Orifice Type Flow Meter
Orifice plates are still the most widely used type of flowmeter in the world today. They offer significant cost benefits over other types of flowmeter, especially in larger line sizes, and have proved to be rugged, effective and reliable over many years. Where a need exists for a rugged, cost effective flowmeter which has a low installation cost and a turndown of not more than 4:1, the orifice plate continues to offer a very competitive solution.
An orifice plate installed in a line creates a pressure differential as the fluid flows through it. This differential pressure is measured via impulse lines by a differential pressure transmitter which converts it into an analogue or digital signal which can be processed to provide a display of the instantaneous rate of flow. The relationship between the rate of flow and the differential pressure produced is very well understood and is fully covered by comprehensive national standards. The relevant standards are BS 1042 and the equivalent ISO 5167. One of the principle advantages of orifice plates manufactured and installed following these standards is that they do not require calibration. This means that orifice plates are very cost effective on larger line sizes.