Liquid Service: In liquid service, it's generally advisable to install the transmitter downstream of the orifice plate. Placing it downstream helps ensure that the pressure readings are not affected by disturbances caused by turbulence or uneven flow patterns associated with the orifice plate. This location provides stable and accurate measurements for liquids.
Gas Service: For gas service, it's common to place the transmitter upstream of the orifice plate. This positioning helps in obtaining accurate pressure measurements in a less dense gas, where pressure variations can be significant. It ensures that the pressure readings are not influenced by pressure drop across the orifice.
Steam Service: In steam service, the choice of transmitter location can vary. Some applications place the transmitter downstream to measure the pressure drop across the orifice. However, it's essential to consider factors like condensation and the potential for wet steam, which can affect measurement accuracy. In such cases, it might be necessary to install the transmitter upstream.
Corner Taps (D and D/2 Taps):
D Taps: These are located at the same cross-section as the orifice plate, one tap on each side of the plate.
D/2 Taps: These taps are located at a distance of one-half the pipe diameter upstream and downstream from the orifice plate, respectively.
Flange Taps (Corner Taps with Flange Connections):
Flange taps are similar to corner taps but involve the use of flanges to make it easier to install and remove the pressure taps. They are often used for larger pipe sizes.
Radius Taps (ISO Taps):
Radius taps are positioned in the pipe wall at a specific radius from the pipe centerline. These taps provide a more stable and accurate pressure measurement compared to corner taps.
Pipe Taps:
Pipe taps are located in the pipe wall itself, usually at the 1/2 and 1/8 pipe diameter locations downstream and upstream of the orifice plate. These taps are commonly used for smaller pipe sizes.
Weldolet Taps:
Weldolet taps involve welding small branch connections (Weldolets) onto the pipe to create pressure taps. They can be positioned at the appropriate locations for pressure measurement.
Vena Contracta Taps:
These taps are located at the vena contracta, which is the point of maximum fluid velocity downstream of the orifice plate. Vena contracta taps are used in some specialized orifice flowmeter designs.