We've been having issues measuring small flows in a high temperature high pressure application.  We're talking 5 pounds/hour of product.  We've used coriolis meters but we're at the limit of what's available commercially.  The flow is a slurry and will plug if it cools, so we need to maintain temperature as well as velocity to reduce plugging/settling in the line.

In one particular application, we have approximately 300# of drop but want to reliably measure flow rate.  What we've been doing is looking at the tank downstream, but when you have multiple flows going into that tank it is impossible to differentiate between them.

I was thinking, why not use a dP transmitter across the valve to determine flow?  We'll have the CV vs gatevalve% open curve, wouldn't it be fairly simple to calculate the flow?

What coriolis were you using? I've seen lots of twin tubes for low flows but don't recall seeing a single straight tube....
I know that twin tubes are vulnerable to preferential tube blocks under such conditions, but a single tube meter with a PD pump would be such that as the tube starts to block the pressure drop increases and the block is moved on.

Assuming single straight flow paths are required then you might try the low flow ultrasonic meter from Flow Technology Inc.  

valves work if +20% uncertainty is okay, they are hardly a flow measuring device.

forget d/p with a slurry at low flows.

use a weigh tank method on the stream of interest .

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