18 Condition Monitoring
condition monitoring solution detects rotational direction Flemming Munk, Chief Engineer, Condition Monitoring at Grundfos Water Utility, provides insight into what he believes is an exciting new condition monitoring solution developed by Danish start-up, EWA sensors.
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s a pump manufacturing company, Grundfos is approached by companies offering condition monitoring solutions for our pump systems on a weekly basis. The business potential of condition monitoring and customer service agreements are huge, and this has triggered an explosion in the number of companies offering Condition Monitoring Solutions (CMS) that can detect every possible machine fault in rotating machinery. As a customer, it can be difficult to navigate between all the CMS offerings, but a simple and fundamental question is: “Can your system detect the rotational direction of my machine?”. For a rotating machine, the RPM and direction of rotation are fundamental parameters, and if the CMS system is not able to measure these two parameters, the foundation for further detection of imbalance, bearing failures, gear issues etc., becomes a little frivolous. It is a good measure of the insight and understanding of rotational machinery that the CMS provides, and will flag, a ‘wannabe’ CMS system. A good CMS takes many years to build and demands deep technical knowledge about applications, signal analysis and sensor design. In this regard another interesting measure is the ISO 18436 certification level of developers. No certification is for me a clear flag, that they are in it for the quick win – I would never consider adopting such a system. However, one system has recently caught my attention – the solution from EWA Sensors. EWA stands for Early Warning Analytics and it is a small start-up company from Denmark. The system measures a range of parameters including RPM, rotational direction, imbalance, cavitation and gear issues, and the founder is ISO 18436 Cat-IV certified from both Möbius Institute and Technical Associated from Charlotte PO - so the company passed the acceptance test . Quarter 2 2023
THE EWA PLATFORM The founder of EWA sensor has chosen to follow a different approach to what we normally see in this age of IoT devices. The sensor is a pure edge device with no cloud support and no human-in-the loop. All analytics are performed by the sensor, using a built-in Cortex-M7 microcontroller. It is a wired sensor for Modbus communication and with 24VDC power. All parameters are accessible to the customer through Modbus/SCADA. The sensor measures vibration, magnetic field and temperature and applies a combination of vibration signature analysis and motor current signature analysis, which make the parameter set very robust. It is a true plug-andplay platform with no pre-configuration of parameters, like motor pole pairs – the sensor will find the number by analysis. The sensor is designed as a pressure capsule and can be used in both dry installed and submerged (10m) applications. For water utility applications, there is generally no benefit in using wireless IoT – if we are going to use 50m of cable to the gateway, it is not a problem to use an additional 4m to the sensor. The sensor is equipped with four LEDs – for power, direction of rotation, Modbus communication and alarm/ machine health. The sensor calculates a large number of condition monitoring parameters, but I want to focus on two that are new to the market. ROTATIONAL DIRECTION Many CMS seek to provide very high-level conclusions in relation to alignment, cavitation, bearing condition etc., but miss fundamental low-level operational parameters. When we are talking about condition monitoring for rotating machinery, it is important to know ‘is my machine rotating or is it standing still’ and if it is rotating ‘what is the rotation direction’ – counter
clockwise (CCW – negative RPM) or clockwise (CW – positive RPM). Many CMS cannot tell if a machine really is rotating as vibration on the line frequency is not a clear sign of an operating machine, it could be the adjacent machine. The EWA sensor measures the rotational direction of the motor every second and provides this information both through an LED on the sensor with CW (green), CCW (red) and no rotation (no light) and outputs it as a Modbus parameter. It sounds very simple, but I don’t see this feature very often. It is an important parameter, as rotational direction can be shifted after a service, if the power cables are incorrectly reconnected by mistake. Numerous real-life cases exist with sewage pumps that have been operating for years in the wrong direction, without anybody noticing anything other than lower performance. If a CMS is not able to measure rotational direction, it is not a condition monitoring system for rotating machinery, but a condition monitoring system for vibrating machinery. As a side-effect of measuring the direction of rotation, the EWA sensor also detects whether the installation is a horizontal or vertical machine. www.bpma.org.uk