Ten Installation Details for Electromagnetic Flow Meters
An electromagnetic meter's rated accuracy assumes correct installation. Poor field installation can produce errors far beyond the catalogue figure.
Location
1. Ensure a full pipe. Electromagnetic meters only measure full-bore flow. Avoid the highest point of the pipe run and downward vertical flow. On vertical runs the media should flow upward.
2. Straight pipe runs. At least 5D upstream and 3D downstream. With an upstream bend, valve or pump, extend upstream to 10D.
3. Avoid negative pressure. Linings can delaminate under vacuum, so do not install on pump suction.
Electrical connections
4. Grounding is critical. The sensor must be reliably earthed independently, with earth resistance below 10 Ω. This is the most common source of electromagnetic meter faults — poor grounding causes jumping or erratic readings.
5. With insulating pipe (such as plastic), grounding rings must be fitted.
6. Route signal cable separately from power cable, at least 200 mm apart. Ground the shield at the sensor end only.
Media and duty
7. Verify conductivity. Media conductivity must exceed 5 μS/cm. Pure water, deionised water and organic solvents cannot be measured.
8. Mind the lining temperature limit. Limits differ markedly: rubber around 80 ℃, polyurethane around 70 ℃, PTFE up to 180 ℃.
9. For solids-bearing media, choose wear-resistant lining and inspect electrodes periodically.
Commissioning
10. Perform empty-pipe and zero calibration at first start-up. Calibrating zero with the pipe full of static media effectively removes offset caused by installation stress.
