Square Edge Orifice Meter

Yes

What type of accuracy are you after? What is the flow rate?

The more info you can give about the use the better answers you will get.

the flow rate is between 60 - 70K SM3/D for import and flow of 100K for export. accurcey of .02.

.........so the differential pressure cell fitted across the orifice simply needs to be calibrated for the greater of those two flow ranges at the pressure in the line. Apart from ensuring that the upstream and downstream pressure taps are a mirror image of each other about the plate, and there are sufficient pipe diameters up- and down-stream, what's the problem <rhetorical question>?

Remember that differential pressure is related to flowrate via the square root function!

if I use portable panameteric meter to verify the actual flow with orifice do you think the reading will be same if not why

The meter can be recalculated and a meter correction factor used to compensate for the non beveled edges, but that will take a laboratory set up. You'll also have problems with upstream lenght and postions of the temperature transmitters.

Ultrasonic can be set up bi-directional. You can install 4 DDB valves and make it a true API/ISO meter run. Or just install two tubes, one for each direction.

Watch out for the beveled edge on your orifice plate...

I can't think of something more frustrating than getting flow meters to measure the same, especially orifice meters. Are you pressure and temperature compensating the meters? Maybe take a 5 minute average of each meter and see how close they are to each other. There are a lot of variables going into your measurement.

I notice that you are reporting in Sm^3/D, do you reliably know the density of the material as well?

If I had a choice, I would go with 2 meter runs as it has the least potential for trouble.