PUMPM SELECTION
More than 60 % of installed pumps operate outside the operating range.
The main task of the pump selection is the right definition of the necessary pump's parameters. If parameters have been defined not properly the selected pump will have problems with efficiency and reliability.
How to select a pump?
The process of a pump selection must take into account different aspects which and some of these aspects are not obvious at this phase Life Cycle Cost analysis.but could have a serious influence on pumping system operation. Everytime pump selection is the process of finding a compromise between CAPEX and OPEX. The best instrument that can help to find this balance is the Life Cycle Cost method.
1. Using pump selection software. Many companies have selection programs on sites and offline versions. It is possible to take into account all aspects and conditions connected with the pump operation.
2. Ask a pump manufacturing company to select a pump. In this case, it is necessary to fill a pump's datasheet and send it to the pump manufacturing company.
This is the best way for customers who do not have enough experience or when special pumps are necessary.
The User cannot take into account important details which will have a great influence on pump operation. Even studying datasheet you will discover many features you have not thought about before.
3. Selection of a pump by yourself. This way is the most suitable for experienced users.
But whatever method you have chosen there are standard steps and information you should know about your system and about pumps you are going to apply.
One of the main goals of the pump selection is the providing effective and reliable pump operation. In other words, it means operating a pump withing the operating range.
The pump selection usually includes the following steps:
1. Type of pumped liquid and it's properties - Clean cold water, contaminated water, hot water, sewage water, oil, highly viscous liquid, chemically active liquid, etc.
Pumped liquid properties.
- name of liquid
- the temperature of the pumped liquid (max, min)
- chemical properties.
- mechanical particles amount
- vapour pressure.
- viscosity at the temperature.
- density.
2. Type of installation
- Horizontal
- Vertical.
- Submersible.
- Semi-submersible.
3. Hydraulic parameters of a pump.
- Flow.
- Head.
- NPSH.
- Inlet pressure.
- Piping system curve.
- Changing of parameters of a system in time, max and min and (load profile), the longest mode of operation
4. Type of pump and pump design.
Mainly the design and the type of a pump are defined by parameters and application.
5. Materials of a pump. Defined by the chemical properties of and sizes of mechanical particles.
6 Pump drive.
- Electric motor.
- Diesel motor.
- Turbine.
7. Pump control. Is it supposed to apply any type of a pump control?
8. Environmental conditions.
- Hazardous area.
- Where a pump will be installed (outside, inside the house, under conopy)
- Outside temperature (min. max)
- Humidity.
- Altitude over sea level
9. Availability of a service and spare parts (especially the cost of spare parts).
10. Economy aspects.
- Price.
- Operation cost.
The most powerful tool for the evaluation of a pump economy is the Life Cycle Cost analysis.
11. Some special requirements are defined by the industry where the pump will be applied. For example, demands to pumps for the oil industry are defined API 610 standard.
12. Time of manufacturing and Delivery time of a pump.
13. Type of shaft sealing
- gland packing
- mechanical seal.
If you have answers on questions, you can do preliminary pump selection.
Hydraulic range of pumps of some model
The required operating point defined by the values of Q and H is plotted on the hydraulic range of the defined pump model.
This point gets in the field of defined pump model. In our case, this is pump #30.
The fact that point lays inside field means that pump will be with reduced (trimmed) impeller.
After preliminary selection of a pump model, we go to the detailed pump characteristics from the catalog.
For operating point which is plotted in the Q-H graph defines the other pump parameters such as impeller diameter, pump efficiency, shaft power, NPSH.