FAQ: Understanding the Key Elements for Machine Condition Monitoring

3. What are the most telling signs that a machine is about to fail?

There are several key indicators, vibration often being the number one change that will occur prior to machine breakdown. Whether a failing pneumatic or hydraulic cylinder or system, an electric motor bearing, or mechanical motion device such as a lead screw, vibration will occur prior to failure. Depending on machine load and duty cycle, early detection often avoids expensive downtime. By installing vibration sensors at key locations, minor changes can then be transmitted to a humanmachine- interface (HMI) and/or control system for analysis. Vibration sensors are available for a wide number of applications. Devices typically operate at 24 VDC and provide switching or analog signals depending on your needs. Applications where vibration sensors are most often used include those where bearing failure is a primary consideration, including HVAC compressor imbalances, electric motor deterioration, drives spindles, and any fan used inside a machine or factory. In pneumatic and hydraulic systems such as heavy metalworking machines like presses or injection molding machines, increased vibration is a common early warning sign of failure.

A second identifier of early failure is temperature. This is especially the case in equipment that doesn’t start and stop regularly, but instead runs 24/7 at a constant temperature rate. Even minor shifts in temperature can be monitored, leading to a better understanding of equipment health. This will allow action to be taken before a breakdown. Temperature sensors and transmitters are designed to operate over a wide variety of ranges depending on your needs. Typical ranges can be from -40 through 572 degrees F, with special sensors programmable from as far as 148 through 1,112 degrees F.

Example applications include machines used in continuous processes, such as chemical processing, paper manufacturing or anywhere else a service interruption could ruin an entire production run. Other applications with high failure consequences include power plant boilers, turbine generators, and equipment located in hazardous environments, which can recognize some of the highest losses.

4. What equipment is needed once I have the sensors in place?

There are two primary approaches, which include the HMI/operating panel approach and the central control room approach—often used together.

First, HMIs provide a visual representation of current conditions, process outputs, and overall machine health for critical manufacturing or process control equipment. HMI operating panels are available with water and dust ingress protection, with enclosures suited for a variety of environments, and coated versions for a wide variety of applications. HMIs can be programmed to prioritize machine measurements for temperature and vibration based on how quickly a change leads to a failure. For lower priority conditions where changes signify a future failure—and where scheduled maintenance can occur—a simple alarm signal might be appropriate. For situations where a change might require more immediate attention a larger graphic or brighter color might be used.

To meet both needs, many HMIs are available with simple screens or complex, multi-color capabilities.

Another approach is for operations to use a central control room to monitor their critical equipment. This is often necessary in harsh environments such as nuclear plants and chemical processing facilities. Condition monitoring can, again, be prioritized to meet your particular needs.

A combination of the two approaches is often used when a company is integral with their IIoT (Industrial Internet of Things) infrastructure. For such operations, condition monitoring might go well beyond the monitoring of mechanical components of single machine or series of machines to include an entire plant.