PUMPS AND PUMPING SYSTEMS
A long time coming
The water industry is finally turning on to the benefits of reliable
rotary lobe pumps and bona fide Maintenance-In-Place
R
otary lobe pumps have come a long,
long way since their initial introduction
to the UK saw some units with non-
elastomer-coated steel rotors in a non-lined
case. Despite the fact that higher quality rotary
lobe units were in successful operation in other
parts of the world, low cost units were not
popular. Many years later one managing
director remembers an instance when he was
asked to leave a customer’s site when he
mentioned the words ‘rotary lobe pump’!
That MD was Börger’s David Brown, who not
only lived to tell the tale but says that rotary
lobe pumps are now starting to become the
preferred industry choice. “It has taken time”, he Following intensive trials to find the most
says, “but as the industry has moved more and
effective method of removing scum and fat at a
flagship wastewater treatment plant in the South
more towards genuine life cycle costs, including
West, one of the UK’s main water companies
all important maintenance issues, the benefits invested in PL200 pumps made by Börger
to be gained from Maintenance-in-Place (MIP)
rotary lobe pumps have proved far too Brown continues: “I can understand why some
favourable to be ignored”. companies are making such a compromise and
Brown points to just one flagship site in north spending so much money in redevelopment,
London to demonstrate the trend. At this major because MIP is such an attractive proposition,
sewage treatment works, no fewer than four key
Börger’s PL300 MIP (Maintenance-In-Place)
but it’s got to be done properly.”
Pump, which for Wessex Water collected four
wastewater applications have so far been
tonnes of grit on its first traverse of Avonmouth’s
With specific reference to maintenance
switched to (or enhanced by) rotary lobe. These Bristol sewage treatment works and life cycle costs, Brown agrees that
include the replacement of submersible shaft- progressive cavity pumps and rotary lobe
driven screen pumps and the introduction of For maintenance teams, being able to get at a pumps are on a par when it comes to wearing
Börger’s rotary lobe pumps to handle large solids pump and then work on it with a minimum parts but argues that rotors are far cheaper to
in a scum tank application. In addition, an of obstacles has been a key success of replace. More importantly perhaps, he points
ongoing odour problem has been resolved with Maintenance in Place, but since MIP has become to the labour costs as verified by water
the addition of 16 priming pumps to clear rotting readily available in the UK (a feature that has companies, which show repair to MIP rotary
sludge at the bottom of storm tanks at the same been designed-in with Börger as standard for lobe pumps of typically 1man/2hours,
site, while a further two rotary lobe units are now over 30 years), Brown warns that some compared to the 2-man/full day cost incurred
used for the sewage plant’s digester house. manufacturers are compromising on designs and for most non-rotary lobe pumps.
a pump’s performance in order to compete.
Ease of maintenance “It seems that to get round life cycle cost Global market?
“Pumps that can’t self-prime mean extra cost requirements, forms of ‘maintenance in place’ “Better late than never”, concludes Brown, “but
and hassle for water companies and their are being increasingly offered,” he said. at last, rotary lobe pumps have become
contractors,” says Brown. “With the rotary lobe, “But when some of them, for example, accepted in the UK. I just think it’s a shame that
the pump doesn’t have to be installed in a wet include the fact that pipework also has to be most people here talk about us being in the
well or submerged environment, so there’s no removed, there’s no saving to be gained for the global market, yet our industry has become
longer a need for maintenance engineers to customer. To achieve a redesign to very insular in some quarters.
work in confined spaces with all the accommodate easier maintenance, the pressure “We’d all like to see more engineers at
complications and costs that can bring”. rating of some pumps can also be affected, exhibitions but it seems harder and harder for
He added: “There’s also no requirement for which denigrates their capacity and capability”. them to be able to afford the time. Yet surely
lifting equipment or such like because the To accommodate MIP, Börger’s MD says that the emphasis should be on investing in
suction capabilities of a well designed rotary in some cases, customers have bought pumps personnel so that they can keep abreast of
lobe pump allow far greater opportunities for to suit an application of less than 1.0 BAR but new technology and weigh up the options?
installation at convenient and advantageous have actually been sold a unit with up to a Money spent on sending engineers to shows
locations. And when a submersible pump is 3BAR or even 6BAR capacity, resulting in would be far outweighed by the long term
down a well, it’s not always that easy to inevitable friction loss, increased energy costs savings made through learning about new or
monitor its performance”. and inferior performance. alternative technology”. ■■■
38 Water & Wastewater Treatment November 2009
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