The plant manager was interested in evaluating different filter efficiencies and media types. While the current E12 filters offered greater engine protection than the previously used M6 filters, the manager was uncertain if they were the optimal solution for the local site conditions and operational needs. Camfil was asked to perform the validation with an on-site CamLab test, followed by an engineering lab analysis.
Site Conditions
The plant is situated by a major freeway in an industrial area that is home to large refineries and petrochemical plants. Although a low dust area, the turbines are exposed to small hydrocarbons and fine particulate. Further, the plant is located right by the Pacific Ocean. This exposes the turbines to heavy rolling fog with a high concentration of salt. Sufficient filtration protection is therefore require to prevent degradation, and filter media should handle high humidity and salt.
The Test
Each turbine at the plant has 720 cartridge filters, rated E12, which is the highest efficiency class commonly used for gas turbine air inlet filters. In an effort to optimize filtration to the environmental conditions, and to minimize the risk of high pressure drop (dP), the current E12 solution was tested against three lower efficiency products: the Tenkay GTC F9 cartridge filter supplied by Camfil, and two different cartridge filters supplied by other global filter companies.
A CamLab, a portable lab for testing filters, was commissioned on site for 3-months. The measured parameters included airflow, filter dP, filter efficiency, ambient temperature, and ambient relative humidity.
At the end of the test, the four filters were sent to Camfil’s test lab located at the Montreal Test & Learn Center where they were retested to validate the results from the CamLab test.
Pressure drop values in Table 1 indicate that the Tenkay GTC and Filter D had the lowest dP, however, Filter B had a 22% higher dP, while Filter A had a 15% higher dP at the end of the on-site testing.
Once the CamLab results were verified, the filters underwent additional comparative tests at the engineering lab: pre- versus post-discharge efficiency, and a deluge test.
Discharged Efficiency
The filters were discharged to indicate their true efficiency class. Table 2 outlines the filters’ discharged efficiency, showing that the Tenkay GTC was the only filter that remained in its efficiency class once discharged.
Deluge Test (Water Spray Test)
Finally, a deluge test was performed, where water was misted on each of the loaded filters from the CamLab test. The results show the difference in sensitivity to simulate rolling fog events of the site between the four filters. It also indicates the relative magnitude of the pressure increases that would be expected when seasoned with contaminants and exposed to precipitation over time.
The test was performed until dP across the filter reached 5" w.g. or 3 hrs. had passed, whichever occurred first. The results of the test are shown in Figure 1, indicating that the Tenkay GTC F9 filter was the only one that successfully lasted 3 hrs. and had the lowest dP at 1.9" w.g.
Table 1: Pressure Drop Results
| Filter |
Pressure Drop inch w.g. (@700 CFM) |
| Filter A (F9) |
0.79 |
| Filter B (E12) Current |
0.84
|
| Tenkay GTC (F9) |
0.69 |
| Filter D (E10) |
0.69 |
Table 2: Discharged Efficiency Results
| Filter |
Discharged Efficiency (EN779:2012 EN1822:2009) |
| Filter A (F9) |
F7 |
| Filter B (E12) Current |
E11 |
| Tenkay GTC (F9) |
F9 |
| Filter D (E10) |
F9 |
Note that for an E10, E11 or E12 filter rating by EN1822:2009, efficiency at the Most Penetrating Particle Size (MPPS: typical range from 0.08-0.15 µm) must be over 85%, 95% or 99.5% respectively on discharged filters.
Note also that for an F9 filter rating by EN779:2012, efficiency at 0.4 µm must be greater than 70%.
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