Part IV: Optimizing Pumping Systems

Pumping systems are used worldwide to transport fluids and operate in most industrial processes. Commercial and residential buildings also rely on pumps for essential services. Pumping systems account for nearly 25 percent of the energy consumed by electric motors, and for 20 percent to 60 percent of the total electrical energy usage in many industrial water and wastewater treatment facilities. Figure 1 shows the potential saving in gigawatt hours per year for optimization opportunities in key energy- intensive industries. The process of identifying, understanding, and effectively eliminating unnecessary losses while reducing energy consumption, improving reliability, and minimizing the cost of ownership over the economic life of the pumping systems is commonly referred to as systems optimization. Besides reducing energy costs, improving the performance of an existing pumping system yields other benefits (Table 1).

Next, the pump systems selected for assessment should be thoroughly evaluated to determine the true system requirements. In some systems, the operating pressures or rates of flow may be excessively high. Occasionally, this analysis will reveal that one or more pumping systems can be turned off without compromising the process. Diagnostics & Data Collection The next step in system optimization is to collect performance data such as rate of flow, suction and discharge pressure, or power consumption, using accurate and repeatable instrumentation. If the testing is not detrimental to the process, then consider a permanent installation. Continuously or intermittently measuring important parameters directly affecting process energy consumption can pay off in a short time. Compare System Curve with Pump Performance Curve Once the data have been collected, it is possible to compare the existing operating conditions to the design conditions and determine whether the pump is appropriately sized. The original pump performance curve is useful to construct a curve for the operating points of the existing system. Comparing acquired test data to the original performance curve provides an immediate sense of the current pump condition. Even comparing a single test point to the original curve can help the user determine whether the first step is to overhaul the pump or investigate the system further. Depending on the system operation and fluid properties, a curve may be corrected for speed, temperature, specific gravity, or viscosity. In most cases, measurements that balance quantitative and qualitative aspects will be sufficient for major decisions regarding system optimization. How to address each case can be determined without spending excessive time calculating error margins. If the piping cannot be changed, simply moving the pump curve closer to the desired operating condition will improve system efficiency. Pump Duty Point

Evaluate the system piping configuration for optimization opportunities. A proper configuration includes a straight-run of pipe leading into the pump inlet to ensure a uniform flow distribution into the pump. Evaluate the use of vanes or other means of “straightening” the flow when this is not possible. Finally, analyze the size and pressure drop of the suction piping to minimize friction losses. Evaluate Opportunities Data analysis should indicate the system components that need to be changed for better efficiency. Some typical ways to optimize pumping systems include: Motors: Every pump needs a prime mover. Electric motors are frequently- used drivers for pumps. The electric power a motor consumes is another important piece of data to evaluate when looking for opportunities to save. Measurement of low voltage motor power is usually easy and an important point in data collection. The power consumption can uncover any potential problems (mechanical or electrical) with the motor and provide a quick method to check for wasted energy.

• Understand the operational deficiencies of the system and the process guarantees
• Identify and understand any and all system problems
• Carefully assess the system under full range of operation
• Use qualified technicians and quality instrumentation to capture field data
• Utilize available historical data from the plant operating system
• Understand the true cost of energy and production downtime
• Model the system and implement scenarios in the computer to optimize energy and economic benefits
• Ensure buy-in from stakeholders in purchasing, operations, maintenance, and management by presenting results that show how each group will benefit from the system upgrade

“Improving the Performance of Existing Pumps” is the fourth article in a series based on the new guidebook Optimizing Pumping Systems, A Guide to Improved Energy Efficiency, Reliability, and Profitability, currently available from Hydraulic Institute (HI) and Pump Systems Matter (PSM). Next month’s article will focus on optimizing new pumping system designs.

?Gregg Romanyshyn is the technical director at the Hydraulic Institute. In this position, he oversees the technical aspects related to the Hydraulic Institute. Mr. Romanyshyn has over 30 years experience involved with pump- related businesses and has been at the Hydraulic Institute for 10 years. The Hydraulic Institute is the largest association of pump industry manufacturers in North America and serves the pump community by providing product standards, guidelines, and references, and is a forum for the exchange of industry information.