An intelligent pump is more than a pump; the product is a combination of a pump, process instrument(s) and variable frequency drive (VFD) with related intelligence embedded in the microprocessor motherboard. While variable speed drives (VSDs)— both mechanical and electronic— have been applied to pumps for decades, the drives on intelligent pumps were the first commercially available VFDs that used pump protection logic to alert end users during upset conditions. Today, several manufacturers offer intelligent pumps with varying performance monitoring and asset protection capabilities. An intelligent pump also typically includes standard process control functions, such as proportional-integral-derivative control (PID) and power (kilowatt) consumption monitoring.
The first intelligent pump was introduced near the beginning of the new millennium. This technology has been instrumental in changing many facets of the pump industry. One change has been the development of a new understanding that control valves do not have to be the de facto flow control device for pump systems. Embedding pump intelligence into VFDs also has led to the view that the pump— along with the instrumentation and control valves— is a key component of industrial automation architecture.
Advantages of Intelligent Pumping
From a process control standpoint, the primary difference between a VFD and a control valve is that the VFD electronically changes motor speed to maintain flow, pressure, level or temperature at set-point, while the control valve mechanically adjusts its opening to meet process control requirements. Both approaches maintain process flow at the required rate but differ significantly in how they impact energy use, equipment reliability and process control performance. VFD speed reduction lowers head (pressure) at the square root of speed, while energy consumption is reduced at the cube root of speed. For example, a small reduction in speed can result in a moderate head reduction and large energy reduction. The reduction in head (pressure) and the accompanying reduction in energy usage are primarily the result of fully opening or eliminating the control valve.
Standard and intelligent VFDs provide the same level of energy savings but can differ significantly in the amount of maintenance savings they provide. Embedded pump protection can alarm, slow down or turn off the pump when the system encounters conditions such as dead-heading, dry-running or cavitation.
The introduction of intelligent VFDs signaled the rise of variable speed pumping as an alternative to control valves, especially in continuous process industries. For the first time, end users could use the electronic platform as a "brain" that learns and adapts pump performance to changing process conditions. This real-time adaptability plays a critical role in achieving process sustainability through uptime, controllability and reliability improvements. An intelligent pump offers far more information about the pump's performance than was ever readily available in the past.
Limitations to Adoption
While plant operators and engineers typically configure standard VFDs through a keypad or laptop in the motor control center (MCC), the PID algorithm and control logic in the VFD are infrequently used. Normally, the control engineers opt for using the same control functions that found in the distributed control system (DCS). The DCS then outputs a speed signal back to the VFD over an analog cable (4-20 mA), a step similar to sending an analog signal to a valve positioner to change the percent that it is open or closed. Digital bus communication can be used, but the majority of plants built before the new millennium use analog signals to communicate from the DCS to the field instruments and valves.
Because the VFD and DCS are in different locations, operators and engineers are often unable to configure the intelligent pump firmware from the DCS. This restriction causes the embedded pump intelligence in the VFD to be underutilized.
While this was an issue with the first generation of intelligent pumps, the growth of wireless communication, the Industrial Internet of Things (IIoT) and cloud computing have made it possible to overcome these limitations. Today, multiple parameters can be transmitted from the MCC to the DCS. Access to the pump-protection logic from the DCS can lead to more visibility and higher utilization rates.
An alternate approach could be to use a third-party software package with the pump intelligence and load that program on the DCS. This could make the intelligent pump compatible with multiple VFD brands and different voltage ratings. The end user could purchase the VFD separately from software package and combine the two using wired or wireless digital communication. In this scenario, the pump intelligence could access the DCS database as well as receive data from the VFD. By accessing data from both control elements, the level of intelligence could potentially be expanded.
While intelligent pump technology has made significant advances in asset protection, the use of wireless communication, cloud computing and/or third-party software offers new approaches that can increase the availability and utilization of pump intelligence. The DCS and related information systems could be able to both configure and display multiple capabilities, including the following:
- Alarm and control actions with data logging, time stamps and trends
- Real-time pump and system curve visibility with mechanical efficiency
- Real-time horsepower and/or kilowatt consumption and specific energy