Efficient, Economical Pumping Solutions
Why aren't pumps sized correctly?
Overdesign. In many instances the process designer will calculate a flow rate - then add a 10-15% margin. The mechanical guy will then consider pipework losses, and add 10-15% margin to make sure. The pump applications engineer will then size the pump, making sure that the duty point is below the curve and adding an allowance for wear. In some instances the duty is based on maximum flow expected or for future requirements but this is never achieved.
The result is a pump specified which absorbs 20-30% or more power than the correct pump needs and an opportunity for energy saving.
Why aren't savings being made already?
In some places they are. Variable speed drives are becoming more popular although they are not suitable for every system. In general the opportunity is not being recognised for a number of reasons.
- There is little awareness of how much a pump costs to run
- Life costing is not considered at the design stage. Contractors will propose the lowest cost - not the most efficient.
- If a pump is delivering sufficient liquid it is considered to be OK
- Production concerns outweigh pumping concerns - there is a reluctance to change anything.
How much does a pump cost to run?
At typical 2009 industrial prices a pump absorbing 15kw running 24 hours/day 365 days/year will cost £10,400 for electricity.
How can savings be made?
It depends upon the installation. A VSD can be used to control the speed in some cases. In others a change of impeller diameter, better maintenance, change of control, pipework modifications, using energy efficient motors and eliminating/reducing bypasses can all contribute to energy savings. Sometimes simply switching a pump off when it is not needed gives considerable savings.
What is different about Epump procedure?
Pump audits can be expensive and time consuming. Epump's five step procedure analyses the installed pumps and selects the 20% or so that will achieve 80-90% of savings. The survey checks NPSHA (a common contributor to poor pump performance), the general installation (pipe sizes, layout) and can help extend the life and time between maintenance of the pump. Pump duties are measured where possible, estimated where not and Epump developed calculators used give a visual performance guide. These also calculate the potential cost saving.
An action plan can then be proposed and on completion further measurement can confirm energy savings.