The definition of a pump is a device which uses suction or pressure to raise or move liquids. Back in Egyptian times, 2000 BC, this meant a long suspended rod with a bucket at one end and a weight at the other. 1800 years later, in arguably the greatest invention of all time, Archimedes devised a mechanical method of lifting low lying water for irrigation and land drainage purposes known as the Archimedean Screw Pump. This method is still very much in use today.
Mechanical pumps require power in order to operate, in 200 BC this source of power was the human hand. Animal, wind and water turbine power sources followed, thanks to the development of mechanical power transmission linkages. Steam engines became the main power source at the end of the 18th century, whilst gas and early oil dominated the 19th century.
In 1790 Thomas Simpson coupled a reciprocating pump to James Watts rotary motion steam engine, to drive municipal water works pumps on the River Thames. This ultimately led to the formation of Worthington Simpson in 1917, which is now a part of Flowserve.
In 1851 John Gwynne filed his first centrifugal pump patent. His early pumps were again steam engine driven but used primarily for land drainage. Allen Gwynne Pumps closed their manufacturing plant within the town of Bedford in 1987, which led to the formation of Bedford Pumps by former members of the pump department at W H Allen. The first electric motor driven pumps finally emerged in the early 1900's. Whilst electric motors now dominate the pump industry, electricity cannot reach all locations and the diesel engine driven pump, with its high torque engine, still plays a significant role in today's mobile pumping market.
Varying pump output and performance
Since Archimedes time there has been a desire to vary the output and performance of a pump. This was originally achieved by changing the rotational speed of the screw or by varying the depth of water over the intake of the screw. Both concepts still hold true today. In 1972 the Swiss engineer, Martin Stähle, invented the ‘Prerostal’ system that much like the Archimedes Screw, varies the output of a Hidrostal screw centrifugal pump without changing its speed! Prerostal uses gravity to drive the pump inlet head, but with the addition of controlled pre-swirl through a specially designed pump basin. This system holds all the non-clog benefits of the Archimedes Screw but with the added advantages of a smaller footprint and lower power consumption and is a great example of how the pump industry tends to enhance and build upon successful designs and experience that have gone before.
All engine driven pumps can adjust performance by changing the shaft speed and or gear ratios on the drive train to the pump. With the fixed speed electric motor driven pump, adjustment to performance was initially possible through belt and pulley drives between pump and motor. This was not really improved upon until dual speed motors became commercially available from the late 1950's on.
It was not until the late 1980's that the possibility to infinitely vary the speed and performance of an electric motor driven pump became commercially available to the wider market. This took the form of the variable speed drive or frequency converter.
Archimedes and the modern equivalent Prerostal system.
Developments in pump technology
It could be argued that the main developments in pump technology have been driven by an end user's application requirement (e.g. to be able to vary a pumps output) since Archimedes' time. This need was progressively met through the many changes to pump power/drive source as new technology became available and was adopted into the pump arena. The alternative to speed control was to throttle a valve or close a sluice gate. This however wastes energy across the restriction barrier to flow.
The need to vary pump performance within an installation experiencing changing system characteristic's, is not that new, the possibility to achieve this comprehensively however, is. Today improved motor and variable speed drive technology provide the solutions to varying load or demand patterns on pumping systems.
Whilst this has opened up new opportunities it has also brought new challenges. The main one ensuring that the latest technology is applied appropriately, therefore delivering the best results that add value to a system, i.e. Whole Life Cost or Totex.
A variable speed drive alone does not always guarantee optimal results in terms of efficiency, reliability or reactive maintenance. This can be apparent on some wastewater applications and systems with a high static head component to a duty point. Here a technology such as a Prerostal (perhaps with dual speed motors) will often deliver a better Whole Life Cost outcome.
The trend to better match pump performance to system requirements looks set to continue and probably intensify, particularly as we run out of options to improve product efficiency and look into the system to obtain further savings.
Having said that we must not lose sight of the fact that not all systems require infinite variability in pump performance and sometimes a belt drive, dual speed motor, fixed speed motor or even the halfway house of a Prerostal system may be the most appropriate Totex solution where fewer set-points of performance are required.
What's the future?
We are all aware there is a limit to product efficiency. As we get closer to that limit, the magnitude of savings which pumps, motors and variable speed drives alone can realise, is decreasing.
Perhaps the next generation of significant savings for pump users belongs to a wider pumping system optimisation approach? This would no doubt require a middle way, taking the right mix of the most appropriate technology combinations for given applications.
By not just looking at the pumps in isolation, but aligning controls and monitoring to adapt and match performance to the more dynamic systems, a lower energy outcome should be possible with improved reliability from planned maintenance driven by monitoring equipment. The BPMA has offered members valuable guidance on many aspects of evolving pump efficiency, standards and testing for some considerable time, helping us all separate fact from fiction. BPMA is also currently actively involved in the developing scene of an ‘Extended Product Approach’ which Europump are currently proposing. Beyond this we are then into the huge diversity and knowledge challenge of ‘System Optimisation’.
Could the future of the BPMA lie more in the realms of optimum system integration for pumps as opposed to the pump itself?
Whatever the challenge may look like we can be assured the BPMA will continue listening to the members, balancing the arguments and representing the British Pump market needs successfully for many years to come.
Andy Wilson, business development manager, Hidrostal Ltd.
4/5 The Galloway Centre, Hambridge Lane, Newbury, Berkshire, RG14 5TL
Tel: +44 (0) 1635 550440