Standard Practice for Determining a Flow-Proportioned Average Property Value (FPAPV) for a Collected Batch of Process Stream Material Using Stream Analyzer Data
Contractual or local regulation, or both, permitting, the FPAPV calculated according to this practice can be used to represent the average property of the quantity of material collected.
Due to the averaging and appropriate weighting of analysis results, the FPAPV estimate of the property for the collected material is expected to be more representative and more precise than an estimate based on a small number of analyses on a few samples.
Note 1—Theoretically speaking, the true property distribution for an infinite number of batches with essentially identical FPAPV’is expected to be Gaussian, centered at the FPAPV value, with a standard deviation that is no less than the long term site precision standard deviation of the analyzer system.
If the measured property value can be used to predict another property value through the use of an appropriate correlation equation, the FPAPV can also be used as a suitable prediction of that property.
The most recently updated FPAPV can be used to represent the property of the material currently accumulated in the tank or vessel for process control or material disposition decisions, or both.
1.1 This practice covers a technique for calculating a flow-proportioned average property value (FPAPV) for a batch of in-line blended product or process stream material that is collected over time and isolated in a storage tank or vessel, using a combination of on-line or at-line measurements of the property and flow rates.
1.2 The FPAPV methodology uses regularly collected on- line or at-line process analyzer measurements, flow, and assessment of other appropriate process measurements or values, to calculate a flow-proportioned average property value in accordance with flow quantity units of material produced.
1.3 When the collecting vessel contains a heel (retained material prior to receipt of the production batch), both the property value and quantity of the heel material can be predetermined and factored into the calculation of the FPAPV for the new batch.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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