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SOP (Standard Operating Procedure) for Venturimeter


  1. Place the apparatus on the hydraulic bench top.
  2. Check all the clamps for tightness.
  3. Check whether the water level in the main tank is sufficient for the suction pipe ofpump to be completely immersed.
  4. Connect the up-stream side of the unit to the bench supply valve with a length of plastic tube.
  5. Connect down-stream end of apparatus to a plastic tube, the free end of which is directed into the hydraulic bench for measuring discharge from venturi.
  6. Set both the apparatus flow control and bench supply valve to approximately one third their fully open positions. Before allowing water to flow through the apparatus check that the air purge valve on the upper manifold is tightly closed.
  7. Switch on the bench supply(pump) and allow water to flow.
  8. For measurement through venturi, open the outlet valve of the venturi meter line and close the valve of the orifice meter line. Air will now be trapped in the upper parts of the manometer tubing and the manifold.
  9. Release the air purge valve sufficient to allow water to rise approximately half way up the manometer scale.
  10. For a good amount of variation in discharge, close the by-pass valve of pump also.
  11. Open the gate valve and start the flow.
  12. Remove any bubbles present in the U-tube manometer through air cock valve. Operate the air cock valve slowly and cautiously to avoid mercury run-away through water. (Adjust both the bench supply and the apparatus control valves to obtain full flow. At this condition the maximum pressure difference between the venturi inlet and throat should be 240 millimetres.
  13. Wait till the flow attains a steady state.
  14. Close the gate valve of the measuring tank and note the initial water level in the tank. Measure the time taken for the water level in the tank to reach a certain level and then calculate the flow rate. Also note the manometer difference. Before taking any measurements, make sure the flow is stable.
  15. Repeat the procedure by changing the discharge by slowly opening the by-pass valve and take the six readings.


  • Keep the other valve closed while taking reading through one pipe.
  • The initial error in the manometer should be subtracted final reading.
  • The parallax error should be avoided.
  • Maintain a constant discharge for each reading.
  • The parallax error should be avoided while taking reading the manometer.

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