My company manufacture large hydraulic control systems for the offshore Oil & Gas industry and are investigating different flushing techniques.
Is there any advantage in flushing 316 stainless steel tube prior to installation into a system, i.e. before cutting and bending. It has been surgested that initial flushing, of the straight tube, will remove the manufacturing scale and other deposits from the bore of the tube. During the cutting & bending of the tube in our factory any subsequent debris would be blown out using high pressure air or nitrogen and this would therefore (possibly) reduce the amount of flushing required at the end of the build process. All other valves, actuators, etc are normally bought in pre-flushed to NAS 6. Has anybody attempted a similar technique?

We have found that blowing a foam hose projectile through tubes or hydraulic hoses to be more effective at cleaning out debris and contamination, than just blowing air or flushing some fluid through. These projectile guns are easy to use and will go through some very long lengths even with curves and bends. Flushing techniques are a little beyond my knowledge but I would think that insuring you have a sufficiently high enough Reynolds number would be a key factor to look at.

Tony,

Of course there are benefits, the cleaner the components are at instalation time, less work to do before start running the system.
Keep in mind that "prevention" is allways cheaper than "correction"

Dear Tony

In order to have a sucesfull flushing for the hydraulic system (prior to installation, or before the start up, or both), the main points you must reach are:
- High Speed of Oil.
- Low viscosity of the oil (lower than the current operation oil). You can reach this with high temperature of the oil with heaters.
- High Efficiency of the filters (Beta 3 > 200).
- Oil Analysis on site.
- NAS 5 or lower (ISO 16/14/11).
- Vibration in the tube (pneumatic vibrators of hammering).

A last comment is that in the start up and comissioning of Equipments in Offshore Oil & Gas Industry, the lower time you spend in Flushing Tasks, and the best ISO Code you reach, mean a lot of money for the final user and the OEM.

For this, your flushing step in the Factory is very important.

Regards