Our tests show that the filterability of some oils is affected simply by water contamination and it is generally accepted that most systems will contain small amounts of water. Condensation can occur in the reservoir due to atmospheric conditions, storage of drums outdoors can allow breathing in of rainwater, and leaky water coolers all contribute to the ingress of water in a hydraulic system.
As far as calcium is concerned, it is clear from laboratory tests that only a few ppm of calcium in the presence of water is required to give rise to filterability problems with some oils. Many industrial environments carry airborne calcium. Calcium is a commonly used additive in engine oils and cross contamination between engine lubricants and hydraulic oils is not uncommon. Hardness salts in town water contain calcium, therefore contamination of a system with water via a cooler provides another source of calcium.
The reality is that the combination of water and calcium in a system is in fact quite likely, so you need an oil that can deal with this.
