The size of your piping system affects your pumping costs. Compute annual and lifecycle cost for systems before making an engineering design decision.

Regardless of the number of pumps, valves and connectors, thermal fluid systems can be designed and built to keep fluid leaks to a minimum while providing reliable performance.
All industrial facilities have a network of piping that carries water or other liquids. According to a U.S. Department of Energy study, 16% of a typical facility's electricity costs are for its pumping system.

The power consumed to overcome the static head in a pumping system varies linearly with flow, and little can be done to reduce the static component of the system requirement. But, several energy- and money-saving opportunities exist to reduce the power required to overcome the friction component of the pumping system.

The frictional power required is dependent on:

• Rate of flow.

• Pipe size (diameter).

• Overall pipe length.

• Pipe characteristics (surface roughness, material of construction,etc.).

• Properties of the liquid being pumped.

Figure 1 shows the annual water pumping cost (frictional power only) for 1,000' of pipe length for different pipe sizes and rates of flow.

Figure 1. Opportunities exist to reduce the power required to overcome the frictional component of the pumping system.

## One Example

A look at a single example shows how optimum pipe sizing can reduce pumping costs.

Table 1. After calculating energy costs, be sure to calculate installation and maintenance costs.
A pumping facility has 10,000' of piping to carry 600 gal/min of water continuously to storage tanks. Table 1 shows how to determine the annual pumping costs associated with different pipe sizes.

The friction factor, based on the pipe roughness, pipe diameter and Reynolds number, can be obtained from engineering handbooks. For most applications, the value of this friction factor will be between 0.015 and 0.0225.
After calculating the energy costs, one should calculate the installation and maintenance costs for the different pipe sizes. Although the upfront cost of a larger pipe size may be higher, it may provide the most cost-effective solution due to the large reduction in the initial pump and operating costs. The equation can be used to estimate frictional pumping costs.

## Suggested Actions to Reduce Pumping Costs

1. Compute annual and lifecycle cost for systems before making an engineering design decision.

2. In systems dominated by friction head, always evaluate pumping costs for a couple of different pipe sizes and try to accommodate pipe size with the lowest overall lifecycle cost.

3. Look for ways to reduce friction factor. If your application permits, the use of plastic or epoxy-coated steel pipes can reduce friction factor by more than 40%, proportionately reducing your pumping costs.

## References

1. Xenergy Inc., United States Motor Systems Market Opportunities Assessment, prepared for the U.S. Department of Energy, December 1998.
2. Mohinder K. Nayyar, Piping Handbook, McGraw-Hill Publications, New York, 1998.
3. Hydraulic Institute, Engineering Data Book, Second Edition, New Jersey, 1990.
4. Improving Pumping System Performance: A Sourcebook for Industry, Motor Challenge and Hydraulic Institute, January 1999.
5. Pumping System Optimization, Training Workshop offered by the U.S. Department of Energy.