Flushing to NAS Standards

Flushing to NAS Standards


Pirtek Asia provides a professional hot oil flushing service using specialised equipment to increase operating efficiency and reduce timescales for your hydraulic systems and equipment. This equipment, and our team of experienced technicians, provides an effective and highly economical service both Onshore as well as Offshore, for the rapid and effective clean up of lub, seal and hydraulic oil systems.

flushing hydraulic system

Hot oil flushing is done using flushing or system oil to remove the fouling from the internals of the piping systems. Flow is crucial during flushing as it determines the cleanliness in the piping systems. Hard particles will wear out bearings and hydraulic slides and cause poor equipment reliability. Up to 80% of the breakdowns and damages are caused by contaminants. Flushing hydraulic and lubrication system with filtered oil to the essential purity level greatly extend the components lifespan up to 20 times, thus damages and shutdowns are greatly reduced.

Pirtek Asia’s very own oil flushing equipment and highly experienced technical personnel is able to achieve cleanliness results to our customers’ satisfaction.

Effective Flushing 

In order for flushing to be effective:

  • Turbulent flow must be achieved
  • Reynolds No. must be > 2500
  • High velocity required to remove  contaminants
  • High quality filtration must be used


Cleanliness Level
Generally speaking, the required cleanliness level to target during flushing is half the level during operation. For example, if the normal operation level is ISO 15/13/11, flush to ISO 14/12/10. Requirements for cleanliness levels of both solid particles and moisture should be achieved.

the required cleanliness level to target during flushing is half the level during normal operation.



The ISO Cleanliness Code, ISO 4406, 1987 is perhaps the most widely used International Standard however the dated NAS 1638 standard is still widely used by many industries.

Oil sample will be submitted to Third Party Lab for oil analysis upon completion of flushing and either Pirtek in-house Report or a Third Party Lab Report will be provided to Customer.














ISO vs NAS Standards