Regarding Life cycle costs
Until a few years ago plant manufacturers and operators only considered acquisition and installation costs when choosing pump systems. To calculate the integrated cost-effectiveness of a product or a system, an overall view about the accumulated costs has to be carried out. The whole amount of costs that occur during a systems lifetime is called Life cycle costs (shortened LCC). With regard to the pump industry the calculation of LCC plays an important role.Pumps have a particularly high lifetime, with an operating time of over 8000 hours (e.g. bath water pumps). Different systems have to be considered separately: In centrifugal pump industry there is a division between clear water and sewage pumps. Whereas sewage pumps need a high operating safety, this can be expected as a basic condition for clear water pumps for the badly damaging medium to be pumped is missing.
Formula to calculate LCC
|
Cic => |
Acquisition costs
(purchasing price of the pump, piping) |
Cin => |
Setup and commissioning costs
(Installation, start-up, instruction) |
Ce => |
Energy costs
(electrical energy absorbed by the motor) |
Co => |
Operating costs
(labour costs for supervision of the system) |
Cm => |
Servicing costs
(regular recurrent and expected repairs) |
Cs => |
Failure costs
(loss of production) |
Cenv => |
Environm. protection costs
(contamination caused by medium to be pumped) |
Cd => |
Shutdown costs
(sales profit of the used pump) |
|
Energy costs are against accepted opinion in many cases the highest cost factor and therefore dominating the LCC. This especially applies for clear water pumps with high operating times per year. The following exemplar calculation clarifies this aspect for three different pump sizes with equal nominal diameter.
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| Demanded operating point: |
Q= 160 m3/h, H= 7,5 m |
|
| Motor alternative 1: |
| 4.0 kW without frequency converter |
Degree of efficiency: 60 % |
|
| Motor alternative 2: |
| 5.5 kW without frequency converter |
Degree of efficiency: 86 % |
|
| Motor alternative 3: |
| 5.5 with frequency converter |
Degree of efficiency: 86 % |
|
If the demanded operating point can be realised by two different pump sizes, the customer usually chooses the smaller and therefore cheaper one that simultaneously has a worse motor efficiency. This means that energy costs and finally LCC increase over a period of time (alternative 1 in the example above). Regarding alternative 2, savings resulting from lower energy costs due to the implementation of a more powerful motor can be distinguished.Alternative 3 shows furthermore the savings resulting from the implementation of a frequency converter. Also in this case the higher purchasing price amortizes with the resulting savings during operating time.
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