By Pat Dixon, PE, PMP
President of DPAS, (DPAS-INC.com)
I recently attended an hour-long technical presentation entitled "The Latest in Process IIoT". Over half of it discussed HART protocol. If you have spent much time in process control, that should tell you something.
HART was introduced in 1986; its 39 years old. It allowed the traditional 4-20 milli-amp signal from an analog transmitter to have an additional digital component super-imposed on it. The additional digital information could give you configuration and calibration information, as well as additional features such as accumulation calculated in the device. For example, if you have a mass-flow measurement for a critical material that you are adding to a tank and want precise control of how much you are putting in, the mass flow meter could do the accumulation itself and send it to the control device through a digital HART signal. Therefore, your control device could have one pair of wires that connects to the mass flow transmitter in the same way as before and get the same 4-20 milli-amp signal for the real-time mass flow measurement, but also enable you to get an accumulation, calibration, and configuration information.
What is new about 39-year-old technology? The answer is not much, other than the fact that it is not the only protocol of its kind.
Around 1999, Fieldbus was introduced. This allowed instrumentation to be connected with a multi-drop cable instead of having to wire each instrument individually. While it does not provide for 4-20 milli-amp signals like HART, it can provide power to the field device, which can reduce the number of power supplies needed. It is a digital-only communication protocol that (like HART) provides a lot more information than just the measured signal.
Over time, new field protocols have proliferated. What used to be a standard analog 4-20 milli-amp approach has become a buffet of services. An engineer designing their control system has choices to make that didn't exist prior to 1986. These more recent protocols put the conversion of analog to digital communication in the transmitter, instead of at a field termination panel at a controller.
The issue that arises with digital field communication is the configuration and maintenance of this instrumentation. To map the signals to meaningful tags/parameters, a configuration data file is loaded into the controller so that it knows what to do with the signals it is receiving. Each instrument can have its own data file that is required to make it communicate.
How do we manage all of those data files? How do we effectively maintain these instruments?
Asset Management is an application that maintains an inventory of assets (like instruments) and can manage the associated configuration files. Having a centralized system makes it much more manageable than having to hunt around for disks or Internet downloads to get devices to talk. When you have operating system or control system upgrades, you want to be able to restore communication to the field without having to figure out what may or may not work after the upgrade.
Instrumentation is one kind of asset. Motors are another kind of asset. There are Asset Management applications that can maintain motor runtimes to help determine when maintenance is merited and can process work orders and maintain a history of prior maintenance. Managing maintenance this way is helpful for any asset, including instrumentation.
Valves are also assets. An Asset Management application that could help diagnose stiction and hysteresis can be very helpful. Work order history and processing is also a desirable attribute of such a system.
More complex equipment, like a compressor, is also an asset. An Asset Management application could be used for maintenance not only of the motor that drives it, but to also include the complete asset. Can we use machine learning in this Asset Management application to predict required maintenance? Can it include maintenance procedures and checklists for the entire unit, not just the motor? Can it include an inventory of spare parts for the asset?
At this point, it should be clear that Asset Management could mean a lot of things. Depending on what assets we are referring to, an Asset Management System could have different meanings.
Motors, valves, and compressors are not new assets. Many of the digital communication protocols to field devices (like HART) are not new. However, the proliferation of these digital protocols has created a new environment in which Asset Management Systems are increasingly desirable. That has led to the application of these systems for instrumentation as well as other assets.
Notice that nowhere in this discussion of Asset Management have we mentioned the Internet. When a controller communicates by HART or Fieldbus to an instrument, the Internet is not in that path. So why is HART pertinent to "The Latest in Process IIoT" (Industrial INTERNET of Things)?
The confusion that arises in Industry 4.0 is that a mash up of technology and terminology produces confusing and interchangeable terms. Asset Management is one of those terms. It is clear why an Asset Management System was not as necessary when every instrument had a pair of wires landed on a termination panel providing a single analog value to a controller. Now that digital field communication has made it more of a necessity, Asset Management Systems are being applied to assets that may or may not include instrumentation. It is another technology that is being branded as part of IIoT, even though there is no inherent Internet component to it.
When considering an investment in an Asset Management System, it should be noted that nearly every instrument or controller on the market today supports HART. However, the vast majority of HART enabled systems do not make use of these capabilities. Even though additional functionality is provided by the digital capabilities, most of the industry with these with digital capabilities just wire in the 4-20 milli-amp signal and do nothing more. To justify an Asset Management System for instrumentation, these capabilities need to be applied.
As with any system, it breaks if it is not used. It may sometimes be more convenient to use a handheld meter to diagnose or maintain an asset in the field, but if information bypasses the Asset Management System you will have a system with bad information. Therefore, investing in such a system requires a commitment to use it.
When you are presented with an Asset Management System, some questions to ask are:
- What assets does it manage?
- Will it include management of data files for digital field communication?
- Are we going to make use of the digital field communication capabilities we have?
- Are we going to be disciplined in our use of the system?
- How does the system commission new assets or decommission out of service assets?
- Will it need to synchronize inventory with an ERP/SAP type of system?
In this confusing era of buzzwords, it can be hard to know what is or is not IIoT. Regardless, Asset Management is an application of growing importance and benefit if used properly.
