Knowing the difference between oil flushes, when to use which, and the proper terminology to describe them is key to extending your equipment life. While our certified field technicians are exceptional at making sure the right flush is applied every time, it is important to us that our customers understand what is happening with their lube oil and are integral part of the overall oil cleanliness management plan.
The main categories of oil flush are:
1. High Velocity Flush
With a descriptive, memorable name, this is the type most customers have heard of. It is the best approach to take during all major maintenance, system failures, or when you large amounts of contaminants/debris are in the system. It is the most effective at removing all lingering materials and particles. High velocity flushes create chaotic flow within the system, breaking off and removing any unwanted, clinging debris. The violent nature of this action requires that bypasses for sensitive system components such as pumps, valves, bearings, orifice plates, accumulator bindings etc. are protected during the flush. Verify results with inspection screens/media and particle counts.
One misconception about this process is that high velocity occurs when high turbulent flow is achieved. While turbulent flow can be achieved at Reynolds numbers around 4,000, this is normally not enough turbulence to remove all damaging debris. Most high velocity flushes target a Reynolds number of 20,000 or 2-3 times the normal system flow rate.
2. System Flush
Most appropriate for light maintenance work and non-critical systems, this flush utilizes system pumps. Like with high velocity flushing, all critical components should be bypassed with jumper hoses and protected. Using system pumps to flush out foreign material will take longer than using an external pump, which is why this method is not recommended for turnarounds or maintenance with a strict deadline.
3. Circulation Filtration
A system in production can undergo circulation filtration, with pumps running in the normal flow pattern. Circulation filtration is limited in scope, but can successfully clean reservoirs or aid in filtering/changing lubricants. External filtration off a reservoir is the typical approach. It is appropriate for annual maintenance, but not for any outage that includes pipe breaks or the opening of bearing housings. Verify results with a lab analysis or field kit.
When changing lubricants or displacing cleaning chemicals (including detergents), a rinse/purge flush is often utilized. The procedure includes draining the system, refilling the reservoir to the minimum circulation level, and then using the system pumps to circulate oil in a normal flow pattern. Usually only a particle count is needed to verify, but labs or field kits may be used if employed during a varnish mitigation procedure.
We always recommend consulting with an oil flush expert if you are unsure which oil flush is appropriate or how to remove contaminates from your system. However, you should have an annual maintenance plan that involves regular lube oil flushes to control ISO cleanliness levels. If you don’t have one in place now, speak to one of our certified technicians about mapping one out and getting into place, or check out our blog on how to develop one.
Source: Larry B. Jordan