I need to configure an orifice flow meter in DeltaV for a project I'm working on. I realize this is more of a process question, but I was wondering if someone might be able to help me. The instrument is a Rosemont 3051 for differential pressure calibrated with a span of 0 to 1100 inH2O. It is a Foundation Fieldbus device.
1. Pretty sure I need to set the L-type for the AI block to "Inverse Squared," is that correct?
2. How do I determine what to set the XD scale and out scale to?
3. Is there anything else I need to configure for the AI block to get the right flow reading in GPM or a similar flow measurement?
Thanks in advance.
I forwarded your post to the Rosemount DP Flow specialist team (you can find the various Rosemount specialist teams here). Here's what I received back:
You mention that your question is relative to a 3051 transmitter. But we manufacture many different transmitters that begin with those first 4 characters. If we have the complete model number then we can respond with the best and most accurate advice.
Assuming that it may be a 3051CD with Fieldbus output, then you will need to set up the full scale DP as the XD Scale, and the corresponding full scale flow rate as the Out Scale. For that scale to represent a flow scale, you would set the L-Type to “Indirect Sq. Rt”.
If using an LCD on the Xmtr, then the LCD Block will need to be set up to represent that AI Block, the Out variable from that AI Block, give it a name, like “FLOW”, and a custom unit of measure like “GPM”.
Regarding your question #2, in order to range the DP to Flow relationship, you first need to have a DP Flow calc sheet that is representative of the primary element and the fluid in the customer’s application. That might be one of our Toolkit DP Flow calc sheets.
Then for example, the calc sheet should show a normal and max and full scale flow rate, and the corresponding calculated DP values at each of those flow rates.
Then in an AI Block you can enter the full scale DP as the XD Scale, and the corresponding Flow Rate as the Out Scale.
In reply to Jim Cahill:
Jim is correct - the variables you need to set are in the AI block. If you assign the AI to the correct fieldbus device (placeholder, if the device isn't connected) and save the module, DeltaV will display the correct options for XD_SCALE units in a drop-down list. It is very importatnt to get the units correct, e.g. inches H2O @68°F (not inches H2O at 4° F, for example) and using the drop-down will help ensure you get it right. The other thing you need to get right out-of-the-box is "channel". Like XD_SCALE, channel will be limited to "valid" options after the module is saved with the AI block assigned to FF. You want channel 1 for pressure (DP).
OUT_SCALE is in engineering units (GPM) and 100% of OUT_SCALE should correspond to full scale on your orifice calculation (the flow that produces 100% of XD_SCALE). Typically 0 flow is 0 inches but you need to set that too.
Attention to "channel" and units of XD_SCALE will be necessary on all device-solved AI blocks. If you don't see a channel parameter it's because you haven't assigned the block to FF yet.
The old school method is to right-click the XD_SCALE or channel parameter and click the BOL topic "Valid units and channel numbers for fieldbus device" topic. But I find it is more reliable to save the module first (no need to download at this point) after which Control Studio will only show you valid choices.