This case study explains how a FRIESS EFR D4 electrostatic oil cleaner purified the hydraulic oil used on pressure-vessel test benches. Fine particles and oxidation products had accumulated in the test oil, leaving residual contamination inside the vessels and increasing warranty risk at customer sites.
A filter manufacturer produces pressure vessels with capacities ranging from 50 to 500 litres. Cast blanks are machined and then washed to remove contamination from inside the filter housings.
After washing, the components are leak-tested with HLP 46 hydraulic oil. The plant operates three test benches, each filled with 2,000 litres of oil. Because every tested component carries out a small quantity of oil, the test oil is not replaced; fresh oil is added regularly only to make up for these process losses.
Oil analysis showed that the test fluid remained heavily contaminated despite the existing filtration system. During residual-contamination analysis, quality assurance traced the contaminants found inside the pressure vessels back to the polluted hydraulic oil.
To reduce residual contamination after pressure testing—and thereby reduce warranty incidents at customer sites—the cleanliness of the test oil had to be improved.
The hydraulic oil was already passing through high-quality fine filters, so the maintenance and quality-assurance teams looked for a cleaning method based on a different principle. The maintenance manager had achieved excellent results with electrostatic oil cleaning in a previous role, leading the company to install a FRIESS EFR D4 electrostatic oil cleaner.
When the unit was commissioned, the maintenance manager took a sample for membrane-patch analysis. A normal test passes 30 ml of oil through a 0.8 µm membrane, but the heavy load of coarse particles and oxidation products completely blocked the membrane after only 10 ml.
Because the contamination load and ongoing contaminant ingress were both high, FRIESS recommended an initial cleaning period of at least three months.
The first follow-up after only two weeks showed a substantial improvement in oil condition: oxidation products had fallen sharply, and the number of coarse particles was markedly lower.
Test membrane after filtering only 10 ml of oil
The cleaning result was so convincing that the maintenance department equipped all three test benches with an EFR D4 electrostatic oil-cleaning system. Quality assurance subsequently recorded far fewer defects caused by residual contamination.
