Hot Oil Flushing Methodology

What is Hot Oil Flushing?

Hot Oil Flushing (HOF) is designed to remove contaminants from the manufacturing process/transportation/site assembly, or a contamination event during operation, of a lube oil circuit, by flushing hot oil through the circuit at a minimum of 150% of its operational flow rate, achieving a minimum of Reynolds 4000 number, a unit of measure for turbulent flow. The theory being that contaminants such as pipe scale, welding slag and particles, are removed at 150% of operational flow and won’t contaminate the system at operational flow rate.

So what is the purpose of Hot Oil Flushing?

1. We HOF for several reasons,
2. New asset pre-commissioning,
3. Lubricant type change,
4. After a contamination event,
5. Scheduled maintenance

All OEM plant and equipment suppliers have their own methodology and specifications for pre-commissioning or hot oil flushing their assets.

Most conform to the two established standards ASTM D6439, and API 614.  The Standards require you to capture bulk particles on the return circuit via a screen or filtration, to prevent tank contamination, as you will require this oil to achieve a cleanliness specification prior to start up.

BioKem Oil Services works with both ASTM D6439 and API 614. Standards. WE believe it’s quite advantageous to capture all bulk particles and contaminants in the return circuit, to keep the lubricant within its ISO 4406 or NAS Class specification.

Also advantageous, is to apply fine filtration and vacuum dehydration, via kidney loop to the lube tank, not only are you removing contaminants and particles from the circuitry, but also purifying the oil to a minimum ISO 4406 code of 16/14/12 (NAS Class 6), and moisture content to below 200 ppm.

Service Oil or Base Flushing Oil?

Depending on the application, a service oil or a base oil similar to the final service oil can be used to flush the circuitry.  This decision is based on the availability of service oil, volume of oil needed for the flush, and the timings between flushing and equipment entering service.  In some circumstances the equipment circuits/spools may not enter service for some time afterwards and the final selection of service oil may not have been made or awarded.  In this circumstance a base oil can be used and then the pipework blown dry with compressed air and a purge of nitrogen or similar gas used.  If service oil is used then the HOF team will need to polish (fine filter) the oil ready for service.

Purging the system

If the circuitry can be sealed at the conclusion of the flushing then nitrogen (or other inert gas) can be used to stave off corrosion.  The methodology is to purge all oxygen from the circuits by venting the system whilst it is filled with inert gas.   Correct safety protocols should be followed as Nitrogen can be dangerous in confined spaces.

What Next?

Should you require a professional service to HOF your circuitry, spools, coolers, lube tanks, manifolds then contact BioKem Oil Services www.biokem.com.au