Sustainability Starts with Understanding System Power Cost

The insights from a Digital Twin transformation have many uses, but perhaps the most important is their ability to help you achieve measurable financial objectives.  This can be a tall order when you’re already consumed by meeting the everyday requirements of your “regular job.”

But, by providing all team members with information that empowers them to understand how their systems are operating, identify the source(s) of any latent or apparent problem(s), and the knowledge about how to best solve or avoid these problems, the Digital Twin to help you meet financial objectives.

Here’s a case study that shows how an integral component of a Digital Twin—the Computerized Modeling and Analysis application PIPE-FLO—identified a problem that was costing a facility $615,000 a year in lost savings.

The Challenge: Eliminate the Pain—and Save Money

An integrated paper mill located in the southeast United States was having a problem with a vat dilution pump in its bleach plant. The system was experiencing persistent cracking on the vat dilution pump discharge header.  A repair required shutting down the plant and draining the discharge header, collecting the fluid in the pipeline, and sending it to the plant’s waste treatment system—a process that would take about eight hours to finish. Some repairs could wait for scheduled maintenance, but other leaks demanded a full shutdown. 

The discharge pipe also vibrated excessively, and even moved around, as liquids flowed through it. Management lived with the situation for six years while “fighting fires” in other parts of the mill; then, it finally decided that it was time to fix the problems with the vat dilution pump. 

The plant personnel initially reasoned that the excessive cracking was the result of thermal stresses caused by rapid heating of the discharge piping during plant startup. They decided to reduce the rate of temperature change during startup, but after a year of trying this workaround, the problem remained.


I’ll demonstrate using a small open loop system with a single pump as an example (figure 1).  This system consists of a supply tank, a pump, a heat exchanger, a flow element, a flow control valve, and a destination tank. The drawing shows the calculated values for the installed instruments, specifically the level and pressures in the tanks, the pump suction and discharge pressures, the flow rate, and the corresponding position of the control valve. 

This provides plant operators with the information needed to operate the system, but provides only limited insight on how efficiently the system is operating and nothing about the operating cost.    

PIPE-FLO’s calculated results (figure 2) show how the energy is used within the system.  The flow rate through the system is set to 400 gpm, based on the set point of control valve ST1-1-FCV1.  The flow rate through the pump produced 204.7 feet head, with an efficiency of 51% based on the pump curve, and requires 43.79 horsepower into the motor shaft. 


Via PIPE-FLO’s calculated results, we can see the energy supplied by the pump and observe the losses associated with the process and control elements.  We can also see how much power is supplied to the pump to provide the required flow rate, along with the pump efficiency.  Notice the head loss across the heat exchanger and the head loss across the control valve needed to maintain the required flow rate.  Finally, you can see that the difference in static head that must be overcome for the system to work. 

Looking at the results, you can see that only half of the power supplied to the pump is used to move the process fluid through the system.  Approximately 40% of the power supplied by the pump is consumed by the control valve. 

What To Do About It

This presents two additional questions: how much does the current system cost to operate, and what can be done to minimize the operating costs? PIPE-FLO v17.5 features a new System Power Cost capability designed to address those questions. 

By entering the local cost of electrical power, and the length of time for system operation, PIPE-FLO calculates the cost to operate the pump element and the operating cost of each item of equipment in the system.   Figure 3  (below) shows the power cost for each item in our sample system.  In this example, the power cost is $.10 / kWhr, the cost is an annual cost, and the system is operating for 100% of the evaluation period. 


With the dissipated power and cost values displayed, everyone can access the financial insight into system operation.  Notice that the pump has an annual input power cost of $28,618; of that, only 51% of the power is used to move the fluid through the system.  We can also see dissipated power, along with the dissipated power cost, for each item in the system.  Notice that the flow orifice ST-1-FE1 consumes 1.04 kW of power and costs $912 in annual operating costs.  Furthermore, control valve ST1-1-FCV1 consumes 6.58 kW of power, with an annual operating cost of $5,766 per year, to limit the flow rate to 400 gpm. 

With this financial insight, everyone can see how much it costs to operate the piping system, and how much power and associate costs is consumed by the pump based on its efficiency. 

Now, to answer the second question: What might be done to reduce or minimize operating costs?

Using the computational power of PIPE-FLO, a new and more efficient pump, possibly with a Variable Speed Drive, can be inserted into the model to simulate system operation along with savings in operating cost. 

The values and savings can be documented using PIPE-FLO’s new System Cost Report with pie charts, along with a listing of the pump input and output power and with the dissipated power cost for each item in the system (figure 4).

Summary & more

Using PIPE-FLO’s System Power Cost feature provides clear and actionable financial and sustainability insights on fluid piping systems. Insights expressed in “dollars and cents” terms that will resonate throughout an organization.

Ready to KNO more about your system power cost? You’ll need to be on v17.5 of PIPE-FLO to access the System Power Cost analysis feature.  You’ll find information on how to download it here.

Watch this video for more details on the System Power Cost functionality in PIPE-FLO.

Ray Hardee P.E. stamp

PIPE-FLO: All You Need To KNO

PIPE-FLO is the engineering standard for Modeling & Simulation Calculations to manage your entire fluid system lifecycle. From design to digital twin simulations, our software is proven to save time and money.
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