WO2006039743A1

WO2006039743A1 - Estimating ownership costs of fluid pumping systems

Info

Publication number: WO2006039743A1
Application number: PCT/AU2005/001557
Authority: WO
Inventors: Heath Seuren
Original assignee: Heath Seuren
Priority date: 2004-10-12
Filing date: 2005-10-10
Publication date: 2006-04-20

Abstract

A method of estimating costs associated with a fluid pumping system, the method including the steps of: obtaining one or more duty points for the fluid pumping system; specifying one or more variable-speed or fixed-speed rotating machines capable of meeting each duty point; for each variable-speed rotating machine at best efficiency, obtaining an operating speed at each duty point; for each fixed-speed rotating machine at best efficiency, obtaining an operating time at each duty point; for each variable-speed rotating machine, calculating increased operating speeds at each duty point due to wear-induced efficiency losses relative to the operating speed at best efficiency; for each fixed-speed rotating machine, calculating increased operating times at each duty point due to wear-induced efficiency losses relative to the operating time at best efficiency; for each rotating machine at each duty point, calculating wear-induced energy costs corresponding to wear-induced efficiency losses based at least in part on the increased operating speeds or the increased operating times.

Description

ESTIMATING OWNERSHIP COSTS OF FLUID PUMPING SYSTEMS

FIELD OF THE INVENTION

The present invention relates to a method and a processor program product for estimating the total cost of ownership of a fluid pumping system.

BACKGROUND OF THE INVENTION

It is generally recognised that the purchase price of rotating equipment, such as a pump or compressor, represents only a small percentage of the total cost of ownership (or lifecycle cost) of a fluid pumping system, while energy and maintenance are, by far, the biggest costs in the life of the system. Therefore, accurately estimating energy and maintenance costs offers a significant long-term cost savings opportunity.

In practice, energy and maintenance costs are interdependent because a pump loses efficiency as its various components wear out. The efficiency of the pump will deteriorate over time, and so the actual efficiency of a pump will not match that of the pump when new. Efficiency degradation due to wear is therefore a very important factor in both the energy and maintenance costs of a pump. During variable-speed pumping operations, adjusting pump output, which is typically accomplished by increasing the pump's speed, is necessary to maintain maximum pumping productivity. The increase in pump speed leads to increased input power, which in turn leads to increased energy costs. A decrease in pump efficiency during fixed-speed pumping operations as wear occurs leads to an increase in the run times due to a decrease in performance. The increased run times similarly lead to increased energy costs.

The efficiency degradation of a pump due to wear naturally builds up slowly over time and repairing the pump is often a balance between the maintenance cost of servicing the pump and the benefits derived from returning the pump to optimum (or at least an increase in) efficiency.

When estimating the total cost of ownership of fluid pumping systems, it would therefore be desirable to take account of the interdependency between energy and maintenance costs due to operating wear in pumps (or compressors). This would enable the costs of maintenance and energy to be balanced, thereby permitting more informed economic decisions about when the degradation of the pump due to wear significantly impacts energy costs such that the pump requires servicing.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a method of estimating costs associated with a fluid pumping system, the method including the steps of: obtaining one or more duty points for the fluid pumping system; specifying one or more variable-speed or fixed-speed rotating machines capable of meeting each duty point; for each variable-speed rotating machine at best efficiency, obtaining an operating speed at each duty point; for each fixed-speed rotating machine at best efficiency, obtaining an operating time at eacfy duty point; for each variable-speed rotating machine, calculating increased operating speeds at each duty point due to wear-induced efficiency losses relative to the operating speed at best efficiency; for each fixed-speed rotating machine, calculating increased operating times at each duty point due to wear-induced efficiency losses relative to the operating time at best efficiency; for each rotating machine at each duty point, calculating wear-induced energy costs corresponding to wear-induced efficiency losses based at least in part on the increased operating speeds or the increased operating times. The method may include the further step of calculating a lifecycle cost for each rotating machine based at least in part on the corresponding wear-induced energy costs. The step of calculating a lifecycle cost for each rotating machine may further be based at least in part on repair costs to restore the rotating machine to best efficiency.

The method may include the further step of determining a lifecycle cost for each rotating machine having the lowest sum of wear-induced energy costs and repair costs.

If two or more rotating machines are specified, the two or more rotating machines may be specified to operate in series or parallel and sequentially or synchronously.

The fluid pumping system may be a liquid pumping system or a gas pumping system. If the fluid pumping system is a liquid pumping system, the one or more rotating machines may be one or more centrifugal pumps. If the fluid pumping system is a gas pumping system, the one or more rotating machines may be one or more centrifugal compressors or fans.

The present invention also provides a method of estimating costs associated with a fluid pumping system, the method including the steps of: obtaining a lifetime over which costs associated with the system are to be estimated; obtaining at least one duty point required of the system; obtaining an annual operating time required at the required duty point; obtaining an electricity rate; specifying at least one variable speed rotating machine capable of meeting the required duty point; obtaining original performance curve data for the specified rotating machine operating at a nominal speed; obtaining a repair cost to restore the efficiency of the rotating machine to the best efficiency point; obtaining a wear time for the rotating machine operating at the nominal speed to lose a predetermined efficiency relative to the best efficiency point; calculating a new speed required for the rotating machine to operate at the required duty point based at least in part on the original performance curve data at the nominal speed and affinity laws; simulating wear in the rotating machine by iteratively calculating worn speeds required for the rotating machine to operate at the required duty point based at least in part on the new speed and efficiency losses relative to the best efficiency point of the rotating machine; for each iteration of wear simulation, calculating, worn performance curve data for the rotating machine at the corresponding required increased speed based at least on the original performance curve data at the nominal speed and affinity laws, wherein the worn performance curve data includes an worn power input; a worn annual energy cost based at least in part on the worn power input, the annual operating time, and the electricity rate; a lifetime energy cost by summing the worn annual energy cost over the lifetime; an annual operating time at the nominal speed based at least on the required annual operating time, the worn input power, and affinity laws; a maintenance cost based at least on the repair cost, the wear time, and the annual operating time at the nominal speed; determining where the energy costs balance the maintenance cost by identifying the iteration of wear simulation having the lowest sum of the lifetime energy cost and the maintenance cost.

The method preferably includes specifying a plurality of rotating machines and, for each specified rotating machine, performing the iterative wear simulation calculations and displaying the lowest sum of the lifetime energy cost and the maintenance cost. The plurality of rotating machines may be specified to operate in series or parallel. The rotating machines in parallel or series may operate sequentially or synchronously. The method preferably includes the further step of calculating lifetime greenhouse gas emissions for each specified rotating machine based at least on the corresponding lowest sum of the lifetime energy cost. The calculated greenhouse gas emissions may be displayed for each specified rotating machine.

The method preferably includes obtaining a plurality of duty points required of the system and performing the iterative wear simulation calculations for each duty point.

The fluid pumping system is preferably a liquid pumping system, such as a water pumping system, and the rotating machine is preferably a centrifugal pump. Alternatively, the fluid pumping system may be a gas pumping system, such as a heating, ventilation or air conditioning system, and the rotating machine may be a centrifugal compressor or fan.

The present invention also provides a processor program product disposed on a processor- readable medium, the processor program product having processor instructions for causing at least one processor to execute the above methods.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention is hereinafter described, by way of nonlimiting example only, with reference to the accompanying drawings, in which:

Figure 1 are head-capacity and efficiency performance curves for a first example of a typical centrifugal pump, "Pump A", at fixed speed; Figure 2 are power and Net Positive Suction Head required (NPSHR) performance curve& for Pump A at fixed speed;

Figure 3 are head-capacity and efficiency curves for Pump A at a new speed to meet a required duty point on a system head-capacity curve;

Figure 4 are head-capacity and efficiency curves for Pump A with no wear and 30% wear; Figure 5 is a graph of wear induced speed increases versus efficiency losses for Pump A;

Figure 6 is a graph of wear induced shaft power increases versus efficiency losses for Pump A; Figure 7 is a graph of wear induced input power increases versus efficiency losses for Pump A;

Figure 8 is a graph of Pump A power costs over 15 years versus efficiency losses;

Figure 9 is a graph of Pump A increases in run times at 100% speed versus efficiency losses; Figure 10 is a graph of Pump A maintenance costs versus efficiency losses;

Figure 11 is a graph of Pump A maintenance and power costs over 15 years versus efficiency losses;

Figure 12 is a higher resolution graph of Pump A maintenance and power costs over 15 years versus efficiency losses; Figure 13 is a table of wear induced power and maintenance cost data for Pump A;

Figure 14 are head-capacity and efficiency performance curves for an alternative second example of a typical centrifugal pump, "Pump B", at fixed speed;

Figure 15 is a table of wear induced power and maintenance cost data for Pump B;

Figure 16 are head-capacity and efficiency performance curves for an alternative third example of a typical centrifugal pump, "Pump C", at fixed speed;

Figure 17 is a table of wear induced power and maintenance cost data for Pump C;

Figure 18 is a graph of the most economical total power, maintenance and capital costs for Pumps A, B and C;

Figure 19 is a graph of Greenhouse gas emissions for Pumps A, B and C; and Figures 20A-F is a sample report generated by a software embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENT

In an exemplary embodiment, the present invention provides a method for estimating, over a lifetime of 15 years, the ownership costs associated with a typical adjustable speed centrifugal pump, "Pump A", equipped with an AC Variable Frequency Drive (VFD) operating in a typical liquid pumping system, such as a water pumping system.

The design flow rate of the liquid pumping system is specified as 264 litres/second for 3000 hours per year. First, the following data relating to Pump A is obtained.

Electricity rate: $0.12 per kilowatt hour.

Motor efficiencies: 1/1 load: 88%; ³A load: 86.5%; Vi load: 84%.

VFD efficiencies: Input frequency 50Hz efficiency: 98%; Minimum efficiency at nominated 30Hz: 95%.

Capital cost: $6,000.

Maintenance interval: 8000 hours of operation. This is the time it takes Pump A to lose 10% of its best efficiency point (BEP).

Maintenance cost: $3,000 at 8000 hours of operation. This is the total cost of restoring Pump A's efficiency to its BEP, including labour, parts, bypass pumping equipment (if required), and other machinery costs such as crane hire etc).

Next, performance curves for Pump A are obtained from the pump manufacturer. Pump manufacturers perform pump tests to determine the operating characteristics of the pumps they manufacture. The pump performance characteristic curves are developed with the pump operating a fixed speed. If the speed of the pump is changed, the curves must be modified in accordance with the Affinity Laws. These laws are expressed in the following equations.

(QiZQo) = (N₁ZN₀) (H₁ZHo) = (N₁ZNo)² (P₁ZPo) = (N₁ZNo)³

Where: Q = Capacity; N = Impeller speed; H = Pump head; P = Pump power; subscript 0 = Pump test speed; and subscript 1 = New pump speed. Figure 1 illustrates head-capacity and efficiency performance curves for Pump A at fixed speed. Power and net positive suction head required (NPSHr) performance curves for

Pump A at fixed speed are illustrated in Figure 2. Using the Affinity Laws, the head- capacity curve for Pump A in Figure 1 is calculated at a new speed needed to pass through the specified design point of 264 litres/second, Figure 3 illustrates the head-capacity curve for Pump A at the new speed, combined with the system curve. The duty point of Pump A and the system in which it is used is the intersection of the pump and system curves. In

Figure 3, the two curves intersect at a capacity of 264 litres/second and a head of 4.27 metres.

The performance of Pump A in use in the system will decrease due to wearing of its hydraulic components. Figure 4 illustrates the wear induced performance degradation of Pump A as its efficiency decreases away from its BEP. When the performance of Pump A degrades due to wearing of the hydraulic components, the only way to maintain the required flow rate is to increase the pump speed via the VFD. As the speed of Pump A is increased, the head-capacity curves will be modified in accordance with the Affinity Laws. Figure 5 illustrates the increase in speed required to restore the performance of Pump A to the required duty point when wear occurs. In each case, a speed increase is accompanied by an increase in the required shaft power of Pump A. Figure 6 illustrates the increases in the shaft power of Pump A for wear induced efficiency losses. Figure 7 illustrates that as the load on the motor increases and the speed of the VFD increases, so too does the input power.

The power costs of operating Pump A in the system at the required duty point are now estimated taking account of wear induced performance degradation. This is done by iteratively nominating a new shaft power or assuming the published shaft power, and applying a reduction in flow and head to achieve the nominated efficiency loss at BEP. To achieve this reduction in flow and head, the same theory behind the affinity laws is applied, ie 1 :1 ratio for flow squared function for head. New speeds are calculated at 1% intervals of efficiency loss as Pump A's efficiency decreases 0-30% relative to its BEP. Based on the calculated new input power, it is possible to calculate the yearly power consumption, as the flow rate delivered by the pump matches the flow rate required, the input power is multiplied by the duty required run hours, and then multiplied by the electricity rate obtained above. This calculation is performed for each set of redefined performance curves with simulated wear at 1% loss intervals, the results are then added together and averaged. For example, the power cost for Pump A when serviced after only a 1% loss in efficiency relative to its BEP is the sum of the power cost for 0% loss and the power cost for 1% loss, divided by 2. This figure is then multiplied by the term of assessment. Figure 8 illustrates the power cost of operating Pump A at the required duty point over the specified 15 year lifetime for 0-30% wear induced performance degradation.

The increases in speed necessary to operate Pump A at the required duty when wear occurs must be taken into account when estimating maintenance intervals. This can be done by recalculating the run times of Pump A at 100% frequency. For example, if Pump A has a nominated service time of 8000 hours to loose 10% of efficiency at the BEP, then if Pump A runs at 25Hz to achieve the required duty, the real run hours for maintenance purposes is only 4000 hours, so Pump A would only have lost 5% off its efficiency after the run clock displays 8000 hours. The real run hours increases as Pump A starts to wear because there is an increase in the speed to achieve the required duty, as illustrated in Figure 9.

Similarly, the increases in speed necessary to operate Pump A at the required duty as wear occurs must be taken into account when estimating maintenance costs. For example, Pump A has a nominated time of 8000 hours to lose 10% efficiency, so if this time is halved to 4000 hours Pump A would only have worn enough to lose 5% efficiency. So a 10% loss matches the maintenance interval specified by the manufacturer, a 9% loss equals the maintenance interval multiplied by 0.9, an 11% loss would therefore equal the maintenance interval multiplied by 1.1 and so on. Based on the nominated time to lose 10% efficiency, a pro-rata service interval for each 1% wear-induced efficiency loss may be calculated for Pump A to be 800 hours (ie 8000 hours multiplied by 0.1). This calculated service interval for 1% efficiency losses may be used to calculate the maintenance costs for each redefined performance curve with simulated wear as follows: (((run times at 100% results for 0% loss + run times at 100% results for 1% loss) x the term of assessment) / the calculated service interval in hours) x the maintenance cost obtained above. The calculated maintenance costs for Pump A at 0-30% wear induced performance losses relative to BEP are illustrated in Figure 10.

Having calculated the power costs and the maintenance costs for Pump A after taking account of wear, the next step is to determine the most economical balance between these two costs. The most economical point is the efficiency loss iteration that has the lowest sum of the power costs and the maintenance costs for the required duty point over the 15 year lifetime. This information can be used to schedule maintenance of Pump A and indicates the best method of running Pump A with the most economical balance between power cost and maintenance cost. Figure 11 illustrates the combined power and maintenance costs for Pump A at 0-30% wear induced performance losses relative to BEP. The combined power and maintenance costs for Pump A are illustrated with greater resolution at 5-30% losses in Figure 12. As best seen in Figure 12, the lowest point on the curve corresponds to a 14% loss in efficiency and this point represents the most economical balance of maintenance and power consumption for Pump A.

Applying the above methodology, a table of calculated power and maintenance data for Pump A at 1% efficiency losses due to wear is developed. As illustrated in Figure 13, the table includes a column of the total power, maintenance and capital cost for Pump A over the 15 year lifetime. As illustrated below, the most economical balance of power, maintenance and capital costs is estimated to be when Pump A has lost 14% of its BEP efficiency due to wear.

Based on the estimated power and maintenance costs, the most economic time to schedule maintenance to restore Pump A to its BEP is when it completes 11200 operating hours at 100% speed. This figure may be converted to the corresponding actual or real run hours displayed on the pump's run meter to assist maintenance scheduling.

Two alternative centrifugal pumps, Pump B and C, will now be compared with Pump A for use in the same system at the same required duty over the same 15 year lifetime. Further, the same motor efficiency and VFD efficiencies are used.

Compared to Pump A, Pump B requires more frequent maintenance at intervals of 4000 hours, but at a lower maintenance cost of $2,000. The capital cost of Pump B is $3,000. Pump C is a highly efficient pump that has the longest maintenance interval at 12,000 hours, however it also has the highest maintenance cost at $3,500. The capital cost of Pump C is $9,000.

Based on this data, the above methodology is repeated for Pump B and Pump C and the respective results are tabulated in Figures 14 and 15. As illustrated below, for Pump B the most economical balance of power, maintenance and capital costs is estimated to be when loses 15% of its BEP efficiency due to wear.

Run

Power cost

Times

Service with wear, this

@ 100% Total Power,

Service cost based Yearly is the average

Efficiency speed Maintenance intervals on Power Cost yearly cost

(figures cost & in Hours correspondi with wear multiplied by displaye Capital cost ng term the term of d in investment hours)

15 2656.43 6000 $12,818.65 $9,005.28 $121 ,870.38 $137,689.04

For Pump C, the most economical balance of power, maintenance and capital costs is estimated to be when it loses 13% of its BEP efficiency due to wear.

Figure 18 illustrates the most economical total power, maintenance and capital costs for Pumps A, B and C. It can be seen that Pump C is the most cost efficient investment with a total cost over the 15 year lifetime of $108,374. Compared to Pump C, Pump B will cost an additional $31,166 in power costs over the 15 year lifetime.

The power data calculated using the above methodology can be use to estimate greenhouse gas emissions associated with operating a particular pump. Greenhouse gas emissions associated with the quantity used in tonnes of carbon dioxide equivalent (t CO2-e) may be calculated with the following equation.

GHG emissions (t CO₂-e) = Q x EF

Where: Q is the electricity used expressed in kWh; and EF is an Emission Factor in kg CO₂-e/kWh that depends on location within an electricity network and represents CO₂, CH₄ and N₂O emissions from power stations. In the present example, an EF of 1.392 in kg CO₂-e/kWh is used based on the Emission Factor for Victoria, Australia published at http ://www. greenhouse. Rov.au/workbook/pubs/workbook.pdf. The above greenhouse gas emission equation may be modified for use with the present method as follows.

Emissions (t CO₂-e) = "Power cost with wear, this is the average yearly cost multiplied by the term of investment" / Power Cost x 1.392 / 1000

Substituting the power cost calculations for Pump C from above, the greenhouse gas emissions for that pump are calculated as follows. Pump C Emissions (t CO₂-e) = $90,703 / $0.12 x 1.392 / 1000

= 1052 tonnes

Figure 19 illustrates the estimated Greenhouse gas emissions for Pumps A, B and C based on the power data calculated using the above methodology. The difference between using Pump B and C is 361 tonnes of emission (tCO₂-e) over the 15 year lifecycle. It will be appreciated that the comparison of Greenhouse gas emissions may be commercially relevant when comparing pump emissions, as this represents tangible financial and greenhouse gas emission savings.

It will be appreciated that embodiments of the method of the present invention can be used to make better decisions on when maintenance should be provided. This may allow reductions in maintenance intervals, and hence less disruptions to the pumping service being provided by the pump system. Further, embodiments may also indicate that it may be cheaper to purchase a pump with a higher up-front capital cost if this solution has a longer lifecycle.

The method of the present invention is preferably implemented as computer software that can be run on an individual computer or on networked computers. The software may include conventional functionality of exemplary pump selection software such as generating system curves, overlaying system curves and pump performance curves, calculating net positive suction head available (NPSHa), searching and listing all pumps from a range that can meet the specified duty point, and performing calculations for multiple pumps operated in series or parallel, either sequentially or synchronously.

Further, the software may automatically screen or filter candidate pumps to ensure that the NPSHr by the pump is less than the NPSHa, and automatically determine if a calculated new speed needed to meet a required duty point overspeeds or exceeds the pump manufacturer's specified or rated operating speed range. This will safeguard against a pump being used outside of acceptable operating limits on the basis of information generated by the software. It will be appreciated that the embodiments described above are intended only to serve as examples, and that many other embodiments are possible within the spirit and the scope of the present invention. For example, the above embodiment required a single duty point for the purpose of simplifying the description only. It will be appreciated that the method of the present invention may be implemented for fluid pumping systems having multiple duty points.

The above embodiment evaluates variable speed pumps as a non-limiting example only. It will be appreciated that the method of the present invention may be applied to fixed speed pumps where the operating speed remains constant, but run time increases as wear induced performance degradation increases. Thus, the method may be adapted to fixed-speed (or direct online) pump operation by iteratively calculating the wear induced increases in run time and their corresponding increases in power consumption and cost. In particular, it will be appreciated that a fixed-speed pump runs at one constant speed and variation in flow and head is a direct result of wear which causes a reduction in flow and head and therefore increases the pump's run time to transfer the nominated amount of flow. An example application of the method of the present invention to a fixed-speed pump is provided below.

Further, the above embodiment was concerned with the use of a centrifugal pump in a liquid pumping system. It will be appreciated that method of the present invention may be implemented for centrifugal compressors or fans used in gas pumping systems, such as heating, ventilation or air conditioning systems.

Figures 20A-F is a sample report generated by a software embodiment of the invention for an example water pump station. As illustrated in Figures 2OA and 2OB, the sample report includes summaries of system data and pump data provided by a user. The sample report also includes in Figure 2OC a summary of configuration options and calculated costs associated with the example pump station. The summary in Figure 2OC indicates that the most efficient configuration is the direct online (or fixed-speed) option with a full lifecycle cost of $324,888 based on a service interval of 4000 hours. The second most efficient configuration occurs in the Synchronous NPSHA configuration with a lifecycle cost of $376,631 based on a service interval of 7200 hours. The third most efficient configuration occurs in the Synchronous User Defined Max Hz configuration with a lifecycle cost that is $378,058 based on a service interval of 7200 hours. Figures 2OD and 2OE are summaries for the direct online option for different duty requirements at different efficiency losses. Figure 2OF is a cost summary for the direct online option. As mentioned above, the direct online option summarised in Figures 20D-F illustrates the application of the method of the present invention to a fixed-speed pump. Specifically, the embodiment software of the present invention calculates wear-induced increases in run times for the direct online pump option to meet the specified duty requirements. Figure 2OF summarises the increased run times for the direct online option for 0-30% efficiency losses due to wear, together with the corresponding increases in power costs.

It should also be noted, as with all software, the processes and functions described herein can be performed in various ways using various hardware and software languages. This description does not intend to limit the performance of these processes and functions to only the methods described herein. Many processes can be performed in a different, but equivalent manner or order than described herein without exceeding the scope of the claimed invention.

Claims

1. A method of estimating costs associated with a fluid pumping system, the method including the steps of: obtaining one or more duty points for the fluid pumping system; specifying one or more variable-speed or fixed-speed rotating machines capable of meeting each duty point; for each variable-speed rotating machine at best efficiency, obtaining an operating speed at each duty point; for each fixed-speed rotating machine at best efficiency, obtaining an operating time at each duty point; for each variable-speed rotating machine, calculating increased operating speeds at each duty point due to wear-induced efficiency losses relative to the operating speed at best efficiency; for each fixed-speed rotating machine, calculating increased operating times at each duty point due to wear-induced efficiency losses relative to the operating time at best efficiency; for each rotating machine at each duty point, calculating wear-induced energy costs corresponding to wear-induced efficiency losses based at least in part on the increased operating speeds or the increased operating times.

2. A method according to claim 1, including the further step of calculating a lifecycle cost for each rotating machine based at least in part on the corresponding wear-induced energy costs.

3. A method according to claim 2, wherein the step of calculating a lifecycle cost for each rotating machine is further based at least in part on repair costs to restore the rotating machine to best efficiency.

4. A method according to claim 3, including the further step of determining a lifecycle cost for each rotating machine having the lowest sum of wear-induced energy costs and repair costs.

5. A method according to any preceding claim, wherein if two or more rotating machines are specified, the two or more rotating machines are specified to operate in series or parallel and sequentially or synchronously.

6. A method according to any preceding claim, wherein the fluid pumping system is a liquid pumping system or a gas pumping system.

7. A method according to claim 6, wherein if the fluid pumping system is a liquid pumping system, the one or more rotating machines include one or more centrifugal pumps.

8. A method according to claim 6, wherein if the fluid pumping system is a gas pumping system, the one or more rotating machines include one or more centrifugal compressors or fans.

9. A processor program product disposed on a processor-readable medium, the processor program product having processor instructions for causing at least one processor to: obtain one or more duty points for the fluid pumping system; specify one or more variable-speed or fixed-speed rotating machines capable of meeting each duty point; for each variable-speed rotating machine at best efficiency, obtain an operating speed at each duty point; for each fixed-speed rotating machine at best efficiency, obtain an operating time at each duty point; for each variable-speed rotating machine, calculate increased operating speeds at each duty point due to wear-induced efficiency losses relative to the operating speed at best efficiency; for each fixed-speed rotating machine, calculate increased operating times at each duty point due to wear-induced efficiency losses relative to the operating time at best efficiency; for each rotating machine at each duty point, calculate wear-induced energy costs corresponding to wear-induced efficiency losses based at least in part on the increased operating speeds or the increased operating times.

10. A method of estimating costs associated with a fluid pumping system, the method including the steps of: obtaining a lifetime over which costs associated with the system are to be estimated; obtaining at least one duty point required of the system; obtaining an annual operating time required at the required duty point; obtaining an electricity rate; specifying at least one variable speed rotating machine capable of meeting the required duty point; obtaining original performance curve data for the specified rotating machine operating at a nominal speed; obtaining a repair cost to restore the efficiency of the rotating machine to the best efficiency point; obtaining a wear time for the rotating machine operating at the nominal speed to lose a predetermined efficiency relative to the best efficiency point; calculating a new speed required for the rotating machine to operate at the required duty point based at least in part on the original performance curve data at the nominal speed and affinity laws; simulating wear in the rotating machine by iteratively calculating worn speeds required for the rotating machine to operate at the required duty point based at least in part on the new speed and efficiency losses relative to the best efficiency point of the rotating machine; for each iteration of wear simulation, calculating, worn performance curve data for the rotating machine at the corresponding required increased speed based at least on the original performance curve data at the nominal speed and affinity laws, wherein the worn performance curve data includes an worn power input; a worn annual energy cost based at least in part on the worn power input, the annual operating time, and the electricity rate; a lifetime energy cost by summing the worn annual energy cost over the lifetime; an annual operating time at the nominal speed based at least on the required annual operating time, the worn input power, and affinity laws; a maintenance cost based at least on the repair cost, the wear time, and the annual operating time at the nominal speed; determining where the energy costs balance the maintenance cost by identifying the iteration of wear simulation having the lowest sum of the lifetime energy cost and the maintenance cost.

1 1. A method according to claim 10, further including specifying a plurality of rotating machines and, for each specified rotating machine, performing the iterative wear simulation calculations and displaying the lowest sum of the lifetime energy cost and the maintenance cost.

12. A method according to claim 11, further including specifying the plurality of rotating machines to operate in series or parallel and sequentially or synchronously.

13. A method according to any one of claims 10 to 12, further including calculating lifetime greenhouse gas emissions for each specified rotating machine based at least on the corresponding lowest sum of the lifetime energy cost.

14. A method according to claim 13, wherein the calculated greenhouse gas emissions are displayed for each specified rotating machine.

15. A method according to any one of claims 10 to 14, further including obtaining a plurality of duty points required of the system and performing the iterative wear simulation calculations for each duty point.

16. A method according to any one of claims 10 to 15, wherein the fluid pumping system is a liquid pumping system and the at least one the rotating machine is a centrifugal pump.

17. A method according to claim 16, wherein the liquid pumping system is a water pumping system.

18. A method according to any one of claims 10 to 15, wherein the fluid pumping system is a gas pumping system and the at least one rotating machine is a centrifugal compressor or fan.

19. A method according to claim 18, wherein the gas pumping system is at least one of a heating system, a ventilation system and an air conditioning system.

20. A processor program product disposed on a processor-readable medium, the processor program product having processor instructions for causing at least one processor to: obtain a lifetime over which costs associated with the system are to be estimated; obtain at least one duty point required of the system; obtain an annual operating time required at the required duty point; obtain an electricity rate; specify at least one variable speed rotating machine capable of meeting the required duty point; obtain original performance curve data for the specified rotating machine operating at a nominal speed; obtain a repair cost to restore the efficiency of the rotating machine to the best efficiency point; obtain a wear time for the rotating machine operating at the nominal speed to lose a predetermined efficiency relative to the best efficiency point; calculate a new speed required for the rotating machine to operate at the required duty point based at least in part on the original performance curve data at the nominal speed and affinity laws; simulate wear in the rotating machine by iteratively calculating worn speeds required for the rotating machine to operate at the required duty point based at least in part on the new speed and efficiency losses relative to the best efficiency point of the rotating machine; for each iteration of wear simulation, calculate, worn performance curve data for the rotating machine at the corresponding required increased speed based at least on the original performance curve data at the nominal speed and affinity laws, wherein the worn performance curve data includes an worn power input; a worn annual energy cost based at least in part on the worn power input, the annual operating time, and the electricity rate; a lifetime energy cost by summing the worn annual energy cost over the lifetime; an annual operating time at the nominal speed based at least on the required annual operating time, the worn input power, and affinity laws; a maintenance cost based at least on the repair cost, the wear time, and the annual operating time at the nominal speed; determine where the energy costs balance the maintenance cost by identifying the iteration of wear simulation having the lowest sum of the lifetime energy cost and the maintenance cost.