DP Flow - ISO 5167 General Principles and Requirements (Part 1)

Sunday, April 28, 2019 | Steve Clark
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Part 1 of ISO 5167 covers the general principles of differential pressure flow meters in circular cross section conduits. It is an essential Part to read in conjunction with the more ‘primary device specific’ Parts 2 through to Part 6 since it identifies terms and symbols used throughout the entire standard. Methods of determining key elements such as diameter ratio, fluid Reynolds number and expansibility factors are identified along with the iterative flow rate equations themselves. Consideration is given to the measurement requirements of fluid pressure, temperature and density.

Installation requirements for the primary differential device itself are detailed with a specific explanation of how and where to measure the pipe circularity and pipe roughness. The required flowing conditions at the primary device are defined as well as the upstream and downstream straight lengths from the primary device. Various designs of flow conditioners and flow straighteners are extensively detailed including the compliance testing requirements.

Part 1 of the standard also describes the practical uncertainty calculations to be performed on the flow rate measurements enabling the user to compare DP meters against other technologies.

Solartron ISA have developed an in-house flow meter sizing calculation program which covers all the ISO 5167 devices as well as some additional proprietary differential pressure elements. The core mathematical computation elements of the software were developed in 1987 and after several enhancements over the years now reside in a windows environment. 

Solartron ISA have been active participants for over 15 years in the ISO/TC 30/SC2 technical committee assigned to ISO 5167. The standard is due for ISO systematic review in 2019.