Specifications :

The oil-flow meter measures flow by inserting an orifice at part of the piping, generating differential pressure before and behind the orifice by means of the flow, and extracting this differential pressure by a suitable method.


Differential pressure (p1-p2) of the main orifice & the flow q have shown in the equation given below. The flow is proportional to the square root of the differential pressure.


Q=cf [2g/ץ(p1-p2)]^1/2


  • ➩ Q: volumetric flow
  • ➩ c: flow co-efficient
  • ➩ f: cross-sectional area of the orifice hole
  • ➩ g: acceleration of gravity
  • ➩ p1-p2:differential pressure
  • ➩ ץ: specific weight of the fluid


The generated differential pressure is sent to the manometer or other differential pressure gauge & a differential flow meter can be formed by attaching a flow scale to this gauge. However, since flow indication is square root scale reading is difficult. Moreover, in the case of remote transmission, it is inconvenient because the evolution operation is performed to obtain linear relations.


Therefore if a bypass pipe connecting before and behind the point of the main orifice is installed and the flow is branched to that pipe to overcome these disadvantages, that flow becomes proportional to the differential.

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