Test Procedure for Filtration Grade of Microirrigation Filter

Microirrigation filters are import to agricultural irrigation systems, while the filtration grade of a filters is an important parameter that can assist to the utility of a filter.

Verification of filtration grade of a filter is intended to be used for verifying the filter manufacturer's declaration about the filtration grade of a specific filter. And the test method may also be used by a filter manufacturer to determine the filtration grade.

This test method uses a Clogging Capacity Meter (CCM) device to compare the filtration grade of the filter under test against the filtration grade of a test filtration screen.

The Test system layout for Verification of filtration grade

Prepare the test system as per Figure 1.

Key

1. pressure point – data logger;
2. filter to be tested Φ1”;
3. water meter Φ1”;
4. flow regulator Φ1”;
5. pressure reg. valve Φ1”;
6. connection union P.E. Φ32;
7. connection union P.E. Φ32;
8. ball valve Φ1”;
9. water checkpoint – CCM;
10. water inlet;
11. water outlet.

Figure 1 — Test system layout

Test procedure for Verification of filtration grade

Adjust system inlet pressure to 4.0 bar, while water flow to the CCM units is blocked.
Allow water to flow through the test system. Adjust the flow rate through the tested filter to the mid-point of the flow rate range declared by the filter manufacturer. Then adjust the pressure at the system inlet to between 3.0 bar and 4.0 bar.
Record the pressure upstream and downstream of the filter and calculate the pressure loss across the clean filter.
top the water flow in the system. Replace the filter medium with a new, unused medium of the same type and characteristics.
Resume water flow in the system and open the valves to both CCM units.
Continuously monitor the increase in pressure loss across the tested filter and across each CCM unit.
Record the time required to reach a pressure loss of 0.5 bar in the upstream CCM (t_up) and in the downstream CCM (t_down). Calculate and take note of the t_down/t_up ratio.
Replace the screens at both CCMs.
If the pressure loss across the test filter exceeds the pressure loss recorded in the clean state by 0.5 bar (see 3. above), abort the test.
Repeat 5 to 9 nine more times, then terminate the test.
Calculate the average of all recorded t_down/t_up ratios. If the result is equal to or greater than five, the filtration grade declared by the manufacturer is correct.

NOTE: Consider the discontinuation of the test if a pressure loss of 0.5 bar is achieved in less than 30 s and if a pressure loss of 0.5 bar in the upstream CCM is not achieved within 60 min.

About the terminology in this article, please refer to Filters Filtration Grade - Verification and Determination.

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