For engine operation, the pressure reducer located at the bulkhead throttles the CNG to the operating pressure of 8 bar in two stages. It compensates for pressure fluctuations that occur due to the emptying of the pressure vessels from a full (200 bar) to an empty pressure vessel (20 bar). The pressure reducer in this way compensates for pressure fluctuations in the high-pressure components and ensures uniform removal of CNG at constant pressure.
| 1 | Filter element (cannot be replaced) | 5 | Coolant circuit connection (pre-heating) |
|---|---|---|---|
| 2 | Piezo pressure sensor | 6 | Closure cap |
| 3 | Pressure-relief valve connection (leads to the outside) | 7 | Coolant circuit connection (pre-heating) |
| 4 | Low-pressure gas line to the distributor pipe (8 bar) | 8 | High-pressure line from the CNG tank module (200 bar) |
The pressure reducer itself does not wear and requires no maintenance. No modifications can be made to it.
Function:
The pressure reducer operates in two stages. With the high-pressure element (6) it reduces the pressure from 200 bar to 18 bar. With the low-pressure element (5) the pressure is reduced again from 18 bar to 8 bar.
The piezo pressure sensor (2) located on the pressure reducer transmits, using the system pressure, the gas quantity in the pressure vessels to the tank indicator in the instrument panel. In this way, the standard tank indicator indicates the fuel supply correctly in each of the two operating modes.
The pressure-relief valve (7) opens the system above a pressure of 230 bar and allows CNG to flow out to the outside via the drain hose. It protects the CNG system from damage which may occur when filling due to incorrectly adjusted or defective filling devices or due to an overpressure caused by a change in temperature.
The CNG passes through the pressure reducer in the following order: After the connection to the CNG high-pressure line (3) first through the filter element (4) and over the piezo pressure sensor (2) to the pressure-relief valve (7). Then to the first pressure stage (6) and over the second pressure stage (5) through the flexible low-pressure line to the distributor pipe.
| 1 | Drain hose connection (leads to the outside) | 5 | Electromagnetic cutoff valve |
|---|---|---|---|
| 2 | Piezo pressure sensor | 6 | Pressure control element, low-pressure (8 bar) |
| 3 | High-pressure line connection for CNG tank module | 7 | Pressure control element, high-pressure (200 bar) |
| 4 | Filter element (cannot be replaced) | 8 | Pressure-relief valve |
Preheating of the pressure reducer by the connected coolant circuit prevents icing of the components and permits temperature adaptation of the CNG in the optimum range.
The only components that may be replaced are the connection ports which are available as a kit from Aftersales. In the event of a malfunction, the entire pressure reducer must be replaced.
| 1 | Connection for engine coolant circuit | 4 | High-pressure line inlet |
|---|---|---|---|
| 2 | Connection for flexible low-pressure line to the distributor pipe | 5 | Safety valve connection |
| 3 | High-pressure line connection |