General information on leak testing for natural gas systems - AH07.54-P-0001-01AN

WARNING: This page does not describe the selected car, but rather 202 other vehicles, including the 2020 Mercedes-Benz SLC300, 2020 Mercedes-Benz SL550, 2020 Mercedes-Benz SL450, 2020 Mercedes-Benz GLA250, and 2019 Mercedes-Benz SLC300. However, it is still accessible from the selected car via links, so may be relevant.

ENGINE 266 in MODEL 245 with CODE 924 (Bivalent natural gas drive)

ENGINE 270 in MODEL 242 with CODE 924 (Monovalent natural gas drive)

ENGINE 271 in MODEL 211, 212 with CODE 924 (Bivalent natural gas drive)

ENGINE 274.9 in MODEL 212 with CODE 924 (Provision for natural gas operation)

Personnel requirements:

As a prerequisite to testing, testing personnel must be qualified and competent to perform leak testing as per the country-specific regulations and laws (possessing at least a certificate or proof of competence for gaseous fuel vehicles).

Safety information regarding the handling of natural gas vehicles must be adhered to.

Personal injury and/or damage to equipment and environmental damage can occur otherwise.

Measurement performance requirements:

Leakages that can be detected by hissing/whistling noises must be removed immediately.

Personal injury and/or damage to equipment and environmental damage can occur otherwise.

An electronic gas trace instrument is used to perform the measurement. The gas trace instrument only serves as an auxiliary aid however.
Measuring instruments must be calibrated regularly as per the manufacturer's instructions.

An electronic gas trace instrument (gas tester) is not capable of recognizing leakage; it can only measure gas concentration. However, the gas concentration can have a number of causes such as natural porosity (permeation) of the lines, accumulation in undercuts, leakage, etc.. One should also note the fact that the devices are generally naturally aspirated, which also means that unpressurized concentrations (no leak) can lead to a measuring value being displayed. It is therefore necessary to confirm a suspected leak using a second measuring method with a leak detection spray.
All components and the connecting points for the high-pressure gas lines and low-pressure gas lines must be checked. The measuring points must always be cleaned using compressed air before the measurement starts. Care must be taken here to ensure that any concentrations of gas are reliably blown away from the measuring point.
The gas components must be checked at various pressures as per specifications.
During measurement ensure that the measuring points are checked with a calm hand, with a uniform distance of 1 to 2 mm to the measuring object and a period of 10 s per revolution.
For measurements < 20 ppm the measuring point is to be designated as sealed.

For measurements > 20 ppm the measuring point is not necessarily leaky, but it is simply that a higher gas concentration has been determined.
In order to clearly recognize a leakage at a measuring point with a measurement > 20 ppm, it is necessary to search around the measuring point using leak detection spray.
Only leak detection sprays specially approved for natural gas may be used.

False measurements can occur otherwise.

The measuring point must be monitored over a period of 3 minutes. If there is no blistering or foam present during this period, then the measuring point is sealed.

In case of leaks, the union nuts at high-pressure gas lines may only be retightened as per specifications once after initial assembly. Personal injury and/or damage to equipment and environmental damage can occur otherwise.

If the line connection is still not leaktight after retightening as per specifications, then the high-pressure gas line must be replaced.