Maintenance
2.6.1 Sampler
Maintenance of the sampler is required from time to time. Special attention should be paid to:
• Rotameter flow rate: It is recommended to check the rotameter flow rate once per month. The rotameter flow rate should be about 10% higher than the flow rate observed on the volume meter.
• Open flow test and leak test: It is recommended to check for optimal flow conditions from time to time. Depending on the sampling location and the setup of the sampling station, this test should be performed once a week or at least once a month.
The following procedure is recommended:
A. Fully close the valve – the rotameter flow rate should be zero (0), the vacuum should read about -0.8 bar and the volume meter gauge should not move. If these three conditions are fulfilled, the tubing from the valve to the pump is ok. If the conditions are not fulfilled, the tubing from the valve to the pump is not vacuum tight. Start searching for the vacuum leak and repeat test A as long as conditions are fulfilled.
B. Fully open the valve and no SFU connected - By closing off the transparent tubing temporarily, e.g. with a small rod or even a finger, the rotameter flow rate should again be zero (0) flow rate, the vacuum should again read -0.8 bar and the volume meter gauge should not move. If these conditions are fulfilled, the tubing from the SFU to the pump is ok. If the conditions are not fulfilled, the tubing from the SFU to the valve is not vacuum tight. Start searching for the vacuum leak and repeat test B as long as conditions are fulfilled. Cause of the vacuum leak can for example be that somebody stepped on the fragile POLY-FLO tube (mechanically deformated) or put a heavy weight on the tube. Replace the leaking part of the tube before commencing air sampling. Repeat test B until conditions are fulfilled. Page: 18
The tubing will also become brittle from exposure to sunlight and should be replaced periodically.
C. Connect the SFU without loaded filters and check that the flow rate is setup to 16 – 17 l/min by manually adjusting the valve. Test C is probably the most important test because this test reveals if there is a problem with the tubing from the SFU to the valve and to the pump. However, all three tests must be performed regularly to ensure a proper operation of the air sampling unit.
2.6.2 Black polyethylene container
Cleaning of the container is required on a regular basis, e.g. every 2-4 weeks. Take the container apart and clean it with water and ethanol. Figure 9 shows overview and detail images of the assembled black polyethylene container.