Oil Flushing System
The objective of flushing a hydraulic, turbine system etc is to eliminate sludge, varnish, debris and contaminated or degraded fluid from conductor walls and other internal surfaces and system dead spots. Reasons for performing a system flush include: 1. Fluid degradation - resulting in sludge, varnish or microbial deposits. 2. Major failure - combined with filter overload disperses debris throughout the system. 3. New or overhauled equipment - to purge 'built-in' debris
Contaminants such as water, rust, loose scale, weld slag, sand, dirt, and oils are removed from the system with a proper pre-operational cleaning, reducing the wear, scoring, and damage bearings, control valves, instrumentation, and critical operating systems are subjected to. Insoluble particles can become trapped in the bearings of rotating equipment and cause significant damage. The dynamic oil film thickness in rotating bearings can be less than a micron, so it is imperative to remove particulate from lubrication systems down to a microscopic level.
Flushing of hydraulic and lubrication oil systems is employed to ensure that new rotating and hydraulic equipment will start up and operate as designed, significantly reducing the potential for premature failure. Maintenance and downtime on equipment can be minimized by performing an effective system cleaning during commissioning and following periodic maintenance and repair services. Any facility that has a low tolerance for failures can use this service key pillar for their preventative maintenance program. When performing a cleaning job, DVT designs the flushing paths in loops to maximize flow rates throughout the system. It is important that all parts of the system see turbulent flow regimes. Turbulent flow occurs when the Reynolds number is greater than 4000.
Generally, most hydraulic and lubrication oil systems are designed for “laminar” flow. This calls for constant operation without cavitations or vibration. Efficient flushing, however, requires turbulent flow in order to dislodge impurities deposited on the inside of the pipe system. Flushing must be performed after pipe installation, but prior to system operation. For an oil flush to be successful, efforts to keep contaminants out must succeed and the flush must be conducted properly. A successful flush ensures that system piping and components meet acceptance criteria for a minimum length of time with a minimum of effort.
The three most important parameters in flushing are:
- Flushing filters
- Flow velocity
- Viscosity/temperature
Flushing is most effective when flow velocity is relatively high and/or viscosity relatively low, creating turbulent flow in the pipe system during flushing.
If RE < 2000 the flow will remain laminar.
If RE is between 2000 and 4000 the flow will be “disturbed” turbulent.
If RE > 4000 the flow will always be turbulent.
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