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A flush generally means the internal cleaning of a machine with the use of a fluid as the cleaning medium. While this sounds like a simple task to accomplish, problems can arise for which you should be prepared.
There are several factors to consider when beginning a flushing project. Understanding how the oils being used interact with each other is paramount to the success of this procedure. In most cases, a flushing fluid will be utilized. If the equipment manufacturer has flushing procedures, they should be considered during this process.
ASTM D6439 describes a successful flush as being when “clean pipe and system components are obtained in a minimum of time and with a minimum of effort.” Therefore, the goal should be to efficiently remove the old oil in a timely and cost-effective manner.
The same ASTM standard also recommends a high oil velocity, at least two to three times the normal system velocity, for a successful oil flush. This is consistent with many procedures written by professionals on this topic. Turbulent flow through the system removes the majority of oil left in gathering places. Some components may be too sensitive for a high-velocity flush. These components should be bypassed and cleaned by other means.
The fluid used for flushing is another point for consideration. A fluid that won’t react chemically with the oil it will be replacing should be sought. Incompatibility between these fluids can form particulates that can be deposited throughout the system.
After flushing, displacement oil should be used to remove any remaining flushing fluid. The displacement oil should be compatible with and approximately the same viscosity as the operating charge to be installed. Flushing fluids and oils should be heated to maximize their ability to flow and their ability to absorb and dissolve contaminants within the system.
Many different types of flushing procedures can be used. Hydroblasting procedures are becoming more prevalent. In this type of flush, water is used in high velocities to spray the inside of the machine to clean and purge the system of oil and other contaminants. Dry, clean and compressed air is then introduced to push out the water and dry the system. The new oil is then introduced. This, coupled with traditional flushing techniques, makes the process more reliable.
A variety of companies specialize in the flushing of complex machine systems. Depending on the complexity of the flush or the manpower available to properly flush a system, these companies offer a great alternative to utilizing onsite labor.
Remember, a proper flush is very important to the health and reliability of a machine and should always be done with the sensitivity of the machine’s components in mind.