas line (A1, B1), the over- / under-pressure valve is traversed by the gas from the fermenter - from top to bottom or from bottom to top. For in-line operation the valve with the gas inlet line (4) is connected to the fermentation tank, and with the gas outlet conduit (12) to the CHP (power cogeneration).
If the connected fermenter has no second gas port with connection to the gas consumers, the gas pipe should be fitted with a bypass pipe, so that during maintenance work on the under- and over-pressure valve, the gas can be directed to the gas consumer.
Parallel gas flow
During parallel operation, the valve is connected to the gas intake line on the fermenter.
In options A1 and B1 flow through of the valve can take place to provide heating.
In options B1 and B2 care should be taken to ensure that the response behaviour of the valve can be influenced by strong suction of gas, particularly without pre-pressure of supporting air.
|1||Gas pipe||5||½"-socket||9||Air inlet|
|2||Service-opening||6||Valve body||10||Blow off pipe|
|3||gas outlet with gas valve||7||Insulation||11||Immersion Pipe|
|4||gas inlet||8||Inspection glass||12||Flange cover|
Frost protection and deployment conditions
The over- and under-pressure valve is heat insulated.
By mounting the over- and under-pressure valve directly to the wall of the digestor, it is ensured that heat can be transferred to the valve. Additionally the valve is heated by the flow of the hot biogas from the fermentation tank.
In vats or fermentation containers with fermentation temperatures below 35°C, the valves (in-line) are connected inline to the gas system. Thus the produced gas flows through the valve completely and keeps it warm.
An antifreeze agent must be added to cold gas for initial filling of a cold tank wherever there is an imminent risk of frost.
In addition, the valve can also subsequently be equipped with a self-regulating explosion-proof heater.