Machine Health Monitoring

Assuming now that we are all on board for predictive maintenance, what do we do next? Our goal is to prevent failures, so, obviously, we need to monitor our machines. This could be done just by inspection (listening to noise, touch for temperature and vibration, visual inspection) or by collecting data. Since the inspection by perception is biased and hard to document, I personally prefer data. Specifically, if we are talking about rotating machines, we need vibration data. With proper processing the vibration data can help diagnose almost any mechanical problem, especially when the data is tracked over time. Other parameters can be monitored as necessary. Temperature, pressure, electrical parameters, etc. - all can yield valuable machine health data.

We will talk about manual "walk around" data collection on a separate occasion. For now we assume a permanent installation. Whether we collect data manually or install permanent sensors, the monitoring system has to have a few layers between Machines and Users that look like this:

Machines --> Instrumentation --> Communication --> Processing and Storage --> Presentation --> Users

Instrumentation layer consists of sensors and data acquisition hardware. To minimize cost of installation the data acquisition hardware should be installed close to the machines. Long sensor wires are not only expensive and hard to install, they sometimes cause deterioration of the analog signal and loss of accuracy. The instrumentation layer outputs data in digital format.

Communication layer transmits the data to a server where it is processed and stored. Today it would be a shame if we ignored standard network infrastructure that makes this transmission easy. Costs are drastically reduced by using standard off the shelf networking components. Standard Ethernet (wired or wireless) and the Internet are the best choice for the communication layer.

Processing and Storage layer is typically a dedicated server computer that runs a few key pieces of software - communication server, digital signal processor, and database. It also contains an alert generator that informs users if something goes wrong.

Presentation layer is a web portal where user can login to monitor the data and control the system. The presentation layer sends to user's browser a program that shows the data in graphic format, gives interactive access to stored data and to all machines regardless of their location. The web portal can be accessed from anywhere with a secure login.

Clearly, the above system architecture is somewhat simplified, but for the purposes of this discussion it is fine. The point we are trying to make here is that today's technology provides tools to make a very inexpensive system that can monitor machine health condition with high accuracy.

Next time we will talk about sensors.