One of the most common and dangerous contaminants found in used hydraulic fluids is silica. This material, which is very hard and abrasive, is commonly found in soils all over the world.
As this material finds its way into mobile and stationary-equipment hydraulic systems, it can result in accelerated wear rates; the higher the level of contamination, the more aggressive the rate of wear within the components that make up the system.
For this reason, the Castrol Labcheck fluid analysis program analyzes every sample of used hydraulic oil for the presence of Silicon (Si), which is the basic element that forms silica in the environment. When silicon is detected, Labcheck reports the level in parts per million (ppm).
Labcheck wear tables utilize specific levels of Si contamination to determine when to flag a sample report as either A (Acceptable), B (Monitor), C (Abnormal), or D (Critical). These levels are based on OEM recommendations, as well as Castrol’s experience with hundreds of thousands of used hydraulic fluid samples from hundreds of different hydraulic systems.
Another very common and dangerous condition found in the hydraulic systems is the formation of foam. Foam is dangerous because it can negatively affect the performance of a system that relies on an incompressible fluid to transmit energy to various actuators and components.
Foam also makes a poor lubricant because it does not prevent wear between moving surfaces, does not cool the surfaces and does not provide a seal to prevent the ingress of contaminants (such as Silica). For this reason, hydraulic fluids are formulated with additives (known as anti-foam or foam suppressants) to suppress the formation of foam.
Castrol Trans-C and Trans-C HT products are formulated with an anti-foam additive that uses a Silicon-based polymer. This additive is identified and reported as Silicon in used oil samples of both products; this is the same element flagged for the abrasive contaminant silica, which was discussed earlier in this memo.
The level of anti-foam additive in these products will vary slightly from batch to batch and can be as high as 20 ppm. Labcheck flagging levels for Si contamination in hydraulic systems using Trans-C and Trans-C HT products are set with an understanding of this impact.
Please keep in mind that the main concern with Silicon contamination in a hydraulic system is the wear that can result from the abrasive nature of silica. If elevated Silicon levels in the fluid are causing wear, a Labcheck report will likely show corresponding elevated wear metal levels (i.e. Iron, Aluminum and Copper) depending on the metallurgy of each hydraulic system. Labcheck has also been programmed with specific wear tables for each of these wear metals; these tables are not dependent on the type of hydraulic fluid being used.
If you have questions or concerns about specific sample results from hydraulic systems, Castrol® has a team of experienced, field-based lubrication engineers that can help you to identify the right product for each application, identify opportunities to improve your maintenance practices, and help you to reduce your operational costs. Please contact your Castrol sales representative for assistance.