Want full visibility of pump performance to facilitate operation as close to BEP as possible within your production constraints – from your cellphone? Then this is the way to go.

Recent independent Internet-based pump monitoring systems have emerged that can quantify the inefficiency cost of your pump, both currently and over its lifetime, identify potential equipment failure before it manifests, and calculate the optimum time to refurbish or replace the unit, thus minimizing the total life cycle cost of the equipment.

The Target: BEP

For example, centrifugal pumps are designed to operate within a very confined envelope. Each pump model has its own unique performance curve based upon tested readings taken during its manufacture. This respective performance curve describes the relationship between flow, head, power and efficiency over the entire flow range.

QBEP is the pump flow rate at its Best Efficiency Point (BEP) in mechanical terms. Ideally, a pump should operate between 80 percent and 110 percent of this flow. Figure 1 demonstrates a typical pump performance, showing BEP and the optimum operating range. 

Figure 1. A typical pump performance curve. 

Many pumps, however, do not operate in the best efficiency zone. Among the reasons for these inefficiencies are incorrect design specifications, changes to system requirement, variable processes, ongoing pump wear, ‘quick fix’ solutions such as bypassing flow or throttling the discharge line, variable speed drives with inadequate control, and insufficient understanding of, or focus on, pump management and its effect on production stability and costs.

For a typical centrifugal pump, the breakdown of life cycle costs is 5 percent capital, 5 percent to 25 percent maintenance (depending on the nature of the product being pumped), and 70 percent to 90 percent power. Pumps that operate more efficiently, i.e. closer to the BEP, will save significant amounts of money every year as these cost elements are reduced.

A pump operating outside its QBEP range consumes excessive power. Because pump efficiency drops off sharply both to the left and right of the BEP, more power is wasted in the form of heat passed on to the fluid. More efficient operation, closer to the BEP range, consequently has a positive effect on production stability and costs.

Pumps currently consume 20 percent of the world’s total electrical power. Studies undertaken by government bodies in the EU and U.S., and independent articles in trade journals, all indicate that potential savings of between 15 percent to 40 percent of this consumption are feasible arising from efficient operation.

Furthermore, pumps operating close to optimum efficiency cost less to maintain and fail less often. Components such as seals, bearings, and shafts seldom fail during normal operation if the pump is selected and operated correctly. Following the recommendations that are given by pump performance monitoring may result in a short-term increase in routine refurbishment in order to maintain cost-beneficial pump efficiency. However, total costs over the life of the pump will be reduced as a result of: 

  1. Refurbishing before excessive wear has occurred allows components to be repaired, not replaced, and 
  2. Premature refurbishing, undertaken to avoid any failure and resultant production downtime, can be avoided.

Operating pumps significantly away from their BEP will adversely affect the pump mechanically,  resulting in component deterioration, pump failure, and major costs in terms of lost production. In a process environment, unstable pump operation has a negative effect on the operating efficiency and/or reliability of other equipment.

For example, in the case of a mill circuit, wide fluctuations in pump performance lead directly to inefficiencies in the entire plant operation. Cyclones operate outside their optimum efficiency bands, resulting in greater re-circulating loads through the mill, and reduced product recoveries.

Pumps operating well off BEP could also suffer catastrophic failures that compromise plant safety. Excessive redundancy is often designed into pumping systems to provide back-up capacity in case of failure. This results in unnecessary capital expenditure, which can be kept to a minimum by greater visibility of pump operations and consequent reduced risk of breakdown.

Traditional on-site condition monitoring has become inadequate on pumps. It is expensive in time and travel, especially with scarce numbers of skilled manpower. The time interval between tests is also too great to detect and rectify problems in a timely manner. Instrumentation attached to the pump may be absent or inaccurate. Once a problem has been detected, destruction of the pump has already begun.

Remote Gets Better

New web-based technology, however, has vastly improved remote performance monitoring. Such technology is designed to provide hands-off monitoring of the pump operation at pre-set intervals (e.g. hourly). Data is collected automatically from transducers attached to the pump and sent to the monitoring website via the user’s existing communications infrastructure (e.g. SCADA) and/or GPRS.

The web-based system analyzes these readings against the pump’s original performance curve and specifications to derive the current efficiency and its variance from BEP (i.e. the degree of wastage). This wastage is quantified and classified into wear, duty and volumetric loss in order to assist in problem identification, facilitate cost/benefit analyses of alternative solutions, and allow remedial action to be taken before excessive costs are incurred or destruction of the pump commences. It also measures the success of the chosen remedial actions and predicts refurbishment intervals for each pump in its specific function.

The web-based system then allows authorized users real-time remote access to the pump performance data via the Internet, giving ongoing visibility into the current operation. A consultancy team, meanwhile, provides users with periodic management reports and technical assistance in dealing with alarm conditions.

The web-based pump monitoring system empowers the pump operator to select the optimum cost justifiable course of action, based on the quantified magnitude and characteristics of the efficiency loss. Some typical remedial options for excessive wear include overhauling the pump, replacing the impeller, and lining the pump’s wearing pumps.

For duty loss, the user could replace the pump with a different model, trim the impeller or change the pump speed, install a variable speed drive, change the control methodology, and make changes to the pumping system (pipes or valves). With volumetric loss, the user can balance flow type pumps, identifying the optimum time to replace wearing parts, or replace bypass or throttling valves in the system with a variable speed drive. 

Bottom Lines

Costs associated with the installation and ongoing operation of a new web-based pump monitoring system will obviously vary from site to site depending on a number of variables, e.g. type and size of pump, characteristics of the product being pumped, current status of instrumentation and communications, geographical location and accessibility, etc.

Similarly, the payback period for the initial capital investment will be affected by these and other factors such as  maintenance history, power unit costs, degree of pump utilization etc. These factors are examined during an initial site audit, in which costs and potential savings are estimated and a business case for installation established.

Certain guidelines hold true for the vast majority of pumping operations. First, in large pumping applications with minimal pump wear (e.g. clear water), the costs of installing the web-based monitoring system and the capital costs of initial relevant remedial action can be recovered from power savings alone in the short term.

Payback periods under one year are frequently experienced. In other applications with greater pump wear, savings in maintenance and plant downtime would increase while power savings may be less dramatic. In both cases, ongoing monitoring costs are far exceeded by savings after the initial costs of instrumentation and installation have been absorbed. Maintenance and refurbishment costs may rise marginally in the short term as inefficient equipment is replaced or refurbished at an earlier stage. These will subsequently return to previous levels or lower.

Certain ancillary costs can be reduced or eliminated with the newer remote monitoring systems. A newer remote system can derive flows accurately after initial calibration, so relatively expensive flow meters are not required. On-site performance testing, either for routine checking or after installation/refurbishing, is more accurately undertaken through the new technology. The savings in power consumption will have a positive environmental impact. If a phased approach is preferred, initial savings can be used to fund later stages of implementation.

The newest remote technology analyzes the incoming data, quantifies the current level of wastage, and classifies it as mentioned above. These analyses facilitate cost/benefit evaluation of possible solutions and allow remedial action to be taken before excessive costs are incurred or destruction of the pump commences. It is also possible to see a baseline against which the success of improvements such as pump coating, trimming impellers or changing the pump speed or model can be measured.

Shortcomings in pump configuration are also exposed, e.g. incorrect pump and/or motor selection, or the largely or totally redundant situation in which one or more pumps in a group are operating in series or parallel.

Taken together, this body of information provides full visibility of pump performance to the operator and/or management. This facilitates operation as close to BEP as possible within production constraints which, in turn, delivers major power consumption and maintenance cost savings.

The newest remote pump monitoring technology also offers many indirect benefits. First, operation of the system and interpretation of the output require minimal user expertise. It also enables best practices for pump operation in a given environment to be established, monitored and, if necessary, amended.

Early warning of significant changes in performance and/or impending equipment failure yields improved plant reliability, safety, and stability; reduced costly production downtime; and less redundancy in the design of new pump stations.

In addition, the movement of surplus pumps from existing installations to other sites offers long-term capital cost reduction. Wasteful travel by skilled staff to perform on-site inspections is greatly reduced. Insufficient on-site instrumentation and incomplete test results become a thing of the past. Disputes between the pump user and the OEM can be resolved by reference to independent performance data stored by the new monitoring system. The newest web-based technology can also be used to facilitate a power load shifting project.

Pumps & Systems, October 2006