Although differential pressure (DP) flow meters are based on a relatively inexpensive and mature technology, selecting and installing these devices is not simple and requires a reasonable level of engineering skill.
With the new Deltatop, Endress+Hauser have implemented a novel solution by supplying a one-stop-shop solution. All the steps related to product selection, engineering, calibration, and manufacturing are now bundled together with Endress+Hauser supplying the Deltatop as a total package under one order number.
Despite its limitations, and because it is a well established technology, using differential pressure for flow applications remains a popular choice. There are no moving parts and the systems can be used over a wide range of pipe sizes from DN4 to DN12000.
In fact, for the largest pipes, this technology remains the most cost effective. The Deltatop is widely used in all industries, for both liquids and gas flow measurement.
Flow meters calculate the flow in a pipe by measuring the differential pressure upstream and downstream of an artificial restriction in the pipe. In certain applications, the restriction needs to be big, such as an orifice plate, and significantly restricts the flow rate which affects the pump efficiency.
In these cases, an averaging Pitot tube is used to make this process more energy efficient. Multiple Pitot tubes are fixed together and an average of the differential pressure reading is taken, providing more stable and repeatable readings. Selecting the most effective measuring equipment, either orifice plate or Pilot tube requires some experience.
Apart from the complex selection methodology, installing the DP flow meter is a labour-intensive and challenging process. A multitude of issues need to be determined well before manufacture and installation.
These relate to high pressure/ high temperature issues and whether to weld or screw in the components; selection of the components at the measuring point such as steam pots to protect the transmitter from steam; installing the primary element; manifold connections; calibration and pre-testing.
Having correctly selected all the component parts, it is then necessary to calibrate and range the system, taking into account low flow cutoff at the low end, and cavitation at high flow rates.
Endress+Hauser uniquely packages the design, engineering and manufacturing, reducing any guesswork and ensuring the best solution the first time. All issues are discussed with an Endress+Hauser engineer and pre-ordered before manufacturing begins, so that the Deltatop arrives on site as a completed unit, ready for installation.
Photo:
Deltabar mounted on orifice plate flow measuring system.
For more information:
phone 1300 363 707
fax 02 8877 7099
email info@au.endress.com
John Immelman, Managing Director
Endress+Hauser Australia Pty Ltd
www.au.endress.com
