Hose Cleanliness – affects Valves, Pumps, System cooling

Valves: Microscopic contamination (similar to erosion) can mill away tolerances which are used for sealing purposes. On spring centering valves, the debris may get caught between the valve and the wall surface. The contamination will cause the slowing down of the motion of the valve or causing sluggish or adverse mechanical actuation.

Abrasive particles enter the clearances between moving parts they score and hone the surfaces to greater tolerances. As these tolerances broaden, system performance is compromised by pressure losses incurred due to fluid leakage from high to lower pressures.

The worst occurrence is when particles that are greater than or equal in size to the orifice openings become wedged between the two surfaces. The contamination may cause wear to occur or it may cause the system components to seize.

Pumps & drives: Microscopic contamination can mill away material, creating leak points. These leak points rob the hydraulic system of pressure and cause poor responsiveness.

System cooling: Working fluid may not flow through to remove contaminants generated from metal to metal contact when passages become blocked. Lower flow rates mean greater heat buildup in systems and thermal breakdown of the working fluid.

 

Hose Cleanliness - Origin of Contamination

Origins of contamination may be from system components, the hydraulic working fluid, the outside environment, or be generated by the system itself. These contaminants, some large and some microscopic, can have a profound impact on the performance and longevity of the hydraulic system.

There are three principal means through which contamination can

occur in a typical hydraulic system. 

Contamination can be:

1.    Generated during system operation

2.    Built into the system during assembly

3.     Ingested by the system during operation

 The working fluid in hydraulic systems should be as homogeneous as possible and free of all visible and microscopic debris for optimum performance. The complete absence of contamination in hydraulic systems is unrealistic, but an acceptable and defined level of contamination is generally considered hydraulic system cleanliness. The best approach to cleanliness is to prevent contamination in the first place. Use clean hose and couplings and keep them clean (i.e. cap ends). Clean hose bore after cutting to length as cutting hose to length is a major contributor to contamination.

Blast from the Past

This old technical note surfaced recently from a Product Application department discussion.  While dated, it does point out that a good technique for evaluating vibration is to determine if there is vibration present beyond the belt drive system.

Learn the Terminology - Fluid Power

Compressibility:  The change in volume of a unit volume of a fluid when subjected to a unit change of pressure.

Contaminant:  Any material or substance that is unwanted or adversely affects the fluid power system or components or both.

Corrosion: The chemical change in the mechanical elements caused by the interaction of fluid or contaminants or both. More specifically related to chemical changes in  metals. The products of change may be introduced into the system as generated particulate contamination.