Reference Filter Weighing Clause Samples

Reference Filter Weighing. The chamber (or room) environment shall be free of any ambient contaminants (such as dust) that would settle on the particulate filters during their stabilisation. Disturbances to weighing room specifications as outlined in paragraph 1.5.2.1. will be allowed if the duration of the disturbances does not exceed 30 minutes. The weighing room should meet the required specifications prior to personnel entrance into the weighing room. At least two unused reference filters or reference filter pairs shall be weighed within four hours of, but preferably at the same time as the sample filter (pair) weighings. They shall be the same size and material as the sample filters. If the average weight of the reference filters (reference filter pairs) changes between sample filter weighings by more than ± 5 per cent (± 7.5 per cent for the filter pair) of the recommended minimum filter loading (paragraph 1.5.1.5.), then all sample filters shall be discarded and the emissions test repeated. If the weighing room stability criteria outlined in paragraph 1.5.2.1. is not met, but the reference filter (pair) weighings meet the above criteria, the engine manufacturer has the option of accepting the sample filter weights or voiding the tests, fixing the weighing room control system and re-running the test.