API Spec 1582:2001 pdf download.SPECIFICATION FOR SIMILARITY FOR API/IP 1581 AVIATION JET FUEL FILTER/SEPARATORS
3.1 GENERAL
The Simplified Flow Model (SFM) is provided as a model for calculating flow parameters to establish that candidate and qualified systems are similar when conventional similarity criteria fail to establish similarity. The SFM is not required for determining similarity. It provides flexibility in qualifying by similarity systems that, otherwise, would require full- scale testing. The Simplified Flow Model (SFM) is a simple model for determining flow parameters between the coalescer and separator elements in a two-stage filter/separator system. The modelling assumptions and details are described in 3.2 – 3.3. An Excel spreadsheet that automates the steps in 3.3 is available from the API.
3.2 DESCRIPTION
The SFM assumes that the fluid is a single phase and that the flow is evenly distributed over all elements; i.e. there are minimal flow mal-distributions due to element variation and dirt loading. It also assumes that the velocity between elements at any cross-section perpendicular to flow is uniform.
3.3 SFM METHOD
The model functions by dividing the filter/separator system into zones (based on vessel cross-section). Each zone is comprised of the three closest elements or two closer elements and the wall. The length of a zone is the average length of the elements that comprise its borders. The flow through each zone is summed by assuming: (a) The flow into the filter/separator system is equal through each filter. (b) The flow exits each filter/coalescer element evenly (radially). (c) The flow into each separator is the same. (d) The radial distribution of flow into separators is evenly distributed. The summed flows are used to calculate linear flow velocities through each zone and residence time in each zone. Example calculations of the SFM are detailed in Annex A and B.
Select two adjacent lines, e.g. wEFAw and wDBw. Define the wall regions joining these lines, e.g. wEDw and wABw. Starting on the right hand side of the longest line, i.e. the line with the most elements, or the line closest to the vessel centre if lines are equal, divide the region between the lines into triangular segments. For consistency, select the first element, move to the next element on the line, move to the element on the next line, then move to the first element, e.g. EFDE. Select the element on the second line that was chosen above, move to the next element on the same line, move to the next unchosen element of alternate line, then move to first element, DBFD. Continue the process until the area between the two lines is broken into regions. On lines next to the vessel wall, e.g. wDCBw, the regions are defined between the line and wall, e.g. wDCw and wCBw.
API Spec 1582:2001 pdf download
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