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Intelligent Pump Systems Tap Major Opportunities for Energy Savings

Pumps have historically been a backbone of many applications, including commercial buildings, municipal water and wastewater management, irrigation and agriculture; and are certainly key contributors in industrial systems found in chemical, oil and gas, and pulp and paper industries. Pumping systems account for nearly 25 percent of the energy consumed by electric motors, and for 20 to 60 percent of the total electrical energy usage in many industrial, water and wastewater treatment facilities. Optimizing these processes presents extensive potential savings opportunities, which far exceed more commonplace activity such as motor maintenance/optimization and fan/compressor system upgrades.

Figure 1. US DOE Pumping Systems

Figure 1. A U.S. Department of Energy study shows pumping systems as among the largest energy efficiency opportunities in industrial facilities.

 

While pumps continue to perform the tasks for which they were designed – movement of liquids/solids – there are several trends impacting the future of pumps and pump systems. Historically, pumps have been supplied as part of larger systems and were frequently misapplied, improperly sized, and generally left to be standalone components in larger systems. Many trends in various industrial markets have increased the visibility of pumping, and ultimately the “pump system” as a key component. Key trends include:

  • Energy efficiency
  • System/process efficiency
  • Environmental concerns

Electrical energy demand is projected to double by 2030, putting the world in the midst of a global energy dilemma. At the same time, environmental trends dictate a need to cut CO2 emissions in half to prevent dramatic environmental impact. While many factors can contribute to both the problem and the resolution, the fact that pumping systems account for nearly 20 percent of the world’s electrical energy demand and range from 25 percent to 50 percent of the energy usage in certain industrial plant operations means improving operational pumping is clearly a key factor.

Figure 2. Global Energy Dilemma

Figure 2. The global energy dilemma: Electrical demand will double by 2030, and environmental concerns say we should cut CO2 emissions by half.

One powerful driver is life cycle costing (LCC), which is essentially an economic evaluation technique that determines the total cost of owning and operating a pump over the total projected life of the pump. Many organizations only consider the initial purchase and installation cost of a system. It is in the fundamental interest of the plant designer or manager to evaluate the LCC of different solutions before installing major new equipment or carrying out a major overhaul. This evaluation will identify the most financially attractive alternative.

As national and global markets continue to become more competitive, organizations must continually seek cost savings that will improve the

Figure 3 - Typical pump life-cycle cost profile

Figure 3. A typical pump life-cycle cost profile shows that initial costs are dwarfed by energy and maintenance costs over the operating life of the pump.

profitability of their operations. Plant equipment operations are receiving particular attention as a source of cost savings, especially minimizing energy consumption and plant downtime. Some studies have shown that 30 percent to 50 percent of the energy consumed by pump systems could be saved through equipment or control system changes, which can have significant impact as can be seen in Figure 3.

Pumping Systems Show Affinity for Energy Efficiency
In the industrial environment, pumps consume almost 25% of all motor energy use. Yet due to a combination of selection, application and demand considerations (combined with the affinity laws, which state that power savings are proportional to the cube of motor speed reduction), the savings potential in the pump realm is often in excess of 50% of total savings potential.

As energy costs continue to increase, pump manufacturers understand that making equipment more efficient will contribute to saving energy. While traditional methods of specifying and purchasing piping, valves, fittings, pumps and drivers often result in the lowest first cost, these methods often produce systems with unnecessary, expensive energy consumption and higher maintenance costs. A business entity that incorporates the energy, reliability and economic benefits of optimized pumping systems can enhance profits, gain production efficiency improvement opportunities, and initiate necessary capital upgrades for long-term business survival. Pump savings potential revolves around several factors, such as:

  • Pump sizing: Pumps are either oversized for the application and/or sized to meet the peak demand required.
  • Operating cycle: Pumps rarely run 24/7 fully loaded – variations exist by time of day, time of year, etc.
  • Pump wear: Over time, best efficiency points (BEPs) must be maintained to optimize energy consumption.
Figure 4. The U.S. Department of Energy Office of Industrial Technology

Figure 4. The U.S. Department of Energy Office of Industrial Technology has determined that pumping system energy savings are potentially greater than energy savings from most other sources combined.

 

Intelligence Comes to Pumping Systems
Let’s take a look at how “intelligent pump systems” can help manage energy consumption, starting with the definition of an intelligent pump system. The ARC Advisory Group defines an intelligent pump as the combination of a pump and a variable-frequency drive (VFD) with digital control capability. The VFD itself is a primary energy savings device due simply to the impact of the affinity laws. The power consumption decreases by the cube of the speed, so a 10 percent reduction in motor speed, while having a nominal effect on flow, reduces energy consumption of the pump by more than 25 percent.

Figure 5 - Affinity Law dynamics

Figure 5. Affinity Law dynamics indicate that a small decrease in centrifugal pump flow and pressure results in a large reduction in energy consumption.

With multi-pump systems, the decision to stage or de-stage is commonly done based on system demand. In a pressure-based system, if there is a drop in pressure, the drives ramp up motor speed. Under conditions of constant demand, a multi-stage system may have multiple pumps running at non-optimal speed. Yet due to inherent fluctuations in demand, altering the number of pumps running may result in the final stage being cycled on and off. As such, consideration of multivariable approach towards the staging or de-staging decision is essential in getting the optimal, energy-efficient control scheme. For a typical pressure-based system, this may involve monitoring torque, flow and time and applying a logic function that can be based in the VFD, a PLC, an HMI or separate logic control functions.

Additional feedback devices need not necessarily bring about an increase in cost. With VFDs, there are ways to approximate the system variables, such as flow, using data the VFD readily tracks, such as torque and current. This allows for smart decision-making in control logic, as described above, and also paves the way for additional pump system functionality. For instance, with approximate flow values, current and torque data available, software can be used to detect leaks and perform appropriate mitigation in the system control logic.

Intelligent pumping solutions also can offer benefits in specific manufacturing systems and/or processes. One such industry where there is particular excitement about intelligent pumping solutions is oil and gas. Most mature onshore oil wells are mature producers, with many producing less than 10 barrels of oil per day. Pumpjack systems, progressive cavity pumps (PCP) and electrical submersible pumps (ESP) work hard to bring oil to the surface, while operators are employing additional recovery techniques to increase productivity.

Many operators use conventional time on/time off pump controls to prevent a pumped off condition from occurring. Although simple to operate and adjust, they do not necessarily maximize production recovery. Process efficiency can be improved with an intelligent pump solution employing a VFD to vary the speed of the equipment to maintain maximum fill rates. There are three types of solutions that can be employed:

  • Torque only: Using pump motor load information to understand well conditions and determine optimal speed. This would be the least costly solutions for wells of depth up to 500 meters.
  • Surface card: This solution uses feedback from a rod-mounted load cell to analyze well conditions. It’s capable of optimizing speed and fill rates for deeper wells.
  • Down-hole card: Advanced algorithms use the rod load at the bottom of the well, maximizing optimization and providing the greatest ROI.

The Environment Comes First
There remains the demand to reduce CO2 emissions to prevent/avoid dramatic climate changes. Intelligent pumping also has a play in this arena. In applications such as dewatering and hydraulic fracturing, many companies are deploying VFD solutions in response to factors including emissions and noise regulations, pump efficiency and longevity, and power/fuel efficiency.

In fact, in numerous states such as California, rebates and/or incentives are available to subsidize conversions to motor-driven, VFD-controlled pumps

In summary, pumps play a major, and often understated, role in most industrial activity. The opportunity to reduce energy consumption and related costs, improve industrial processes and contribute to environmental well being are all benefits that can be attributed using intelligent pump systems in many of these applications. Challenge your business to determine how you can realize the benefits of intelligent pumping!

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