Dont pump away profits
May 1st 2004 Pumps account for a huge % of the total invested capital of UK industry. Failure to operate these assets economically wastes 100,000s annually. Paul Poste of Pruftechnik discusses these unmeasured costs
Throughout UK industry investment in pumps and pumping systems accounts for a significant percentage of the total industry operating costs. When you combine energy costs with capital investment and maintenance costs, pumps and associated systems can represent as much as 40% of the entire capital investment of a company. No wonder then that great care is taken to specify the correct and most energy efficient system for the application. All too frequently, however, the care and attention given to specification is let down by inadequate attention to proper installation and on-going maintenance. Without careful attention to detail in the installation of all pumps the plant operator is simply pouring money down the drain.
Assuming correct selection and efficient operating specification, what can possibly go wrong during the operation of the system to create such a situation, and what if anything can a mere maintenance engineer do to contribute to a more efficient and trouble free plant operation?
There is substantial evidence to suggest that of all installed rotating machine systems such as pump sets more than 50% will fail prematurely because of poor initial alignment between the driver and driven components.
The consequences of poor shaft alignment will impact on all aspects of the plant maintenance budget causing:
Unnecessary expenditure on components such as mechanical seals, bearings, shafts, couplings etc.
Unnecessary expenditure on power consumption, it costs more to drive poorly aligned machine sets.
Unnecessary expenditure on maintenance labour to repair the damaged machines.
Unscheduled plant shut down and repair causing lost production.
Ultimately these costs have a negative effect on the profitability of the production plant and on the long term employment prospects of every employee. Installing flexible couplings is not a solution to the problems identified above. The coupling invariably can withstand misalignment of for example 1 or 2mm, but the pump set components cannot. Misalignment does not simply disappear as if by magic. It is passed on to the adjacent components (in this case) of the pump set such as mechanical seals and bearings, these components are quickly damaged by the forces of misalignment that are transferred to them. Fig 1 shows graphically the effect of heat transfer into key components caused by misalignment. Mechanical seals and bearings are not designed to operate at elevated temperatures for prolonged periods of time. It therefore makes sense to do everything possible when installing equipment to ensure that the initial installation is as good as possible.
But extending component life is not the only benefit of good shaft alignment. Studies carried out independently in the mid 1990s by ICI provided a significant assessment of just how much energy a poorly aligned pump set consumes. At the ICI Runcorn site a study was made into the effects of misalignment on a water pump set operated in a controlled environment. The test pump installed in a closed loop system, was initially accurately aligned better than 0.03 mm, over a period of 6 weeks it was then progressively misaligned to determine what additional power was consumed to drive the pump. At each predetermined misalignment interval the power drawn was measured and plotted on a graph as shown in Fig 2.
Power savings on operation of a pump set, just by aligning it correctly, in the order of 2 or 3% are not uncommon. Taken over the entire asset base of a company such energy savings can amount to many tens of thousands of pounds each year. But sadly there are still many thousands of rotating machine systems operating with excessive misalignment and being repaired every year because that is what is expected to happen. It should not be so, machines are not designed to fail annually! By taking simple steps when installing new or repaired equipment significant savings can be made year on year. Using a range of independent assessments such as the ICI study above, PRUFTECHNIK has produced a Return On Investment calculator that can be applied to virtually any shaft coupled pump system to reveal the potential costs that can accrue from poor initial alignment of pump sets etc. The calculator takes into account key costs such as: Wasted energy It costs more money to drive a badly aligned pump set; Premature mechanical seal failure bad alignment impacts directly on mechanical seal life and replacement intervals; Bearing failure and replacement when pumps are stripped for replacement of seals new bearings are usually installed irrespective of condition; Unnecessary labour costs.
The resulting calculator is to quote Colin Sims of Thames Water A really useful insight into how basic maintenance functions can impact on plant operating profitability every year. In an operation such as theirs incorporating thousands of close coupled assets the potential savings offered by good shaft alignment practice is enormous.
For a free 160 page handbook on shaft alignment and a copy of the ROI calculator contact: Pruftechnik, Tel; 01543 417722,
info@pruftechnik.co.uk
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