Permanent magnet motors and smart pumps are making an impact in all sectors. Environmental, political and commercial pressures mean the drive for greater efficiency and better energy use has a special appeal for water and wastewater, writes Brian Attwood.
At the recent Emerson Global Users Exchange – the annual get together and knowledge share for 1,600 individuals from more than 50 countries – spokesman Roel Van Doren shared a key fact about business efficiency.
Two thirds of the largest multi-billion dollar projects fail on one of two criteria, he said: they don’t hit deadline or they don’t hit budget. The ‘secret’ is to succeed at both.
Time and money is a bottom line consideration in the pumps sector, irrespective of scale, but there’s increasing division over how those concepts are measured.
Increasingly, though, expense and downtime are being reckoned over much longer time frames. This alters radically one’s perspective about the costs involved – financial and otherwise.
In the case of the water and wastewater sector, one is dealing in a commodity for which industrial and consumer demand is rising exponentially. At the same time, governments are placing increasingly stringent quality requirements on suppliers, with UK regulator Ofwat seeking greater focus on lifecycle considerations.
Consumers often spur politicians’ demands yet themselves add to pressure on the system, explains Chris Harvey, market development manager for Flygt Pumps at Xylem [pictured left]: “The water and wastewater industries face continuing pressure to reduce their impact on the environment through both energy and carbon reductions as well as protecting it from flooding and spillages. However, much of what they do is governed by the specific nature of the wastewater flowing in.”
The proliferation of disposable products – cleaning wipes, cotton buds and even clothing thrown down toilets and sinks – has shifted the focus of pumping station teams, says Harvey, to resolving the impact of non-biological solids, rather than dealing with system hydraulics.
More work must be done therefore to process the water available, in order to make optimal use of energy consumption and increase pumps’ return on investment.
The addition of more variables in terms of what outcomes are demanded and what needs must be addressed in the operation of pumps has increased the requirement to adapt faster. Pumping stations and systems must be reassessed at various intervals during their working life, cautions Harvey.
Traditionally, the key factors for pump selection have been forward flow, plus the distance, undulations and height through which liquid must travel. A tougher call is to ascertain the internal condition of the pipe/rising main, says Harvey.
“A relatively small increment in flow, in long rising mains, can require a significant increase in required pump pressure. However, the more pressure the pump has to generate to pass a given flow, the more power it consumes.”
Predictability, variability and effective control are key safeguards of efficiency. Such considerations have driven interest in two key developments in the sector cited by The Pump Centre’s John Howarth: permanent magnet motor pumps (PMMP) and the growth of the smart pumps market overall.
PMMPs are increasingly making inroads against industry stalwart, the induction motor pump. The latter depends on electric current to move its rotor, which is constructed with windings to mirror those of the stator; whereas the PMMP uses magnets to turn its rotor.
Another distinguishing feature is the PMMP’s reliance on a variable frequency drive (VFD). While induction motors can function without these, the net effect is a lack of speed control.
Grundfos Pumps has been a pioneer in the PMMP market and launched the first circulator pump incorporating a permanent magnet motor onto the market back in 2001 [see image above]. Rick Child, energy optimisation manager for the company, explains the benefits: “Permanent magnet technology, along with variable speed controls, allows pumps to meet strict efficiency regulations.
“It is the ability of these pumps to match their speed to the changing requirements demanded by the system in which they operate, that makes them such an energy efficient choice. An efficient pump will also impact on maintenance costs.”
There are traditional alternatives to using a VFD, of course – throttling the pump using a valve or blocking air flow – but, warns Grundfos, decreasing flow on a fixed speed pump wastes energy (and money), moving the pump down the efficiency curve. Drives permit the user to dial the exact flow and pressure requirements.
While pump efficiency may be regarded in many quarters as a peripheral concern, the industrial facts of life suggest otherwise. As energy management leader Schneider Electric notes, global population is expected to rise from 3.4 billion to some 6.3 billion in the 41 years to 2050 and with it water demand.
In 2016 Schneider estimated that, while nearly a quarter of industrial energy motor use was accounted for by pumps, 40% of the total cost of ownership (TCO) was accounted for by electricity costs and some three quarters of all pumps were oversized.
Efficient flow
PMMPs bring the benefit of smaller size and variable speed but the game changer in the war on industrial inefficiency is data responsiveness. This relates not only to the information dialled to a drive, but also the back catalogue of detail about product performance, mixed with the ability to respond in real time (combining smart products and systems).
Xylem’s Flygt Concertor has led the way in the wastewater sector with the first system incorporating integrated intelligence. Able to work with pumps ranging from 2.2-7.7 kWm, its features include IE4 motor efficiency, integrated power electronics, N-hydraulics and intelligent controls.
Among its testing grounds has been Northumbrian Water’s Butterknowle sewage pumping station where frequent breakdowns created too-frequent site visits and disruption. Anti-blockage protocols ensured detection and prevention of incidents by running the impeller back and forward to clear debris – a process carried out 22 times before alerting engineers.
The results, including an absence of interventions during the six-month trial period and electricity savings of more than £2,000 annually, have been mirrored elsewhere, says Xylem, with energy savings of 70%, inventory and vacuum cleaning costs reductions of 80% and cabinet size halved, compared with traditional systems.
Seepex has been an early adopter with its Smart Dosing Pump for a variety of other industrial settings and laboratory applications. Combining progressive cavity pump and sophisticated control, the SDP includes an integrated PLC to ensure standalone operation when necessary, with sensors on the pump feeding back information. It also allows easy integration into higher-level controls and automation systems and can be operated by handheld panel for fieldbus systems.
Keeping things simple
While intelligent and PMM pumps will feature increasingly in all process sectors, the brakes to adoption remain thanks to the perception that these products are costly, complex and disruptive.
Where purchase price is concerned, there is little dispute. But, as Seepex’s business development and marketing manager Lesley Eaton emphasises: “You have to consider the downstream processes as well as the cost of the pump; in the food industry it’s the intangible time taken, time to do calibrations and then (in the case of diaphragm pumps) if there’s any maintenance, you have to recalibrate it.
“Also product quality – if you’ve got smart dosing you’re going to have a better quality end product.” Where dosing is concerned, she explains, smart dosing makes for a better and more precise product quality and consistency.
It is the ability of these pumps to match their speed to the changing requirements demanded by the system in which they operate, that makes them such an energy efficient choice. An efficient pump will also impact on maintenance costs
Rick Child, energy optimisation manager, Grundfos Pumps
Grundfos’ Rick Child concurs: “There are a wide range of factors that need to be considered, especially as we know the initial cost of the pump only accounts for just 5% of its total life cycle cost.”
Of the balance, he says some 85% is attributed to energy, with the remaining 10% for service and maintenance. Their combined message is that it pays – literally – to take the long view when assessing a potential purchase.
As for complexity, this varies considerably. Seepex’s progressive cavity dosing pumps, for example, veer firmly towards simplicity.
Explains Eaton: “There’s one control variable because they are volumetric and that’s speed. And it’s linear accuracy so it’s not complex to caibrate.
“It’s got a closed loop feedback and a flow meter after the pump discharge: you only need to set the required flow rate, which you can do on HMI or SCADA, and then the pump adjusts to maintain this requirement.”
She also questions the common assumption that sophisticated products and increased automation necessarily present all users with a skills challenge.
“There’s a move towards greater efficiency and more integrated equipment which can only increase because we are in the midst of a skills shortage and processes need to be automated. Yes, you need skilled people to automate but you don’t always need so many to run processes.
“If you’ve got plug and play, you don’t need people who can do the calibration curves. Smart working doesn’t always mean highly skilled – one engineer can programme a lot of things that then work automatically.”
But, she cautions, there may be legitimate bars to the adoption of innovative products such as PMMPs and smart pumping systems. Companies might lack the higher-level control systems – SCADA and suchlike – to enable integration, so it helps that products can operate on a standalone basis too.
Onward march of change
Likewise, expansion of the PMMP market does not determine the imminent demise of the induction motor pump, cautions Child. Sales may decline but not disappear. “Permanent magnet motors are currently limited in terms of the applications they can be used in, due to their motor size (in our case 11 kW). Therefore, for larger applications, other options such as fixed speed with variable speed drives will still need to be specified.
“It will depend on [whether] the pump is required for a new or replacement situation, the application type and if it is being used in conjunction with a frequency converter.”
Yet an overriding logic remains in favour of greater adoption of PMMPs and smart pumps in general. As Harvey points out, the asset base of any water company and the UK’s 36,000 wastewater pump stations contain a plethora of different models with specific flow and head characteristics.
This creates a nightmare for stocking emergency spares, while lack of adequate data increases the tendency to make ‘like for like’ replacement based on availability rather than correct selection.
The result is pumps that frequently do not deliver optimum performance – risking failures, impeller replacements and unnecessary downtime. Plus, it reinforces the likelihood that oversizing – that prime contributor to energy waste – continues for another generation.
