Hot Oil Flushing

Hot Oil Flushing is done to clear any contaminants present in the pipe and oil after installation. The sole purpose of this process is to avoid damage caused by contaminants/dirts to the end using equipment. The pipes are cleaned by creating a turbulent flow in the system and passing them through filters until the desired cleanliness value is obtained. The cleanliness in the pipe is measured in terms of NAS/ISO/SAE Values.

The main requirements for hot oil flushing are:

  1. Fluid Velocity of the Flushing Oil
  2. Viscosity/Temperature of the Flushing Oil  
Hot Oil Flushing for Pipes

1. Fluid Velocity

Hot Oil Flushing of pipes will be more effective when the velocity of flow of the fluid in the pipeline is more. The minimum fluid velocity required for flushing is based on a fluid velocity corresponding to a Reynolds No. of 4000 and above in order to get turbulent flow. The velocity of the fluid can be found out from the formula:
V= Fluid Velocity in m/s
Re = Reynolds No= 4000 (The value can be more if more efficient and quick flush is required)
γ = Kinematic viscosity of the flushing oil in m2/s
D = Internal Diameter of the pipe in m

Based on the velocity obtained the minimum flow rate required to flush the system is calculated as below:
Q = A x V x 6000
Q = Flow Rate in lpm (litre per minute)
A = Area of Bore of the Pipe in m2
V= Velocity of the pipe in m/s

HPU Flow Rate Calculator (for Turbulent Flow)

2. Viscosity/Temperature of the flushing Oil

Viscosity and temperature of the flushing oil plays a pivotal role in deciding the flow rate required for flushing. An ideal flushing oil should have low viscosity and a high specific gravity. On the other hand viscosity should also not be too low either so that the liquid will not be able to carry loose particles which may fall down due to less gravity. Heating the oil to around 50 – 60 Deg Centigrade will help in loosening stubborn dirt or grease and hence drive them from the pipeline. It also decreases the viscosity which will in turn increase the fluid velocity.
Our team is well versed with hot oil flushing and have executed hot oil flushing projects in record time. We have the best flushing machines and cleanliness monitors to carry out such operations.